BIFIDOBACTERIUM

35 plus species including:

SPECIES

Bifidobacterium bifidum
Bifidobacterium breve
Bifidobacterium dentium (formerly B. eriksonii )
Bifidobacterium globosum
Bifidobacterium infantis

MICROSCOPIC APPEARANCE

Gram Stains: Gram-positive. The cells often stain irregularly. Non-acid-fast.
Morphology: Pleomorphic, coryneform rods. They usually appear clubbed or branching and may display bifurcated ends. Some species occasionally exhibit swollen coccoid forms.
Size: 0.5-1.3 by 1.5-8.0 micrometers.
Motility: They are non-motile, with some species being regularly motile.
Capsules: No.
Spores: Non-sporeforming.
Other: Bifidobacterium spp. are sometimes arranged in pairs, "V" arrangements, in chains, and in palisades of parallel cells or rosettes.

MACROSCOPIC APPEARANCE

Bifidobacterium dentium produces a white, convex, shiny colony with irregular edges on solid media. Growth in broth is diffuse.

METABOLIC PROPERTIES

Anaerobic. Acetic and lactic acid are produced from glucose.

KEY BIOCHEMICAL REACTIONS

HABITAT

Found in the mouth and intestine of man, other warm-blooded animals and insects, also found in sewage and clinical specimens.

PATHOGENICITY

These organisms are usually considered non-pathogenic. However, they have been implicated in human infections including abscesses. B. dentium appears to have the most possible pathogenic potentiality as a result of isolation from human dental plaque and caries. (2)

RECOMMENDED MEDIA

For culture: Tomato Juice Agar, V9 Agar, SabDex, MRS Agar or MRS Broth.
For selective isolation: None recommended.
For maintenance: SabDex, V9 Agar, or Tomato Juice Agar.

INCUBATION

Temperature: 39-40 degrees C.
Time: 2-3 days.
Atmosphere: Anaerobic. Some Bifidobacterium spp. may grow aerobically with an enriched atmosphere containing 10% CO 2 .

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.


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