PLESIOMONAS

SPECIES

MICROSCOPIC APPEARANCE

Gram Stain: Gram-negative.
Morphology: Round ended, straight rods.
Size: 0.8-1.0 micrometers by 3.0 micrometers.
Motility: Motile by two to five lophotrichous polar flagella; swarming does not occur.
Capsules: None.
Spores: None.

MACROSCOPIC APPEARANCE

Colonies appear grayish, shiny, opaque with a smooth surface.

KEY BIOCHEMICAL REACTIONS

METABOLIC PROPERTIES

Facultatively anaerobic. Chemoorganotrophic, having both fermentative and respiratory type metabolism. Acid production from mannose, but gas is not produced.

HABITAT

P . shigelloides does not belong to the normal intestinal flora of man; in only a few instances has man been found to be a symptomless carrier of the organism. In various animals a carrier state is more frequent; Plesiomonas has thus far been isolated from fish, other aquatic animals, and from mammals such as swine, dogs, cats, goats, sheep and monkeys.

PATHOGENICITY

With few exceptions, P . shigelloides has not been isolated from wounds or inflammatory processes. The species does, however, play a role as a pathogen of the human intestine. Cases of diarrhea in various degrees of severity are increasingly reported. Symptoms range from loose stools to watery, choleriform excrements. A number of epidemic outbreaks of diarrhea attributed to P . shigelloides as the causative agent, have been reported from Africa, India, and Japan. (2)

RECOMMENDED MEDIA

For culture: Nutrient Agar, Tryptic Soy Agar (TSA), Blood Agar 5%.
For selective isolation: MacConkey Agar, SS Agar, Hektoen Enteric (HE) Agar, and XLD Agar.
For maintenance: Tryptic Soy Agar for short-term maintenance and Lyophilization for long-term storage.

INCUBATION

Temperature: 35-37 degrees C.
Time: Up to 48 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.


022699na