HomeHealth articlesfolliculitisWhat Is Gram-Negative Folliculitis?

Gram-Negative Folliculitis: Symptoms, Diagnosis, and Treatment

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Gram-negative folliculitis is the result of long-term anti-bacterial treatment or bacterial interference and replacement of the gram-positive flora.

Medically reviewed by

Dr. Dhepe Snehal Madhav

Published At April 4, 2023
Reviewed AtJanuary 2, 2024

What Is Gram-Negative Folliculitis?

Gram-negative bacterias are bacteria that do not take gram staining. Gram-negative folliculitis is an acne disorder caused by a bacterial infection. The bacteria causing the infection include Serratia marcescens, Escherichia coli, Klebsiella, Pseudomonas aeruginosa, and Proteus species. The infection can be a result of long-term antibacterial treatment with Tetracycline and topical antibiotics in acne patients. Other skin conditions that are called gram-negative bacteria include spa pool folliculitis cast by pseudomonas bacteria. This bacteria can withstand increased alkalinity, riveted temperatures, and high organic content of hot pools. The other infection is skin folliculitis due to Aeromonas hydrophila which arises with an area of skin injury exposed to contaminated fresh water.

The appearance of gram-negative folliculitis is seen in acne patients in whom oral treatment with Tetracycline has not resulted in an improvement after three to six months of treatment. The occurrence of gram-negative folliculitis in acne patients is generally underestimated because bacteriology and correct sampling is rarely performed.

Gram-negative folliculitis is an infection caused by gram-negative bacteria. It can occur as a complication in patients with rosacea and acne vulgaris that develops in patients with prolonged intake of systemic antibiotics.Gram-negative folliculitis can mostly occur in patients with acne who have a flare-up of pustular or cystic lesions and in patients whose acne is resistant to treatment. It can also occur in the setting of hot-tub immersion and in patients infected with HIV (human immunodeficiency virus).

What Are the Symptoms of Gram-Negative Folliculitis?

  • Gram-negative folliculitis presents as an acne-like pustular rash. It is often misdiagnosed as a worsening of acne as it is usually seen in patients with existing acne.

  • These lesions are generally seen around the area of the upper lips under the nose, cheeks, and chin.The skin on the face may become red and flushed due to inflammation.

  • Small, red bumps or pustules that are usually tender or painful to touch may appear on the face, neck, and upper chest.

  • The pustular rashes are generally superficial with relatively few papules and comedones. Such lesions are generally caused by E.coli, Serratia species, and Klebsiella. The pustules may develop a crusty outer layer as they heal.

  • In some patients, the lesions are nodular, deep, and cyst-like and are caused by proteus species that invade deeply into the skin producing puss, abscesses, and cysts.

  • Gram-negative folliculitis can cause recurrent outbreaks of acne, even after successful treatment with antibiotics.

  • In severe cases, gram-negative folliculitis can cause scarring or hyperpigmentation of the affected skin.

How Is Gram-Negative Folliculitis Diagnosed?

  • Gram-negative folliculitis can be easily diagnosed by the healthcare physician only by looking at it.

  • If early treatment does not clear up, a certain investigation needs to be done such as scraping of the skin to rule out yeast under the microscope, a swab culture test to determine the cause of infection, and a skin biopsy to rule out other conditions.

  • The diagnosis of gram-negative folliculitis is made based on the presence of a pustular rash that does not heal even after anti-acne antibiotics.

  • The diagnosis of the gram-negative antibiotics is made by cytology and microscopy. The bacteria appears pink or red with a gram stain.

  • Bacterial culture identifies the bacteria causing the infection. These bacteria are then checked for antibiotic sensitivity.

How Is Gram-Negative Folliculitis Treated?

  • The treatment for gram-negative folliculitis depends on the type and severity of the condition. Dermatologist figures out ways to control folliculitis, check whether a drug is causing the symptoms, and avoid scars and making them less noticeable.

  • Lotions, pills, or gels to help bacterial control infection are generally antibiotics. Infection-control pills or oral antibiotics and or not used to treat folliculitis.

  • Gram-negative folliculitis in patients with rosacea and acne is treated with Isotretinoin 0.5 to 1 mg/kg daily for four to five months.

  • Bacteria are generally sensitive to Trimethoprim and Ampicillin.

  • Isotretinoin suppresses the drying of the mucous membrane and sebum production, especially the nasal membrane that the bacteria inhabits.

  • Isotretinoin offers the most useful cure for gram-negative folliculitis. It is a synthetic beta-carotene derivative that is highly efficacious when used in patients with severe nodulocystic acne unresponsive to conventional therapy.

  • The best results are obtained in patients with gram-negative folliculitis and severe rosacea with orally administered Isotretinoin. Isotretinoin probably has multiple modes of action that include alteration of the pattern of keratinization within the follicle, inhibition of sebaceous gland activity, inhibition of Propionibacterium acne growth within the follicle, and inhibition of inflammation.

  • Minor surgeries or opted when there is a large boil or carbuncle. A small cut is made into the lesion to drain the pus. This relieves the pain, lowers the risk of scarring, and speeds the recovery. The area is then covered with sterile gauze to absorb any leaking pus.

  • Laser hair removal is a helpful treatment for gram-negative folliculitis. This treatment requires multiple visits to the dermatologist.

  • Benzoyl peroxide is an over-the-counter topical medication and is also an FDA-approved prescription medication for the treatment of gram-negative folliculitis. It is bactericidal with activity against Cutibacterium acnes (C. acnes) on the skin and within the hair follicles.

  • Benzoyl peroxide has mild sebostatic and keratolytic effects and is most effective when used combined with other acne vulgaris therapies. In contrast to other topical antibiotics, drug resistance has not appeared to develop with Benzoyl peroxide use.


Gram-negative folliculitis can be a reason for prolonged antibacterial treatments in patients with acne and rosacea. It is induced by the alteration of facial skin flora and the nasal mucous membrane by a decline of gram-positive bacteria and an accumulation of gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, Klebsiella species, Serratia marcescens, and Proteus mirabilis. The acne patients who have not had a clinical improvement after three to six months of treatment with Tetracyclines antibiotics should be tested for gram-negative folliculitis. The infection is generally not diagnosed as it is underestimated, likely because bacteriological studies are rarely requested by doctors and also due to the increased use of oral Isotretinoin for acne management. The most effective treatment for gram-negative folliculitis is oral isotretinoin (0.5 to 1 mg/kg/day for four to five months).

Dr. Dhepe Snehal Madhav
Dr. Dhepe Snehal Madhav



folliculitisgram-negative folliculitis
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