Detection of Extended-Spectrum ß-lactamases Production by Escherichia coli: A Phenotypic Comparative Study

Resistance to antibiotics is a serious concern and immediate steps are required to crub the resistance gained by microorganisms. Extended spectrum beta- lactamases (ESBLs) producing E.coli (Escherichia coli) is rapidly increasing and making antibiotics difficult to treat around the world. The screening of ESBL producers among Escherichia coli was done by method Double Disk Synergy Test (DDST), using ceftazidime and ceftriaxone disc and Combined Disc Test (CD) using ceftazidime-clavulanic acid according to Clinical and Laboratory Standard Institute (CLSI) protocol. In the DDST method, out of 60 clinical isolates of Escherichia coli, 22 were found ESBL positive isolates, and among 22 positive isolates 18 strains shows increase in zone of inhibition by both ceftazidime and ceftriaxone disc. The remaining 4 ESBL isolates, 3 of them showed zone of inhibition to ceftazidime and only 1 isolate showed inhibition by ceftriaxone disc. Similarly, in CD method apart from 22 isolates detected by DDST method it detected 1 more isolate as ESBL producers. Furthermore, the CD method detects inducible beta- lactamase in III generation of cephalosporin sensitive isolate. Our study showed 22 isolates were found by DDST method and 23 isolates by CD method. This study results showed the prevalence of ESBL in E. coli were 36.66% by DDST and 38.33% by CD tests and we conclude that combined disk test (CD) is better than DDST for detection of ESBL