Propionibacterium species are nonsporulating, gram-positive anaerobic bacilli that are considered commensal bacteria on the skin. They are usually nonpathogenic and are common contaminants of blood and body fluid cultures. These species are slow-growing and require at least 6 days for growth in culture.[1]
Propionibacterium species belong to the genera of coryneforms and are the best studied because of their association with acne vulgaris. Propionibacterium species, however, can also cause numerous other types of infections, including endocarditis, postoperative shoulder infections, and neurosurgical shunt infections. These are discussed later in the article and are classified as ”endovascular”, ”orthopedic”, ”neurosurgical”, and ”other” infections.
Propionibacterium acnes is found briefly on the skin of neonates, but true colonization begins during the 1-3 years prior to sexual maturity. During this time, numbers of P acnes rise from fewer than 10/cm2 to about 106/cm2, chiefly on the face and upper thorax. P acnes grows in the lipid-rich microenvironment of the hair follicle. In acne vulgaris, P acnes produces inflammatory mediators that result in acne papules, pustules, and nodulocystic lesions.
Propionibacterium granulosum is found in the same areas but at numbers about one hundredth of those of P acnes.
Both P acnes and P granulosum may be isolated from the gastrointestinal tract.
Propionibacterium avidum is found in the axilla rather than on exposed areas and increases in numbers at puberty.
Propionibacterium propionicus has been implicated as a less-common causative agent of a disease process similar to that of actinomycosis. The most common cause of actinomycosis is Actinomyces israeli infection