The qualitative and quantitative phenotypic expression of haemolysins along with presence of genes encoding a- and b-haemolysin were determined in 32 Staphylococcus aureus isolates from milk of cattle and buffalo with clinical mastitis. Overall haemolytic reactions on sheep blood agar revealed five (15.62%) isolates to show complete haemolysis, 20 (62.50%) isolates to show partial haemolysis, four (12.50%) isolates to show both complete and partial and three (9.37%) did not show any haemolysis. All the 32 (100%) isolates from both cattle (16) and buffalo (16) produced a-toxin, the maximum titre of which was 1: 5120. Whereas beta-toxin was produced by 11 (68.75%) cattle isolates and by seven (43.75%) buffalo isolates with maximum titre of 1:1280 and 1:240, respectively. Delta toxin was detected to be produced by only five (15.62%) isolates, two from cattle and three from buffalo. The genotypic characterization revealed an overall hla gene prevalence in 96.8% isolates from both cattle and buffalo wherein a single amplicons of 534 bp was produced while hlb gene was amplified by 84.3% (13 cattle and 14 buffalo isolates) producing single amplicon of 833 bp.
Staphylococcus aureus, Cattle, Buffalo, Mastitis, Haemolysis, hla and hlb gene
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