[Changes in the antimicrobial susceptibility of Escherichia coli isolates from nosocomial versus community-acquired urinary tract infections].

INTRODUCTION

We studied the variations in Escherichia coli sensitivity patterns to commonly used antimicrobial agents in urinary tract infections, by stratifying isolates according to year and source.

MATERIAL AND

METHODS

Retrospective analysis of the sensitivity of 14,319 E. coli urine isolates to 14 antimicrobials during the period of 1994-2001. Sensitivity comparison by source of the isolate began in 1996, and included 13,263 isolates originating in the hospital and 2,350 originating in the community.

RESULTS

Penicillins were the least active antibiotic agents against the E. coli isolated (sensitivity 40.9%), followed by cotrimoxazole (66.4%), nalidixic acid (70.8%) and norfloxacin (76.1%). Sensitivities to the other antimicrobials tested remained near 95%. Sensitivity of E. coli isolates to most of the antimicrobials tested decreased gradually during the 8-year period, with a marked decrease for nalidixic acid and norfloxacin (76.0% down to 63.3% and 85.1% down to 66.6%, respectively). Nevertheless, sensitivity of E. coli to nitrofurantoin and ampicillin-sulbactam/amoxicillin-clavulanic acid increased; no significant differences were observed regarding cefazolin, gentamicin and fosfomycin. Sensitivity was higher in community E. coli isolates than in nosocomial isolates. The greatest differences corresponded to cephalosporins (OR = 2), nitrofurantoin (OR = 1.72), and ampicillin-sulbactam/ amoxicillin-clavulanic acid (OR = 1.57). Antimicrobials with significant differences in sensitivity between isolates of different sources decreased gradually from 6 (1996) to 1 (2001).

CONCLUSIONS

Penicillins, cotrimoxazole and quinolones can no longer be considered the antimicrobials of choice for empirical treatment of E. coli urinary tract infections. Along the study period, we observed a reduction in the initial susceptibility differences among hospital and community isolates.