DOI: 10.36347/sajb.2017.v05i11.003

Pages: 790-793

AmpC β- lactamases, which are often plasmid mediated, confer resistance to a wide variety of β-lactam and β-lactam inhibitor combinations. These are commonly detected phenotypically but the studies demonstrating their genotypic characterization are lacking. Hence, the present study was designed to determine the occurrence of plasmid mediated AmpC β-lactamase genes and their types among the clinical isolates of Escherichia coli. Two hundred and fifty consecutive, non-duplicate clinical isolates of E.coli recovered over a period of one year (January 2014-December 2014) were screened for AmpC production by cefoxitin resistance. Boronic acid disc potentiation (DDST) and modified 3 dimensional tests (M3DT) were used for phenotypic detection of AmpC production. AmpC genotypes ACC, FOX, MOX, DHA, CIT and EBC were detected by multiplex PCR. Among the 250 isolates, 90 (36%) were found to be cefoxitin resistant. DDST test was positive in 27 (30%) while M3DT in 29 (32.2%) of cefoxitin resistance (90) strains. By PCR, the plasmid encoded AmpC genes were detected in 27.7% (25/90) isolates which gave an overall prevalence of 10% (25/250). The gene detected in all the isolates was CIT only. Multidrug resistance (MDR) was noticed among 24% (6/25) AmpC producing strains. A high percentage of plasmid-encoded AmpC enzymes and MDR among them suggests plasmid mediated spread of drug resistance in E. coli in the present study. The exact detection of plasmid mediated AmpC β- lactamases (PMABLs) by using genotypic tests along with the phenotypic tests would be helpful in rational antimicrobial therapy, epidemiology and infection control.