All 127 streptococci of serological group B isolated from bovines and humans were resistant to bacitracin (0.04 U) and gentamicin and susceptible to penic'illin. Of the bovine isolates examined 10 ' %, 8 'XI, 22 'YO, 2 and 30 %I were resistant to bacitracin (10 U), cefoxitin, clindamycin, erythromycin and tetracycline respectively. Of the human isolates 52 %, 21 ' X I , 38 'XB, 3 ' X I and 65 % were resistant to bacitracin (10 U), cefoxitin, clindamycin, erythromycin and tetracycline respectively. Most of the bovine strains were susceptible, most of the human strains were resistant to bacitracin and tetracycline. A relation of tetracycline resistance to group B streptococcal microcapsule was proposed. Pigmentation studies revealed generally a weak pigmentation of bovine and a strong pigmentation of human group B streptococci. Antibiotic resistance patterns together with the ability to form a yellow to orange-red pigment might be used for characterization of individual cultures of group B streptococci.
Protein X of Streptococcus agalactiae is a surface protein frequently associated with strains isolated from cases of mastitis of dairy cows. By immunizing cows with purified protein X, we obtained an antibody response which was restricted to X-bearing strains of S. agalactiae in a whole-cell enzyme-linked immunosorbent assay. This response resulted in an increase in the opsonic activity of serum for strains bearing protein X, as assessed through the augmentation of the chemiluminescence response of phagocytosing polymorphonuclear cells and through an increased ingestion of bacteria, although the proportion of ingested bacteria which were killed (about 60%) remained unchanged. Protein X behaved as a target of opsonins and, as such, could be a protective antigen worth incorporating in a vaccine against S. agalactiae mastitis.
The protein X of Streptococcus agalactiae is a surface antigen borne by a high proportion of strains isolated from bovine mastitis. We have tested the capacity of two strains of X-bearing Streptococcus agalactiae to induce mastitis in dairy cows. The reference X-strain (411.07) produced an intramammary infection with local clinical signs in the three inoculated quarters. Another X-bearing strain (443.31) of bovine origin produced infection in all 11 quarters inoculated with only 25 or 85 colony-forming units. In naive cows, strain 433.31 induced less exudation of plasma into the milk, shedding of bacteria, macroscopic alteration, and a lower somatic cell count (SCC) than did the reference strain. Only one quarter spontaneously eliminated the infection before antibiotic treatment 9 days after inoculation. The serum of all the cows contained naturally acquired or induced antibodies to the challenge strain (443.31) and possessed opsonic activity. Before inflammation occurred, the milk was almost devoid of antibody or opsonic activities. The early phase of infection was characterized by rapid multiplication of streptococci in the milk, followed by a sharp drop in bacterial counts concomitant with the onset of inflammation. Three cows immunized with protein X displayed higher SCC and bactericidal activity in milk from the inoculated quarter at the onset of inflammation than non-immunized cows. Two of the three immunized cows underwent an early and transient febrile episode and eliminated the infection.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.