Extended spectrum beta-lactamase producers among the multidrug resistant uropathogens

Abstract

The incidence of extended spectrum β-lactamase (ESBL) producing strains among clinical isolates has been steadily increasing over the past few years, resulting in the limitation of therapeutic options. The purpose of this study was to isolate and identify the multidrug resistant strains (MDR) and to screen those Extended Spectrum β-lactamase (ESBL) producing isolates in urine samples. A total of five hundred and ninety eight (598) urine specimens were collected and processed by conventional microbiological method. Antimicrobial susceptibility testing (AST) of the isolates was done by Modified Kirby-Bauer disc diffusion method on Muller Hinton Agar (MHA). Screening of ESBL producers among the MDR isolates was performed by using Ceftazidime (30µg) and Cefotaxime (30µg) discs which were further confirmed using Ceftazidime and Cefotaxime in alone and combination with clavulanic acid as per CLSI 2013. One hundred and eleven (18.60%) isolates were obtained from the significant growth results in which Escherichia coli 79(71.7%) was the most predominant gram negative isolates. Among the 111, 74(66.66%) were observed as MDR and of which 47 were primarily screened as ESBL producers. Out of these 30(63.82%) were confirmed as ESBL producers and majority of ESBL producers were E. coli (n=26, 68.42%) isolates. Of the two different combined discs used, CAZ and CAZ-CV 30/47 (63.82%) were observed as better for ESBL testing in comparison to CTX and CTX-CV 27/47 (57.44%). Among the tested antibiotics Nitrofurantoin (85.3%) was found to be most effective drugs for gram negative isolates and Gentamicin (83.3%) for Gram-positive isolates. However the practice of using only single screening agent for ESBL detection should be discouraged. Hence use of more than one screening agents and combined disc assay should practiced for ESBL detection. Furthermore, Regular surveillance of MDR and ESBL detection in clinical observations was suggested to estimate their current occurrence.