13 plus species including:


(Acnes group)

(Dairy group)


Gram Stain: Gram-positive.
Morphology: Pleomorphic, branched and unbranched rods, coccoid forms, or bifid, but they are not filamentous. Cells are often "club-shaped" with one end rounded and the other tapered. Cells occurs in singly, in pairs or short chains, in "V" or "Y" configurations, or in clumps with a "Chinese character" arrangement.
Size: 0.5-0.8 micrometers by 1.0-5.0 micrometers.
Motility: Non-motile.
Capsules: None.
Spores: None.
Other: Readily confused with some species of Corynebacterium or Clostridium .


On Blood Agar, colonies appear convex, semi-opaque, and glistening. Colonies have been seen pigmented in an array of colors from white to red.



Some species are facultatively aerobic (acnes group) while others are variably aerotolerant (dairy group). Chemoorganotrophic; metabolism is primarily fermentative, with complex nutritional requirements. Hexoses (e.g. glucose) or lactate are fermented mainly to propionic and acetic acid.


Propionibacterium species are the predominant indigenous flora of the skin, but also can be recovered form the gastrointestinal tract, upper respiratory tract, especially the anterior nares, and the urogenital tract. Because of their presence on skin, Propionibacterium are often contaminants of specimens such as blood or other body fluids obtained through skin puncture.

Acnes group commonly found in the extraintestinal regions of humans.

Dairy group commonly found in cheese and other dairy products.


Found as secondary agents of infected sinuses, wounds, and abscesses in humans and other animals.

Specifically, the "acnes group" is associated with human skin and intestinal infections, while the "dairy group" is associated with cheese and dairy products. Various Propionibacterium spp., particularly P . acnes , have been implicated in infections of corneal ulcers, heart valves and prosthetic devices (e.g. artificial joints), and ventricular shunts. These infections often lead to osteomyelitis, bacteremia, endocarditis, and meningitis.


For culture: Tryptone Yeast Extract, Glucose Medium with 0.5% Tween ® 80.
For selective isolation: Yeast Extract, Sodium Lactate Medium (dairy).
For maintenance: Cooked Meat Medium for short-term maintenance and Lyophilization for long-term storage.


Temperature: (acnes group) 30-37 degrees C.
(dairy group) 30-32 degrees C.
Time: (acnes group) 48 hours.
(dairy group) 48 hours under nitrogen.
Atmosphere: Anaerobic.


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.

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