Study of the microbial landscape of milk of dairy cows with serous catarrhal mastitis

The study was aimed at investigating the microbiological profile of milk from cows with serous catarrhal mastitis (n=30) with determination of the species composition of pathogens, their associations and sensitivity to antibacterial drugs. Milk samples were analyzed using standard bacteriological methods, including cultures on specialized media (wort agar, yolk-salt agar, Endo agar), identification according to the “Bergie’s Bacteria Identifier” and serogrouping of E. coli. Sensitivity to 12 antibiotics was assessed by the disco-diffusion method. 82 cultures of opportunistic microorganisms (10 species, 5 genera) were isolated, among which gram-positive bacteria dominated (62,2%): Staphylococcus aureus (18,4%), Streptococcus uberis (17,1%) and Escherichia coli (15,9%). It was found that 36,7% of mastitis cases were associated with three-component microbial associations. The highest efficiency was demonstrated by cloxacillin (82,9% of susceptible strains), enrofloxacin (71,9%) and neomycin (50,0%). High resistance was noted to cefazolin (64,7%), benzylpenicillin (56,1%) and tetracycline (63,4%). The results emphasize the need for combination therapy (e.g. cloxacillin + neomycin) to overcome polymicrobial infections.