Intramammary immunization with live-attenuated Staphylococcus aureus protects mice from experimental mastitis

Abstract

Female mice were immunized by the intramammary route with live‐attenuated Staphylococcus aureus according to different schedules and challenged with virulent S. aureus. Immunization in late pregnancy or early lactation induced a significant decrease (P<0.05) in the number of S. aureus CFU recovered from glands after the challenge and a significant increase (P<0.05) in the levels of milk and serum specific IgG and IgA antibodies. Mice immunized before pregnancy were not protected from S. aureus challenge. Immunization did not increase the number of somatic cells in milk when compared with control mice. Protection from S. aureus intramammary infection may be achieved if mice are locally immunized during late pregnancy or early lactation.

Attenuation and Persistence of and Ability To Induce Protective Immunity to a Staphylococcus aureus aroA Mutant in Mice

“…However, low levels of polymorphonuclear leukocytes and mononuclear cells and less damage were observed in the mammary gland after administration of the aroA mutant compared with the wild-type strain in the mouse mammary gland. Furthermore, in previous experiments, we have seen that the number of leukocytes was not increased in milk after ima administration of an attenuated S. aureus strain (23). Recently, Brouillette and Malouin (4) have demonstrated that after bacterial inoculation in the mouse mammary gland, polymorphonuclear infiltration, tissue damage, and S. aureus-host cell interactions are similar to those found in the bovine mammary gland.…”

“…Both the S. aureus parental strain and the FB306 aroA mutant were investigated for their abilities to colonize the lungs, spleens, and mammary glands of mice. Previous results from our laboratory were considered to choose the different times postchallenge (21,23). Groups of mice were infected i.p.…”

“…A booster injection containing the same dose was administered 7 days later by the same route. Fourteen days after the second injection, mice were challenged by the ima route with 0.05 ml of an RN6390 suspension (5 ϫ 10 5 CFU/gland) or with a suspension containing 1 ϫ 10 6 CFU/gland of S. aureus MB319 (23). Viable bacterial counts were performed on mammary gland homogenates.…”

Capsule-Negative Staphylococcus aureus Induces Chronic Experimental Mastitis in Mice

“…Groups of 22 to 30 pregnant mice were used for each experiment, and pregnancies were synchronized in order to have all births within a 24-h period. The mouse mastitis model was described previously (9). Briefly, 7 to 10 days after parturition, lactating mothers were separated from the pups and anesthetized with ketamine (60 mg/kg) (Ketalar; Parke-Davis) and xylazine (5 mg/kg) (Rompun; Bayer).…”

“…Because most cows with chronic mastitis suffer from the subclinical, persistent type of disease, we sought to determine whether capsule production influences the pathogenesis of this disease. An experimental mouse model of S. aureus-induced mastitis (9), recently validated by Brouillette and Malouin (4), was chosen to test our hypothesis. Our results indicate that S. aureus lacking a capsule persisted in the murine mammary gland longer than isogenic encapsulated strains.…”