Prevalence and antimicrobial susceptibility of extended-spectrum beta-lactamase producing urinary isolates of Escherichia coli in outpatients

INTRODUCTION: In Gram-negative bacteria, the production of beta-lactamases is the most important mechanism of resistance to beta-lactam antibiotics. In the Banja Luka region, there were no extensive researches on the prevalence and antimicrobial resistance of the extended-spectrum beta-lactamase (ESBL) producing Escherichia coli (E. coli) isolates. OBJECTIVE: The aim of the present study was to determine the presence of ESBL producing E. coli isolates as the cause of the urinary tract infections in outpatients, the distribution of these ESBL isolates according to age and gender of patients and their susceptibility to antimicrobials. METHODS: Urine specimens obtained from outpatients were cultured on chromogenic CPS-ID3 media. All plates showing significant (> 10(5) cfu/ml) growth of E. coli in pure culture were further processed. Antimicrobial susceptibility testing was performed on VITEK TWO Compact using AST-GN27 cards for testing Gram negative bacteria and detection of ESBL producers. RESULTS: Out of 2,195 isolates, 177 (8.1%) were ESBL producers. Ninety-two isolates were obtained from female patients (5% of E. coli isolated from women) and 85 isolates from male patients (23% of E. coli isolated from men). High percentage of ESBL isolates was detected in the infant age group under one year (36.7%) and in the age group over 60 years (28.8%). All ESBL isolates were susceptible to imipenem and resistant to ampicillin, piperacillin, cefazolin, cefotaxime, ceftazidime and cefepime. There was a significant resistance to amikacin (79.1%), gentamicin (76.8%), amoxicillin/clavulanate (54.8%) and trimethoprim/sulphamethoxazole (45.8%). Resistance to nutrofurantoin was 13.6%. CONCLUSION: This study has demonstrated the presence of ESBL producing E. coli urinary isolates in outpatients, and their extensive susceptibility to imipenem and nitrofurantoin.