Taxonomy
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Phylum Actinobacteria, Class Actinobacteria, Order Actinomycetales, Suborder Corynebacterineae, Family Nocardiaceae, Genus
Rhodococcus,
Rhodococcus equi (Magnusson 1923) Goodfellow and Alderson 1977.

Historical synonyms:
Corynebacterium equi Magnusson 1923, Corynebacterium pyogenes (equi) Miessner and Wetzel 1923,
Corynebacterium (pyogenes) equi roseum Lutje 1923, Mycobacterium equi (Magnusson) Jensen 1934, Corynebacterium purulentus
Holtman 1945.
Gram-positive rods variable in length from almost coccoid to long curved clubbed
forms, oval or coccoid forms in material from the animal body or cultures on solid
media; bacillary form in broth cultures. Capsulated. Produces filaments on GYEA
which soon fragment into rods and coccoid elements.
Grows well, mucoid, on ordinary media. On GYEA produce smooth, shiny orange to
red colonies. Some cultures produce abundant slime. Black moist colonies appear
on agar containing 1:500 potassium tellurite. Nonhaemolytic. Aerobic, facultatively
anaerobic. Grows at 10-40 ºC, 37 ºC optimum.
Isolated from pneumonia in foals, from the genital tract of mares, from buffalo cow following abortion, from aborted equine foetuses,
from the submaxillary lymph glands of swine. Survive in soil for at least 1 year.
Isolated from pneumonia in foals, from buffalo cow following abortion, from aborted equine foetuses.
Low pathogenicity for laboratory animals; peritonitis or local abscesses may occur if large doses are injected by appropriate route, not
intravenous.
  1. Goodfellow M. and Alderson G., 1977. The Actinomycete-genus Rhodococcus: A home for the ‘rhodochrous’ Complex. J. Gen.
    Microbiol. 100, 99-122.
  2. Cummins C.S., Lelliott R.A. and Rogosa M., 1975. Genus Corynebacterium Lehmann and Neumann 1896. In: Buchanan R.E. and
    Gibbons N.E. (Editors), Bergey’s Manual of Determinative Bacteriology, Eight Edition, The Williams & Wilkins Company, Baltimore,
    602-617.
Positive results for catalase, nitrate reduction, acid production  from: glucose.

Negative results for gelatin hydrolysis, tyrosine hydrolysis, acid production from: arabinose, dextrin, fructose, galactose, inositol,
lactose, maltose, mannitol, mannose, rhamnose, sorbitol, sucrose, trehalose & xylose.

Variable results for urease.
Rhodococcus equi
(c) Costin Stoica
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