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
Authors: Cullen Ivor M. , Manecksha Rustom P. , McCullagh Eddie , Ahmad Sarfraz , O'Kelly Fardod , Flynn Robert J. , McDermott Ted , Murphy Philip , Grainger Ronald , Fennell Jerome P. , Thornhill John A. 
Published: September 2011

Study Type – Therapy (practice patterns cohort)

Level of Evidence not applicable

What's known on the subject? and What does the study add?

Epidemiological and resistance patterns of bacterial pathogens in urinary tract infections show large inter‐regional variability, and rates of bacterial resistance are continually changing due to different regional antibiotic treatment regime. In Ireland and the UK, trimethoprim or nitrofurantoin is usually recommended for empirical treatment of uncomplicated cystitis in the community whilst parenteral cephalosporins, aminoglycosides, quinolones and co‐amoxyclav are reserved for complicated UTIs.

Neither penicillins nor trimethoprim represent suitable empirical antimicrobial agents for UTI in this study population. The high rate of ciprofloxacin resistance in encountered is suggestive of an over‐reliance on this agent in this population and with resistance rates approaching 30%, empirical use of quinolones for urology patients is inadvisable. E. coli UTIs have remained extremely sensitive to nitrofurantoin across all three patient sample groups in this population and the resistance rate has not changed significantly over the eleven‐year study period.

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.

WHONETTM 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.