Assessing antimicrobial resistance in Shiga toxin-producing Escherichia coli O157 isolates from human clinical cases in the United States, 2010-2021.

AIMS: To characterize antimicrobial resistance (AMR) patterns and temporal trends among Shiga toxin-producing Escherichia coli O157 (STEC O157) clinical isolates from humans in the United States.

PATIENTS AND METHODS: 1,995 STEC O157 isolates collected from cases between 2010 and 2021 were analyzed. Resistance to antimicrobials was assessed, and temporal trends were evaluated using the Mann-Kendall test. Associations between AMR and demographic factors, including age and region, were examined using logistic regression models.

RESULTS: Resistance was most common to tetracycline (12.4%) and sulfisoxazole (9.9%), with temporal increases observed in resistance for these agents, along with chloramphenicol and trimethoprim-sulfamethoxazole (Mann-Kendall tau = 0.69-0.87, p < 0.001). Regional differences in AMR were noted for tetracycline, trimethoprim-sulfamethoxazole, and chloramphenicol. Cases aged 20-39 had higher odds of resistance to trimethoprim-sulfamethoxazole compared to those aged 0-4.

CONCLUSIONS: Since antimicrobials are not recommended for treating STEC O157 infections in humans, the sources of resistant strains could be foodborne, direct animal contact, the environment, or treatment for bacterial coinfections. The increase in the prevalence of AMR among STEC O157 strains in humans warrants investigation into the factors driving the emergence of resistant isolates. These findings call for an "One Health" approach for antimicrobial stewardship to mitigate AMR risks.