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news: PR Newswire
Human Health Risk of Antibiotic Use in Food Animals is Extremely
Small
SAN DIEGO, Sept. 27 /PRNewswire/ -- A group of human microbiologists, risk
assessors, veterinarians and animal health experts has concluded that while a
theoretical hazard to human health arises from the use of antibiotics in food
animals, an examination of the facts shows that the actual risk is extremely
small.
The independent expert group evaluated available data on the effects of
antibiotics in humans and animals and attempted to confirm or deny a link
between antibiotic resistance in animals transferring to humans. They met
yesterday in San Diego, a day prior to the opening of the 42nd Interscience
Conference on Antimicrobial Agents and Chemotherapy (ICAAC), the world's
premier scientific meeting on infectious diseases and antimicrobial agents.
"In 50 years of antibiotic use in animals and man, the development of
resistance in animals has not made a major impact on human and animal health,
and such a development seems unlikely to happen overnight now," said Ian
Phillips, M.D., Emeritus Professor of Medical Microbiology at the medical
school of Guy's and St. Thomas' Hospitals, University of London.
Dr. Phillips, who is chairing the group of experts, said that evaluating
available facts persuaded the group that whereas the use of antibiotics in
humans and animals undoubtedly leads to resistance, and while some resistant
organisms reach man via the food chain, little additional harm results from
resistance, even when infection occurs.
Much of the debate over the issue of antibiotic resistance has centered on
the use of antibiotics in animals to promote growth. The case against
antibiotic growth promoters has relied very heavily on antibiotic-resistant
enterococci, a group of bacterial organisms that cause no disease in animals
but can cause disease in man and which might be zoonotic (transmittable from
animals to man under natural conditions). However, new surveillance data show
that enterococci resistance is increasing in areas where antibiotic growth
promoters have been withdrawn.
"Vancomycin-resistant enterococci (VRE) and Synercid-resistant E. faecium
are becoming more prevalent as a cause of infections in humans in Europe at a
time when these resistant organisms are becoming less prevalent in animals and
food products following the antibiotic growth promoter ban," observed group
member Ronald N. Jones, M.D., referring to two commonly used antibiotics that
are effective against various bacteria including enterococci. Dr. Jones is
Principal Investigator of the SENTRY Antimicrobial Resistance Surveillance
program, a global network of healthcare facilities monitoring resistance
levels in human bacteria, providing the world's largest database of antibiotic
resistance.
"SENTRY Program data from parts of the world where Synercid was used for
patients show an increasing prevalence of resistance in the absence of the
genetic mechanisms of resistance commonly found in most animal strains," Dr.
Jones continued. "We thus conclude that the increasing prevalence of
resistance was not due to passive acquisition of resistant strains of animal
origin, but due to antibiotic use in humans," he said.
A major topic of the group discussion was the possible adverse effects of
antibiotic bans on animal health and well-being. This issue has been studied
extensively in Denmark, where the use of antibiotic growth promoters was
phased out beginning in 1997 through 1999.
"Danish farmers have found that banning antibiotic growth promoters has
caused pigs to get more cases of diarrhea, especially baby pigs," said group
member John Waddell, D.V.M., a Nebraska veterinarian who has toured several
Danish pig farms. "The pigs have slower post-weaning growth rates and
increased production costs."
Dr. Waddell added that Danish pigs, because of increased prevalence of
diarrhea and other diseases, require more therapeutic antimicrobials,
according to DANMAP, the Danish national database that tracks patterns of
antibiotic usage and resistance from human and veterinary medicine and food
hygiene. While only 48,000 kilograms (kg) of antibiotics were used in Denmark
for treatment of food animals in 1996, that amount increased to about 57,000kg
in 1997; to 57,300kg in 1998; to 61,900kg in 1999; to 80,600kg in 2000; and to
91,602kg in 2001 -- an increase in use of more than 90% since the withdrawal
of growth-promoting antibiotics.
"At the same time, human cases of salmonella and campylobacter have
reached record levels in Denmark and the proportion of multiple antibiotic-
resistant salmonella DT104 has doubled since 1997," Dr. Waddell said.
The group of experts concluded that banning any antibiotic usage in
animals, in the absence of a full risk assessment, is not useful and could
even be harmful to both human and animal health.
"Rather than banning the use of antibiotics in animals, we believe that
efforts should focus on reducing the transmission of all food-borne pathogens
regardless of their antibiotic susceptibility," commented Dr. Phillips. "This
can only occur through insistence on good hygienic practices on farms, in
abattoirs, during distribution and marketing of food, and in the proper
handling and cooking of food, and must be accompanied by consumer vigilance.
Considerable progress has been made in the U.S. as demonstrated by the decline
over the past five years of food-borne illness reported by the Centers for
Disease Control and Prevention (CDC)."
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