This article presents the statistical data and results of own research on microbiological study of the udder secret from cows with subclinical and clinically expressed mastitis in 20 farms (27 dairy farms) of dairy direction of the Vologda region. The decisive value in the frequency of seeding from the affected shares of the udder of cows is coccal microflora, the largest share of which is occupied by conditionally pathogenic and pathogenic staphylococci (30,2% and 23,2%, respectively). Significant variability (from 0 to 100,0) of indicators of particular microflora from the secretion of the udder of cows with mastitis indicates significant differences in the etiology of the disease on farms region. Pathogenic and opportunistic staphylococci containing enterotoxins of types A, C, D, B and E from the udder secret indicates the potential danger of such milk for both calves and people. The article is executed in accordance with the state order № 0578-2014-0030.

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As a result of microbiological studies of the udder secretion of lactating cows, conducted in ten livestock farms in the Vologda, Yaroslavl and Kostroma regions, 280 cultures of pathogenic and opportunistic microorganisms, as well as lactic acid and other non-pathogenic flora were isolated from 271 samples of the studied milk. At the same time, it was revealed that S. aureus occupies a leading place in the spectrum of the selected pathogenic microflora. In 2019, the species composition of the pathogenic microflora in the above-listed farms was represented by isolates of Staphylococcus aureus – in 24,3% of cases, then Streptococcus Agalactiae– in 9,3%, enterobacteria – in 5,3% and opportunistic Staphylococcus – in 3,2% of cases. S. aureus was allocated by us in seven farms out of ten, the percentage of its allocation ranged from 9,1% to 58,9%. At the same time, other pathogenic flora was isolated in the studied farms in smaller quantities. So opportunistic Staphylococcus was detected in three agricultural enterprises out of ten in 6,2 % – 11,5% of cases, Streptococcus Agalactiae – in seven – from 9,1% to 36,0%, enterobacteria in five – from 1,5% to 30,8% of cases, respectively. When determining the sensitivity between isolates of S. aureus with other microorganisms in different concentrations by the method of "hole" in meat-peptone agar, the negative influence of Staphylococcus aureus on pathogenic (enterobacteria and Streptococcus Agalactiae), as well as lactic acid and the other non-pathogenic microflora was revealed. This fact indicates that in the conditions of intermicrobial relations, Staphylococcus aureus has the ability to have an antagonistic effect on the listed flora. The article was completed in accordance with state assignment №0578-2014-0030.