MOLECULAR CHARACTERIZATION OF VIRULENCE GENES IN ESCHERICHIA COLI ISOLATED FROM NEWBORN DIARRHEIC CALVES

Document Type : Original Article

Authors

1 Department of Bacteriology, Mycology and Immunology, Faculty of Veterinary Medicine, Kafrelsheikh University 33516, Egypt.

2 Animal Health Research Institute

Abstract

The present study was designed to elucidate the prevalence and characteristics of pathogenic Escherichia coli strains from diarrheic calves. A total of 120 fecal samples were collected from diarrheic calves from different cow's farms at Kafrelsheikh Governorate, Egypt. E. coli was isolated with a percentage of 20% (24/120). Serogrouping of E.coli isolates showed 12 types belong to different "O" serogroups; the most prevalent serogroups among isolates were O111, O103, O26, O55, O128, O15, O91 and O20. A total of 12 E. coli isolates were screened by multiplex PCR assay for the presence of virulence genes characteristic for E.coli, that is, shiga-toxin producing gene(s) (stx1, stx2), intimin (eaeA) and enterohemolysin (hlyA). Out of the 12 isolates, 11 were positive for one or both stx1and stx2 (91.6%), 8 isolates for hlyA(66.6%) and 4 isolates for eaeA (33.3%). PCR results showed that 9 (75%) isolates carried stx1 gene, 9 (75%) possessed stx2 gene while 7 isolates (58.3%) gave positive amplicon both for stx1 and stx2 genes. All shiga toxin genes (stx1 and/or stx2) positive samples were positive for the hlyA and eaeA genes. Both virulence genes eaeA and hlyA in the same sample were observed in 36.36% of the shiga toxin positive strains. As a result, this study shows that stx1 and stx2 were found as the most common virulence gene markers of E. coli strains isolated from calves with diarrhea.

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