Prediction of trimethoprim/sulfamethoxazole resistance in community-onset urinary tract infections

Abstract

Objectives: This study aimed to predict trimethoprim/sulfamethoxazole (SXT) resistance in patients with community-onset urinary tract infection (UTI) due to Enterobacteriaceae based on patient-specific risk factors.

Methods: This was a retrospective case-control study in Prisma Health facilities in central South Carolina, USA, including three community hospitals, affiliated emergency departments and ambulatory clinics, including adult patients with community-onset UTI due to Enterobacteriaceae (1 April 2015 to 29 February 2016). Multivariate logistic regression was used to examine risk factors for SXT resistance.

Results: Among 351 unique patients with community-onset UTI, 71 (20.2%) had SXT-resistant Enterobacteriaceae urinary isolates. Overall, median age was 64 years and 252 (71.8%) were female. A multivariate model identified prior urinary infection/colonisation with SXT-resistant Enterobacteriaceae (OR=8.58, 95% CI 3.92-18.81; P<0.001) and SXT use within past 12 months (OR=2.58, 95% CI 1.13-5.89; P=0.02) as predictors of SXT resistance among urinary isolates. Most patients with UTI (285; 81.2%) had no risk factors for SXT resistance. SXT resistance rates increased from 13% in the absence of risk factors to 31% in patients with prior SXT use, 66% in those with prior urinary infection/colonisation with SXT-resistant Enterobacteriaceae and 73% in the presence of both risk factors.

Conclusion: SXT resistance in Enterobacteriaceae urinary isolates may be predicted based on prior urine culture results and SXT use within the previous year. Utilisation of a patient-specific antibiogram may allow empirical SXT use in patients with community-onset UTI in the absence of risk factors for resistance.

Keywords: Antibiogram; Antimicrobial stewardship; Enterobacteriaceae; Escherichia coli; Urine culture.