Increasing prevalence of ciprofloxacin resistance in extended-spectrum-β-lactamase-producing Escherichia coli urinary isolates

Purpose To describe the incidence and drug susceptibility profiles of uropathogenic extended-spectrum-β-lactamase-producing Escherichia coli (ESBL-EC) during a 10-year period and to identify differences in resistance patterns between urological and non-urological ESBL-EC isolates. Methods Retrospective analysis of 191,564 urine samples obtained during 2001 to 2010 at the University Hospital Basel, Switzerland. The computerized database of the Clinical Microbiology Laboratory and the Division of Infectious Diseases and Hospital Epidemiology was used to identify ESBL-EC positive urine samples. ESBL-EC isolates were stratified according their origin into two groups: Urology and non-Urology isolates. Results The rate of ESBL-EC positive urine samples increased significantly during the study period (3 in 2001 compared to 55 in 2010, p < 0.05). The most active agents were imipenem, meropenem, and fosfomycin (100 %), followed by amikacin (99.1 %) and nitrofurantoin (84 %). The least active substances were ampicillin-clavulanate (20 %), sulfamethoxazole (28 %), and ciprofloxacin (29.6 %). ESBL-EC isolates from urological and non-urological patients showed similar susceptibility profiles. However, ESBL-EC isolates from urological patients were significantly less susceptible to ciprofloxacin compared to non-urological isolates (14.7 vs. 32.7 %, p < 0.05). Conclusions The rate of urinary ESBL-EC isolates is increasing. Their susceptibility to nitrofurantoin, fosfomycin, and carbapenems is excellent, whereas ampicillin-clavulanate, sulfamethoxazole, and ciprofloxacin demonstrate only low susceptibility. In particular, the use of ciprofloxacin should be strictly avoided in urologic patients with suspicion for an ESBL-EC urinary tract infection as well as routine antibiotic prophylaxis prior to urological interventions if not explicit indicated by current international guidelines or local resistance patterns.