Occurrence and detection of AmpC β-lactamases among Enterobacteriaceae isolates from patients at Ain Shams University Hospital

Background: AmpC β-lactamases are often plasmid mediated that hydrolyze all β-lactam antibiotics except cefepime and carbapenems. Aim of the study: We aimed to evaluate the presence of AmpC β-lactamase among Enterobacteriaceae isolates separated from patients with nosocomial infections,and to detect the genetic basis for AmpC production in these strains. Subjects and methods: 50 AmpC β-lactamase Enterobacteriaceae were analyzed for the presence of AmpC production. Three phenotypic AmpC confirmation assays (AmpC E test,the disk approximation test,Amp C EDTA disc) were able to detect the majority of AmpC-positive strains correctly. Molecular detection of plasmid mediated AmpC by multiplex PCR was conducted on them. Results: The results show that from the 148 total isolates obtained from ICU admitted patients with suspected nosocomial infections,50 (33.8%) were AmpC β-lactamase isolates. For the 50 AmpC isolates,all phenotypic Amp C tests gave a positive result. Among these isolates,plasmid encoded AmpC genes were detected by multiplex PCR in 46 (92%) isolates,which included Klebsiella pneumoniae (n = 22) (47.8%),Escherichia coli (n = 15) (32.6%),and Proteus mirabilis (n = 9) (19.6%). One E. coli,one K. pneumoniae,and two P. mirabilis isolates showed no AmpC gene. The most prevalent AmpC gene was that belonging to family CMY-1 which was detected in 73.9% (34/46) of all isolates. Conclusion: It could be concluded that: Amp C producing isolates among Enterobacteriaceae strains have been increasingly recognized in the Ain Shams University Hospital.Thus,molecular identification of the genes encoding AmpC would be essential for a reliable epidemiological investigation of their transmission in hospitals. © 2015 Production and hosting by Elsevier B.V.