- 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?
-
- 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.'
-
- 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. '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, sug gesting 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 coc cidiostats, 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.
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- Guardian Unlimited © Guardian Newspapers Limited
2003
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- http://observer.guardian.co.uk/foodmonthly/story/0,9950,1013286,00.html
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