[Pathogenic role of strains of specific Escherichia coli serotypes in the development of mastitis in cows. II. Milk changes].

The studies were carried out on 14 cows which were injected into their udders field (pathogenic) E. coli strains from serological groups: 093, 086, 010, museum strains (non-pathogenic) from groups: 0132, 0120, 093 and E. coli endotoxin (serogroup 093). For studies of each strain or endotoxin 2 cows were used. From the experimental animals milk was taken three times before and after 2, 4, 6, 9, 12, 18, 24, 36, 48 hours and 3, 4, 5, 6, 7, 10, 14 days after infusion of the microorganisms or endotoxin. In the material taken the behaviour of bacteria, cells, endotoxin, antibodies and free histamine was determined. The studies showed that E. coli strains introduced into the udder multiplied particularly intensively in the first 6 hr, and their presence in the infected quarters lasted from 3 days (laboratory strains) to 6 - 10 days (field strains). In many experimental quarters the presence of endotoxin (by passive hemaglutination) was found, but it was detected shortest in those quarters into which it was introduced in the form of phenol-water extract, and the longest in cows infected with field E. coli strains. The level of specific antibodies decreased (in the first hours after introduction of antigens), and then between the 5th and 14th day it increased 2 - 4 times in relation to the initial titre. The number of cells started to increase after 2 hr from the infusion of the strains or endotoxin; the highest values (on average over 50 mln) were found between the 18 - 36th hr, and the return to initial standards after 10 - 14 days. An increase of free histamine was also observed, the values of which after 6 - 36 hr exceeded the initial standard 2,5 times.