Research Article of American Journal of Microbiology and Immunology
A contribution on Coliforms causing mastitis in cows with reference to serotypes and virulence factors of E. coli isolates
Sayed, S. M.
Egypt- Animal Health Research Institute (Assiut Regional Lab., Bacteriology Dept.)
Escherichia coli (E. coli) is the predominant coliform species causing intramammary infections. Where in the present study, E. coli isolates were 18 strains (17.82%) followed by Enterobacter aerogenes 3 strains (2.97%) and Klebsiella pneumoniae one strain (0.99%) from 101 clinical mastitic milk samples of cows. Eighteen E. coli isolates were serotyped to nine different serogroups; O111:H4 (3), O127:H6 (3), O26 (2), O126 (2), O119:H6 (1), O114:H21 (1), O55:H7 (1), O44:H18 (1), O124 (1) and (3) untyped. Virulence tests were performed on the 18 isolated E. coli, it was found that 15 isolates (83.3%) were serum resistant, 13 isolates (72.2%) had Congo Red binding activity, 6 isolates (33.3%) were invasive and one isolate (5.6%) had haemolytic activity. PCR was applied to detect the presence of Shiga like toxin producing E. coli (stx1 and stx2 genes) on the nine different strains (one strain for each serogroup), where stx1 and stx2 were found in 8 (88.9%) and 4 (44.4%) of the nine examined strains, respectively. While stx1 and stx2 genes were found together in 3 strains (33.3%). Conclusions: E. coli isolates usually posses one or more virulence factors that may help in establishment at the infection site and subsequently causing clinical bovine mastitis.
Keywords: Coliforms, E. coli, serotypes, virulence factors, stx1 and stx 2.