Antimicrobial sensitivity of pathogens causing subclinical mastitis in goats in Bulgaria

The aim of this study was to analyze the antibacterial sensitivity of microbial isolates causing subclinical mastitis in goats. The classical Bauer disk-diffusion assay was used to determine the sensitivity of the coagulase-negative staphylococcal (CNS) isolates and isolates belonging to other genera. In all the tested isolates, the highest rates of resistance were observed to be to Oxacillin (81.25%) and Novobiocin (75%), followed by Penicillin (68.75%), Tetracycline (37.5%) and Amoxycillin (31.25%). There was low prevalence of resistance to Cefotaxime (12.5%), Thiamphenicol (6.25%), Cefuroxim (6.25%), Cefuroxim (6.25%), Amikacin (6.25%), Sulfamethoxazole + Ttrimethoprim (6.25%) and Gentamicin (6.25%). Staph. intermedius showed resistance to the highest number of antimicrobial agents, four ones (28.57%), whereas Staph. haemolyticus was the least resistant isolate, which was sensitive to nearly all of the tested antimicrobials and showed intermediate sensitivity to only three ones (21.43%). Among the microorganisms other than CNS, B.brevis and Å.coli showed resistance to the highest number of antimicrobial agents (42.86%).