The changing pattern of antimicrobial resistance within 42,033 Escherichia coli isolates from nosocomial, community and urology patient-specific urinary tract infections, Dublin, 1999-2009

Abstract

Objective: To investigate the changing pattern of antimicrobial resistance in Escherichia coli urinary tract infection over an eleven year period, and to determine whether E. coli antibiotic resistance rates vary depending on whether the UTI represents a nosocomial, community acquired or urology patient specific infection.

Patient and methods: A retrospective analysis of the 42,033 E. coli urine isolates from the 11-year period 1999-2009 in a single Dublin teaching hospital was performed. WHONET(TM) software was used to analyse the changing pattern of sensitivity and resistance of E. coli to commonly used antibiotics over the study period. The origins of the urine samples were stratified into three groups: inpatients with nosocomial UTIs; urine originating from the emergency department and general practice (community UTIs); and UTIs in urology patients.

Results: Urinary tract infections in the urology patient population demonstrate higher antibiotic resistance rates than nosocomial or community UTIs. There were significant trends of increasing resistance over the 11-year period for ampicillin, trimethoprim, gentamicin and ciprofloxacin, and significant differences in co-amoxyclav, gentamicin, nitrofurantion and ciprofloxacin resistance rates depending on the sample origin. Ampicillin and trimethoprim were the least active agents against E. coli, with total 11-year resistance rates of 58.3 and 33.8%, respectively. The overall gentamicin resistance rate was 3.4% and is climbing at a rate of 0.7% per year (P < 0.001). Within the urology patient population the resistance rate was 6.4%. Ciprofloxacin resistance approaches 20% in the nosocomial UTI population and approaches 30% in the urology population; however, it remains a reasonable empirical antibiotic choice in this community, with an 11-year resistance rate of 10.6%.

Conclusions: E. coli remains the commonest infecting uropathogen in the community and hospital setting with its incidence climbing from 50 to 60% of UTIs over the 11-year period. Neither penicillins nor trimethoprim represent suitable empirical antimicrobials for UTI and ciprofloxacin resistance in this Dublin-based study renders it unsuitable empirical therapy for nosocomial UTIs and UTIs in the urology population. The dramatic 11-year rate increase in gentamicin resistance is of paramount concern.