Pseudomonas aeruginosa mastitis outbreaks in sheep and goat flocks: antibody production and vaccination in a mouse model.

Pseudomonas aeruginosa is most often associated with sporadic clinical mastitis. Outbreaks among more than 15 Israeli dairy sheep and goat herds presented clinical signs, including gangrenous infections. Characterization of the P. aeruginosa isolates revealed the presence of multiple environmental strains in the various farms, and it was hypothesized that the infected herds were temporarily immunocompromised. In spite of the variability of the isolates, because of the economic impact on the small-ruminant farms, we decided to search for common antigens that might induce an immune response that would protect the animals from the various P. aeruginosa strains present in the herds. Responses to selected isolates, representative of various animals and farms, were further studied in mouse models for capability to induce antibodies and to protect from homologous and heterologous challenge after immunization with an experimental primary vaccine. 1-D-SDS-PAGE tests revealed two patterns of protein bands among the various P. aeruginosa isolates, whereas the immunoblot and ELISA tests of sera of mice immunized with either MA-58, GE-61 monovalent, or (MA-58 + GE-61) bivalent bacterial vaccine preparations revealed two subgroups with low mutual cross-reactivity. Immunization with a vaccine prepared from either of the subgroups protected mice only from the homologues but not from the heterologues, whereas the bivalent vaccine protected mice from both subgroups.