Prevalence of extended-spectrum-ß-lactamase (ESBL) and metallo-ß-lactamase (MBL) antibiotic resistance genes in Enterobacter species in Pretoria Academic Hospital

Abstract

The prevalence of blaCTX-M, blaSHV and blaTEM extended-spectrum beta-lactamases (ESBLs) and VIM metallo-beta-lactamases (MBLs) producing Enterobacter are increasing worldwide. Multidrug resistance due to the presence of these resistance genes in the Enterobacteriaceae family is an important reason for therapy failure during treatment with 3rd generation cephalosporins and carbapenems. Methods for the detection of ESBL and MBL can be phenotypic or genotypic. Molecular techniques such as multiplex polymerase chain reaction (PCR) assays can be used for the simultaneous detection of various resistant genes. This study investigated the prevalence of ESBLs and MBLs antibiotic resistance genes in Enterobacter species in Pretoria Academic Hospital using a multiplex PCR assay, which simultaneously detected the blaCTX-M, blaSHV, blaTEM and VIM genes. Ninety seven (97) consecutive clinical Enterobacter isolates (16 E. aerogenes and 81 E. cloacae isolates) were collected from the diagnostic division of the Department of Medical Microbiology. The following results were obtained in E. aerogenes: blaCTX-M, blaTEM, blaSHV were detected in 13% (2/16) while blaCTX-M, blaTEM were detected in 13% (2/16) of the isolates. A total of 75% (12/16) of the isolates were negative for all three genes. In the E. cloacae isolates: blaCTX-M, blaTEM, blaSHV were detected in 7% (6/81) while blaCTX-M, blaTEM were detected in 28% (23/81) and blaTEM, blaSHV were detected in 20% (16/81). Only the blaTEM gene was detected in 6% (5/81) of the E. cloacae isolates. In 30% (21/81) of isolates none of the genes were identified. None of the Enterobacter isolates analysed in this study were positive for the VIM gene. According to the results obtained in this study, the prevalence of ESBL antibiotic resistance genes in Enterobacter species is 56% (54/97) in this clinical setting. It is therefore essential to include molecular technique as part of the surveillance to monitor the circulation of these resistant genes in a clinical setting.