Antimicrobial resistance and extended-spectrum b-lactamase production of Enterobacteriaceae from inpatients and outpatients with urinary tract infection

Abstract number: P1652

Kurutepe S., Surucuoglu S., Gazi H., Ecemis T., Dinc G., Tunger O.

Objectives: Extended-spectrum b-lactamases (ESBL) are important resistance traits for nosocomial isolates Enterobacteriaceae and their spread in the community generates increasing concern. This study was performed to investigate the prevalence of ESBL producers in Enterobacteriaceae isolated from both inpatients and outpatients with urinary tract infection and their resistance to antimicrobial agents.

Methods: A total of 965 strain of Enterobacteriaceae were isolated from urine samples; 434 isolates from inpatients and, 531 from outpatients from June 2006 to September 2007. Suspected strains are presumptively defined as ESBL producers according to result of disc diffusion method, using ESBL marker antibiotics ceftazidime (CAZ), cefotaxime (CTX) and aztreonam (ATM). Those isolates were retested with double-disc sinergy test (DDST)-CAZ, CTX, ATM and amoxicillin-clavulanic acid (AMC) disc implementation (CLSI). Enhancement of inhibition zone (or so called ghost zone) indicated presence of ESBL. Antimicrobial susceptibility to b-lactam antibiotics, gentamicin, trimethoprim-sulfamethoxazole, ciprofloxacin, nitrofurantoin was performed by disc diffusion method according to the recommendations of the CLSI.

Results: The species distribution as follows: Escherichia coli 79.3%, Klebsiella spp. 12.7%, Entrobacter spp. 3.2%, Proteus spp. 3.0%, Citrobacter spp. 1.0%, Morganella morganii 0.4%, Serratia marcescens 0.3%, Pantoea agglomerans 0.1%. The average prevalence of ESBL producers was 47.0% among isolates from inpatients and 8.7% among outpatient isolates. Approximately 95% of the ESBL-producing strains belonged to just two species E. coli (n = 194/25.4%) and Klebsiella spp. (n = 45/36.9%).

The resistance rates of non-ESBL producers and ESBL producers to imipenem 0.0% versus 1.6%, to nitrofurantoin 5.7% versus 30.5% (p = 0.000), to gentamicin 15.3% versus 63.6% (p = 0.000), to ciprofloxacin 25.8% versus 58.0% (p = 0.000), to trimethoprim-sulfamethoxazole 38.2% versus 68.8% (p = 0.000) respectively.

Conclusion: ESBL production has been obsorved in large percantage of urinary isolates and their expression is usually associated with multi-drug resistance. Thus, surveillance of ESBL dissemination appears to be important also community acquired infections.