Antimicrobial susceptibility of Staphylococcus spp. isolated from mammary parenchymas of slaughtered dairy cows

The high prevalence of the great resistance to antimicrobials shown by the aetiological agents of infectious bovine mastitis, often leads to chronic r ecurrent mastitis, one of the main causes of early culling of dairy cows. T he purpose of this study was to determine che ill vitro susceptibility patt ern of Staphylococcus spp. isolated from mammary parenchymas of slaughtered dairy cows, to different anti-microbials. A total of 45 Staphylococcus spp . strains [33 coagulase-negative Staphylococcus (CNS) and 12 Staphylococcus aureus (SA)] were used. These strains were tested with 12 different antimi crobials by the Kirby and Bauer standardized disc diffusion method; 84.44% and 86.66% of the 45 strains were resistant to ampicillin and penicillin, r espectively. The highest sensitivity was to cephalothin (84.44%), gentamici n (80%) and to sulphazotrin (77.77%). CNS showed higher resistance (P < 0.0 5) than SA. The in vitro susceptibility pattern of Staphylococcus spp. stra ins isolated from mammary parenchymas studied in che present investigation was similar to that observed in recent studies of in vitro and in vivo susc eptibility patterns of Staphylococcus spp. isolated from cases of bovine ma stitis.