A recent study found MRSA in swine and their human handlers for the first time in the U.S., suggesting that superbugs are now a problem outside of hospitals.
The reason, said scientists who met last week on Capitol Hill for a public briefing, is antibiotics given to livestock to promote quick weight gain.
Humans may be at a low risk of contracting antibiotic-resistant diseases from handling or eating meat from animals that contracted an antibiotic-resistant disease.
The danger of contracting such a disease is still greater in hospitals, where more than 94,000 people contracted MRSA and more than 18,000 died of it in 2005, according to the most recent statistics from the Centers for Disease Control and Prevention. About 85 percent of patients contracted their infections in hospitals.
But the widespread practice of giving antibiotics to cattle, hogs and chickens means more Americans are handling and consuming potentially infected meat.
MRSA stands for Methicillin-resistant Staphylococcus aureus. It is a skin infection that can enter the bloodstream of often otherwise-healthy people through cuts or incisions and can cause pneumonia. It often starts with painful boils that drain puss, according to the CDC.
In 2007 and 2008 Tara Smith, assistant professor of epidemiology at University of Iowa, tested about 300 swine and a few dozen of their human handlers from two farming systems, each made up of several farms, across eastern Iowa and western Illinois.
Of the 210 hogs tested from the first production system, 70 percent tested positive for MRSA, and of the 14 workers tested, about nine had the bacteria. Of the hogs and workers tested from the much smaller second production system, none tested positive for MRSA.
"Obviously, these are two farming systems in this area. We're not sure how representative these are to the bigger picture," Smith said in an interview. She explained her results at the briefing.
Sen. Olympia J. Snowe, R-Maine, and Sen. Edward M. Kennedy, D-Mass., proposed legislation in February 2007 to phase out the use of nontherapeutic antibiotics in animal agriculture. She and Kennedy plan to reintroduce the bill, said Snowe's press secretary, Julia Wanzco.
"Sen. Snowe certainly believes the effectiveness of disease-fighting antibiotics can be severely compromised by their overuse for agricultural purposes," Wanzco said.
About 70 percent of antibiotics and related drugs used in U.S. animal agriculture are used nontheraputically, said Margaret Mellon, director of Food & Environment Program at the Union of Concerned Scientists.
The use of nontherapeutic antibiotics in livestock feed in the U.S. began about 50 years ago, and the public health community has been "concerned about it since the beginning," Mellon said. "Any use of antibiotic, whether it's in human medicine or in animals, will elicit antibiotic-resistant bacteria," Mellon said.
The reason for resistance development in bacteria is evolutionary.
"It's kind of back to junior high evolution concepts - why do bacteria or other things evolve?" said Glenn Morris, director of the Emerging Pathogens Institute at the University of Florida, who spoke at last week's briefing.
Many bacteria are common among humans and animals, including salmonella, E. coli, staph and MRSA. Antibiotic-resistant bacteria that develop among livestock may be transmitted to their human handlers or to consumers when they eat or handle meat.
Though the likelihood of contracting antibiotic-resistant bacteria from food is low, it is possible, Morris said.
"In a hospital, if you're using a lot of antibiotics, you're going to have a higher percentage of bacteria that carry resistance genes," he said. "We are using antibiotics, but we've been doing that for a while, but the resistance genes are starting to appear in other reservoirs where antibiotics are being used."
The difference is this: Because a low percentage of the population is hospitalized, the exposure to resistant bacteria in hospitals is relatively low, but the risk for those individuals is very high. On the other hand, everyone eats, and if a food source is infected with resistant bacteria, the exposure is high with a low risk of contraction.
"On an individual basis the risk is very, very low, but when you sum that across an entire population that then becomes a very substantial risk," Morris said.
Mellon said this is "huge resistance problem," and is adding to the cost of treating diseases.
"The bacteria you carry on your skin can cause an infection that can be incredibly difficult to treat," Mellon said. "There is a lot of concern about MRSA because it is an infection that recently moved from the hospital."
Mellon said the solution is to "reduce the use of antibiotics on the farm as well as in human medicine, and the most obvious places are feed efficiency and growth promotion."
She added, "Healthy animals don't need antibiotics."
Mellon said the use of nontheraputic antibiotics in livestock feed "never made sense from the public's point of view," but to argue it is "going up against the pharmaceutical community and the agriculture industry."
"Whenever you use antibiotics you're going to start generating resistance," she said. "You use them, you lose them."Kansas City Infozine
