Antibiotic resistance of isolates of Staphylococcus spp. and Streptococcus spp. causing mastitis on dairy farms in Ukraine

Mastitis is the most common pathology of cows that causes large economic losses to dairy farms. Mastitis is often caused by a group of infectious associated pathogens that can be transmitted among animals. Most often, the pathological process in subclinically and clinically sick animals is caused by coccal gram-positive microflora. A major problem is the mechanisms by which microorganisms acquire resistance to one or more antibacterial agents. Thus, standard treatment regimens used on the farm become ineffective. The publication presents the results of the study of antibiotic resistance of 45 isolates of Staphylococcus spp. and 22 isolates of Streptococcus spp. In this study, the chromogenic media CHROMagarTM Mastitis, CHROMagarTM Orientation and CHROMagarTM MH Orientation were used, which helped to speed up the isolation and identification of cultures. Phenotypic antibiotic resistance profiles were determined using the agar diffusion method. Staphylococcus aureus and coagulase-negative Staphylococcus (CoNS) showed a high level of resistance to beta-lactams of the penicillin class of benzylpenicillin – 60% and 66.7%. Streptococcus disgalactiae and Streptococcus agalactiae showed high resistance to tetracycline – 46.7% and 35.3%. At the same time, Streptococcus agalactiae had a high resistance to clindamycin of 35.3%. Streptococcus disgalactiae to benzylpenicillin – 29.4%, Streptococus uberis to clindamycin – 75%. The lowest resistance was observed to the antibiotic vancomycin in 6.7% of isolated staphylococci and 13.3% of streptococci. MAR index of more than 0.2 was observed in 75% of Streptococus uberis, 60% of CoNS and 52.9% of Streptococcus agalactiae. More than 50% of all studied isolates had multiple resistance to antibiotics most commonly used on Ukrainian farms. Key words: Streptococcus spp., Staphylococcus spp., antibiotic resistance, mastitis, infectious mastitis, gram-positive bacteria.