Gram-negative folliculitis

Gram-negative folliculitis is an infection caused by gram-negative bacteria. The infection may occur as a complication in patients with acne vulgaris and rosacea and usually develops in patients who have received systemic antibiotics for prolonged periods.  Gram negative folliculitis should be considered in patients with acne who have a flare-up of pustular or cystic lesions and in patients whose acne is resistant to treatment.

  • Although gram negative folliculitis is largely a complication of acne vulgaris and thus is expected to follow the age distribution of that entity, a slightly increased age at onset has been observed. The tendency for gram-negative folliculitis to begin after the early teenage years is most likely because most patients who develop gram negative folliculitis have undergone treatment of acne with a broad-spectrum antibacterial agent for a prolonged period.  


Folliculitis is caused by an infection of hair follicles, usually from the bacteria. The condition is classified as either superficial or deep, based on how much of the hair follicle it involves. Deep folliculitis is usually more severe. Systemic antibiotics, such as tetracyclines, can alter the nasal flora. The resultant overgrowth of gram-negative bacteria can lead to folliculitis.


Gram negative folliculitis is an advanced form of inflammatory acne. When inflammatory acne persists beyond treatment and even worsens, gram negative folliculitis sets in. After continued resistance to antibacterial treatment, the body gradually develops immunity to the antibiotic, eventually producing acne that is worse than ever before. Four percent of people who have inflammatory acne will go on to develop gram negative folliculitis.

There are two clinical variants of gram negative folliculitis:

Type 1

  • Is the most common, about 80% of cases, with the presence of multiple papules and pustules in the middle of the  face
  • Superficial pustular lesions without comedones

Type 2

  • It occurs approximately in 20% of patients.
  • Characterized by deep, nodular, and cystic lesions.

Treatment of gram-negative folliculitis

Since it results from antibiotic-resistant bacteria, treating gram negative folliculitis used to be very difficult. Sufferers can be prescribed systemic, bacteriostatic antibiotics such as ampicillin, although there is conflicting evidence about the effectiveness of antibiotics on gram negative folliculitis.

Because of the risk of serious side effects, especially in women of childbearing age, a medical observation and evaluation is mandatory before treatment.

Gram negative folliculitis usually clears promptly with:

  • Antibiotics to which the organisms are sensitive (e.g. ampicillin, trimethoprim).
  • Isotretinoin, which appears to act by suppressing sebum production and drying out the mucous membranes, especially the nasal mucous membranes, which is where causative bacteria are found.
› Gram-negative Folliculitis


acne vulgaris, rosacea, cystic, papules, pustules, antibiotic, comedones,

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