CHROMOBACTERIUM

SPECIES

Chromobacterium violaceum
Chromobacterium fluviatile
Chromobacterium lividum (now Janthinobacterium lividum )

MICROSCOPIC APPEARANCE

Gram Stains: Gram-negative. Often with barred or bipolar staining and lipid inclusions.
Morphology: Rods with rounded ends, sometimes slightly curved.
Size: 0.6-0.9 micrometers by 1.5-3.5 micrometers in length.
Motility: They are motile by means of both a single polar flagellum and usually 1-4 subpolar or lateral flagella.
Capsules: None.
Spores: None.
Other: These organisms usually appear singly, occasionally in pairs, elongated forms and short chains. No resting stages.

MACROSCOPIC APPEARANCE

Young colonies appear large and creamy-yellow colored. The colonies turn violet, beginning with the edge, with prolonged incubation. In fluid media, a violet ring is formed at the meniscus. In TSI and KIA, acid is formed with no blackening in the butt. The slant reaction is variable in TSI, depending on the strain; no acid reaction occurs on the slant of KIA. On MacConkey Agar, Chromobacterium spp. appears as pale violet colonies. Growth on EMB is very slow.

METABOLIC PROPERTIES

Aerobic. Chemoorganotrophic, having mainly a fermentative metabolism.

KEY BIOCHEMICAL REACTIONS

HABITAT

This organism is normally found in soil, fresh and salt water, and in tropical countries.

PATHOGENICITY

Chromobacterium violaceum occasionally causes serious pyogenic or septicemic infections in mammals, including humans. This organism rarely causes infections in humans, but when it does it usually manifests as skin abscesses or as overwhelming septicemia with pulmonary, liver, and subcutaneous abscesses; the eye may also be involved. The portal of entry of human infections is probably the skin, although organisms may also gain entrance through the ingestion of contaminated material.

RECOMMENDED MEDIA

For culture: Tryptic Soy Agar (TSA), Brain Heart Infusion Agar (BHI), Nutrient Agar.
For selective isolation: MacConkey, Kligler Iron Agar, Triple Sugar Iron Agar.
For maintenance: Tryptic Soy Agar (TSA), Brain Heart Infusion Agar (BHI), Tryptic Soy Broth, Peptone Water. Brucella with Glycerol or Skim Milk may be used for storage at -70 degrees C. Lyophilization may be used for preservation.

INCUBATION

Temperature: 5 and 35 degrees C.
Time: Several days (violet pigment after prolonged incubation).
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 of Microbiology, Washington, D.C.

5. Howard, B.J., et al. 1994. Clinical and Pathogenic Microbiology , 2nd ed. Mosby, St. Louis, IL.


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