Monitoring of antibiotic sensitivity of causative agents of subclinical mastitis of cows on dairy farms of the Ternopil region

Abstract

Goal. To determine the sensitivity of the causative agents of subclinical mastitis of cows to antimicrobial drugs. Methods. The study was conducted during 2024–2025 in 9 dairy farms of the Ternopil region with a livestock of 200 to 1,400 Holstein cows with an unobtrusive method of keeping animals. Subclinical mastitis of cows was diagnosed by the mastidin test. Methods were used: cultural microbiological (sowing samples on nutrient media, testing for oxidation-fermentation of carbohydrates by bacteria, studies of the hemolytic activity of bacteria on blood agar, catalase activity of pure cultures, DNA activity of staphylococci and their plasmocoagulation reactions), as well as microscopic (microscopy of pure cultures of microorganisms). Sensitivity of mastitis pathogens to antibiotics was determined by a disc-diffusion method. The obtained data were processed by the method of variational statistics using the Statistica 10.0 program. Results. It was established that in dairy farms, the most common pathogens of subclinical mastitis of cows were microorganisms of the genus Staphylococcus (from 30.8 to 90.3% of cases of diseases), as well as the genus Streptococcus and bacteria of the E. coli group (BECG) (from 6.7 to 38.4%). Antimicrobial susceptibility studies indicated the presence in most isolated pathogens of multiple antibiotic resistance. From 50.3 to 100% of the isolated staphylococci of mastitis pathogens showed resistance to 13 antimicrobial drugs, from 7.7 to 42.7% of cultures — to 10 drugs from 23 studied, 51.1–100% of microorganisms of the genus Streptococcus and BECG were resistant to 9 drugs, almost 48.9% of their strains — to 14 antibiotics. Conclusions. To reduce the occurrence of resistance in microorganisms and its spread, to develop effective treatment regimens for mastitis of cows, it is necessary to systematically monitor the antibiotic resistance of pathogens in farms, which involves the diagnosis of mastitis, the isolation of pathogens, and the study of their sensitivity to antimicrobial drugs.