Isolation, Identification, biochemical and molecular characterization of potential source of enterotoxigenic strains of Staphylococcus aureus from the bovine raw and mastitis milk

Abstract

Staphylococcus aureus is the primary cause of subclinical bovine mastitis, which presents serious problems for the dairy sector. The purpose of this study was to assess the contribution of coagulase-positive S. aureus to subclinical mastitis and investigate any possible risk factors associated with it. One hundred milk samples were aseptically taken from cattle and buffalo in Pakistan's Sheikhupura and District Lahore. The Surf Field Mastitis Test (SFMT) was used to screen the samples, and those that tested positive were processed for bacterial isolation, biochemical characterization, and molecular identification using PCR that targeted the genes for coagulase (coa), mecA, and enterotoxin A. Of the positive samples, 38.6 % (27/70) had no bacterial growth and 61.4 % (43/70) produced staphylococcal isolates on mannitol Agar. All isolates had the coagulase gene (720 bp), and 46.5 % (20/43) of them had S. aureus validated by PCR analysis. Notably, the presence of the mecA gene (630 bp) indicated that 40 % (8/20) of the S. aureus isolates were methicillin resistant. The enterotoxin A gene was not detected in any of the isolates, indicating that S. aureus-induced mastitis is not associated with it. The results show a strong correlation between the occurrence of the disease and possible risk factors, highlighting S. aureus coagulase-positive strains as a key pathogen in subclinical mastitis. This study emphasizes the necessity of focused approaches to better prevent mastitis, manage S. aureus infections, and lessen the effects on the dairy industry.