A new study led by researchers at the George Washington University suggests that E. coli from meat products may be responsible for hundreds of thousands of urinary tract infections in the United States each year. The study, “Using source-associated mobile genetic elements to identify zoonotic extraintestinal E. coli infections,” was published online March 23 in the journal One Health.
The team of scientists, led by Lance B. Price and Cindy Liu from GW’s Milken Institute School of Public Health, developed a new genomic approach for tracking the origins of E. coli infections. Using this method, the team estimated that between 480,000 and 640,000 urinary tract infections (UTIs) in the United States each year may be caused by foodborne E. coli strains.
“We’re used to the idea that foodborne E. coli can cause outbreaks of diarrhea, but the concept of foodborne E. coli causing urinary tract infections seems strange—that is, until you recognize that raw meat is often riddled with the E. coli strains that cause these infections,” said Price, professor of environmental and occupational health and the founder and co-director of the GW Antibiotic Resistance Action Center. “Our study provides compelling evidence that dangerous E. coli strains are making their way from food animals to people through the food supply and making people sick–sometimes really sick.”
E. coli is far and away the most common cause of urinary tract infections, causing upwards of 85% of cases each year. Women are at greater risk of developing UTIs, which can range from simple bladder infections to life-threatening bloodstream infections.
E. coli can live in and infect people and animals, including animals raised for meat in the United States. When food animals are slaughtered, the bacteria that inhabit their guts–including E. coli–can contaminate the meat products and put people at risk for exposure.
Data from the U.S. Food and Drug Administration (FDA) suggests that a majority of raw meat products are contaminated with E. coli. Currently, only specific types of diarrhea-causing E. coli, such as E. coli O157:H7, are monitored with any seriousness in the United States. But this new research suggests that other strains may also pose serious health risks.
In this study, the researchers collected raw chicken, turkey and pork purchased from major grocery store chains in Flagstaff, Arizona, and isolated E. coli from these meat samples. At the same time, the researchers collected urine and blood E. coli isolates from patients hospitalized at the Flagstaff Medical Center for urinary tract infections.
By analyzing the genomes of E. coli from meat and those from people, the research team identified segments of E. coli DNA unique to strains that colonize food animals versus humans, then developed a new predictive model to differentiate E. coli from the two sources.
Previous work by the same team, investigating a single sequence type of E. coli, had linked contaminated meat to urinary tract infections. In the latest study, the team used their new predictive model to look at all E. coli sequence types and showed that about 8% of E. coli urinary tract infections in the Flagstaff area could be attributed to meat.
Scaling from Flagstaff to the U.S. population overall suggests that foodborne E. coli may cause hundreds of thousands of urinary tract infections across the country every year, the researchers note.
Coauthor Paul Keim, a professor of microbiology at Northern Arizona University (NAU), said the “unprecedented study design…is a powerful approach to public health research.”
The foodborne E. coli strains identified in the current study not only were associated with urinary tract infections, but also were capable of causing serious kidney and bloodstream infections. Left unchecked, E. coli bloodstream infections can be deadly. It is estimated that between 36,000 and 40,000 people die from E. coli bloodstream infections in the United States each year, but it is currently not known what portion of these originate from foodborne exposures.
“People often dismiss bladder infections as minor annoyances, but the bladder is a major gateway to patients’ kidneys and bloodstream,” said Liu, associate professor of environmental and occupational health at GW and co-director of the GW Antibiotic Resistance Action Center. “People over 55 and vulnerable populations such as cancer and transplant patients are at the highest risk for life-threatening blood infections, but young, healthy people are also at risk.”
The study suggests producers and the FDA could do a better job of monitoring potentially dangerous pathogens in food, particularly raw meat sold in grocery stores across the country. At the same time, consumers can take steps on their own to limit their exposure to contaminated food. For example, the authors say, home cooks can wash their hands carefully when preparing or handling raw meat and can use separate surfaces to prepare raw and cooked foods.
The GW team led a multi-center group of researchers who collaborated on this paper. Price and Liu started the work while at Northern Arizona University. NAU also collaborated on the E. coli strain processing and genome sequencing, while the UTI E. coli were collected by the clinical microbiology team at the Flagstaff Medical Center led by lab manager Lori Gauld. Bioinformatic analysis leading to the source conclusions were performed at GW. The study was supported by GW, NAU, the Wellcome Trust, the National Institutes of Health and the Cowden Endowment for Food Microbiology.
