Therapeutics in Dermatology
A reference textbook in dermatology

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Gram-negative folliculitis

13 January 2014, by BORGES-COSTA J.


Folliculitis is characterized by superficial follicular inflammation and pus within the epidermis. Gram-positive bacteria, namely Staphylococcus aureus and Streptococcus pyogenes, are the most frequently identified bacteria in skin infections, but Gram-negative bacteria can account for roughly 25% of superficial skin infections.

Gram-negative folliculitis is mainly observed in patients under antibiotherapy for acne vulgaris or rosacea, immunosupressed patients or after swimming in pools without adequate water care [4]. The most frequent bacteria in Gram-negative folliculitis are identified in table I.


Gram-negative folliculitis can occur in patients on antibiotics for acne, more rarely on prolonged antibiotherapy for other diseases, and is characterized by a flare of lesions with pus around the mouth and nose. A medical evaluation is necessary, treatment with antibiotics must be discontinued and treatment with retinoids may be initiated. Because of the risk of serious side effects, especially in women of childbearing age, a medical observation before this therapy is mandatory.

Gram-negative folliculitis associated with water exposure is characterized by itchy red lesions or with pus on the trunk, generally three days after contact with water in crowed pools or without adequate water care. Sometimes they can also occur after contact with wet towels or sponges in spas. Treatment is generally not necessary and appliance of topical steroids must be avoided, because it makes lesions worse. If the lesions do not improve or are too itchy or extensive, a medical evaluation should be performed.

Gram-negative folliculitis has a good prognosis, leaving only residual pigmentation that disappears by itself after a few months. Nevertheless, patients on immunosuppressive drugs, as organ recipient patients, and those with HIV infection have a higher risk of complications. A medical observation must therefore be performed in these patients.


Table I Most frequently identified bacteria in Gram negative folliculitis
Bacteria in Gram-negative folliculitis

Pseudomonas aeruginosa

Proteus mirabilis

Citrobacter freundii

Aeromonas hydrophila

Enterobacter spp

Escherischia coli

Serratia marescens

Salmonella panama

Acinetobacter spp

Klebsiella spp


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