Phenotypic and Molecular Characterization of Plasmid Mediated AmpCβ-Lactamases amongEscherichia coli,Klebsiellaspp., andProteus mirabilisIsolated from Urinary Tract Infections in Egyptian Hospitals

Abstract

The incidence of resistance by Enterobacteriaceae toβ-lactam/β-lactamase inhibitors combination is increasing in Egypt. Three phenotypic techniques, comprising AmpC disk diffusion and inhibition dependent methods using phenylboronic acid (PBA) and cloxacillin, were compared to PCR based method for detection of plasmid mediated AmpCβ-lactamase in common urinary tract isolates. A total of 143 isolates, includingE. coli,Klebsiella pneumonia, andProteus mirabilis, were collected from urinary tract infections cases in Egyptian hospitals. Plasmid encoded AmpC genes were detected by PCR in 88.46% of cefoxitin resistant isolates. The most prevalent AmpC gene family was CIT including CMY-2, CMY-4, and two CMY-2 variants. The second prevalent gene was DHA-1 which was detected inE. coliandKlebsiella pneumonia. The genes EBC, FOX, and MOX were also detected but in small percentage. Some isolates were identified as having more than onepAmpCgene. The overall sensitivity and specificity of phenotypic tests for detection of AmpCβ-lactamase showed that AmpC disk diffusion and inhibition dependent method by cloxacillin were the most sensitive and the most specific disk tests. PCR remains the gold standard for detection of AmpCβ-lactamases. This study represents the first report of CMY-2 variants of CMY-42 and CMY-102β-lactamase-producingE. coli,Klebsiella pneumonia, andProteus mirabilisisolates in Egypt.