Morphological, biochemical, antigenic, and cytochemical relationships among Haemophilus somnus, Haemophilus agni, Haemophilus haemoglobinophilus, Histophilus ovis, and Actinobacillus seminis

Publisher Website
Google Scholar
Abstract
Morphology, biochemical reactions, pigmentation, antigens and cell envelope proteins were examined in 12 strains of H. somnus, H. agni, H. ovis and A. seminis. All of the strains except A. seminis are related and are considered as a single Haemophilus-Histophilus (HH) group. In immunodiffusion tests, HH group bacteria had at least 2 antigens common to all members of the group, sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that they have similar cell envelope protein profiles. A quantitatively variable yellow pigment with absorption maxima of 430-435 nm was present in strains of H. somnus and H. agni. The HH group did not produce catalase and grew only in air containing 10% CO2. Of 10 HH group bacteria, 9 required thiamine monophosphate for growth. A. seminis was distinguished from the HH group by its lack of yellow pigment, production of catalase, growth in air, lack of a thiamine monophosphate requirement and different cell envelope protein profile. In gel immunodiffusion tests, A. seminis antigens produced 2 lines of partial identity with the HH group when antiserum against H. somnus was used. Reference strains of H. influenzae, A. lignieresii and H. haemoglobinophilus were compared with the test strains. In immunodiffusion tests, a single antigen was common to H. haemoglobinophilus, A. seminis and the HH group. No similarities between any of the test strains and H. influenzae or A. lignieresii were noted. The close relationship of H. somnus, H. agni and H. ovis suggests that these unofficially named bacteria may belong to a single taxon.