Phenotypic detection of ESBL-producing Enterobacteriaceae using combined disk diffusion, ESBL HiCrome agar, and E-test: A comparative study

Abstract

Background: Extended-spectrum beta-lactamases (ESBLs) are in a rising trend in recent years, creating confusion for physicians to choose appropriate antimicrobials for treatment. Aim: The aim of the study is to detect ESBL-producing Enterobacteriaceae by using rapid detection tests such as combined disk diffusion, ESBL E-test strips (based on cefotaxime and cefotaxime+clavulanate), and ESBL HiCrome agar and compare the efficacy of these tests. Materials and Methods: Samples were processed using conventional methods. Bacterial antibiotic susceptibility testing was done on Mueller-Hinton agar according to the Clinical and Laboratory Standards Institute guidelines. All Enterobacteriaceae isolates were subjected to ESBL HiCrome agar, combined disk diffusion, and E-test. Results: Out of 5299 samples, 2097 (39.57%) were culture-positive, and 200 (9.5%) Enterobacteriaceae isolates were obtained. The majority of the isolates were Escherichia coli (67.5%), followed by Klebsiella pneumoniae (25%), Proteus mirabilis (3.5%), Proteus vulgaris (2%), and Citrobacter freundii (2%). 29.5% of all Enterobacteriaceae isolates were found to be ESBL producers by combined disk diffusion, ESBL HiCrome agar, and E-test methods, which showed 100% concordance. Conclusion: It is important to identify ESBL-producing Enterobacteriaceae from clinical samples for the judicious use of antibiotics. For early detection of ESBL-producing Enterobacteriaceae isolates, combined disk diffusion, ESBL HiCrome agar, and E tests were found to be equally effective in detecting ESBL production.