FRANCISELLA

6 plus species including:

SPECIES

Francisella tularensis
Francisella novicida
Francisella philomiragia

MICROSCOPIC APPEARANCE

Gram Stain: Negative, faintly staining.
Morphology: Cocci or coccobacilli or rods, depending upon species and conditions. Highly pleomorphic.
Size: 0.2 micrometers in diameter to 0.2 0.7 micrometers in length.
Motility: Non-motile.
Capsules: Rarely produced.
Spores: None.
Other: Formerly Pasteurella tularensis .

MACROSCOPIC APPEARANCE

Smooth gray colonies are formed on Glucose-Cysteine-Blood Agar and are surrounded by a characteristic green zone of discoloration.

KEY BIOCHEMICAL REACTIONS

METABOLIC PROPERTIES

Obligately aerobic; Chemoorganotrophic. Carbohydrates are metabolized slowly, with acid resulting, but not gas.

HABITAT

F. tularensis is widely distributed in nature and is found in all continents throughout the world except Australia and Antarctica. The two main regions in which numerous infections of humans have occurred over a relatively large area are the U.S.A. (all states except Hawaii) and southern Russia. F. tularensis has been isolated from approximately 100 types of wildlife, about one-half of which have transmitted tularemia to man. Other forms of transmission can occur from biting insects and/or ingestion of improperly cooked meat or contaminated water. Transmission has also been noted via inhalation of airborne organisms especially during processing of agricultural products contaminated by infected rodent excreta.

PATHOGENICITY

F. tularensis is a highly pathogenic organism causing a plague-like illness ( tularaemia ) in man. F. tularneissi has great invasive ability and is able to penetrate the unbroken skin. Although humans of all ages, sexes and races are susceptible, man-to-man transmission is extremely rare. Human tularemia is an acute, febrile, granulomatous, infectious, zoonotic disease. The clinical picture and severity vary appreciably according to the route of infection ad the virulence of the organism. F. novicida is less virulent then F. tularenisis . It is experimentally pathogenic for white mice, guinea pigs, and hamsters producing lesions similar to those of tularemia. Human infections by F. novicida have not been reported.

RECOMMENDED MEDIA

For culture: Chocolate Agar or Thioglycollate with Supplements.
For selective isolation: Modified Thayer-Martin Agar or Martin Lewis with Lincomycin.
For maintenance: Skim Milk or Brucella with 20% Glycerol at -70 degrees C. for long-term storage.

INCUBATION

Temperature: 35 degrees C.
Time: 2-4 days, and look for very small colonies surrounded by a green zone of discoloration.
Atmosphere: Aerobic and Facultatively Anaerobic.

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.


022699na