Contaminated meat

If Max eats up all his chicken, he'll grow to be a big, strong boy. Unless it kills him first.
Bacteria from the cut-price meat that we eat can remain in the gut for years and, warn scientists, breed superbugs untreatable in humans.
So are we sitting on an antibiotic-resistant time bomb?
Andrew Purvis Sunday August 10, 2003 The Observer

Even as you pick up the tray of cut-price chicken thighs, your life expectancy has plummeted. Ten years from now, as a result of this penny-pinching impulse buy, you could die - untreatable by modern medicine - in the intensive-care unit of a British hospital, the victim of a killer bug implanted in your gut and waiting for its Big Moment. It's a complex tale of poor slaughterhouse hygiene, gene transfer, microbiology and pure chance, but at its centre is the antibiotic avoparcin - a 'growth promoter' once given to chickens and pigs to help them gain weight efficiently.

Though our story is about poultry, it could just as easily be about the pork chop, sausages, or salami sticks in your shopping basket. When you read this, you will understand why the check-out staff at supermarkets put your meat in a bag separate from your tomatoes; you will realise the importance of food hygiene and appreciate the true danger of cross-contamination.

Banned in Europe since 1997 due to fears about human health, avoparcin is no longer used or manufactured anywhere in the world - yet its legacy remains in the environment, and in the guts of animals generations later. Because it was given at very low dosages (fewer than 50 parts per million in feed or drinking water), avoparcin didn't kill bacteria outright but allowed some - the most resistant to it - to survive. Exposed to other drugs, these can in turn become more resistant to several antibiotics, creating a 'superbug'.

At the time of purchase, it has to be said, the chicken's pathology is relatively benign - if a little unsavoury. Most farm animals, and indeed most humans, carry millions of harmless bacteria called enterococci in their faeces and gut - and these can be transferred to the surface of meat at slaughter, often through unclean blades or the mechanical scoops inserted through the birds' backsides to eviscerate them. As the chicken oozes unappetisingly on the top shelf of your fridge, wrapped in a leaky carrier bag, blood drips on to the cheddar cheese below - the classic 'cross contamination' sequence - and seeps through its paper wrapper.

Making yourself a cheese sandwich next day, you don't notice the bacteriological accompaniment - but you have inadvertently eaten uncooked enterococci. As the chicken itself is grilled for dinner, atomising the evidence and rendering the meat safe, the microbiological time bomb is ticking away in your stomach. Because the enterococci are harmless, you notice no symptoms. For a few days, the bugs struggle to survive inside their new human host - and they will quickly die. But before they do, they will pass on their gene for antibiotic resistance (acquired through repeated exposure to avoparcin) to other bacteria, notably enterococcus faecalis and enterococcus faecium, bugs that live in the gut of humans.

'We now know there are little pieces of mobile DNA,' says Professor Laura Piddock, Professor of Microbiology at Birmingham Medical School, 'which can detach themselves from the animal enterococcus and jump across to the human type. It's a form of bacterial sex. You then have a resistant bacterium in your body, which can sit there waiting in your gut. You don't know when you ate the resistance gene - it could have been last week, it could have been 10 years ago. It isn't a problem if you're a normal, healthy individual, but if you go into hospital for a kidney transplant or similar operation, you will be very vulnerable. You can be infected by that organism or, worse, it can spread through an entire hospital ward through the oral-faecal route.'

In other words, if you don't wash your hands, resistant bacteria can attach themselves to food, cutlery, bed linen, clothing and surgical instruments, infecting wards and colonising the intestines of other patients. In the physically robust, these human enterococci can cause minor urinary infections and stop wounds healing. In the less strong - such as long-term hospital patients, people with kidney failure, the elderly and anyone with a compromised immune system - they can lead to raging infections of the blood stream (bacteraemia), heart muscle (endocarditis) and brain (meningitis), often resulting in death. And so, when you are admitted to hospital for minor heart surgery a decade after you ate that tainted cheddar sandwich, the superbugs are waiting to colonise your chest and kill you.

Known as VRE (Vancomycin Resistant Enterococci), these bugs are among the most indestructible isolated from humans and are virtually untreatable in their most resistant form. Though minor infections usually respond to penicillins, macrolides or tetracyclines - three families of antibiotics in widespread use today - there is nothing modern medicine can do about the more serious outbreaks. In the past, doctors used two expensive and potentially toxic medicines, teicoplanin and vancomycin, injected by syringe. In 1986, however, the first vancomycin-resistant enterococcus was found in France and, a year later, it was isolated in the UK. Similar bacteria with 'multiple resistance' have been found worldwide, including the US - and there is nothing left in the medical armoury to treat them. 'These are infections of the 1990s, 2000 and beyond,' says Professor Piddock. 'Due to advances in modern medicine, which have ensured that seriously ill patients tend to live, we are seeing a whole new spectrum of diseases, some of which are very difficult to treat- including VRE.'  [NOTE: the usual progression of "technological advances" from short-term convenience to long-term disaster is repeated again - ljf]

One of the main reasons is the widespread use of antibiotic growth promoters such as avoparcin - which is chemically related to vancomycin (both are classed as glycopeptides). 'As long ago as 1969,' Professor Piddock explains, 'the Swann Committee [commissioned by the Government] recommended that no agent used in human medicine should be used for growth promotion in animals - and people have stuck to that. However, there are drugs used in animals with a different name and chemical structure which are so similar to those used in people that the bacteria cannot distinguish between the two. As far as they are concerned, it is the same molecule - so they become resistant to the human drug.'

One such drug is ciprofloxacin, the antibiotic many Americans turned to when anthrax attacks were threatened after 11 September 2001. It is one of the fluoroquinolones, a family of antibiotics that includes several used to treat farm animals, mainly chickens and turkeys. 'We're particularly concerned about this one,' says Dr Caroline Willis, a clinical scientist with the Health Protection Agency in Southampton, 'because it is a first-line agent for treating serious hospital infections.' It is also the first line in drugs for fighting salmonella, E. coli and campylobacter - serious food-poisoning bugs that affect 100,000 people in England and Wales each year and account for 100 to 200 deaths. Campylobacter poisoning, though its symptoms are the least severe, is on the increase, with cases doubling since 1990. Last year, 60,000 people fell victim to it and 80 died. Of those 60,000, an estimated 9,000 would have had the ciprofloxacin-resistant strain which may not respond to that particular medicine. It is Dr Willis's job to look for bacteria in food and find out how resistant they are to human medicines. In a recent examination of raw chicken imported from Thailand and Brazil, she found that 78 per cent of the campylobacter bacteria isolated were resistant to ciprofloxacin (compared to 10 per cent in UK samples); among E. coli bacteria, 47 per cent were resistant (compared to zero resistance in chicken produced in Britain). 'This suggests that a drug related to ciprofloxacin is being used quite freely in chicken production in these countries,' Dr Willis concludes. 'Because 20 to 30 per cent of our chicken is imported from places like Thailand, we are sitting on an antibiotic-resistant time bomb.'

What Dr Willis means is a situation where more and more bacteria fail to respond to treatment - allowing human diseases to run rampant, as in the pre-antibiotic era. Already, the food-poisoning bug Salmonella typhimurium DT104 is resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline (all used in human medicine) and is failing to respond to trimethoprim and ciprofloxacin as well. Between 1990 and 1996, there was a tenfold increase in DT104 cases in Britain - though this has been brought under control by mass vaccination of poultry - and this strain results in twice as many hospitalisations and 10 times as many fatalities as other types of foodborne salmonella. In 1998, the most serious recorded outbreak occurred in Denmark, when 22 people fell ill after eating infected pork. Of those, seven were admitted to hospital and four failed to respond to treatment with fluoroquinolone (the antibiotic of choice for serious food-poisoning episodes). One previously healthy 62-year-old woman died due to intestinal perforation, after a five-day course of fluoroquinolone failed to kill the resistant bacteria before surgery.

Nor is it just DT104 that is failing to respond to first-line drug regimes. 'In campylobacter coli, a strain of the food-poisoning bug which originated in pigs, human resistance to erythromycin is now running at 13 per cent,' says Richard Young, policy adviser to the Soil Association. 'It's the only safe drug used to treat children with the infection, so we are talking about 200 to 300 children per year who will be untreatable with this drug.' Erythromycin is one the macrolides family, banned as growth promoters in 1999. 'Since then,' says Young, 'the quantity prescribed by vets has actually gone up, from 23 tonnes in 1998 to 55 tonnes now - which is a move in the wrong direction. I believe that, literally within a decade or so, we are going to see a large number of people dying from drug-resistant infections for which there are simply no effective antibiotics.'

The culprit, he believes, is the indiscriminate use of antibiotics in food animals - and in this he is not alone. After hearing evidence from the World Health Organisation and others in 1997, the EU banned avoparcin because of fears about resistant superbugs spreading from poultry to humans. In 1999, both Tesco and Marks & Spencer said they would no longer stock chickens that had been fed antibiotic growth promoters (AGPs), and EU legislation in the same year outlawed six more. This leaves only four such products (avilamycin, flavomycin, monensin and salinomycin) licensed for farm use - and these, too, will be withdrawn from all EU countries, including Britain, by January 2006.

In June this year came further evidence that the tide against antibiotic growth promoters was turning. In a well-publicised announcement, the McDonald's fast food company in Illinois directed some of its meat suppliers to stop using AGPs by the end of 2004 while telling others to cut back. The total ban applies mainly to suppliers of chicken, who routinely use 24 growth promoters which are closely related to human medicines - including virginiamycin, believed to be the cause of outbreaks of the VRE super-bug in the US. 'We would love to be a catalyst for change industry-wide on antibiotic use,' said Robert Langert, McDonald's senior director for social responsibility.  [Now, there's an oxymoron ljf]  'People have been arguing about this all night and day, but now we are taking some practical steps and expect we'll make some real progress.'

It isn't the first time such a clarion call for reform has been issued by a major player in the food world - and last time the tune was short-lived. In 2000, British poultry farmers working under the Assured Chicken Production scheme - represented by the Little Red Tractor logo, and accounting for 85 per cent of all chickens sold in the UK - agreed very publicly to discontinue the use of antibiotic growth promoters. In 2002, however, a clause was added to the ACP standard, saying AGPs could be used preventatively in feed 'under veterinary supervision on welfare grounds' - and this remains the case, though the guidelines are currently under review. 'They claim the drugs are necessary to control disease,' says Richard Young of the Soil Association, 'but using them in this way is not permitted in the EU.' Antibiotic growth promoters, which are classed as feed additives, have never been evaluated for safety as veterinary medicines. In May this year, Margaret Beckett, the Secretary of State for Agriculture, agreed. In a letter to the Soil Association - the licensing body for organic farming, which is lobbying for a radical reform of intensive farming methods - she admitted that using growth promoters in this way 'could be illegal under EU legislation' and resolved to look into the matter. For its part, Assured Chicken Production says preventative use of AGPs reduces the need for therapeutic antibiotics - the ones, they say, which are more closely related to human medicines.

In fact, growth promoters are only the tip of the antibiotic iceberg. While 43 tonnes of AGPs (measured by weight of active ingredients) were sold in Britain in 2001, the overall quantity of antibiotics used on farm animals was 463 tonnes - more than 10 times as much. This figure has risen from 452 tonnes since 1998, suggesting that the fears voiced by medical experts have largely gone unheeded. Though the up-to-date total will be less (due to the phasing out of AGPs and some drugs used in human medicine), a 1998 report for MAFF - now Defra, the Department for Environment, Food and Rural Affairs - listed no fewer than 61 antimicrobials used to treat farm animals which had implications for human health. These were those antibiotics used in agriculture 'which may affect the antimicrobial resistance status of foodborne pathogens, or contribute to the resistance pool in man'.

In addition to these, Richard Young is worried by the coccidiostats, powerful drugs such as nicarbazin, lasalocid and narasin which are used to treat parasitic infections in poultry and game. While the Veterinary Medicines Directorate (VMD), which monitors residues in food animals, says 99 per cent of poultry and 97 per cent of eggs are free of such chemicals, Young believes the figures could be wrong by as much as 2,000 per cent due to the way in which data is collected. He claims that four per cent of all eggs and 10 per cent of all chicken livers tested in the UK contain residues of coccidiostats, some of which are toxic in high dosages and cause irregular heart activity.

Pigs, too, are routinely fed or injected with up to 10 antibiotics in their lifetime (on average, 15g of medicine for every pig reared in Britain, compared to 4g per pig in Denmark), while lambs may be given 'antihelmintics' to control outbreaks of nematodirus disease (caused by a parasitic worm) and most dairy cattle will have antibiotics pumped directly into their teats to fend off mastitis. However, because all food animals in Britain are subject to a 'withdrawal period' before slaughter, allowing antibiotics to be purged from the system, it is unlikely that such drugs enter the food chain in sufficient quantities to affect our health. However, as Richard Young points out, not all farmers abide by the rules governing withdrawal - and poultry farmers in particular sell off smaller, surplus birds ahead of the main flock (known as 'thinning') before they are taken off drugs. Could the occasional antibiotic residue, which scientists say can't exist, cause an allergic reaction and make some people ill?

Steven Saunders, chef-proprietor of the Sheene Mill Hotel and Restaurant in Melbourn, Cambridgeshire, is convinced they can. 'My mother never gave me penicillin because I reacted badly to it,' he says, 'and to me it makes perfect sense that I'm allergic to antibiotics in meat. I can enjoy a meal, I can have dinner with friends - but if I eat the chicken, I know how I will feel next day. My stomach churns, I'm out of sorts. It's the same with Indian food: I can cook it myself and never suffer - but if I go to an Indian restaurant, I probably have the cheapest form of catering chicken that is intensively farmed, and I know it's going to get me. By the next morning, it has.'

Long before organic food was fashionable - or even a household term - Saunders began eating a chemical-free diet and serving naturally-reared meat in his restaurant. 'I sourced my ducks from Aylesbury,' he says, 'my chickens from a place near Thetford - and my restaurant at the time, called the Pink Geranium, started getting incredible reviews.' By using meat that was free of antibiotics, Saunders became better known as a chef and found himself ideally positioned to be an outspoken advocate of organic farming - but is meat produced in this way really any safer? 'From a microbiological point of view,' says Professor Piddock, 'I doubt it. Organically reared animals carry the same bugs, they get ill, they are treated with antibiotics - but probably less than in conventional farming. They have a better life, they are healthier, and organic meat certainly tastes better. That, I imagine, is more to do with diet than a lower dependency on antibiotics.'

Despite Saunder's organic zeal, the science also suggests that stopping the routine use of antibiotics in food production may not be the answer. When Denmark banned avoparcin (in 1995) and virginiamycin (in 1998), there was initially an encouraging result. The proportion of avoparcin-resistant enterococci found in chickens fell from 73 per cent to five per cent in a five-year period, while the fraction of virginiamycin-resistant enterococci almost halved. But the decrease in resistance came at a price in terms of animal welfare, with higher mortality rates in young pigs (which are also fed avoparcin) and an increased incidence of gastroenteritis. In both Denmark and Sweden, the amount of antibiotics prescribed therapeutically by vets has risen since growth promoters were banned, reflecting a higher incidence of sickness in animals.

'That may be true,' says Steven Saunders, 'but that is because the whole farming system needs a rethink. The only reason animals are given these antibiotics is because they are living in such terrible conditions. They are produced intensively simply to keep up with demand - but why do we need all this cheap meat - the sausages, the burgers, the chicken tikka masala? I think we eat too much meat anyway, so farmers don't have to produce all these thousands of chickens, do they? People can eat pasta instead, until meat is a quality product again.'

For the time being, that quality product does come from animals reared organically. Living under better welfare conditions, they don't need antibiotics administered constantly in their feed or given prophylactically (as an insurance policy against disease, rather than as a treatment). However, they may be given the odd homeopathic remedy. 'Most organic farms will use homeopathy to some extent,' says Will Best, who keeps 140 dairy cows, 100 younger cattle and 100 ewes on his 500-acre farm near Cerne Abbas in Dorset. 'We have a herdsman, Phil Hansford, who has developed an in-depth understanding of it. He wrote The Herdsman's Introduction to Homeopathy which nearly all the organic herdsmen have.'

Under Hansford's guidance, a cow suffering from pneumonia was once prescribed beryllium instead of the vet's antibiotics, followed by two further remedies for ticks (which were challenging her immune system) and swollen lymph glands. 'That required considerable input, intelligence and detective work,' says Best, 'but after a few days the cow got better. I cannot remember the last time we used an antibiotic on a bovine, though we have done occasionally on sheep. As far as the cattle are concerned, the situation just doesn't arise - and I think this shows in the quality and purity of our milk, which is sold under the Manor Farm label.'

In conventional dairy farming, Best explains, the main antibiotic use is what is known as dry-cow therapy. 'The average cow does about 10 months milking, followed by two months off before she calves again,' says Best, 'and in that period, a dose of long-acting antibiotic is pushed up each of the cow's teats to prevent mastitis. The idea is that, during the dry period, the antibiotic won't be flushed out by the milk.' However, such are fears about antibiotic resistance, a product has been developed by Pfizer in New Zealand which eliminates the need for drugs. Teatseal is a chemically inert silicone plug pushed up the cow's teat canal to seal it, preventing bacteria from entering. 'It's marvellous for the trade,' says Best, 'because they sell it at the same price as the antibiotic.' However, the product is good news for the consumer as well. 'If the average dairy farmer follows this recommendation,' Best calculates, 'the routine use of antibiotics in milk will come down by 50 to 60 per cent.'

For the time being, antibiotic use on farms in Britain continues to rise - and even if this were reversed, its legacy would continue. According to the World Health Organisation, there is now a variant of Salmonella typhimurium DT104 (resistant to at least seven human antibiotics) which has multiple resistance built into its genetic make-up permanently. In other words, even if antimicrobial drugs were banned completely in food animals, the variant known as R-type ACSSuT would remain resistant to these human medicines.

More disconcertingly, research conducted in 2001 suggests that one in 10 British children under the age of 10 may carry multi-resistant superbugs in their digestive systems, limiting the drug options available to them. Researchers at St Bartholomew's Hospital found that 11 per cent of stool samples contained bacteria such as E. coli that were resistant to chloramphenicol, a drug rarely given to children - suggesting they had acquired resistance without having taken the antibiotics. Though animal antimicrobials were not directly implicated, a spokesman for the Public Health Laboratory Service said: 'The usage of antibiotics is the driving factor in the development of resistance. Therefore, ways of reducing resistance must focus on the amount of antibiotics to which the population is exposed.' Though the drugs prescribed at doctors' surgeries certainly play a part, half the antibiotics dispensed in Britain every year are used in our food.

What's in your gut?

Vancomycin resistant enterococci (VRE)

Source: Mainly chicken, also pork. Anything cross-contaminated with it.

What it is: A bacterium in the faeces and gut of humans, dangerous if spread through poor hygiene. Common in hospital wards. A different type of drug-resistant enterococcus is carried by chickens and pigs, and this transfers its 'resistance gene' to the human bacterium, making it untreatable.

Resistant to: Vancomycin, the most powerful human antibiotic available. Also teicoplanin, the penicillins, the macrolides and the tetracyclines.

Cases: No official figures, but one study found VRE present in the stools of 15 per cent of kidney patients and 2 per cent of the general population (1.2m people). But VRE can now pass on its resistance gene to MRSA (Methicillin Resistant Staphylococcus Aureus), a hospital 'superbug' infecting at least 13,000 patients a year for whom vancomycin is the last defence.

Symptoms: Urinary tract disease, poor wound healing, untreatable infections of the blood, heart muscle and brain. Potentially fatal.

Likely culprit: Avoparcin (now banned), an antibiotic growth promoter given to chickens and pigs, chemically related to vancomycin.

Salmonella typhimurium DT104

Source: In one case in Denmark, pork.

Other suspects are roast beef, ham, salami sticks, chicken legs and unpasteurised milk. What it is: A multi-resistant strain of the salmonella bug.

Resistant to: Ampicillin, streptomycin, chloramphenecol, sulfonamides and tetracycline. Now failing to respond to trimethoprim and ciprofloxacin.

Cases: At the last count (2001), 2,085.

Symptoms: Nausea, stomach cramps, diarrhoea, fever and headache. Can be fatal in children and the elderly.

Likely culprit: Related animal antimicrobials given to poultry and pigs.

Campylobacter coli

Source: Uncooked poultry (particularly from Brazil or Thailand) or cross-contamination from it; other raw meats, unpasteurised milk.

What it is: A resistant strain of campylobacter, the fastest growing food-poisoning bug.

Resistant to: Erythromycin, the only safe antibiotic for treating food-poisoning in children. Campylobacter strains in general are resistant to ciprofloxacin.

Cases: Campylobacter accounted for 60,000 poisonings and 80 deaths last year. In 9,000 cases, the bug was resistant to ciprofloxacin. Each year, 200-300 children with it are untreatable with erythromycin.

Symptoms: Gastroenteritis with fever, abdominal cramps and diarrhoea that is often bloody. It can be fatal.

Likely culprit: The macrolides - antibiotic growth promoters (now banned) - given mainly to pigs and still prescribed therapeutically by vets in UK. In ciprofloxacin resistance, enrofloxacin - still licensed for use in poultry - implicated.

  During the past decade, Trichinella spiralis infection has become widespread among domestic pigs in most of Central and Eastern Europe (i.e. Bulgaria, Byelorussia, Croatia, Georgia, Latvia, Lithuania, Moldavia, Romania, Russia and Serbia), with prevalence reaching 0.16% nationally, and up to 50% in some villages. Although, in recent years, tighter veterinary controls at slaughterhouses have decreased infection among domestic pigs, these controls are still lacking in villages, where many households keep several pigs. Furthermore, the high prevalence of Trichinella infection in domestic pigs has resulted in an increase of infection in wild boars and other sylvatic animals.

  A study was carried out in northeastern Italy during 2000 and 2001 to investigate the occurrence of Campylobacter jejuni and Campylobacter coli in animals, cattle, pigs, and broilers, and raw meat, beef, pork, and chicken. Campylobacter spp. were detected in 53.9% of the cattle, 63.5% of the pigs, and 82.9% of the broilers examined. Chicken meat was frequently contaminated (81.3%), while lower rates were found in pork meat (10.3%) and beef (1.3%). The resistance to antibiotics of the strains was also investigated, and compared to that of human clinical isolates. C. coli was generally more resistant than C. jejuni. Resistance to quinolones was frequently observed in C. coli isolated in chicken meat (78.6%); slightly lower rates were found in C. jejuni isolated in broilers (42.2%), chicken meat (52.8%), and humans (38.2%). C. coli was also frequently resistant to tetracycline in all sources, while resistance to streptomycin was most frequently observed in pig isolates (89.4%).

PMID: 12593931

  Worldwide, verotoxin-producing Escherichia coli (VTEC) have been recognized as the cause of many sporadic cases or major outbreaks of human illnesses involving consumption of contaminated meat, especially beef. Although sheep products have not been linked to reported human illnesses, their role as a food safety risk factor should not be ignored. The objective of this study was to assess VTEC prevalence in two groups of ewes (20 each) grazing an irrigated pasture or arid range in a western United States environment (Nevada) over 1 year (summer of 1999 to summer of 2000). A random sample (n = 504) of potential VTEC isolates were tested for verotoxicity and were screened for the presence (polymerase chain reaction [PCR]) and expression (VTEC-reversed passive latex agglutination assay) of the toxin genes (i.e., VT1 and VT2). Forty-one VTEC isolates (16 having only the VT1 gene and 25 having both VT1 And VT2 genes) were detected in both groups of ewes. Except for seven isolates, the genotype and phenotype data matched. All the isolates (nonmotile [H-]) were non-O157:H7 VTEC (i.e., O91:H- [n = 25], O128:H- [n = 9], and untypeable ones [n = 7]). More infected ewes (nine versus three [45% versus 15% - ljf]) and different VTEC strains were found in the irrigated pasture than in the arid range. Because our ewes were shedding two VTEC serotypes known to cause human illnesses, it is beneficial to identify VTEC-positive sheep before slaughter as an initial control point before entering the food chain.

PMID: 12671179

  The incidence of Salmonella in 60 samples of poultry products of national origin available for consumers obtained from two local butcher shops and one canteen of the city of Porto and the susceptibility to antimicrobial agents allowed for human or animal therapy were evaluated. The results show that poultry samples are frequently contaminated with Salmonella (60%), belonging to 10 different serotypes. Salmonella enteritidis and S. hadar were the most prevalent serotypes. In addition, a high number (75%) of the Salmonella isolates was resistant to one or more antimicrobial agents and eight different resistance profiles were recorded. Resistance to nalidixic acid and enrofloxacin was demonstrated for 50% of the isolates and the occurrence of resistant and multiresistant S. enteritidis isolates were less frequent than for S. hadar. This study suggests a high incidence of Salmonella on Portuguese poultry products and shows that they could be a potential vehicle of resistant Salmonella foodborne infections.

PMID: 12568749

  Orf of the hand is considered as an uncommon viral infection which is usually acquired through contact with infected sheep and goats. Indirect infections through contaminated knives or meat have been reported. Many authors feel that the disorder is more common than reported because the disease is often misdiagnosed and the course is usually self-limiting with spontaneous healing within several weeks.Diagnosis is mainly made by patient's history and clinical course. It is important to know the benign nature of human orf, since complications seem to be caused by overtreatment.

PMID: 12658338

  The annual incidence of food-borne infections in the Netherlands is estimated to be 250,000 or more; registration, however, is lacking. Meat, poultry, milk and eggs are contaminated primarily by intestinal animal commensals (Salmonella, Campylobacter, E. coli O157:H7, Yersinia enterocolitica) or secondarily by animals, humans and the environment during processing (typhoid fever, Shigella, Listeria, Clostridium, hepatitis A virus, Norwalk virus, parasites). The guidelines for the prevention of contamination are insufficient. Intensity of production and the economic importance of fast, large-scale production are given priority over food safety. Information fails to reach the consumer.

PMID: 12701391

  Shellfish are readily contaminated with viruses present in water containing sewage because of the concentration effect of filter feeding. Hepatitis A virus (HAV) is the main cause of acute hepatitis worldwide and may lead to severe illness or even death. It is transmitted through fecal and oral routes and causes widespread endemic and asymptomatic infections in young children. Here we describe a method for the detection of HAV RNA in shellfish involving the extraction of total RNA from oyster meat followed by reverse transcription-polymerase chain reaction (RT-PCR). Virus recovery from oyster extracts artificially seeded with HAV strain HM 175 was examined by RT-PCR. The minimum detection limit was 3.3 focus-forming units of HAV, and the recovery rate was 75.7%. This method was used to assess the viral contamination of four shellfish beds in Santa Catarina State, Brazil, over a 1-year period. Six (22%) of 27 samples collected in autumn and winter from one shellfish bed tested positive for HAV.

PMID: 12636311

  BACKGROUND: Seafood is an important source of long-chain polyunsaturated fatty acids (LCPs), which are essential for normal growth and development. However, the nutritional benefits could be limited by polychlorinated biphenyl (PCB) contamination. In particular, inhibition of desaturase activities by PCBs may affect the maintenance of arachidonic acid (AA) status during development.
  OBJECTIVE: The aim was to evaluate AA status in a birth cohort from a fishing community with a high seafood intake and a wide range of PCB exposures.
  DESIGN: We measured LCP concentrations in paired mother and umbilical cord serum samples obtained from 182 consecutive births in the Faroe Islands, where PCB-contaminated whale blubber forms part of the diet. PCB exposure was determined from maternal concentrations.
  RESULTS: Serum phospholipid AA concentrations averaged 9.14% and 16.5% (by wt) in maternal and cord serum, respectively. After adjustment for gestational age and concentrations of linoleic, alpha-linolenic, and eicosapentaenoic acids, a decrease in AA concentrations of 0.17% (by wt) (95% CI: 0.03%, 0.31%) and 0.31% (by wt) (95% CI: 0.10%, 0.52%) was seen in maternal and cord serum, respectively, for each doubling of PCB exposure.
  CONCLUSIONS: Increased PCB exposure was associated with a modest decrease in serum AA concentrations, which is in accordance with the experimental evidence of desaturase inhibition by PCBs. Such interference with LCP utilization could attenuate the beneficial effects of the essential lipids contained in seafood. Because AA is of key importance for growth and development, these results suggest that this possible mechanism for PCB toxicity deserves to be explored.

PMID: 12600866

  This study examined the incidence of Salmonella in Spanish poultry products. Samples included chicken carcasses, chicken parts (wings, legs and giblets-livers and hearts) and processed chicken products (red sausages, white sausages and hamburgers). The average detection rate was 49%, with the highest (55%) in chicken carcasses (skin) and the lowest (20%) in hamburgers. The chicken carcasses purchased in supermarkets were more contaminated (75%) than those from poulterers shops (25%). Salmonella Enteritidis, S. Poona, S. Paratyphi B and S. Worthington were isolated in 34.3%, 11.4%, 2.8% and 1.4% of the samples, respectively. One (1.4%) red sausage sample harboured two serotypes (S. Enteritidis and S. Worthington). This fact emphasizes the usefulness of subtyping several Salmonella isolates from the same sample in epidemiological studies.

PMID: 12457592

  A new human toxic syndrome, azaspiracid poisoning (AZP), was identified following illness from the consumption of contaminated mussels (Mytilus edulis). To discover the aetiology of AZP, sensitive analytical protocols involving liquid chromatography-mass spectrometry (LC-MS) were used to screen marine phytoplankton for azaspiracids. Collections of single species were prepared by manually separating phytoplankton for LC-MS analysis. A dinoflagellate species of the genus, Protoperidinium, has been identified as the progenitor of azaspiracids. Azaspiracid-1, and its analogues, AZA2 and AZA3, were identified in extracts of 200 cells using electrospray multiple tandem MS. This discovery has significant implications for both human health and the aquaculture industry since this phytoplankton genus was previously considered to be toxicologically benign. The average toxin content was 1.8 fmol of total AZA toxins per cell with AZA1 as the predominant toxin, accounting for 82% of the total.

PMID: 12565733

  A party of 57 people dined together in a restaurant in Hamamatsu City on December 11, 2001. The next day, 22 of them developed symptoms of acute gastroenteritis, such as diarrhea, vomiting, and fever. Examination of 4 fecal specimens from these patients by ELISA for Norovirus (Norwalk-like virus, NV) detected both genogroup I (GI) and genogroup II (GII) NV in all the 4 specimens. In addition, RT-PCR and real-time PCR methods for NV detected the NV gene. Approximately one month after the outbreak of the food poisoning (acute gastroenteritis) by NV, 4 individuals in the same party developed type A hepatitis. Both RT-PCR and real-time PCR methods for hepatitis A virus (HAV) detected the HAV gene in their fecal specimens. The party of these patients ate purple Washington clam (Saxidomus purpuratus, imported from China) steamed with red pepper. Since this food appeared to have caused the viral infections, the one with the same lot number was subjected to viral examinations, which successfully detected the NV GI, NV GII, and HAV genes. These results led to the conclusion that the clam contaminated with NV and HAV had caused the food poisoning. The DNA sequences of the NV detected in the patients and the clam had 74 to 99% homology, indicating strains of various genotypes. All the strains of HAV that were derived from the patients and the clam were genotype 1A, and these sequences had over 95% homology, but were not completely identical. This outbreak led to the demonstration of imported fishery products as a cause of type A hepatitis, and indicated the need for guiding and enlightening people on the importance of adequate cooking of bivalves.

PMID: 12661084

  OBJECTIVE: To describe the clinical and epidemiological aspects of a trichinellosis outbreak in the region of La Vera that took place during January and February 2002, related to the consumption of pork meat infected with Trichinella britovi.
  MATERIAL AND METHODS: When the first suspected case was discovered, the presumed infected meat was checked and all the people who might have eaten it were examined. An epidemiological interview and a clinic evaluation were carried out in each patient.
  RESULTS: We found 52 exposed people that had eaten the presumptive infected meat, 35 males and 17 females, with an age ranging from 2 to 86 years old. A confirmed positive diagnosis was established in 16 patients. The most frequent symptoms were: diarrhea (present in all the cases), fever, myalgia and facial edema. Eosinophilia was an early and characteristic analytic sign. All diagnosed cases were found to have positive serology, although this was not a required criterion to start medical treatment. Treatment was started once the clinical suspicion of trichinellosis was determined, based on compatible clinical signs and eosinophilia. There were no complications and none of the patients required hospitalization. The meat sample was claimed by the Health Authorities and destroyed, thus avoiding further extension of the outbreak.
  CONCLUSIONS: Sporadic outbreaks of trichinellosis have been described in Spain. In the present paper an outbreak caused by Trichinella britovi has been studied. Early diagnosis suspicion and its communication to the Health Authorities allowed the control of the outbreak and the identification of the contaminated meat. Treatment must be started after clinical suspicion and eosinophilia.

PMID: 12703156

  In the Netherlands Salmonella Paratyphi B variant Java increased in poultry from less than 2% of all isolates before 1996 to 60% in 2002. Despite exposure to contaminated meat is high, human patients with Java infection are rare (0.3% of all isolates). However, 50% of the human isolates showed PFGE profiles identical to the poultry clone. Resistance to flumequin in S. Java increased from 3% between 1996-2000 to 19% in 2001, and 39% in 2002, while that of other serotypes in poultry remained at about 7%. S. Java is also fast becoming less sensitive to ciprofloxacin.

PMID: 12631972

  A cross-sectional study was undertaken to determine the presence and prevalence of salmonellae in retail raw chicken meat and giblets (gizzard and liver) in supermarkets in Addis Ababa (Ethiopia). A total of 301 samples (244 chicken meat, 32 gizzards and 25 livers) were collected from 22 randomly selected supermarkets and examined for the presence of Salmonella. For the isolation and identification of salmonellae, the technique recommended by the International Organization for Standardization (ISO 6579, 1998) was used. Salmonellae were detected from 54 (17.9%) of the 301 samples examined. Chicken meat and giblet samples in 68.2% (15/22) of the supermarkets were contaminated with salmonellae. The contamination level of Salmonella was higher in chicken giblets as compared to chicken meat, which were respectively 12.3%, 53.1% and 28.0% in chicken meat, gizzard and liver samples. Out of the 54 Salmonella isolates, nine different serotypes were identified: Salmonella Braenderup (31.5%), S. Anatum (25.9%), S. Saintpaul (14.8%), S. Uganda (11.1%), S. Haifa, S. Group B, S. Rough form and S. Typhimurium (each 3.7%) and S. Virchow (1.8%). The high level of Salmonella contamination of chicken meat and giblets observed in the present study indicated the need in an improvement in the microbiological quality of retail chicken in Ethiopia.

PMID: 12592931

  The central nervous system is particularly vulnerable to prenatal exposure to methylmercury. Due to the widespread exposure to methylmercury from fish, several prospective environmental epidemiology studies have been initiated, in which the maternal exposure during the pregnancy is related to the neurobehavioural development of the children. We have studied a Faroese birth cohort prenatally exposed to methylmercury from maternal intake of contaminated pilot whale meat. At seven years of age, clear dose-response relationships were observed for deficits in attention, language, and memory. An increase in blood pressure was also associated with the prenatal exposure level. The exposure limit for mercury has therefore been decreased.

PMID: 12561779

  Sulfa-antibiotics (sulfonamides) are widely used in veterinary medicine. Meat and milk from treated animals can be contaminated with sulfa residues. Current sulfonamide assays are unfit for screening of food, because they are either too laborious, insensitive or specific for a few sulfa compounds only. An immunoassay for detection of all sulfas in a single reaction would be useful for screening. Previously we have improved the broad specificity sulfa binding of antibody 27G3 with random mutagenesis and phage display. In order to improve the properties of this antibody further, mutants from the previous study were recombined and more mutations introduced. These new libraries were enriched with phage display and several different mutant antibodies were isolated. The cross-reaction profile of the best mutant was better than that of the wild-type antibody and the mutants of the previous study: it was capable of binding 10 of the tested 13 sulfonamides within a narrow concentration range and also bound the rest of the sulfas 5- to 11-fold better than the mutants of the previous study.

PMID: 12646691

  Shellfish (oysters and/or clams) were obtained from 37 commercial harvesting sites in 13 Atlantic coast states from Maine to Florida and one site in New Brunswick, Canada. Gill washings from each of 25 shellfish at each site were examined by immunofluorescence microscopy (IFA) for oocysts of Cryptosporidium. Gill washings from another 25 shellfish at each site were grouped into five pools of five shellfish each. DNA from each pool was utilized for PCR and genotyping. Oocysts were found in 3.7% of 925 oysters and clams examined by IFA in shellfish from New Brunswick and 11 of 13 states. Cryptosporidium DNA was detected by PCR in 35.2% of 185 pools. Cryptosporidium parvum genotypes 1 and 2, and Cryptosporidium meleagridis,all of which have been identified in infected humans, were identified at 37.8% of the sites. Gill washings from every site were tested for the presence of infectious oocysts by biological assay in neonatal BALB/c mice but no mice were found infected, suggesting that either the oocysts were no longer infectious or infections in mice were below the level of detection. Collectively, these findings indicate that Cryptosporidium species, indicative of pollution from human and animal feces and potentially infectious for humans, were found in commercial shellfish from 64.9% of sites examined along the Atlantic coast by either microscopy or molecular testing. Previous reports link periods of high rainfall with the elevated numbers of pathogen contaminated shellfish. Because shellfish in the present study were examined during a period of exceptionally low precipitation, the data are thought to underestimate the number of Cryptosporidium contaminated shellfish likely to be found during periods of normal or above normal precipitation.

PMID: 12489014

Between 1995 and 2000, a prospective survey was undertaken to investigate the levels of contamination of raw retail chickens (n = 1,127) with salmonella and campylobacter. The levels of contamination over the 6-year period were 11 % (95 % CI +/- 6.5%) for salmonella, and 57% (95% CI +/- 95%) for campylobacter. S. Bredeney (20%) and S. Enteritidis (18%) were the dominant serovars. Although salmonella contamination was higher than in an earlier survey we conducted (7%), since 1998 it has declined to 6%. Many S. Enteritidis isolates (43%) were associated with one large integrated poultry organization that appears to have successfully managed the contamination, and the serovar has not been isolated since 1998. Contamination ranged from 0 to 44% between different producers. There was no significant difference between producers contributing large and small numbers of samples, although some small producers had much poorer contamination rates than others. S. Bareilly, S. Bredeney, S. Enteritidis and S. Virchow showed associations with particular producers. Campylobacter contamination remains high. Contamination ranged from 47 to 81% between different producers. This study did not show a temporal association between contamination of chickens and human campylobacter infections, indicating that many cases of human campylobacteriosis, particularly during seasonal peaks, do not originate from chickens. Control measures that have reduced salmonella contamination have been largely ineffective against campylobacter and new interventions are needed. Most raw chickens are contaminated with these pathogens, and communicating the importance of minimizing this risk to caterers and the public is vital in reducing human infections.

PMID: 12558349

  Vancomycin-resistant enterococci (VRE) have been a cause of increasing concern chiefly regarding the infection of hospital patients. There is suspicion, but limited evidence, that food and environmental spread may be important. Biomonitoring by examination of bivalve shellfish was used to assess the occurrence of VRE entering the environment. Using pre-enrichment and Lewisham and Slanetz and Bartley agars, 2/125 (1.6%) of shellfish were found to contain enterococci resistant to high levels of vancomycin. Lewisham agar allows relatively rapid identification of VRE. In a second phase of the work using pre-enrichment and Slanetz and Bartley agar, 4/151 (2.7%) shellfish and 5/27 (18.5%) raw chickens contained VRE. Using filtration and pre-enrichment, no VRE were found in 54 unchlorinated water samples. The study shows that environmental prevalence of VRE is low, and that raw chickens are frequently contaminated.

PMID: 12371649

  In the 1980s and 1990s, the Government of Canada closed and/or issued advisories for a number of shellfish fisheries in coastal areas of British Columbia because of dioxin contamination. Only the direct health risks (i.e., cancer) of consuming contaminated shellfish for the general population were considered by the Government in the formulation of risk management options. A focus on the direct risks does not provide an adequate basis for risk decisions as the countervailing risks which may be created from management measures may easily be overlooked. This study describes the potential health impacts of risk management options for aboriginal coastal peoples in the management of dioxin contamination. Gold River and Powell River in British Columbia, Canada, are the areas of focus. The cancer risks of consuming dioxin contaminated shellfish for these sites are estimated. To assess the countervailing risks of management decisions for comparison, a scenario was developed in which First Nations peoples substitute shellfish with store-bought foods in their diets in the event of a fishery closure or advisory. Increases in mortality due to coronary heart disease are estimated. The results suggest that the health risks of dietary changes among aboriginal peoples may be as significant as those related to eating dioxin contaminated shellfish.

PMID: 12590781

  Studies show that the pathogen Arcobacter is present in beef, poultry, and pork. Several methods have been reported for the isolation of this organism, but none has been adopted as the standard. This has limited the significance of field comparison studies. In the present study, we compared the efficiencies of four Arcobacter isolation methods using raw ground pork collected from slaughter facilities across the United States. We also evaluated the effect of meat fat level and age of animals on the prevalence of Arcobacter in ground pork. The methods chosen for comparison of isolation efficiency were those of Collins, a modified version of the Collins method (Direct Collins), deBoer, and Johnson Murano (JM). These were chosen based on published reports in which they were used to detect Arcobacter in pork products. The JM method was found to be the most successful in consistently detecting Arcobacter, isolating it in 64 of 200 [32%] pork samples compared with the Direct Collins method, which isolated Arcobacter in 52 of 200 of those same samples. The Collins method and the deBoer method found Arcobacter present in only a fraction of the samples. The level of contamination was found to vary among the plants, ranging from 0% to 68% prevalence, with 32% overall for all four plants tested. Additionally, ground pork low in fat had a higher contamination frequency (20%) when compared with high-fat pork (4%). Results also showed that meat from younger animals was more frequently contaminated than that from older animals.

PMID: 12430689

  Animal feed is at the beginning of the food safety chain in the "farm-to-fork" model. The emergence of variant Creutzfeldt-Jakob disease has raised awareness of the importance of contaminated animal feed, but less attention has been paid to the role of bacterial contamination of animal feed in human foodborne illness. In the United States, animal feed is frequently contaminated with non-Typhi serotypes of Salmonella enterica and may lead to infection or colonization of food animals. These bacteria can contaminate animal carcasses at slaughter or cross-contaminate other food items, leading to human illness. Although tracing contamination to its ultimate source is difficult, several large outbreaks have been traced back to contaminated animal feed. Improvements in the safety of animal feed should include strengthening the surveillance of animal feed for bacterial contamination and integration of such surveillance with human foodborne disease surveillance systems. A Hazard Analysis and Critical Control Point program should be instituted for the animal feed industry, and a Salmonella-negative policy for feed should be enforced.

PMID: 12228823

  Contaminated poultry meat has been identified as one of the principal foodborne sources of Salmonella. The development of rapid detection assays for Salmonella would enable official agencies and food industries to identify contaminated foodstuffs in a more timely manner. In addition, these diagnostic tools could allow more 'real time' decisions to be made regarding end product acceptability. In this study, a survey was carried out to determine the prevalence of Salmonella in raw broiler carcasses. A total of 198 neck skin samples were obtained from within 40 flocks at a commercial broiler slaughtering facility. The presence of Salmonella was assessed by traditional culture methods and by a Salmonella-specific polymerase chain reaction (PCR) test. Salmonella was recovered from 32 (16%) of all samples using traditional culture methods. In contrast, the PCR assay proved to be more sensitive and detected Salmonella DNA in 38 (19%) of the samples tested. The pathogen was detected in 45 (23%) of the 198 samples when culture and PCR results were combined. The sensitivity of the PCR test was also greater than culture when detecting Salmonella from within flocks (53% of flocks by PCR, 30% of flocks by culture). The combination of both tests revealed that 55% of the flocks were contaminated with Salmonella. The PCR assay proved to be a highly specific and sensitive method for detecting Salmonella and the incorporation of a routine PCR test in conjunction with standard culture could be effective in providing a more accurate profile of the prevalence of this pathogen in broiler carcasses.

PMID: 12223162

  In the Netherlands S. Paratyphi B variation Java increased in poultry from less than 2% of all isolates before 1996 up to 40% in 2001. This development in poultry runs in parallel with that in Germany and appears not to occur in other European countries. A German study shows that in the late nineties it concerns isolates of only one multi-resistant clone of Java (in Holland as well) whilst isolates before the middle nineties were genetically much more heterogeneous and sensitive to antibiotics. Although the exposition of humans to contaminated poultry meat is relatively high, human patients with a Java infection are rare. Treatment of poultry flocks with quinolones was about 13% in 2000-2001. Resistance to flumequin of Java increased from 3% between 1996-1999 to 20% between 2000-2002 whilst that of other serotypes in poultry remained about 7%. Java is also fast becoming less sensitive to ciprofloxacin which is the antibiotic of first choice in serious cases of salmonellosis. The ministries of public health, agriculture and the production boards, with their research institutes, together with the poultry meat production chain integrations have recently decided to work together in order to determine the public health importance of the Java epidemic in poultry and finding measures for effective control in the poultry industry.

PMID: 12425215

  Nutritional intakes and contaminant burdens should be assessed jointly in individuals who are at high risk of environmental exposures to contaminants through food. In this study, the authors used shore surveys and community contacts to recruit 91 individuals who frequently consumed Great Lakes fish. These individuals provided dietary intake information and fasting blood samples for lipid and contaminant analyses. Participants ate an annual median of 88 meals of Great Lakes fish. Asian-Canadians consumed more total fish meals (i.e., Great Lakes, non-Great Lakes, and other) (medians = 213.0 females, 223.0 males) than Euro-Canadians (medians = 131.0 females, 137.5 males). The higher total fish consumption by Asian-Canadians was associated with a lower percentage of energy derived from fat, higher protein and iron intakes, and higher plasma concentrations of omega-3 essential fatty acids (e.g., median docosahexaenoic acid levels [microgram/l] in Asian-Canadian females = 5.48, males = 4.38; in Euro-Canadian females = 2.93, males = 2.27). Plasma organochlorine contaminant lipid weight concentrations varied by country of origin and by gender (e.g., median total polychlorinated biphenyls [microgram/kg] in Asian-Canadian females = 490.6, males = 729.0; in Euro-Canadian females = 339.6, males = 355.5). Age was the most consistent predictor (+ve) of contaminant concentrations, followed by years spent in Canada (for Asian-Canadians). Associations with sport fish consumption variables were less consistent than for the aforementioned predictors. Given both the health benefits and potential risks of fish consumption, policies that address diverse ethnocultural groups should support continued consumption of sport fish, but from less-contaminated sources than are currently used.

PMID: 12641195

  BACKGROUND: Meat recovered mechanically from bovine vertebral columns for use in burgers, sausages and other meat products may have been contaminated with bovine spongiform encephalopathy (BSE) from recovered spinal cord and dorsal root ganglia (DRG). We quantified UK exposure to BSE in beef mechanically recovered meat (MRM) by birth cohort (born pre-1940, in 1940-1969, post-1969), gender and calendar period (1980-1989, 1990-1996) because information on any two of BSE exposure intensity, vCJD incubation period and the new cases of vCJD tells us about the third.
  METHODS: Synthesis of evidence on BSE epidemiology, MRM production, infectivity in spinal cord and DRG, and UK dietary consumption.
   FINDINGS: Production of beef MRM peaked at 5000 tonnes in 1987, was nil in 1989 but recovered to 2000 tonnes in 1995 when it ceased altogether; reportedly 90% was used in burgers. Mean weight of spinal cord recovered per carcass was 3.3 g (95% credible interval 0.24-12.02 g) before the specified bovine offal (SBO) legislation and 1.5 g (0.02-8.30 g) after the legislation; whereas recovered weight of DRG (as infectious as spinal cord) was 27 g. Recovery of spinal cord from 1-year pre-clinical bovines peaked in 1988 at 238 g and of DRG in 1993 at 4250 g (medians). Median infectivity (5th and 95th percentiles) consumed in beef MRM was 33 250 (30 550-35 950), 65 600 (60 250-71 050) and 14 350 (13 150-15 600) bovine oral (Bo) ID50 units for the post-1969, 1940-1969 and pre-1940 birth cohorts in 1980-1989; and 44 250 (41 300-47 350), 39 600 (37 100-42,400) and 8750 (8100-9350) Bo ID50 units in 1990-1996. Males consumed almost 58% of infectivity in both periods. If the worst-case level of infectivity pertained, exposure, instead of halving in 1990-1996, would be sustained at around its 1980-1989 level for the two older birth cohorts and would have doubled in 1990-1996 for the post-1969 birth cohort.
  INTERPRETATION: SBO legislation in 1989 contributed only a 6% reduction in the infectivity in beef MRM. Salient sensitivity issues are highlighted.

PMID: 12501956

  Information about the proportion of truly Salmonella-free herds is required for an evaluation of the epidemiological situation, the development of control strategies and their implementation. Findings regarding the presence of salmonellas in faeces and intestinal lymph nodes as well as the presence of Salmonella antibodies in meat juice from slaughtered pigs were obtained in the context of a study conducted by a number of institutes. These data were used for an analysis of the validity of data on the prevalence of infected animals within herds and on the prevalence of infected herds. The proportion of batches or herds with exclusively negative individual findings was found to depend not only on the true proportion of truly Salmonella-free animals within herds but quite essentially also on the distribution of the proportion of infected animals within herds, the sensitivity of the methods of examination and sample sizes. When taking into account the existing dependencies, it was found that among the swine, the real numbers of Salmonella carriers were much higher than shown by bacteriological and serological examination. Regarding salmonellosis in swine, also a number of contaminated herds must be expected which is far higher than that shown by the number of herds with positive findings in at least one animal. Even a low contamination of all or almost all herds would result in the numbers of 'negative' batches observed, i.e. batches with exclusively negative individual findings. A rating of the salmonella exposure of herds as high, low, or very low is possible and may, and should be, used for measures of consumer protection, irrespective of the proportion of truly Salmonella-free herds.

PMID: 12489712

  Meat samples and fecal specimens from adult cattle were collected in Changchun, China and were examined for presence of Shiga toxin-producing Escherichia coli (STEC) serogroup O157. STEC O157 strains were isolated from 2 (5%) of 40 beef, 1 (3.3%) of 30 pork, and 3 (1.7%) of 176 adult cattle fecal samples. The strains belonged to phage types (PT) 4, 8, or 47. Two beef strains and a strain previously isolated from a patient in Shandong, China, were PT-4 and showed a similar PFGE pattern, suggesting the possibility of food-borne transmission. It is suggested that cattle are a reservoir of STEC O157:H7 and meat products are contaminated by this pathogen in Changchun, China as well as in other countries.

PMID: 12499691

Highlights:

Results: From 1973 through 1997, states and local health departments reported 604 outbreaks of foodborne disease in schools. The median number of school outbreaks annually was 25 (range, 9 to 44). In 60% of the outbreaks an etiology was not determined, and in 45% a specific food vehicle of transmission was not determined.  Salmonella was the most commonly identified pathogen, accounting for 36% of outbreak reports with a known etiology.  Specific food vehicles of transmission were epidemiologically identified in 333 (55%) of the 604 outbreaks.  The most commonly implicated vehicles were foods containing poultry (18.6%), salads (6.0%), Mexican-style food (6.0%), beef (5.7%) and dairy products excluding ice cream (5.0%). The most commonly reported food preparation practices that contributed to these school-related outbreaks were improper food storage and holding temperatures and food contaminated by a food handler.

In fiscal year 2000 >27.4 million children each day got their lunch through the National School Lunch Program.

Between 1973 and 1997, >600 foodborne disease outbreaks in schools were reported to CDC. These outbreaks resulted in nearly 50 000 illnesses, >1500 hospitalizations and 1 death.

  Although approximately 95% of disease caused by nontyphoidal salmonella is transmitted by foodborne vehicles, four documented salmonella outbreaks in the 1990s have been traced to contact with young poultry. No environmental studies of source hatcheries were completed. This case-control study was performed by comparing culture-confirmed Salmonella Infantis in Michigan residents, identified between May and July 1999, with two age- and neighbourhood-matched controls. Eighty environmental and bird tissue samples were collected from an implicated hatchery; all salmonella isolates underwent pulsed-field gel electrophoresis (PFGE) analysis. The study included 19 case-patients sharing the same PFGE subtype and 37 matched controls. Within 5 days before illness onset, 74% of case-patients resided in households raising young poultry compared with 16% of controls (matched OR 19.5; 95% CI 2.9, 378.1). Eight hatchery samples yielded Salmonella Infantis with PFGE subtypes matching the patients' isolates. This investigation identified birds from a single hatchery as the source of human illness and confirmed the link by matching PFGE patterns from humans, birds and the hatchery environment. Subsequent public health interventions reduced, but did not eliminate, transmission of poultry-associated salmonellosis. Five additional PFGE-linked cases were identified in Spring 2000, necessitating quarantine of the hatchery for depopulation, cleaning and disinfection.

PMID: 12211587

  The majority of interactions between microorganisms and animals are based on convenient relations for both of them. Symbiotic microorganisms, like intestinal microbiota, produce important vitamins for animals and protects them from putative pathogens. In general, for monogastric animals, the main contribution of intestinal microorganisms is to supply with growth factors the animal diet, and in some cases they are responsible for providing essential vitamins (e.g. vitamin K). Some particular and relatively few microbes like viruses, bacteria, fungi, protozoa and algae are responsible for animal illness. Because microorganisms are easily dispersed, display physiological diversity, and tolerate extreme conditions, they are ubiquitous and may contaminate and grow in many products, including food and raw materials. Foodborne diseases are caused by consumption of contaminated food or beverages. Many different disease-causing pathogens can contaminate food, so there are many different foodborne infections. In addition, poisonous chemicals and biological toxins can cause disease if they are present in food. To know how a particular disease is spreading is an important matter to take appropriate steps to stop it. For example Escherichia coli O157:H7 infections can spread through contaminated food (meat, vegetables, cheese, etc.), contaminated drinking water or juices, contaminated swimming water and from person to person. Among foodborne pathogens, the most frequently detected are bacteria, but also parasitic protozoa and worms, viruses, natural toxins and other pathogenic agents like prions are important agents for foodborne diseases. Particular pathogenic types of E. coli, classified by their specific pathogenic mechanisms (toxins, adhesins, invasiveness, etc.) are actually known as E. coli virotypes. Enterohaemorrhagic E. coli (EHEC), which constitute the main part of this review, were also named verotoxigenic E. coli (VTEC) or Shiga toxigenic E. coli (STEC). EHEC strains cause haemorrhagic colitis (HC), haemolytic uremic syndrome (HUS) and thrombotic thrombocytopaenic purpura (TP) in humans. They synthetize shigatoxins (verotoxins) which are potent cytotoxic substances, adherence factors and enterohaemolysin. EHEC are responsible for many outbreaks of bloody diarrhoea caused by contaminated foods: beef, milk, fruits, juice, water, etc. The most important serogroups among EHEC are O26, O111 and O157, being O157:H7 the most relevant serotype in foodborne outbreaks. The normal intestinal microflora of cattle was found to be the most relevant reservoir of EHEC strains.

PMID: 12189946

  Although there have been numerous studies investigating the prevalence of campylobacters in animals and raw meats, there are limited data on the persistence of these organisms in ready-to-eat (RTE) foodstuffs. Although poultry is now well established as a major reservoir of thermophilic campylobacters, it is widely assumed that hazard analysis critical control point (HACCP) controls in commercial and industrial settings are effective in eliminating this hazard through thorough cooking of RTE products. Therefore, it was the primary aim of this study to investigate the effectiveness of HACCP controls in eliminating campylobacters in such cooked RTE foods by attempting to isolate viable organisms from product. Concurrently, the results of this study demonstrate that local poultry is highly contaminated with campylobacters. Commercially available RTE foodstuffs (n = 2,030) consisting of 1,061 poultry-related cooked products and 969 other products were analyzed and were not found to contain thermophilic Campylobacter spp. In addition, 107 raw chickens (63 fresh birds and 44 frozen birds) were sampled, and 94% of the fresh birds and 77% of the frozen birds examined were demonstrated to be contaminated with campylobacters, with Campylobacter jejuni, Campylobacter coli, and Campylobacter lari accounting for 69, 30, and 1% of the contaminating organisms, respectively. In general, commercially available RTE foodstuffs, including cooked poultry, are not commonly contaminated with campylobacters and thus do not appear to represent a significant cause of clinical infection of Campylobacter spp. in Northern Ireland. However, raw poultry produce, including fresh and frozen chicken, frequently tested positive for campylobacters. Implementation of HACCP systems by food processors will help to minimize and/or eliminate the risk posed by this organism to the consumer.

PMID: 12182488

  DNA was extracted from 71 meat samples obtained from UK retail outlets. All of these DNA preparations gave the expected polymerase chain reaction products when amplified with primers specific for the species from which the meat originated. A second polymerase chain reaction analysis, using primers specific for the Toxoplasma gondii SAG2 locus, revealed the presence of this parasite in 27 [38%] of the meat samples. Restriction analysis and DNA sequencing showed that 21 of the contaminated meats contained parasites genotyped as type I at the SAG2 locus, whilst six of the samples contained parasites of both types I and II. Toxoplasma- positive samples were subjected to further polymerase chain reaction analysis to determine whether any carried an allele of the dihydropteroate synthase gene that has recently been shown to be causally associated with sulfonamide resistance in T. gondii. In all cases, this analysis confirmed that parasites were present in the samples and, additionally, revealed that none of them carried the drug-resistant form of dihydropteroate synthase. These results suggest that a significant proportion of meats commercially available in the UK are contaminated with T. gondii. Although none of the parasites detected in this study carried the sulfonamide-resistance mutation, a simplified procedure for monitoring this situation merits development.

PMID: 12117502

  Sulfa antibiotics (sulfonamides) are derivatives of p-aminobenzenesulfonamide that are widely used in veterinary medicine. Foods derived from treated animals may be contaminated with these drugs. However, current immunobased sulfonamide detection methods are unfit for screening of products because they are either too insensitive or specific for a few compounds only. An immunoassay capable of detecting all sulfas in a single reaction would be ideal for screening. For development of a binder capable of binding all sulfas, a protein engineering approach was chosen and the properties of monoclonal antibody 27G3 were improved with mutagenesis followed by selection with phage display. Several different mutant antibodies were isolated. The cross-reaction profile of the best mutant antibody was significantly improved over that of the wild-type antibody: it was capable of binding 9 of the tested 13 sulfonamides within a narrow concentration range and also bound the rest of the sulfas, albeit within a wider concentration range.

PMID: 12105945

  During July 2002, the Colorado Department of Public Health and Environment (CDPHE) identified an outbreak of Escherichia coli O157:H7 infections among Colorado residents. This report summarizes the results of an ongoing epidemiologic and laboratory investigation that has linked 28 illnesses in Colorado and six other states to eating contaminated ground beef products recalled by ConAgra Beef Company on June 30, 2002. To date, seven patients have been hospitalized; five developed hemolytic-uremic syndrome (HUS).

PMID: 12186220

  Azaspiracids have recently been identified as the toxins responsible for a series of human intoxications in Europe since 1995, following the consumption of cultured mussels (Mytilus edulis) from the west coast of Ireland. Liquid chromatography-mass spectrometric (LC-MS) methods have been applied in the study reported here to investigate the new human toxic syndrome, azaspiracid poisoning. Separation of azaspiracid (AZA1) and its analogues, 8-methylazaspiracid (AZA2) and 22-demethylazaspiracid (AZA3), was achieved using reversed-phase LC and coupled, via an electrospray ionisation source, to an ion-trap mass spectrometer. These azaspiracids have now been identified in mussels from Craster (north-east England) and Sognefjord (south-west Norway) using source collision induced dissociation-MS and multiple tandem MS detection. AZA1 was the predominant toxin and toxin profiles were similar to those found in contaminated Irish shellfish. This is the first report of the occurrence of these azaspiracids outside Ireland with the significant implications that these toxins may occur in shellfish throughout northern Europe.

PMID: 12076644

  As part of a semi-quantitative risk assessment of 10 seafood hazard/product combinations, a risk assessment tool was used to generate a Risk Ranking. The tool is in a spreadsheet software format and provides a risk estimate, which is scaled between 0 and 100, where 0 represents no risk and 100 represents all meals containing a lethal dose of the hazard. A full description of the tool is contained in Ross and Sumner (this issue). Based on their ranking, seafoods in Australia fell into three risk categories. Hazard/product pairs with ranking < 32 included mercury poisoning (Relative Risk = 24), Clostridium botulinum in canned fish (RR = 25), or in vacuum-packed cold-smoked fish (RR = 28), parasites in sushi/sashimi (RR = 31), viruses in shellfish from uncontaminated waters, (RR = 31), enteric bacteria in imported cooked shrimp (RR = 31) and algal biotoxins from controlled waters (RR = 31). It is noted that there have been no documented cases of food-borne illness from any of the above hazard/product pairings in Australia. Those with rankings 32-48 included Vibrio parahaemolyticus in cooked prawns (RR = 37), V. cholerae in cooked prawns (RR = 37), Listeria monocytogenes in cold-smoked seafoods (RR = 39), scombrotoxicosis (RR = 40), V. vulnificus in oysters (RR = 41), ciguatera in the general Australian population (RR = 45), L. monocytogenes in susceptible (RR = 45) and extremely susceptible populations (RR = 47) and enteric bacteria in imported cooked shrimp eaten by vulnerable consumers (RR = 48). Almost all the hazard/product pairs in this category have caused the outbreaks of food poisoning in Australasia. Those hazard/product pairs with rankings >48 included ciguatera from recreational fishing in susceptible areas (RR = 60), viruses in shellfish from contaminated waters (RR = 67) and algal biotoxins from uncontrolled waters in an algal event (RR = 72). There have been significant (>100 cases) food poisoning incidents involving viruses and biotoxins in shellfish, while ciguatera poisoning is prevalent among coastal communities in Australia's warmer waters.

PMID: 12076038

  A total of 4,581 Salmonella strains isolated from nonhuman sources, including foodstuffs associated with foodborne Salmonella outbreaks, from January 1996 through December 2000 were serotyped at the Enteropathogens Laboratory, Instituto Adolfo Lutz, Sao Paulo, Brazil. Among the 123 different serotypes identified, Salmonella enterica subsp. enterica serotype Enteritidis (Salmonella Enteritidis) was the most prevalent (32.7%), ranking first for almost every kind of source. The next most common serotypes were Salmonella Senftenberg (10.3%), Salmonella Hadar (6.8%), Salmonella Agona (5.1%), and Salmonella Typhimurium (2.4%). Rough strains belonging to the subspecies S. enterica subsp. enterica (4.8%), S. enterica subsp. arizonae (<1%), S. enterica subsp. diarizonae (<1%), and S. enterica subsp. houtenae (<1%) were also detected. Foodstuffs (including poultry meat for consumption) contained 38.1% of the studied Salmonella strains, poultry flocks (from several farms under salmonellosis control by the owners) contained 21.7%, the environment contained 10.6%, sewage contained 9.4%, water contained 6.6%, animal feed contained 4.4%, chill water from poultry-processing operations contained 2.2%, and other sources contained 7.0%. Foodstuffs extensively contaminated with Salmonella strains were poultry meat (40%), cow meat (11%), desserts (8%), mayonnaise (6%), sausage (5%), and unpasteurized shell eggs (4%), and there were several other food sources (26%). Homemade mayonnaise was the most common vehicle for Salmonella foodborne outbreaks, and Salmonella Enteritidis was the serotype most isolated (95%) from that source. According to these data and previously published data concerning Salmonella strains isolated in Sao Paulo State, almost the same serotypes have predominated among nonhuman sources for the last decade.

PMID: 12092719

  The cheap availability of chlorine gas, together with the development of industrial chlorinating procedures in the 20th century, led to the production of a wide range of organochlorine compounds many with a variety of commercial applications, including usage as insecticides and defoliants and polychlorinated biphenyls (PCBs) used as coolants in electricity supply transformers. However, it was soon found that many of these technologically valuable chemicals suffered from a major disadvantage in that they resisted biodegradation and that the continued use of these compounds would lead to their persistence and accumulation in the environment and thus enter the human food chain. Despite regulatory bans or strict limits on usage being imposed on organochlorine pesticides in most countries, these compounds continue to be detected in measurable amounts in the eco-system including marine life. In general, organochlorine levels in fish intended for human consumption are low and probably [probably?? - ljf] below levels likely to adversely affect human health. Populations at higher risk than most people are those subsisting largely on fish and other marine life. Additionally, fish oils obtained from contaminated fish, if consumed in substantial quantities by infants and young children, might present potential health problems if levels are not continually regulated. Behavioral and neurological effects have been reported in children and ascribed to the consumption of PCB contaminated diet including fish. Another current major human health concern, yet to be resolved, about organochlorine contaminants in the human diet relates to the potential ability of many of these chemicals at low doses to act as "endocrine disruptors".

PMID: 11983271

  The presence of Clostridium perfringens in eight slaughter houses from Costa Rica was analyzed using the Most Probable Number (MPN) technique, in order to assess the risk of acquiring a food borne intoxication due to consumption of contaminated meat. C. perfringens was detected in 29 (88%) out of 33 soil samples collected from the slaughter house surroundings (average 6.7 x 10(2) MPN/g), as well as in 70 (93%) out of 75 intestinal contents of slaughtered animals (average 3 x 10(4) MPN/g), in 42 (55%) out of 76 samples of slaughtered meat (average 2.2 x 10(4) MPN/g) and in 30 (61%) out of 49 retail meats (average 8 x 10(3) MPN/g). In addition, the presence of this bacterium was evaluated in ten retail meat markets located in the Metropolitan Area of Costa Rica, where it was isolated from 15 (75%) out of 20 samples of ground meat and from 28 (36%) de 78 stew meat samples (average 1.9 x 10(3) and 7.5 x 10(2) MPN/g, respectively). Only one out of 35 samples of cooked meat obtained from 32 restaurants that utilize heated water baths (average temperature of 82 degrees C) was positive for C. perfringens (4 MPN/g, temperature 72 degrees C). Out of 1121 bacterial isolates obtained, 250 were evaluated for enterotoxigenicity. Only 3 (1.2%) of these tested positive for enterotoxin production, probably because most wild strains are not toxin producers, even though they can be induced to produce it as a result of repeated thermal shocks. The present results urge the adoption of adequate preventive measures and high sanitary standards in the meat processing industry in Costa Rica, in order to minimize the risk of food-borne intoxications caused by C. perfringens, due to its widespread distribution and potential human health hazard.

PMID: 12184149

  Hepatitis A virus (HAV) infection is endemic in Puglia (South Italy). Epidemiological studies indicate that shellfish consumption, particularly mussels, is a major risk factor for HAV infection, since these products are eaten raw or slightly cooked. Nested reverse transcriptase-polymerase chain reaction (RT-PCR) has been shown to be a sensitive technique for the detection of HAV in mussels. The aim of the present study was to detect the presence of HAV in a large sample of mussels by nested RT-PCR and to confirm the presence of infectious viral particles in positive samples by cell culture infection and RT-PCR confirmation. Two hundred and ninety samples of mussels from different sources were collected between December 1999 and January 2000. One hundred samples were collected before being subjected to depuration, 90 after depuration, and 100 were sampled in different seafood markets. HAV-RNA was detected in 20 (20.0%) of non-depurated mussels, in 10 (11.1%) of depurated samples, and in 23 (23.0%) of samples collected in the shellfish markets, without any significant difference in the prevalence of positive samples by collection sources (chi2 = 4.79, p = 0.09). Of the 53 samples found positive by nested RT-PCR, 18 (34.0%) resulted positive by cell culture assay. No relationship between viral contamination and bacterial contamination was found (p = 0.41). This study confirms the usefulness of molecular techniques in detecting HAV in shellfish and, thus, for the screening of a large sample of naturally contaminated mussels. Improved shellfish depuration methods are needed to obtain virus-safe shellfish and reduce the risk for public human health.

PMID: 11999106

  The study has been carried out on 898 food samples of animal origin: bovin meat, ovin, porcin, rabbit, turkey and chicken in 1998 from auto-control food service of Chahed laboratory. II consisted in studying and identifying salmonella serovars and to determine the nature of the most contaminated meat products. The results of the study are as follows: 3.7% of meat product samples are contaminated by salmonella. On the 480 samples of bovin meat, 4.2% are contaminated by salmonella. 3.8% ovin meat is contaminated by salmonella, 1.7% turkey meat and 3.6% chicken meat. Rabbit meat are not contaminated by salmonella. As far as the products of a bovin origin are concerned the results are as follows: 2.7% of meat is contaminated by salmonella, 5.3% of mechanically separated meat and 7.7% of giblets are also contaminated. Therefore salmonella contaminates 4.3% of red meat and 2.6% of fowl. S. anatum, Corvallis, typhimurium, Braenderup, Zanzibar, Enteritidis, Livingstone are different detected serovars. S. anatum represents 40% of contamination whereas. S. typhimurium represents 12% Of contaminations.

PMID: 12416357

  Human exposure to mercury intoxication through contaminated fish ingestion has been well studied, mainly among Japanese population. The Brazilian population, particularly in the Amazon region, is now in focus due to findings of fish contamination. Major health impacts caused by mercury affect mostly people who have a regular fish diet. A continuous checking for mercury content in the most consumed fish could prevent human intoxication. A simple, non-instrumental method to allow a continuous checking of the mercury content in fish was developed. Based on this method, we are proposing a prevention action where community agents can be trained to perform fish analysis. Technical Schools and Universities located nearby the affected areas would be in charge of quality control programs for the fish analysis as well as for the selection, training and update for operators.

PMID: 11960187

  The objective was to describe the current epidemiology and trends in New Zealand human leptospirosis, using descriptive epidemiology of laboratory surveillance and disease notification data, 1990-8. The annual incidence of human leptospirosis in New Zealand 1990-8 was 44 per 100,000. Incidence was highest among meat processing workers (163.5/100,000), livestock farm workers (91.7), and forestry-related workers (24.1). The most commonly detected serovars were Leptospira borgpetersenii serovar (sv.) hardjo (hardjobovis) (46.1%), L. interrogans sv. pomona (24.4%) and L. borgpetersenii sv. ballum (11.9%). The annual incidence of leptospirosis declined from 5.7/100,000 in 1990-2 to 2.9/100,000 in 1996-8. Incidence of L. borgpetersenii sv. hardjo and L. interrogans sv. pomona infection declined, while incidence of L. borgpetersenii sv. ballum infection increased. The incidence of human leptospirosis in New Zealand remains high for a temperate developed country. Increasing L. borgpetersenii sv. ballum case numbers suggest changing transmission patterns via direct or indirect exposure to contaminated surface water. Targeted and evaluated disease control programmes should be renewed.

PMID: 11895088

  Outbreaks of gastroenteritis that are suspected to be of viral origin are on the rise. Thus, there is a need for regulatory agencies entrusted with food safety to develop adequate techniques for the detection of viruses in foods. We have established a general procedure for the detection of hepatitis A virus (HAV) in shellfish that, with minor modifications, is also applicable to fresh produce such as cilantro. Total RNA was isolated from shellfish or cilantro, followed by isolation of poly(A)-containing RNA. Because HAV genomic RNA contains a poly(A) tail, the isolation of poly(A)-containing RNA also enriches HAV genomic RNA. Reverse transcription was used to convert the RNA to cDNA, and then amplification was carried out by polymerase chain reaction (PCR). Reamplification with internal primers was used to improve the quality and the quantity of amplified DNA, allowing for post-PCR analysis such as sequence identification of the viral strain. With this procedure, multiple samples could be analyzed in four working days by a single trained individual. The nominal sensitivity of detection of the procedure was 0.15 TCID50 (50% tissue culture infective dose) per 0.62 g of tissue with a test virus. The direct RNA isolation protocol avoided pitfalls associated with whole-virus purification procedures by replacing virus precipitation steps involving polyethylene glycol and Procipitate with phenol extraction. The method is straightforward and reliable. We successfully used this procedure to detect naturally occurring HAV in clams involved in a gastroenteritis outbreak, as well as in cilantro artificially contaminated with a test virus.

PMID: 11858194

  The consumption of contaminated seafood has been reported as an important route of human exposure to metals in Taiwan. We consider the concentrations of TBT, Cu, Zn, Cd, As, and the consumption of oysters of Taiwanese to be the important information related to public health in Taiwan. Therefore, the aim of this study was to evaluate the public health risks associated with TBT, Cu, Zn, Cd and As from shellfish for the general population and fishermen of Taiwan. In general, TBT concentrations in various oysters ranging from 0.32 to 1.51 microg/g dry wt. varied with sampling locations. The highest TBT, Cu, and Zn geometric mean (GM) concentrations in oysters of 1.51, 1180 and 1567 microg/g dry wt. were obtained from the Hsiangshan coastal area. The values of oyster consumption for fishermen were 94.1 and 250 g/day for typically and maximally exposed individuals, respectively. In particular, the highest intake (250 g/day) from fishermen was almost two times greater than that of the general population (139 g/day). The THQ (target hazard quotient) values of Hsiangshan's fishermen are 3.87 and 20.50 for TBT and Cu for maximally exposed individuals are higher than other oyster culture areas. It is interesting that those consuming oysters from Hsiangshan, Lukang, Taishi caused abnormally high THQs of TBT and other metals (100% over 1.0), and TBT was attributed to only 3-21% of the total THQs in different fishermen of Taiwan. Our results suggest that current environmental levels of TBT and other metals are associated with a significant potential threat to human health for fishermen resident in coastal areas of Taiwan.

PMID: 11874040

  The natural contamination of shellfish with diarrheic shellfish toxins (DSP) has important public health implications. To avoid the economic effects of toxic episodes on shellfish farmers and the related industry, research on artificial methods alternative to the natural detoxification of shellfish is needed. Because the usual thermal processes are not efficient, alternative technologies have to be studied. Here preliminary results are presented about the lability of the DSP toxin okadaic acid in a supercritical atmosphere of carbon dioxide with acetic acid. Most of the toxin is eliminated (up to 90%), and the biological activity against its target enzyme is also severely affected (up to 70% reduction). Detoxification of contaminated shellfish requires a partial dehydration, and the detoxification yield is lower than that obtained with free toxin. Mass spectrometry experiments suggest that acetylation of the toxin molecule is not the basis of the inactivating mechanism, but a conformational change is suggested. This is the first report of the use of supercritical fluids to inactivate toxins.

PMID: 11782215