More things to worry about - antibiotic resistant bacteria in animal feed.
February 26, 1999
Bacteria Resistant to Powerful Antibiotics Are
Discovered in Chicken Feed
By DENISE GRADY
Bacteria that are resistant to the most powerful antibiotics used to treat
infections in people have been found in chicken feed, researchers are
reporting, a finding that is likely to fuel concerns about the threat to
public health from widespread use of antibiotics.
The researchers studied only a small amount of feed. Still, they said, finding
such organisms on the threshold of the human food supply was an ominous
sign. They said their discovery might be the first report of such contamination
in the United States. The scientists, from the University of Maryland, are
reporting their findings on Friday in the British medical journal The Lancet.
Although animal feed is not expected to be germ free and the bacteria were
not harmful to healthy people, the organisms' ability to withstand potent
antibiotics may pose a threat to public health, the scientists said. If people
who eat or handle contaminated chicken become infected, the harmless
bacteria may pass their genes for drug-resistance to other, dangerous
organisms. Or, in patients with lowered immunity from AIDS or treatments
for cancer or organ transplants, the once-harmless microbes may turn
dangerous.
Illnesses caused by drug-resistant bacteria can be fatal, or require treatment
with several drugs. Such infections are increasing in the United States and
Europe.
Many scientists attribute the growing strength of microbes to the overuse of
antibiotics, in people and in agriculture. Nearly half the 50 million pounds of
antibiotics produced in the United States are used in animals, mostly as feed
additives to promote growth.
In any population of bacteria, some may naturally be more resistant to
antibiotics, and when infections are treated with the drugs, the resistant
microbes may survive and multiply. Each time antibiotics are given, they may
be less effective because more bacteria are resistant.
"Studies show that rather than a single bad strain in a hospital, there are
hundreds, if not thousands," said Dr. J. Glenn Morris Jr., head of hospital
epidemiology at the University of Maryland in Baltimore, and an author of the
Lancet study, which was published as "a research letter," a report less
comprehensive than an article. "The more we look, the more we find these
multiresistant organisms everywhere. Where are they coming from?"
Dr. Morris said he and his colleagues, who had seen patients die from
drug-resistant infections, thought the organisms might be coming from
different sources, and wondered if one might be food. They knew that in
Europe, use of a powerful antibiotic in animal feed had been linked to resistant
infections in both livestock and in people who ate meat from infected animals.
To find out whether some infections could come from what the animals ate,
the researchers tested commercial chicken feed they had bought in a closed
sack and opened under sterile conditions.
They did not expect to find anything, Dr. Morris said, so they were shocked
to find bacteria known as enterococci, normal inhabitants of the intestine in
people and animals, that were resistant to multiple antibiotics.
Most disturbing, Dr. Morris said, the organisms were resistant to
vancomycin, a powerful drug that was long considered the last line of defense
against dangerous infections. But deadly infections resistant to the drug began
showing up in people in the United States in the past few years. The
organisms have never been detected in chickens in the United States, Dr.
Morris said.
"If it's in feed," he added, "it may subsequently show up in chickens and serve
as another mode of introduction into human populations."
Dr. Morris would not name the manufacturer of the feed and said he had no
explanation for how it might have become contaminated, or how the
enterococci became resistant to antibiotics.
He said the feed did not contain antibiotic additives.
The nation's largest chicken producers use no bagged feed, said a spokesman
for one, Tyson Foods, who said they make their feed.
Dr. Stephen F. Sundlof, director of the Center for Veterinary Medicine at the
Food and Drug Administration, said he was puzzled by the report, because
feed pellets were normally produced under such high temperatures and
pressure that bacteria would die.
But, Dr. Sundlof said, "if the feed is contaminated, and from consuming that
feed, our livestock become reservoirs for vancomycin resistant enterococci,
then potentially we could have a problem."
Copyright 1999 The New York Times Company |
