OPSONIZATION OF STAPHYLOCOCCUS-AUREUS WITH A FIBRONECTIN-BINDING PROTEIN ANTISERUM INDUCES PROTECTION IN MICE

The virulence of Staphylococcus aureus opsonized with an antiserum rai sed against a recombinant fibronectin-binding protein (FnBP) was compa red with homologous, non-opsonized bacteria (treated with pre-immune s erum) in a mouse mastitis model. Virulence was evaluated comparing the number of bacteria recovered from the infected mammary glands and acc ording to the type of lesions produced. The average number of bacteria recovered from the mammary glands inoculated with S, aureus opsonized with FnBP-antiserum was significantly lower (up to 10(7) cfu/ml) than the average number of bacteria recovered after inoculation with non-o psonized bacteria (up to 10(10) cfu/ml). Gross examination of infected mammary glands showed that 65% of glands infected with opsonized bact eria developed low grade/or had no pathological changes, and 35% devel oped severe mastitis whereas, 75% of glands inoculated with non-opsoni zed bacteria developed severe mastitis and 25% low grade mastitis or h ad no pathological changes. According to the histopathological examina tion eight out of 10 glands inoculated with opsonized bacteria produce d disseminated focal necrosis or had no pathological changes and two g lands produced non reactive necrotic lesions. In contrast, only three out of 10 glands inoculated with non-opsonized homologous bacteria dev eloped disseminated focal necrosis and had no pathological changes whi le seven glands developed total necrosis. (C) 1995 Academic Press Limi ted