The Propionibacteria belong to the class Propionibacterineae. These are slow-growing gram positive rods (bacilli) anaerobic bacteria.
The species of Propionibacterium include acnes, australiense, avidum, cyclohexanicum, freudenreichii, granulosum, jensenii, microaerophilum, propionicum and thoenii. They are flora of the body and gastrointestinal tract. They are also found in foods. P. freudenreichii, as an example, is used in Swiss cheese producing its flavor (propionate) and holes.
Generally, the Propionibacteria are considered non-pathogenic. The members of this genus are opportunistic pathogens. However, P. acnes and granulosum have been reported as causing human infections. P. Acnes and granulosum produce Cytotaxin that has a role in the inflammatory process of acne vulgaris.
In addition, these bacteria interfere with the lipid metabolism of sebaceous glands and their infectious process is the probable cause of comedons and pimples of acne (acne vulgaris).
Also, P. acnes and granulosum have been isolated from the lungs of individuals with sarcoidosis and have been cited as one source of antigenic stimulation that gives rise to the lymphatic inflammatory condition of sarcoidosis.
Finally, P. Acnes infection is considered as one of the causes of blepharitis (inflammation of the eye lids).
Opportunistic infections by Propionibacteria include brain abscesses, dental infections, endocarditis, peritonitis related to dialysis, conjunctivitis keratitis (contact lens), infections from prosthetic devices and bone.
Gram positive Bacilli are found in damp indoor spaces.
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