A study from the Milken Institute School of Public Health links supermarket food to antibiotic-resistant infections.
Lance Price, a microbiologist at the George Washington University, and his research team are well acquainted with the meat aisles of grocery stores in Flagstaff, Ariz. Twice a month in 2012, they purchased every available brand of turkey, chicken and pork at each supermarket in the city. During that same period, the researchers also gathered blood and urine samples from patients at Flagstaff Medical Center.
|Klebsiella pneumoniae (CDC)|
They found that the retail meat and Flagstaff patients shared an unexpected intruder: Klebsiella pneumoniae—a type of colonizing bacteria that can lead to urinary tract infections, bloodstream infections and pneumonia.
The researchers’ study, published in the journal Clinical Infections and Diseases, is the first to show that contaminated meat may be a vehicle for transmitting this bacterial pathogen to humans.
More alarming, many of the strains of Klebsiella were resistant to antibiotics, a finding that underscores public health concerns regarding antibiotic use in food animal production. The U.S. Food and Drug Administration reported that in 2012, more than 32 million pounds of antibiotics sold in the United States were for food animals, a 16 percent increase since 2009.
“Here is yet another way that using antibiotics in food animals can potentially lead to drug-resistant bacteria in people, treatment failures and then possibly death,” said Dr. Price, a professor in the Milken Institute School of Public Health and founding director of the school’s Antibiotic Resistance Action Center. “We’re creating the formula for the evolution of superbugs.”
While the U.S. food safety system has focused much of its attention on germs like Salmonella and Campylobacter, Klebsiella is not commonly thought of as a foodborne illness. Unlike classic foodborne bacteria that cause immediate symptoms, Klebsiella is an opportunistic pathogen that operates similarly to extra-intestinal pathogenic Escherichia coli (E. coli)—silently colonizing the gut as it waits to take advantage of a person’s weakened immune system. Results from Dr. Price’s research show that the “usual suspects” that contaminate meat may not capture the full scope of what is making us sick.
“We have to get beyond this dogmatic view of what a foodborne pathogen is,” he said. “Diarrhea is what we think about when we think about food poisoning. But it turns out that the problem is probably a lot bigger than that.”
To understand the link between Klebsiella and human infections, the researchers isolated the bacteria from both the retail meat and from blood and urine samples in patients suffering from infections during the same period. Then, using whole genome sequencing, the researchers assessed their genetic similarities.
Dr. Price and his colleagues found that 47 percent of the 508 meat products and 10 percent of the 1,728 patient samples harbored Klebsiella. When they analyzed the relationship between the bacteria found in meat and the type found in humans, some isolate pairings were nearly identical.
Lance Price, a professor in the Milken Institute School of Public Health, warns that the overuse of antibiotics in food animals is “creating the formula for the evolution of superbugs.”
Moreover, 32 percent of the Klebsiella strains found in meat and 8 percent in patients were multi-drug resistant. This worries Dr. Price, who believes that continued use of antibiotics in livestock could break down the dam that is protecting us from a flood of potentially lethal bacteria.
“We’re creating this population of drug-resistant Klebsiella, some of which could be bleeding over to the human population and causing drug-resistant infections,” he said. “If you have Salmonella poisoning, you usually get better. But with Klebsiella, once you have an infection, it’s pretty serious. And the only treatment is an antibiotic.”
Consumers can take precautions to protect themselves against drug-resistant infections by purchasing meat that has been raised without antibiotics and safely handling and storing products. Dr. Price, himself, avoids ground turkey altogether—a recent study showed that 90 percent of the samples tested contained disease-causing bacteria. But winning the fight against superbugs will take more than personal choices from individuals, Dr. Price notes.
“From a policy perspective, I hope this study spurs our federal agencies to do more surveillance,” he said, “and to broaden the scope of bacteria that they’re monitoring.”
This multi-center study was led by Dr. Price and Gregg Davis in the Milken Institute SPH, along with researchers from the Translational Genomics Research Institute, Flagstaff Medical Center, the VA Healthcare System-Minneapolis, Statens Serum Institut in Copenhagen, the University of Minnesota and the Johns Hopkins University School of Medicine.