Detection of mecA, mecI and mecR1 genes in methicillin-resistant Staphylococcus aureus strains of bovine origin isolated from Family Dairy Farms, Mexico

Abstract

In Mexico, as in other countries, Staphylococcus aureus is one of the main pathogens causing bovine Mastitis. This disease is usually treated with β-lactam antibiotics; however, in Mexico there are some reports of resistant Staphylococcus aureus to these antibiotics. The molecular mechanisms of methicillin-resistant Staphylococcus aureus have not been widely studied yet. In this study, we identified Staphylococcus aureus isolated from bovines by detecting the femB gene, while resistance to β-lactam antibiotics was determined by in vitro antimicrobial susceptibility, and the genes blaZ, mecA, as well as regulator genes mecR1 and mecI, were identified by PCR. The results showed Staphylococcus aureus presenting higher resistance to β-lactam antibiotics and to erythromycin. The blaZ gene was identified in only 38 isolates (44.7%). Four Staphylococcus aureus isolates carried the mecA gene and were considered as methicillin-resistant Staphylococcus aureus; they were grouped as follows according to their regulator genes: one carried both mecI and mecR1genes (group A); in two of them neither the mecI gene nor the mecR1 gene (PB domain) were found (group C); and one isolate did not carry any regulator gene (group D). In conclusion, we identified the presence of methicillin-resistant Staphylococcus aureus and Staphylococcus aureus resistant to β-lactam antibiotics in family dairy production in the State of Mexico. This resistance might be regulated by different genotypes of the mecA, mecR1 and mecI genes present in methicillin-resistant Staphylococcus aureus.