Extended-spectrum β-lactamases producing multidrug resistance Escherichia coli, Salmonella and Klebsiella pneumoniae in pig population of Assam and Meghalaya, India

AIM: The present study was conducted to record the prevalence of extended spectrum β-lactamases (ESBLs) producing Escherichia coli, Salmonella spp., and Klebsiella pneumoniae from pig population of Assam and Meghalaya and to record the ability of the resistant bacteria to transfer the resistance genes horizontally. MATERIALS AND METHODS: Fecal samples (n=228), collected from pigs of Assam (n=99) and Meghalaya (n=129), were processed for isolation and identification of E. coli and Salmonella spp. All the isolates were tested for ESBLs production by double disc synergy test (DDST) followed by screening for ESBLs producing genes (bla(TEM), bla(SHV), bla(CTX-M), and bla(CMY)) by polymerase chain reaction (PCR). Possible transfer of resistance encoding genes between enteric bacterial species was carried out by in vitro and in vivo horizontal gene transfer (HGT) method. RESULTS: A total of 897 enteric bacteria (867 E. coli and 30 Salmonella) were isolated and identified. Altogether 25.41% isolates were confirmed as ESBL producers by DDST method. Majority of the isolates were E. coli followed by Salmonella. By PCR, 9.03% isolates were found positive for at least one of the target resistance genes. bla(SHV) was absent in all the isolates. bla(CMY) was the most prevalent gene. All the E. coli isolates from Assam were negative for bla(TEM). A total of 2.76% isolates were positive for bla(TEM) + bla(CMY). On the other hand, 0.67% isolates were positive for bla(CTX-M) + bla(CMY) genes. Only 0.33% isolates carried all the three genes. Altogether, 4.68% bacteria carried the resistance encoding genes in their plasmids. bla(TEM) gene could be successfully transferred from Salmonella (donor) to E. coli (recipient) by in vitro (5.5-5.7×10(−5)) and in vivo (6.5×10(−5) to 8.8×10(−4)) methods. In vivo method was more effective than in vitro in the transfer of resistance genes. CONCLUSION: The pig population of Assam and Meghalaya are carrying multidrug resistance and ESBLs producing E. coli and Salmonella. The isolates are also capable to transfer their resistance trait to other bacterial species by HGT. The present finding could be considered as a serious public health concern as similar trait can also be transmitted to the human commensal bacteria as well as pathogens.