Department of Research & Evaluation News

Nearly 1 in 5 urinary tract infections (UTIs) in Southern California could be due to E. coli strains transmitted through contaminated meat, according to a new study of Kaiser Permanente Southern California members. The research also found that those living in low-income neighborhoods were at increased risk of these infections.

The study was published in mBio in October 2025.

“While more research is needed to distinguish foodborne transmission from other possible exposures and confirm these findings, reducing foodborne exposure to the highest-risk E.coli strains on raw meat could prevent a significant number of UTIs each year,” said study author Sara Y. Tartof, an infectious disease epidemiologist with the Kaiser Permanente Southern California Department of Research & Evaluation. “We recommend practicing safe food handling for protection.”

Consuming contaminated or undercooked meat, especially poultry, is a known source for E. coli that can lead to UTIs, although UTIs most often occur when bacteria from the gut enter the urinary tract through the urethra. UTIs are among the most prevalent infections globally, affecting women and the elderly disproportionately and resulting in significant health care costs. E. coli is the primary cause of UTIs and is commonly found in raw poultry and meat.

However, estimating how often foodborne strains lead to infection has been challenging.

Researchers from Kaiser Permanente Southern California and George Washington University collected more than 5,700 E. coli samples from patients with UTIs and retail meat samples from corresponding neighborhoods from 2017 to 2021. They utilized a genomic modeling approach to estimate whether each strain originated from humans or animals.

Among the research findings:

• 18% of UTIs in the study population were associated with E. coli strains of animal origin, categorized as foodborne UTIs.
• People living in high-poverty areas had a 60% higher risk of foodborne UTIs compared to those in wealthier neighborhoods.
• The highest-risk strains were most often found in chicken and turkey.
• Women and older men were especially vulnerable.

In the research paper, the study authors highlighted the need for further research to clarify transmission routes, improve source attribution models, and expand understanding to other regions and infection types. The study authors hope to conduct future research that refines host-origin prediction models and applies them to bloodstream infections and other E. coli diseases.

The researchers suggest that people—especially those at heightened risk of bacterial infections such as those who are immunocompromised, older, or have chronic conditions—should be cautious when handling raw meat, including frozen meat. Preventive steps, such as thorough handwashing, avoiding cross-contamination in the kitchen, and ensuring proper cooking of meat products, are important to reducing exposure.