Image of Keith S. Kaye, M.D., MPH

U.S. physicians are having more trouble finding effective first-line antibiotics for common urinary tract infections as antimicrobial resistance rises, a new study suggests.

Investigators calculated the overall prevalence of antimicrobial-resistant Escherichia coli in urine samples from adult and adolescent women between 2011 and 2019. They found that more than a quarter of the E coli from these samples were resistant to trimethoprim-sulfamethoxazole, 21% did not respond well to fluoroquinolones, and 4% did not respond to nitrofurantoin, all antibiotics of choice. 

Fully 6.4% of the tested E coli isolates had evidence of antibiotic-resistant enzymes, 14% were resistant to two or more antibiotics, and 4% were resistant to three or more, reported Keith S. Kaye, M.D., MPH, director of the University of Michigan Medical School’s Division of Infectious Diseases in Ann Arbor, MI.

The prevalence of multi-drug resistance not only increased during the study period but was found to vary widely by U.S. census region — information clinicians could use to help make UTI treatment decisions, Kaye and colleagues wrote.

“Knowledge of regional antimicrobial resistance rates helps inform empiric treatment of community-onset uncomplicated UTI and highlights the antimicrobial resistance burden to physicians,” they concluded.

In nursing homes, up to a third of urinary tract infections may be antibiotic resistant, according to another recent investigation. 

The current study was published in the journal Clinical Infectious Diseases.