[Bacteriological findings in samples of milk from cows studied for the causative agent of mastitis].

Milk samples (483,413 on the whole), collected from 237,026 cows, were investigated in the State Veterinary Institute at Pardubice in the period from 1983 to 1987. In the individual years, the proportion of cows whose milk contained the mastitis-inducing bacteria ranged from 18.0 to 24.8%, the average being 21.0%. Streptococcus agalactiae was identified most frequently as the causative agent of mastitis in the examined cows (6.4%); then followed Streptococcus dysgalactiae (3.7%), Staphylococcus aureus (3.4%), and Streptococcus uberis (1.9%). The presence of the beta-haemolytic streptococci with group antigens C, G and L was demonstrated in the milk of 720 cows (i. e. 0.3%) and the remaining species of streptococci were identified in 1.0% of the cows. Coliform microorganisms were detected in 0.6% and Actinomyces pyogenes in 0.1% of the cows. The remaining bacterial species were isolated from the milk of 3.6% of the cows. Coaglucase-negative staphylococci dominated in this group. Over the five years of study, the occurrence of Streptococcus agalactiae in the examined stocks declined from 10.8 to 3.5% but the occurrence of other streptococci and staphylococci increased.