شناسايي ايزوله هاي باليني اشريشياكلي مولد بتالاكتامازهاي وسيع الطيف ESBLs بر پايه تعيين MIC سفتازيديم، سفترياكسون و سفپيم

Detection of Extended-Spectrum Beta-Lactamase Production in Clinical Isolates of Escherichia coli Based on MICs of Ceftazidime, Ceftriaxon and Cefepim

Background: Extended-Spectrum B-lactamases (ESBLs) are plasmid-mediated enzymes that hydrolyze the oxyimino p-lactam substance such as third-generation Cephalosporins (Ceftazidim, Ceftriaxone, Cefotaxime). Presence of ESBL-producing organisms results in decrease in efficacy of extended-spectrum Cephalosporines in treatment of serious clinical infections caused by these organisms. So the treatment options are limited and failure treatment and antibiotic resistance are the consequence of inadequate options. Materials and Methods: A total of 160 isolates of Escherichia coli were collected from clinical samples of three hospitals in Tehran. MICs for Ceftriaxone, Ceftazidim and Cefepime were determined by standard agar dilution method. A MIC above 1 mg/L to any of these three was subjected to confirmatory testing as per CLSI method. Results: Primary phenotypic tests revealed that 56.68% (n=89) of E.coli isolates produced extended-spectrum beta-lactamases. Using of clavulanic acid in confirmatory tests, ESBL production was confirmed in 96.7% (n=86) of isolates with primary positive phenotype. The presence of an ESBL was not confirmed in 3.3% (n=3) of the screen positive isolates. Conclusion: This study showed that ESBL productions in clinical isolates of E. coli in Tehran cityʹs university hospitals were extremely high and it is suggested detection of ESBLs as routine tests in order to increase the effectiveness of treatment.