MICROCOCCUS

9 plus species including:

SPECIES

KEY MICROSCOPIC APPEARANCE

Gram Stain: Gram-positive.
Morphology: Spherical, occurring in pairs, tetrads, or irregular clusters, not in chains.
Size: 0.5 micrometers by 2.0 micrometers.
Motility: Usually non-motile.
Capsules: None.
Spores: None.

MACROSCOPIC APPEARANCE

Colonies appear circular, smooth, entire, convex and usually pigmented in shades of yellow or red. Some strains may produce matted colonies.

KEY BIOCHEMICAL REACTIONS

METABOLIC PROPERTIES

Strictly aerobic. Chemoorganotrophic. Acid without gas is produced from glucose. Acid production from other carbohydrates varies with species.

HABITAT

The primary natural habitat is mammalian and human skin. Secondary habitats for Micrococcus spp. include meat, dairy products, soil and water, and sand.

PATHOGENICITY

Until recently, very little was known about the pathogenicity of micrococci. The Micrococcus strains isolated from various infections were most probably misclassified as staphylococci. Recent reports, however, confirm that micrococci may be associated with human infections, particularly in immunosuppressed patients. (2) Micrococcus spp. appear as agents of infection causing endocarditis. These organisms are sapropytic, facultatively parasitic, or parasitic but not pathogenic.

RECOMMENDED MEDIA

For culture: Blood Agar 5% or Nutrient Agar.
For selective isolation: FTO Agar.
For maintenance: Blood Agar 5% or Nutrient Agar for short term maintenance.
Brucella with 20% Glycerol or Skim Milk for long-term storage at -70 degrees C. Lyophilization may be used for preservation.

INCUBATION

Temperature: 25-37 degrees C.
Time: 18-24 hours.
Atmosphere: Aerobic.

REFERENCES

1. Holt, J.G., et al. 1994. Bergey's Manual of Determinative Bacteriology , 9th ed. Williams & Wilkins, Baltimore, MD.

2. Holt, J.G., et al. 1986. Bergey's Manual of Systemic Bacteriology , Vol. I & II. Williams & Wilkins, Baltimore, MD.

3. The Oxoid Vade-Mecum of Microbiology . 1993. Unipath Ltd., Basingstoke, UK.

4. Murray, P.R., et al. 1995. Manual of Clinical Microbiology , 6th ed. American Society for Microbiology, Washington, D.C.

5. Internet: www.hardlink.com /Bacterial Database Search, February, 1998.

6. Hensyl, B.R., et al. 1990. Stedman's Medical Dictionary , 25th ed. Williams & Wilkins, Baltimore, MD.

7. Koneman, et al. 1997. Color Atlas and Textbook of Diagnostic Microbiology , 5th ed. Lippincott, Philadelphia, PA.

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