FUSOBACTERIUM

25 plus species including:

SPECIES

Fusobacterium gonidiaformans
Fusobacterium mortiferum
Fusobacterium naviforme
Fusobacterium naviforme
Fusobacterium necrophorum
Fusobacterium nucleatum
Fusobacterium russii
Fusobacterium ulcerans
Fusobacterium varium

MICROSCOPIC APPEARANCE

Gram Stain: Negative.
Morphology: Typically spindle shaped rods. May or may not exhibit characteristic fusiform morphology.
Size: Variable.
Motility: When occasional motility occurs presence of peritrichous flagella; Usually no motility occurs.
Capsules: None.
Spores: Occasionally.
Other: Cultures should be stained for spores.

MACROSCOPIC APPEARANCE

Colonies are 1-2mm and are circular to slightly irregular. They may be convex to pulvinate, translucent, often displaying a "flecked" appearance when viewed by transmitted light.

METABOLIC PROPERTIES

Obligately anaerobic, with some exceptions being microaerophile. Chemoorganotrophic. Metabolizes peptones or carbohydrates. Non or weakly fermentative. Major product of metabolism is butyrate.

Fusobacterium spp. do not grow on the surface of agar plates incubated aerobically or in air enriched to 5-10% with CO 2 .

KEY BIOCHEMICAL REACTIONS

HABITAT

Occurs in mixed infections with other anaerobic and capnoeic organisms. Often located in cavities such as the gingival sulcus and in the intestinal, genital tracts, as well as in ulcerations of humans and animals.

F. nucleatum and F. necrophorum are found as indigenous flora in the upper respiratory and intestinal tract.

PATHOGENICITY

Some species are pathogenic and occur in various purulent or gangrenous infections and in organ infarcts. F. nucleatum and F. necrophorum may be implicated in infection throughout the body, but with some predilection for the lower respiratory tract, head and neck, peridontium, gingivae, and central nervous system. Of the seven fusobacteria encountered in humans infections, F. nucleatum is isolated most often. It is an important pathogen, particularly in head and neck and lower respiratory infections.

F. necrophorum may be very virulent in certain types of infections. In postanginal sepsis (Lemierre's syndrome) the infection begins with a membranous infection, such as tonsillitis, and proceeds to septicemia with metastatic infection that can include lung abscess, empyema, liver abscess, ostemyeletis, and purulent arthritis. (1) Other species of Fusobacterium are isolated infrequently.

RECOMMENDED MEDIA

For culture: Brain Heart Infusion (BHI) Agar, Chocolate Agar, Brucella with H & K Agar, Cooked Meat Medium, Thioglycollate Broth with Supplements, and complex media containing peptone promotes optimum growth.
For selective isolation: LKV Agar or BBE Agar.
For maintenance: Cooked Meat Medium, Thioglycollate Broth with Supplements, Brucella Agar with H & K, or Brain Heart Infusion (BHI) Agar. Skim Milk Media may be used for long-term storage at -70 degrees C.

INCUBATION

Temperature: 35 degrees C.
Time: 48 hours.
Atmosphere: Anaerobic with 5% CO 2 .
pH: Near 7.

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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