The efficacy of non-carbapenem antibiotics for the treatment of community-onset acute pyelonephritis due to extended-spectrum β-lactamase-producing Escherichia coli

Objective: Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli has become an important cause of community-onset urinary tract infections. We aimed to evaluate the efficacy of non-carbapenem antibiotics for acute pyelonephritis (APN) due to ESBL-producing E. coli. Methods: We conducted a retrospective cohort study of patients with community-onset APN due to ESBL-producing E. coli at a single centre in Korea from 2007 to 2013. Outcomes included both microbiological and clinical failure. To adjust for non-random assignment of antibiotics, the propensity score method of inverse probability of treatment weighting and a multivariable analysis using Cox proportional hazards modelling were employed to estimate the efficacy of non-carbapenem antibiotics as compared with carbapenems. Results: Of 152 eligible patients, 85 (55.9%) received carbapenems and 67 (44.1%) received non-carbapenems. Non-carbapenem antibiotics used in this cohort included aminoglycosides (n=30), β-lactam/β-lactamase inhibitors (n=13), fluoroquinolones (n=12) and trimethoprim/sulfamethoxazole (n=5). Microbiological failure was observed in 16 patients receiving carbapenems (16/83, 19.3%) versus 4 patients receiving non-carbapenem (4/67, 6.0%). After weighting, the risk of microbiological failure was similar between the two groups [weighted hazard ratio (HR) 0.99; 95% CI 0.31-3.19]. In a multivariable regression analysis combined with weights, the estimate did not change (weighted adjusted HR 0.96; 95% CI 0.41-2.27). The clinical failure rate was also similar in the two groups (weighted HR 1.05; 95% CI 0.24-4.62). Conclusions: These results suggest that non-carbapenem antibiotics were as effective as carbapenems as definitive therapy for treating community-onset APN caused by ESBL-producing E. coli if they are active in vitro.