Phenotypic detection of AmpC beta-lactamases among ESBL-producing clinical isolates of Escherichia coli and Klebsiella spp. from several clinical centers of Mashhad

Introduction and Objectives: The gram-negative bacteria with multi-drug resistance have increased continuously frequency over the past few years. The bacteria produce AmpC β-lactamases and/or extended spectrum β-lactamases (ESBLs) are of particular concern. The present study was designed to determine the prevalence of AmpC β-lactamases among ESBL-producing these clinical gram-negative bacteria.Materials and Methods: This study was conducted on 300 ESBL-positive isolates (51 Klebsiella spp. and 249 E.coli). Samples were collected in the period from February 2016 to April 2018. These isolates were obtained from various clinical specimens and previously were identified by standard biochemical methods and ESBL production was confirmed by the double-disk synergy test (DDST).128 isolates were screened for presumptive AmpC production by using a commercial test kit, D68C AmpC detection set (MASTDISCS™ID, UK) and 172 isolates were screened for presumptive AmpC- production according to examining their susceptibility to cefoxitin (30 μg) and cefoxitin with phenylboronic acid (PBA) based on Kirby-Bauer disk diffusion method.Results: Of 300 clinical ESBL-positive isolates, sixty-three isolates were found to be AmpC-positive by this phenotypic method (12 Klebsiella spp. and 51 E. coli) and 47(15 Klebsiella spp. and 32 E. coli) isolates were shown probably multi-drug resistant phenotype.Conclusion: Our findings indicate that the prevalence of AmpC β-lactamases and multi-drug resistant phenotype among clinical ESBL-producing isolates of Escherichia coli and Klebsiella spp. were significantly increased. This study highly recommends performing screening and phenotypic tests for AmpC detection in a routine diagnostic laboratory work.

Keywords:

AmpC β-lactamases , Extended Spectrum β-Lactamases (ESBLs) , Escherichia coli , Klebsiella spp