Causes and treatment of acne.

Causative Agent

Propionibacterium acnes is associated with Acne vulgaris (pimples), but it is not the sole cause of it. Propionibacterium acnes is a Gram positive, non-spore forming, anaerobic pleomorphic bacillus found in clinical specimens. The morphology and arrangement of Propionibacterium acnes is similar to that of Corneybacterium, but is non-toxigenic. Propionibacterium acnes is normal flora but ferments glucose leading to the production of propionic acid. It can also produce catalase along with indole, nitrate, or both indole and nitrate ("Propionibacterium acnes3").

Being an anaerobe, one might think that this bacterium would be more common in the intestines or tissues that are normally not exposed to the open air. However, this is not the case. Propionibacterium acnes loves air-exposed areas and is common around the nose and face. Even though it grows as an obligate anaerobe, Propionibacterium acnes survives in these areas because it lives in the sealed chamber-like habitats of sebaceous follicles.

English: Propionibacterium acnes grown in thioglyc...

English: Cystic acne on the back.

English: Acne Vulgaris: A: Cystic acne on the face...

Sebaceous follicles are glands in the skin attached to hair follicles located in the face, neck, back, and chest. These glands produce a substance called sebum. It is this oily substance on which the Propionibacterium acnes feeds. The sebum along with hair follicles and dead cells contribute to the sealing of the hair follicle to allow these bacteria to grow anaerobically. Within the sebaceous follicles, the sebum mixes with shed cells causing overgrowth of Propionibacterium acnes. The bacteria release lipases in order to digest the great amount of sebum that has been produced. The digest products (fatty acids) combine with bacterial antigens to create an inflammation causing the hair follicle to erupt. The bursting of the follicle leads to the lesions or pimples that are characteristic of acne ("Organisms Associated with Skin Defects and Diseases10").

Pathogenicity and Disease Symptoms

Acne is one of the most...