DETECTION OF ENTEROTOXIN AND HEMOLYSINS GENES IN Staphylococcus aureus ISOLATED FROM BOVINE MASTITIS

Staphylococcus aureus is an important pathogen associated with disease in human and animals, besides being the most common etiological agent of clinical and subclinical bovine mastitis. Persistence of S. aureus in the mammary gland is related with the production of more than 30 virulence factors. The aim of this study was to determine the frequency of genes encoding staphylococcal enterotoxin (sea, seb, sec, sed and see) and α and β hemolytic toxins (hla and hlb) in S. aureus strains isolated from bovine mastitis. A total of 110 strains of S. aureus isolated from bovine mastitis in the states Rio de Janeiro and Minas Gerais, belonging to the Embrapa´s collection (1994 to 2000) were used in the study. Strains were reactivated and cultivated on Agar Brain Heart Infusion at 37°C for 24 h. DNA extraction was performed by the guanidine method. The strains were confirmed as S. aureus, by PCR for detection of gene nuc. It was also used multiplex PCR for the identification of enterotoxins genes sea, seb, sec, sed and see and for hemolysin genes hla and hlb. A hundred percent (110/110) of the strains were confirmed as S. aureus. Moreover, 81.82% (90/110) of the strains harbored both genes hla and hlb, whereas 4.55% (5/110) did not exhibit neither hla and hlb genes. It was also observed that 12.73% (14/110) of the strains had only the gene hla but not hlb, while, only one strain [0.91% (1/110)] exhibited the gene hlb but not hla. On the other hand, it was observed that 100% (110/110) of the strains did not have harbored any enterotoxin genes sea, seb, sec, sed and see. In conclusion, the genotypic results of the present study showed that there was a high percentage of S. aureus isolated from cattle that harbored both hla and hlb hemolytic toxins genes; moreover, interestingly, all strains investigated in this study for the presence of enterotoxinas sea, seb, sec, sed and see genes did not exhibit none of these genes that are associated with food poisoning. These results might help us to understand the distribution of enterotoxin and hemolysin genes among bovine mastitis isolates, which is important for the epidemiology of the disease in cattle and in the human population.