Detection and Characterization of AmpC Β-Lactamases in Indian Clinical Isolates of Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca

The aim of the study was to determine the prevalence of AmpC producing E. coli, Klebsiellapneumoniae and Klebsiellaoxytoca and to evaluate and compare four different phenotypic methods viz; Modified Three Dimensional Test, AmpC Disk Test, AmpC Disk Test with Tris-EDTA and Inhibitor based detection test for the detection of AmpCβ-lactamases in these isolates, collected during a period of 2003 to 2009 from various hospitalsof Delhi, India. Characterization of these enzymes was carried out by polymerase chain reaction (PCR) as well as by nucleotide sequencing. Phenotypic results showed that Inhibitor based detection test, Modified three dimensional test and AmpC disk test detected 40.8% of E. coli and 34% of Klebsiella spp. to be AmpC producers. However, Inhibitor based detection test was found to be simple, highly specific and sensitive in detecting these enzyme producers. PCR and nucleotide sequencing showed the presence of blaCMY-2 and blaACT-1 genes in all the positive isolates.