Haemophilus somnus
Taxonomy
Morphology
Cultural characteristics
Biochemical characters
Ecology
Pathogenicity
References
Phylum Proteobacteria, Class Gammaproteobacteria, Order Pasteurellales, Family Pasteurellaceae, Genus Haemophilus,
Haemophilus somnus
Bailie 1966.
H. somnus has been described as a member of the genus Haemophilus. By current standards it does not qualify for inclusion in the
genus.
De Ley et al., (1990) suggested that
H.  agni & H. somnus be transferred to genus “Histophilus”, “Histophilus ovis” being a senior
synonym for
H. agni. However, none of these names are valid, and no types have been designated.

Old synonyms:
Haemophilus-like organism Kennedy, Biberstein, Howarth, Frazier and Dungworth 1960; Actinobacillus actinoides-
like organism Bailie, Anthony and Weide 1966;
Actinobacillus sp. Gossling 1966; Haemophilus somnifer Miles, Anthony and Dennis
1972.
Gram-negative coccobacilli, short rods or filaments, nonmotile, most strains are not
capsulated.
Colonies on Beef blood agar are smooth, raised, 0.5-1.0 mm in diameter in 24 hours
and 1-2 mm in 72 hours. Growth occurs on blood and chocolate agars, and on
serum-yeast extract PPLO-agar under 5-20% CO
2. Hemolysis is negative.
Does not require V-factor or X-factor but requires CO
2  for growth. Occasional cultures
apparenyly adapt gradually to fully aerobic growth. Growth on Mac Conkey agar is
negative.
Found in mucous membranes of the normal bovine respiratory and genital tracts.
Cause septicemia and meningoencephalomyelitis in cattle and is involved in respiratory and genital infections (including abortions ).
Potential cause of respiratory disease in American bison.
Have been reported experimental infections of mice, guinea pigs, rabbits, sheep & calves.
  1. Mogens Kilian, 2004. Genus III. Haemophilus. In:  Bergey’s Manual of Systematic Bacteriology, Second edition,Vol two, part B,
    George M. Garrity (Editor-in-Chief), pp. 883-904.
  2. J. G. Holt et al., 1994. Facultatively Anaerobic Gram-Negative Rods. Subgroup 3. Family Pasteurellaceae. In: Begey’s Manual of
    Determinative Bacteriology, 9th-edition, Williams & Wilkins, pp 194-196.
  3. N. W. Dyer: Haemophilus somnus bronchopneumonia in American bison (Bison bison). J Vet Diagn Invest 13:419–421 (2001).
  4. J. A. Jackson, J. J. Andrews & J. W. Hargis: Experimental Haemophilus somnus Pneumonia in Calves. Vet Pathol March 1987 24:
    129-134.
  5. R. P. Gogolewski, C. W. Leathers, H. D. Liggitt, and L. B. Corbeil: Experimental Haemophilus somnus Pneumonia in Calves and
    Immunoperoxidase Localization of Bacteria. Vet Pathol May 1987 24: 250-256.
Positive results for nitrates reduction, oxidase, indole production, acid production from:
D(+) glucose (without gas), D(+) xylose, mannitol, D(-) sorbitol, D(-) fructose, D(+)
mannose, maltose & trehalose.

Negative results for catalase, urease, arginine dehydrolase, lysine decarboxylase, ornithine decarboxylase, acid production from:
glycerol, L(+) rhamnose, cellobiose, lactose, D(+) melibiose, sucrose (saccharose), raffinose, inulin, esculin & salicin.


Variable results for ONPG, acid production from: L(+) arabinose, dulcitol, meso-inositol & D(+) galactose.
(c) Costin Stoica
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