12 plus species including:



Gram Stain: Gram-negative.
Morphology: Straight rods, sometimes approaching a spherical shape.
Size: 0.5-0.8 micrometers by 1.0-3.0 micrometers.
Motility: Most are motile under 30 degrees C. and non-motile at 37 degrees C.
( Yersinia pestis is always non-motile).
Capsules: None.
Spores: None.
Other: Commonly categorized as a fastidious bacteria.


Colonies grown on Nutrient Agar appear translucent to opaque. After 24 hours of growth, colonies may appear gray-white and slightly muccoid. After 48 hours, most species diameters increase and the centers become elevated and take on a "Chinese Hat" shape.



Facultatively anaerobic. Chemoorganotrophic, having both a fermentative and respiratory type metabolism. Acid without gas is produced from glucose.


Occur within a broad spectrum of habitats including humans, animals, especially rodents and birds, soil, water, dairy products and other foods. Also, habitat will vary according to specie group e.g.:

1. Yersinia pestis - rodent-flea-rodent.
2. Yersinia pseudotuberculosis and Yersinia enterocolitica - intestinal pathogens.

For the most part, the geographical distribution of Yersinia spp. is widespread, and the organism has been isolated from all continents. The incidence of infectious disease varies with the seasons and tends to be highest during cold season.


The pathogenicity of Y. intermedia , Y. kristensenii and Y. frederiksenii in man and animals is not clearly established. They tend to behave more like opportunistic pathogens than true pathogens. (2)

Other species are occasional opportunistic human pathogens and others are nonpathogenic. Y. ruckeri is a fish pathogen responsible for red mouth disease, especially in rainbow trout. An inflammation of the mouth and the throat is the main characteristic. Yersinia pestis is the causative agent of 'Urban' and 'Sylvatic' Plague. Yersinia pseudotuberculosis is a causative agent for chronic diarrhea, and severe septicemia.


For culture: Nutrient Agar or Tryptic Soy Agar (TSA), Blood Agar 5%.
For selective isolation: Cefsulodin-Irgasan-Novobiocin (CIN) Agar, MacConkey Agar, Salmonella Shigella (SS) Agar, XLD Agar and Hektoen Enteric (HE) Agar.
For maintenance: Nutrient Agar or Tryptic Soy Agar (TSA) for maintenance. TSB with 20% Glycerol for storage at -70 degrees C. Lyophilization may be used for preservation.


Temperature: a. 25 degrees C.
b. 35 degrees C.
Time: a. 48 hours.
b. 24 hours followed by 24 hours at room temperature.
Atmosphere: Aerobic.
pH: 7.2-7.4.


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: /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.

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