There is a type of acne caused by gram negative bacteria. This is very unusual. All other acne are caused by gram positive bacteria.
Gram negative bacteria generally cause infections of organs inside the body and very rarely on the skin. Any infection caused by a gram negative bacteria is considered serious.
Gram stain just denotes whether the cell membrane of the bacteria is stained positive or negative with a special stain. In general, gram negative bacteria have the potential to secrete toxic byproducts which can cause intense inflammation and infection.
The acne caused by the gram negative species is severe and requires prolonged antibiotic treatment. Individuals who take antibiotics for long periods for other conditions are the ones who are most prone to gram negative bacteria acne.
Gram negative folliculitis is a rare condition and occurs equally in both males and females.
Gram Negative Folliculitis is a bacterial infection characterized by pustules and cysts. The cysts are extremely large and conspicuous. The cysts are generally painful to touch.
The unfortunate thing is that many of these gram negative bacteria are resistant to most antibiotics. The basic treatment for this type of acne is with Accutane and a few select group of antibiotics.
The response to treatment is variable but scars always occur.