The coexistence of several microbial species at the same site of bovine mammary gland parenchyma infection and their mixed infections

The purpose of this study was to analyse both negative results of bacteriological cultures and the coexistence of several pathogens at the same intramammary inflammatory focus within bovine udder parenchyma in order to compare the health status of cows’ udders in 1985 and 2021. Mastitis was diagnosed on the basis of anamnesis, clinical inspection of the udder, milk quality, and somatic cell counts (SCC on the Fossomatic 5000-FC). In 1985, joint bacteriological and mycological diagnosis was based on the guidelines established for bovine mastitis by FIL-IDF (1971), while for 2021, it was based on the National Mastitis Council (NMC) laboratory Handbook on bovine mastitis (Hogan et al., 1999). In the first study (1985), mainly the genus Staphylococcus was isolated, but at present other species may be involved in cases of mastitis. In both periods, both subclinical and clinical cases were registered. In addition, the milk yield of cows was observed to increase over time, with concomitant deterioration of mammary gland immunity. The phenomenon of biofilms was documented in the study, which may be explained not only by the low efficacy of antibiotic therapy against udder disease but also by impaired immunity in cows, as the lymphocytes trapped in the biofilm matrix were inactive with respect to both cellular and humoral responses.