Molecular types and antimicrobial resistance profile of Staphylococcus aureus isolated from dairy cows and farm environments

Abstract

The aim of this study was to assess the prevalence of Staphylococcus aureus in cows with subclinical mastitis and detect enterotoxin genes and patterns of antimicrobial resistance. Out of 180 animals, subclinical mastitis was detected in 78 cows (46.99%) and three buffalo (21.43%). The prevalence of clinical mastitis was low (3.61%). S. aureus could be isolated from mastitic milk (67/81), udder swabs (38/81), floor swabs (13/27), milking machine liner (5/8), and healthy animals- milk (12/22). All the strains were confirmed by PCR targeting amplification of the femA gene. Out of 52 PCR-confirmed S. aureus samples, 17 were enterotoxin-producing strains. The pattern of enterotoxin production was revealed as: seb (1.92%), sec (21.15%), sed (7.69%), and see (1.92%). The pattern of superantigens and methicillin resistance was revealed as: etb (1.92%), tst1 (25%), and mecA (3.85%). Combination of sec and tst1 and the rare distribution of sea, seb, and sed was observed. S. aureus isolates were sensitive to netilmicin (85.88%), amikacin (80%), tobramycin (76.47%), and gentamicin (68.24%) and resistant to penicillin (91.76%), oxacillin (71.76%), and kanamycin (63.53%). Antimicrobial resistant genes blaZ, ermB, and tetK were also detected in the isolates. This study provides a baseline for monitoring antimicrobial resistance in S. aureus strains associated with bovine mastitis in India.