Analysis of the sensitivity of microorganisms to antimastitis drugs

In 2023, we studied 448 milk samples from 8 agricultural enterprises in the Vologda region. Of these, 490 cultures (109.4 %) were isolated, including pathogenic and opportunistic microorganisms – 174 cultures (35.5 %), of which coccoid microflora (S. aureus, opportunistic staphylococci, group C and B streptococci) accounted for 131 cultures (26.7%), enterobacteria (E. coli, Citrobacter freundii) allocated 3 times less – 43 crops (8.8 %). The percentage of microbial excretion varied markedly between farms and varied within the following limits: S. aureus from 0 to 32.3 %, opportunistic staphylococci from 4.2 to 29.4 %, group C and B streptococci from 0 to 29.8 %, enterobacteria from 0 to 15.6%. The sensitivity to complex antimicrobial drugs of a particular type of microorganism isolated from the milk of cows of the same farm was determined up to 5 times a year. These were mainly representatives of gram–positive (S. aureus) and gram-negative (E. coli) microflora in the 4th and 8th farms, respectively. In 5 other farms, sensitivity was determined 2 times and in 1 farm 4 times per year. Over the entire study period, antibiotic sensitivity was studied in 16 cultures of S. aureus, 13 cultures of opportunistic staphylococci, 13 cultures of E. coli and 5 cultures of streptococci of groups C and B. In two farms, the sensitivity of isolated microorganisms (E. coli, S. aureus) to the drugs used to treat cow mastitis was analyzed at different time intervals – in the 4th farm, the sensitivity was analyzed 6 months after the first determination, and in the 8th farm after 8 months. According to the research results, the growth retardation zones of microorganisms for antibacterial agents used in farms decrease after 6 and 8 months, that is, microbial cultures acquire resistance to complex antimicrobial drugs used for a long time.