Molecular characterization of emerging multi-drug resistant Escherichia coli isolates of swine from Northeast India

Abstract

Background: In India, trends of antibiotic resistance from animal source are largely confined to phenotypic listing of resistant antibiotics. Thus, considering the lack of comprehensive study, the present study aims to undertake molecular characterization of MDR faecal Escherichia coli from pigs raised on intensive farms of Northeast India, a region needing special attention due to sharing of international borders with the South East Asian countries. Methods: We analysed 125 faecal samples from apparently healthy swine of four farms located in Northeast India. Antibiotic sensitivity against 9 groups of antibiotics (25 agents) and ESBL identification were undertaken. MDR genes (blaTEM, blaCTX-M, blaSHV, blaOXA, aac, aadA, cat, sul1, sul2, strA, tetA, tetB) were further typed by PCR using specific primers. Plasmid profiling, RFLP, transconjugation/transformation, RAPD were done. All the techniques were carried out according to previously described protocols with minor variations. Results: 90% (113) of the isolates were MDR with 26 resistance patterns. Out of 125 isolates, 42 were ESBL suspected and 40 isolates possess single sized to multiple plasmids. There was high frequency of ESBL-positive isolates in a single farm (n = 42, 36 positive – 85.7%). Overall blaTEM was the commonest genotype (85.7%), blaCTX-M (61.9%), blaOXA(17%) and blaSHV was absent. One or multiple resistance genes were detected; sul2 (100%), strA (95.2%), tetA (92.9%), sul1 (76%), aadA (71.4%) and tetB (50%) followed by cat (42.9%) and aac (26.2%), all were likely plasmid-encoded and transmissible. RFLP and RAPD results gave a very diverse and heterogeneous nature of the isolates. Conclusion: This study is the first report of molecular characterization of MDR E. coli isolates from swine in Northeast India and highlights the alarming prevalence of MDR E. coli isolates in faeces of apparently healthy pigs on study farms. In Northeastern India, keeping view of the border proximity and existing trade, the probability of rapid spread of such emerging pathogens of public health significance is much higher. Lastly, surveillance of antibiotic resistance and antibiotics use in livestock farming in India is an urgent need.