Abstract

One important feature of Staphylococcus aureus virulence is due to its ability to attack the cell membrane of host cell with a large array of membrane-damaging toxins and peptides such as hemolysins. Therefore, this study was undertaken to perform phenotypic and genotypic characterization of S.aureus hemolysins isolated from milk of cows with clinical mastitis. A total of 173 milk samples were collected from two dairy farms and were subjected for S.aureus bacteriological isolation procedures, 55 S.aureus isolates have been recovered with a percentage of 31.79%. S.aureus isolates were evaluated for their Alpha (  ) and Beta (  ) hemolysins production on sheep and bovine blood agar. Alpha hemolysin were detected in 50 (90.90%) strains, beta-hemolysin were detected in 47 (85.45%) strains either alone or in combined. However, non-hemolytic S.aureus strains were detected in 5 (9.09%) strains. On titration,  -toxin titers were much more than that for  -toxin. Based on PCR results, the overall prevalence rate of hla was higher than hlb and these results were correlated with their phenotypic hemolytic activity on blood agar plates. In conclusion, the high prevalence rate of  and  -hemolysins in S.aureus isolated from mastitis suggests that hemolysins could have significant role in pathogenesis of mastitis, in addition, the capability of S.aureus strains to produce alpha and beta hemolysin indicates that these toxins might be necessary for the establishment of the S.aureus in mammary glands.

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