EN
The purpose of the study was determining the in vitro sensitivity of Streptococcus agalactiae, other Streptococcus sp., Staphylococcus aureus, coagulase-negative staphylococci, Escherichia coli, and Arcanobacterium pyogenes strains to antibiotics commonly used in veterinary praxis. These pathogens were isolated from cows with clinical or subclinical mastitis in 2006-2007. The activity of 10-14 antibiotics to each bacterial species was examined. The sensitivity was tested by disk diffusion method and performed according to CLSI guidelines in Mueller-Hinton agar. Streptococcus agalactiae strains were mostly sensitive to amoxicillin (93.6%), cefquinom (96%), cefapirin (94.1%), cefoperazone (88.9%), bacitracin (87.1%), and cephalexin (79%). Other streptococci were most susceptible to amoxicillin (91.4%), cefquinom (84.1%), bacitracin (89%), and cephalexin (79.7%). Amoxicillin/clavulanic acid (97.4%), cloxacillin (90%), cefquinom (92.9%), cephalexin (90.5%), and bacitracin (88.6%) were the most active against Staphylococcus aureus. Coagulase-negative staphylococci were sensitive to amoxicillin/clavulanic acid (100%), cefquinom (89.2%), cephalexin (89.3%), bacitracin (86.1%), rifaximin (86.8%), and cefapirin (86.5%). Norfloxacin (85.1%), enrofloxacin (83.9%), and marbofloxacin (84.4%) were active against Gram-negative bacilli. Only amoxicillin (87.1%) from ten analysed antibiotics exhibited very high activity against Arcanobacterium pyogenes.