Detection of plasmid-mediated AmpC-?-lactamases among clinical isolates:Adiagnostic and therapeutic challenge

Introduction and Aim: The AmpC enzymes are cephalosporinases that impart resistance to a wide range of ?-lactam, ?-lactam/?-lactamase inhibitor combinations, and monobactams, but are sensitive to fourth generation cephalosporins and carbapenems. Identification techniques for AmpC beta lactamases are not yet adapted for the clinical laboratory, which is likely to underestimate this resistance mechanism. Detection and determination of the magnitude of AmpC is therefore critical for successful treatment and for the prevention and control of these resistant bacteria.The present study was intended to determine the prevalence of plasmid mediated AmpC genotypes among clinical isolates at atertiary care hospital of South India.   Materials and Methods:It was a cross-sectional study. 94 isolates [E. coli (n=31) and K. pneumoniae (n=63)] were recovered between January 2020 and June 2020. Samples underwent an initial cefoxitin screening test and a subsequent genotypic study with multiplex polymerase chain reactions for AmpC subtypes. Antimicrobial susceptibility characteristics of these clinical isolates have also been investigated.   Results:Thirty-seven clinical isolates were cefoxitin-resistant and genotypic analysis showed that 22 cefoxitin-resistant isolates are AmpC positive, respectively. These AmpC producers are multidrug-resistant and Klebsiella pneumoniae is the dominant strain among them. Among them single AmpC production mechanism included blaDHA producers (n=5), blaCIT producers (n=4), blaEBC producers (n=3) and blaFOX producers (n=1) and 9 isolates showed multiple AmpC genes.   Conclusion: AmpC isolates emergence is worrisome and emphasizes the need for further surveillance in this region. It is proposed that hospitals improve the surveillance of AmpC ?-lactamase in clinical isolates and suggest using carbapenems to treat infections caused by AmpC-producing bacteria.