Determination of Inherent Antibiotic Drug Resistance and Pathogenic Potential of Different E. coli Phylotypes from Diarrheic Calves in Arid and Semiarid Regions of India

Abstract India has a large population of dairy animals, and calf diarrhea is a major concern in the dairy sector. Escherichia coli have varying degrees of virulence; however, this study aimed to understand the association of different phylotypes with calf diarrhea and elucidate their inherent virulence potential as well as their antimicrobial drug resistance potential. In the current study, the phylogenetic analysis showed that the majority of the isolates (19/35; 54.28%) belonged to phylotype B1, followed by A (9/35; 20%), E (4/35; 11.42%), C (2/35; 5.71%), and F (2/35; 5.71%).On the basis of virulence genes, isolates were classified into ETEC (25.71%), STEC (48.57%) and non-ETEC/STEC (25.71%). PhylotypesB1 and F predominated in virulence potential, followed by phylotypesC and E. Both isolates of phylotype F were found to be STEC pathotypes. PhylotypesF and B1 were found to carry antimicrobial resistance genes against all four classes of antimicrobials, while phylotype E carried antimicrobial drug resistance genes for three classes, and phylotypes C and A showed the least number of resistance genes. In conclusion, isolates belonging to phylotypes B1 and F were of high pathogenic potential due to the carriage of a higher number of virulence and antibiotic resistance genes.