Antimicrobial resistance surveillance of gram-negative bacteria isolated from intensive care units of four different hospitals in Turkey - Evaluation of the prevalence of extended-spectrum and inducible beta-lactamases using different E-test strips and direct induction methods

Abstract

Background: The aim of this study was to determine the antimicrobial resistance of gram-negative rods (GNRs) isolated from surgical intensive care units and to establish the prevalence of extended-spectrum beta-lactamases (ESBLs) and inducible beta-lactamases (IBLs). We also wished to determine the widespread beta-lactam substrate in ESBL-positive GNRs by two different E-test strips and to discuss the value of the routine utilization of these substrates together. Methods: Out of 348 nosocomial gram-negative strains isolated with similar methods, 236 strains with resistance to the beta-lactam group of antimicrobials using the E-test method were included in this study. Two different strips were used for the detection of ESBLs: cefotaxime/cefotaxime + clavulanic acid (CT/CTL) and ceftazidime/ceftazidime + clavulanic acid (TZ/TZL). For IBLs, the double-disk method was used. Results: The order of frequency of the strains, starting with the most frequent, was Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. In the 236 strains, the ESBL positivity rate was found to be 19.5% with TZ/TZL and CT/CTL strips, while it was 13.2% for IBL in 348 strains. Seventy-one percent of ESBL-positive strains gave parallel results with TZ/TZL and CT/CTL. ESBL positivity with only TZ/TZL or only CT/CTL was found to be 18 and 8%. Conclusions: Our study showed that except for imipenem, amikacin and ciprofloxacin, there was a high resistance to other antimicrobials, and multiresistance rates were increased in the strains in which ESBLs and IBLs were detected. In particular, the increasing prevalence of ESBLs in K. pneumoniae and IBLs in P. aeruginosa emphasizes the importance of the problem of infection control and antibiotic administration policies. Although it was seen that the prevalence of substrate templates in the detection of ESBL positivity was similar, we think that it is more useful to use two different strips together to obtain precise results. Copyright (C) 2001 S. Karger AG, Basel.