A recent investigation by Canada’s CBC TV news found two-thirds of samples collected at major grocery stores in Vancouver, Toronto, and Montreal had bacteria resistant to at least one antibiotic, raising new concerns about the pervasive use of antimicrobials in food animal feed.
The CBC TV’s Marketplace bought and sampled over 100 pieces of chicken and sent them to a lab for analysis, unsurprisingly, the lab found E. coli, Salmonella, Campylobacter. What was surprising is that some of the bacteria were resistant to six, seven, or eight different types of antibiotics, according to the account.
“This is the most worrisome study I’ve seen of its kind,” Rick Smith, head of Environmental Defense, a consumer advocacy group told CBC Canada.
Scientists have long linked the rise in antibiotic resistance to the overuse of antibiotics in both human medicine and animal agriculture, but only in the past few years have these superbugs grabbed high-profile headlines.
Maryn McKenna, an infectious disease expert and author of “Superbug,” says that CBC’s investigation is indicative of a much wider problem.
“I think this kind of reporting is worth doing,” wrote McKenna on her Wired Science blog. “Nothing brings the threat of agricultural antibiotic use home to people like showing them that resistant bacteria are living on the meat they might have brought home last night.”
“Don’t think for a moment this is just a Canadian problem,” added McKenna.
As McKenna notes, a team of researchers in Greece analyzed meat samples in their country over a period of three years and recently released their findings. Their study found E. coli from chicken had high rates of resistance to ciprofloxacin, an important drug used for fighting serious infections in humans. They also found high rates of resistance to tetracycline, also important for human medicine, in pork and chicken.
“These results indicate that meat can be a source of resistant bacteria, which could potentially be spread to the community through the food chain,” wrote the researchers.
Scientists in several other countries, including the U.S., have reported finding resistant strains of bacteria on meat products.
In 2008, the U.S. National Antimicrobial Resistance Monitoring System (NARMS) released a report detailing the prevalence of resistant bacteria on retail meat products. A collaboration of the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention, the NARMS team took 5,236 meat samples over a years time.
Just looking at poultry, the study found that 38.2 percent of chicken breast Salmonella isolates in 2008 were resistant to three of more antimicrobial classes, 51 percent of isolates in ground turkey were resistant as well, an increase in both compared to past years.
From 2002-2007, multidrug resistance to three or more antimicrobial classes ranged from 20-34.4 percent among chicken breasts and 20.3-42.6 percent for ground turkey. More than 15 percent of chicken breast and ground turkey isolates showed resistance to 4 or more classes or antibiotics in 2008.
McKenna says the emerging body of science on the topic suggests a fix to the problem. “Whatever country they are occurring in, the solution is the same,” writes McKenna. “Drug-resistant bacteria in food won’t diminish until we reduce the amount of drugs that food animals receive while they are raised.”
Though the exact numbers on drugs given to food animals is a hotly debated topic, by all accounts it’s a lot. The Union of Concerned Scientists estimates about 70 percent of all antibiotics used in the U.S. are given to food animals, Ralph Loglisci, of Johns Hopkins Center for Livable Future, recently put the number closer to 80 percent.
The Animal Health Institute, the trade group for veterinary pharmaceutical companies, disputes those figures. In a recent white paper, AHI called those numbers “faulty, non-scientific assumptions,” but did not provide its own estimate.
Bacteria on chicken will be destroyed if the meat is cooked to a minimum safe temperature of 165 degrees, as measured with a food thermometer. It is important, however, to ensure that raw poultry and its juices do not come in contact with foods, such as salads, that will be eaten raw by guarding against cross-contamination of cutting boards, utensils, kitchen counters, etc.