UTI Study Maps Escherichia coli Antimicrobial Resistance Trends in the United States

Investigators evaluated resistance to fluoroquinolones, nitrofurantoin, and trimethoprim-sulfamethoxazole in patients with uncomplicated urinary tract infection.

Escherichia coli rates of resistance to fluoroquinolones and trimethoprim-sulfamethoxazole were greater than 20% from 2011 to 2019 in patients with uncomplicated urinary tract infection (UTI), according to authors of a retrospective, multicenter cohort study published in Clinical Infectious Diseases. The study also found significant increases in the yearly rates of E coli drug-resistant phenotypes in urine samples.

The investigators reviewed data on E coli isolates in urine cultures collected from female study participants aged 12 years and older at US outpatient facilities between January 2011 and December 2019. Urine cultures were noncontaminated and associated with E coli identification and susceptibility reports. The review included only the first isolate collected from each patient within 30 days, unless an isolate from one patient had different drug susceptibilities.

The investigators looked for rates of antimicrobial resistance, defined as not susceptible to fluoroquinolones, nitrofurantoin, or trimethoprim-sulfamethoxazole.  They also assessed for extended-spectrum B-lactamase production (ESBL+) and identified E coli isolates with 2 or more and 3 or more drug-resistance phenotypes.

To understand resistance differences by region, they developed geospatial heat maps showing the proportion of isolates with each drug-resistance phenotype at the county level. The investigators added a secondary analysis to account for changes in minimum inhibitory concentration (MIC) breakpoints over the study period.

Of 1,513,882 E coli isolates, 25.39% (95% CI, 25.32-25.46) were not susceptible to trimethoprim-sulfamethoxazole, 21.10% (95% CI, 21.03-21.16) were not susceptible to fluoroquinolones, and 37.68% (95% CI, 3.73-3.79) were not susceptible to nitrofurantoin.

Overall, 6.36% (95% CI, 6.32-6.40) of the E coli isolates were ESBL+, 14.36% (95% CI, 14.30-14.41) had 2 or more drug-resistance phenotypes, and 3.81% (95% CI, 3.78-3.84) had 3 or more drug-resistance phenotypes.

Shown in geospatial heat maps, the highest prevalence of drug-resistance phenotypes (besides ESBL+) occurred in the East South Central US census region, and the lowest prevalence occurred in the New England region. The highest ESBL+ rate (9.2%) occurred in the Pacific region.

Over the course of the study period, the ESBL+ rate increased every year (excluding 2018) — from 4.1% in 2011 to 7.3% in 2019, with a yearly relative increase of 7.7% (95% CI, 7.2-8.2; P <.0001). Nonsusceptibility to trimethoprim-sulfamethoxazole remained at 25% or greater, with no significant yearly trend. Fluoroquinolone nonsusceptibility decreased significantly over the study period (P <.0001) but remained above 20%. Nitrofurantoin nonsusceptibility showed a yearly relative decrease of 6.1% (95% CI, -6.5 to -5.6; P <.0001).

The prevalence of E coli isolates with 3 or more drug-resistance phenotypes increased from 3.1% in 2011 to 4.0% in 2019, with a yearly relative increase of 2.7% (95% CI, 2.2-3.2; P <.0001), while the prevalence of E coli isolates with 2 or more drug-resistance phenotypes decreased by 1.0% (P <.001) over that period of time.

The study authors pointed out that their results “highlight the need to educate physicians on best prescribing practice” in the southern-border region of the United States, where geospatial maps showed areas of high E coli nonsusceptibility rates, which are “often attributed to the availability of over-the-counter antimicrobial treatments, compounded by under-trained staff, in pharmacies outside the US.”

Disclosure: Multiple study authors declared affiliations with biotech, pharmaceutical, and/or device companies. This research was supported by GlaxoSmithKline PLC. Please see the original reference for a full list of disclosures.


Kaye KS, Gupta V, Mulgirigama A, et al. Antimicrobial resistance trends in urine Escherichia coli isolates from adult and adolescent females in the United States from 2011–2019: rising ESBL strains and impact on patient management. Clin Infect Dis. Published online June 18, 2021. doi:10.1093/cid/ciab560