Actinomyces israelii
Taxonomy
Morphology
Cultural characteristics
Biochemical characters
Ecology
Pathogenicity
References
Phylum Actinobacteria, Class Actinobacteria, Subclass Actibacteridae, Order Actynomycetales, Suborder Actinomycinae, Family
Actinomycetaceae, Genus Actinomyces,
Actinomyces israelii (Kruse 1896) Lachner-Sandoval 1898.

Historical synonyms:
Actinomyces israelii serotype I (Johnson, Moore, Kaneko and Moore 1990); Corynebacterium israeli (Kruse)
Haupt and Zeki 1933;
Proactinomyces israeli (Kruse) Negroni 1934; Streptothrix israeli Kruse 1896; Discomyces israeli (Kruse)
Gedoelst 1902;
Actinobacterium israeli  (Kruse) Sampietro 1908; Nocardia israeli (Kruse) Castellani and Chalmers 1913;
Brevistreptothrix israeli (Kruse) Lignieres 1924.
Gram-positive diphtheroid rods, occurring as branching filaments. Non-motile.
Non-spore-forming.
Colonies are small, with or with no filaments at the edge after 24 h on BHI agar and
blood agar; after 7-14 days the colonies are 0.5-3 mm in diameter, rough, convex,
circular to irregular, pulvinate or heaped, undulate, erose or lobate , white to cream-
white and friable to hard. The surface may be granular or convoluted producing
“molar-tooth” or “raspberry-like” colonies. Some strains produce smooth colonies,
umbonate or pulvinate, opaque, soft and grayish white.
In BHI broth grows as granules of variable size in clear medium. Alpha haemolysis is
variable. Grows optimally at 37 ºC.
The normal habitat is the oral cavity of man, including  tonsillar cripts and dental calculus.
Sensitive to penicillin, tetracyclines, cephalosporin and lincomycin.
Causes human actinomycosis and occasionally infections in cattle. The source of infection is endogenous.
Experimental infections in hamsters, mice and rabbits.
  1. Slack J.M., 1975. Genus Actinomyces Harz 1877. In: Buchanan R.E. and Gibbons N.E. (Editors), Bergey’s Manual of Determinative
    Bacteriology, Eight Edition, The Williams & Wilkins Company, Baltimore, 660-667.
  2. Johnson J.L., Moore L.V.H., Kaneko B. and Moore W.E.C., 1990. Actinomyces georgiae sp. nov. , Actinomyces gerencseriae sp.
    nov. , Designation of Two Genospecies of Actinomyces naeslundii, and Inclusion of A. naeslundii serotypes II and III and
    Actinomyces viscosus serotype II in A. naeslundii Genospecies 2. Int J Syst Bacteriol Vol. 40, No. 3, 273-286.
Positive results for esculin hydrolysis, H2S production, reduction of methyl red, acid production from: arabinose, cellobiose, fructose,
galactose, glucose, inositol, lactose, maltose, mannitol, mannose, melibiose, raffinose, ribose, salicin , sucrose & xylose.

Negative results for catalase, gelatin hydrolysis, indole production, starch hydrolysis, urease, Voges-Proskauer test, acid production
from: adonitol, dulcitol, glycerol, rhamnose & sorbitol.

Variable results for nitrate reduction, acid production from: amygdalin, esculin, glycogen, inulin, melezitose, starch & trehalose.
(c) Costin Stoica
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