Characterization of enterovirulent Escherichia coli isolated from yak calves died of diarrhoea in India

Abstract

Shiga toxin producing (STEC), enteropathogenic (EPEC) and enterotoxigenic Escherichia coli (ETEC) were isolated from 29 diarrhoeic yak calves from two districts of Arunachal Pradesh, India (West Kameng and Tawang) during 2005 to 2011. The STEC (28) and EPEC (12) isolates belonged to 25 different O serogroups. Among the 28 STEC isolates, 8 (28.5%) isolates carried only stx1, 10 (35.7%) isolates were positive for both stx1 and stx2, 10 (35.7%) isolates carried only stx2. The stx variants such as stx1c, stx2c, stx2d and stx2e were detected in 7 (25%), 9 (32.1%), 1 (3.5%) and 4 (14.28%) isolates, respectively. Among the 12 EPEC isolates, 2 (4.65%) strains were ‘typical’ possessing bfpA gene. The ehxA and saa genes were present in 19 and 4 isolates, respectively. Among the 14 ETEC isolates, 6 (42.8%), 7 (50%), 5 (35.7%), 5 (35.7%), 7 (50%) and 6 (42.8%) isolates carried genes coding for STa, STb, LT, F5, F41 and EAST1, respectively. The present study detected LT, STb, F41 as the most prevalent type in yaks associated with diarrhoea. Further, the STEC, EPEC and ETEC isolates showed resistance against furazolidone (40%), nitrofurantoin (39%), nalidixic acid (38%), erythromycin (38%), kanamycin (38%), amikacin (37%). The dendrogram revealed clonal relationship among the isolates after RAPD/ERIC analysis. The study could not detect any specific RAPD/ERIC cluster associated with origin, serotypes or virotypes of the isolates. Thus, it was concluded that genetically diverse, multi-drug resistant enterovirulent E. coli were associated with death due to diarrhoea in yak calves in India.