Streptobacillus moniliformis isolated from otitis media of conventionally kept laboratory rats

Streptobacillus moniliformis (Sm) was isolated from the middle ear of two inbred albino rats (strain CAP/Kuv) suffering from murine respiratory mycoplasmosis and purulent bilateral otitis media. The animals were kept under conventional conditions and used for immunological studies. The biochemical pattern of the isolate was identical with that of four other Sm strains of different origin but differed in its ability to lyse erythrocytes in sheep blood agar. This is the first Sm strain with hemolysis described. Pathogenicity of the strain was demonstrated in C57BL/6Han mice known to be susceptible to streptobacillosis. Three of five mice inoculated orally developed characteristic signs of a septic lymphadenitis. In the homologous system and with Sm strain ATCC 49567 as antigen, all five sera showed positive titers in the indirect immunofluorescence assay. Possible improvements in the diagnosis and the role of this "forgotten pathogen" in laboratory animal medicine are discussed.