Characterization of shiga toxin producing (STEC) and enteropathogenic Escherichia coli (EPEC) in raw yak (Poephagus grunniens) milk and milk products.

Thirty-one shiga toxin-producing (STEC) and 6 enteropathogenic Escherichia coli (EPEC) were isolated from 87 raw yak milk and 63 'churpi' samples. Of 18 stx(1) positive isolates (48.6%), 14 carried stx(1c) (77.7%). Subtyping of 28 stx(2) positive isolates (75.7%) revealed the presence of stx(2c) (9, 32.1%), stx(2d) (3, 10.7%), stx(2e) (1, 3.57%) and stx(2f) (3, 10.7%) variants. Furthermore, intimin (eaeA), enterohaemolysin (ehxA), autoagglutinating adhesin (saa), iha (adherence conferring protein), efa1 (EHEC factor for adherence), bundle forming pilli (bfpA) and toxB (type III secreted protein encoded on LEE Island, similar to toxin B of Clostridium difficile) genes were detected in 14, 16, 12, 4, 3, 2 and 2 isolates, respectively. Univariate and multivariate analysis depicted that both stx(1) and stx(2) or their variants were more likely to occur in isolates from Arunachal Pradesh (p<0.04) rather than Sikkim. Dendogram constructed on the basis of RAPD and ERIC PCR profile distributed the STEC and EPEC isolates in separate clusters irrespective of their sources and serotypes. The STEC and EPEC isolates exhibited resistance against erythromycin, amikacin, azithromycin, amoxicillin, ampicillin+cloxacillin, cephalothin, furazolidone, gentamicin, kanamycin, streptomycin and tetracycline. This is the first ever report on occurrence and characterization of STEC and EPEC isolated from yak milk and milk products.