Investigation of Virulence Factors in Escherichia Coli Isolated from Clinical and Subclinical Bovine Mastitis

Escherichia coli, an opportunistic environmental pathogen, is one of the commonest causes of bovine clinical mastitis in the early lactation period. Shiga toxin-producing E. coli (STEC) whose pathogenesis is associated with enterotoxigenic genes (stxI, stxII, and eaeA) cause serious acute illness and long-term side effects in both animals and humans. The aim of this study was to investigate the rate of virulence factors of E. coli isolates from cows with mastitis in the Chaharmahal-Bakhtiari province, Iran. Milk samples from 400 cows with mastitis were obtained, cultured in MacConkey agar to select Gram-negative microorganisms and E. coli was further identified by microbiological tests. After DNA extraction, multiplex PCR amplification using specific primers was performed. Out of 400 samples, 42 specimens were found to be E. coli-positive according to the microbiological tests. The PCR results indicated that 14 out of 42 isolates carried the eaeA gene, 4 isolates were positive for the gene of F41 fimbriae and 10 for stxI and stxII genes.