PCR-Based Detection of Extended-Spectrum β-Lactamases (blaCTX-M-1 and blaTEM) in Escherichia coli, Salmonella spp. and Klebsiella pneumoniae Isolated from Pigs in North Eastern India (Mizoram)

Cephalosporins are major antimicrobials used to treat serious infections. However, their effectiveness is being compromised by the emergence of extended-spectrum β-lactamases (ESBLs). A total of 138 enteric bacteria were isolated from 53 faecal samples of pigs collected from different districts of Mizoram, of which 102 (73.91 %) were Escherichia coli, 26 (18.84 %) were Salmonella spp. and 10 (7.25 %) were Klebsiella pneumoniae. Phenotypic confirmatory test (Double Discs Synergy Test) showed that 8 (5.80 %) E. coli isolates were ESBLs producer. PCR analysis confirmed that out of the eight isolate, 7 (5.07 %) harboured blaCTX-M-1 gene and/or blaTEM gene. Of the eight positive isolates, 7 (5.07 %) and 3 (2.17 %) were found to be positive for blaCTX-M-1 gene and blaTEM gene, respectively, of which 3 (2.17 %) isolates were positive for both the genes. Only 4 (2.90 %) E. coli isolates carried blaCTX-M-1 gene alone. Agarose gel electrophoresis showed that all the isolates were carrying plasmids ranging between 0.9 and ~30 kb. Out of the seven isolates positive for blaCTX-M-1 and/or blaTEM, 2 (1.84 %) isolates were confirmed for blaCTX-M-1 gene in their plasmid. Only one E. coli isolate was found to be positive for both the genes in its plasmid. The resistance plasmid could not be transferred to a recipient by in vitro horizontal gene transfer method.