Antimicrobial Susceptibility of Staphylococcus spp. Isolated from Mammary Parenchymas of Slaughtered Dairy Cows

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Abstract
The high prevalence of the great resistance to antimicrobials shown by the aetiological agents of infectious bovine mastitis, often leads to chronic recurrent mastitis, one of the main causes of early culling of dairy cows. The purpose of this study was to determine the in vitro susceptibility pattern 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 antimicrobials by the Kirby and Bauer standardized disc diffusion method; 84.44 % and 86.66 % of the 45 strains were resistant to ampicillin and penicillin, respectively. The highest sensitivity was to cephalothin (84.44 %), gentamicin (80 %) and to sulphazotrin (77.77 %). CNS showed higher resistance (P < 0.05) than SA. The in vitro susceptibility pattern of Staphylococcus spp. strains isolated from mammary parenchymas studied in the present investigation was similar to that observed in recent studies of in vitro and in vivo susceptibility patterns of Staphylococcus spp. isolated from cases of bovine mastitis.