Molecular characterization of Shiga-toxigenicEscherichia coliisolated from diverse sources from India by multi-locus variable number tandem repeat analysis (MLVA)

Abstract

SUMMARYIn a first study from India, a diverse collection of 140 environmental and clinical non-O157 Shiga-toxigenicEscherichia colistrains from a large geographical area in north India was typed by multi-locus variable number tandem repeat analysis (MLVA). The distribution of major virulence genesstx1,stx2andeaewas found to be 78%, 70% and 10%, respectively; 15 isolates were enterohaemorrhagicE. coli(stx1+/stx2+andeae+). By MLVA analysis, 44 different alleles were obtained. Dendrogram analysis revealed 104 different genotypes and 19 MLVA-type complexes divided into two main lineages, i.e. mutton and animal stool. Human isolates presented a statistically significant greater odds ratio for clustering with mutton samples compared to animal stool isolates. Five human isolates clustered with animal stool strains suggesting that some of the human infections may be from cattle, perhaps through milk, contact or the environment. Further epidemiological studies are required to explore these sources in context with occurrence of human cases.