Morphological, Biochemical and Fluorescent Antibody Studies of Haemophilus Somnus

Haemophilus somnus was the tentative name given in 1969 to a fastidious gram negative pleomorphic coccobacillus which was consistently isolated from cattle affected with a clinical syndrome called thrombo embolic meningoencephalitis (TEME)(1). The organism was initially classidied as an Actinobacillus actinoides- like organism, but because of its demand for a blood base for primary isolationit was reclassified as Haemophilus-like. Bailie then designated the species name somnus, referring to the sleepiness commonly exhibited by TEME affected cattle(1). In this study, the biochemical reactions of 50 H. somnus isolants recovered from bovine specimens submitter to the South Dakota Animal Diseased Research and Diagnostics Laboratory over a period of 20 months were compared with two reference H. somnus strains plus 13 closely related organisms. A fluorescent antibody conjugate was prepared from the reference strain and used for rapid identification of H. somnus in pure culture as well as in tissues infected with the organism