Risk Factors for Trimethoprim and Sulfamethoxazole-Resistant Escherichia Coli in ED Patients with Urinary Tract Infections

Background: While trimethoprim-sulfamethoxazole (TMP-SMX) is recommended as one of the first-line empiric therapies for treatment of acute uncomplicated cystitis, institutions that observe resistance rates exceeding 20% for Escherichia coli (E. coli) should utilize alternative empiric antibiotic therapy per the Infectious Diseases Society of America (IDSA). Identifying risk factors associated with TMP-SMX resistance in E. coli may help guide empiric antibiotic prescribing for urinary tract infections (UTIs).

Methods: This multicenter, retrospective study included adult patients who were discharged from 12 emergency departments (EDs) with a urine culture positive for E. coli between January 1, 2019 and December 31, 2019. Logistic regression was used to assess the relationship between potential risk factors and TMP-SMX resistance. The overall institutional antimicrobial resistance rates for E. coli were compared to the rates seen in the study population of ED urinary isolates.

Results: Among 427 patients included from a randomized sample of 500 with a urine culture positive for E. coli, 107 (25.1%) were resistant to TMP-SMX. Three predictors of TMP-SMX resistance were identified: recurrent UTI (OR 2.27 [95% CI 1.27-3.99]), genitourinary abnormalities (OR 2.31 [95% CI 1.17-4.49]), and TMP-SMX use within 90 days (OR 8.77 [95% CI 3.19-28.12]). When the antibiotic susceptibilities for this ED cohort were compared to the institutional antibiogram, the TMP-SMX resistance rate was found to be higher in the ED population (25.1% vs 20%).

Conclusions: TMP-SMX should likely be avoided as first-line therapy for UTI in patients who have recurrent UTIs, genitourinary abnormalities, or have previously received TMP-SMX within the past 90 days. The use of an ED-specific antibiogram should be considered for assessing local resistance rates in this population.