Recent studies reveal that nearly 1 in 5 urinary tract infections (UTIs) in Southern California may be attributed to strains of Escherichia coli (E. coli) that originate from food-producing animals. This groundbreaking research, led by scientists from George Washington University and Kaiser Permanente Southern California (KPSC), analyzed over 5,700 extraintestinal pathogenic E. coli (ExPEC) isolates obtained from UTI patients and retail meat samples collected from stores in the patients' neighborhoods.
Utilizing advanced comparative genomic analysis and a model developed to trace the host origin of each isolate, the researchers found that 18% of the UTIs were linked to ExPEC strains sourced from meat. Alarmingly, the study also indicated that UTIs in patients living in high-poverty neighborhoods were 60% more likely to be caused by these zoonotic (animal-to-human) ExPEC strains. The findings were formally published in the journal mBio.
This research builds on over a decade of work by Dr. Lance Price, founding director of George Washington University's Antibiotic Resistance Action Center. In a 2018 study, Price and his team discovered that a specific E. coli strain, responsible for severe UTIs worldwide, was notably prevalent in chicken and turkey meat. A follow-up study in 2023 indicated that 8% of E. coli isolates from human UTIs in Flagstaff, Arizona, were linked to retail meat, suggesting a growing concern surrounding foodborne E. coli as a source of UTIs.
Traditionally, foodborne E. coli is associated with gastrointestinal illnesses. Certain strains, such as Shiga toxin-producing E. coli, are closely monitored by health officials to prevent contamination in the food supply. However, the work of Price and his colleagues highlights that foodborne ExPEC strains entering the urinary tract are an underestimated contributor to the approximately 8 million UTIs diagnosed in the United States each year. While most UTIs are mild, they can escalate into serious conditions, including invasive infections and sepsis.
To quantify the relationship between UTIs and zoonotic E. coli strains, the research team, which included experts from universities like Cambridge and Johns Hopkins, employed whole-genome sequencing on 2,349 clinical E. coli isolates collected from KPSC regional labs between February 2017 and May 2021. Most patients were predominantly Hispanic (37.0%) and non-Hispanic White (31.7%), residing in areas with varying poverty rates.
The team also analyzed 3,379 E. coli isolates from retail samples of chicken, turkey, beef, and pork purchased weekly from major grocery chains. Notably, contamination was highest in turkey samples (82%), followed by chicken (58%), pork (54%), and beef (47%), with higher contamination observed in meat from stores located in high-poverty areas.
The researchers examined the core genomes of human and foodborne E. coli isolates and identified 17 human- and animal-associated mobile genetic elements (MGEs). Their statistical model combined this data to ascertain the origin of each isolate. If animal-associated MGEs were prevalent in E. coli from UTI samples, it indicated an animal source. The model estimated that 17.7% of human clinical E. coli isolates originated from food-producing animals, primarily chickens and turkeys.
Interestingly, the zoonotic E. coli strains were found to be less resistant to common UTI treatments compared to non-zoonotic strains. This observation may support the effectiveness of the FDA's efforts to restrict medically important antibiotics in livestock. Despite criticisms of the FDA's regulations, studies in countries with lax antibiotic regulations in livestock have shown significantly higher levels of antibiotic resistance in bacteria transmitted from animals to humans.
Another startling finding was that the highest proportion of zoonotic ExPEC isolates (21.5%) was found in patients from high-poverty areas. After accounting for age, sex, and race/ethnicity, individuals in these areas had a 1.6-fold increased risk of zoonotic ExPEC infections compared to those in low-poverty regions. While the underlying causes of this link are not fully understood and warrant further investigation, Price speculates that the quality of meat products available in poorer neighborhoods may play a role.
Recognizing meat as a potential source of exposure to zoonotic E. coli is essential for reducing the burden of UTIs. The study suggests that regulatory agencies should consider testing meat for various E. coli strains, not just those causing gastrointestinal illnesses. Consumers are advised to adopt safe food-handling practices, including thoroughly cooking meat, washing hands and surfaces, and preventing cross-contamination. Price emphasizes the importance of treating every piece of meat as potentially contaminated, highlighting the need for heightened awareness and precaution.
