Gram-Negative Folliculitis
Gram-negative folliculitis is a follicular infection belonging to the group of acneiform eruptions. It develops mainly in people with acne vulgaris who have been treated with long courses of oral antibiotics, especially tetracyclines such as doxycycline and minocycline, or macrolides.
The problem starts with a shift in the natural microbial balance of the skin and the nasal vestibule. Prolonged oral antibiotics suppress gram-positive bacteria (including Cutibacterium acnes and harmless gram-positive cocci), upsetting the local ecosystem. This opens the way for gram-negative bacilli (Enterobacter, Klebsiella, Escherichia coli, Proteus, Pseudomonas aeruginosa), normally confined to the gut or nasal lining, to overgrow, invade the openings of the pilosebaceous follicles and trigger acute inflammation with pustules.
At Haute-Derma, diagnosis rests on a careful history of antibiotic use, assessment of the skin lesions and detailed microbiology testing, so that an effective treatment plan can be put in place.
Clinical Features and Differential Diagnosis
Gram-negative folliculitis is recognized by unexpected changes during acne treatment:
- Treatment failure or sudden flare: a patient on oral antibiotics for acne notices the skin suddenly worsening, with pustules erupting quickly or no longer responding to the current antibiotic.
- Lesion type: densely clustered superficial pustules, or deeper inflamed nodules and cysts that can be painful.
- No new comedones: the inflammatory lesions appear acutely without any increase in new whiteheads or blackheads.
- Distribution: lesions tend to cluster on the central face, especially around the sides of the nose, around the mouth, on the cheeks and on the chin.
Haute-Derma's Approach to Diagnosis and Treatment
- Clinical diagnosis and microbiology: the doctor examines the lesions, reviews any long-term oral antibiotic use, and takes pus for direct microscopy and bacterial culture with sensitivity testing to identify the exact gram-negative species.
- Stopping the current oral antibiotic: a key principle is to discontinue the tetracycline or macrolide being used for acne, so the disruption of the skin microbiome does not worsen.
- A targeted medical treatment plan: guided by the sensitivity results, the doctor prescribes suitable treatment such as oral isotretinoin (which shrinks the sebaceous glands and changes the follicular environment) or an antibiotic active against the gram-negative organism.
- Restoring the skin's microbial barrier: patients are advised to use gentle soap-free cleansers and barrier-supporting moisturizers, and to avoid squeezing spots or using harsh exfoliating products that damage the skin.
Common Types of Gram-Negative Folliculitis
| Type | Causative Organism and Clinical Features |
|---|---|
| Superficial pustular type (Type I) | Caused by Enterobacter, Klebsiella or E. coli. Small, superficial pustules concentrated around the nose and mouth. |
| Deep nodulocystic type (Type II) | Caused by Proteus mirabilis. Deep inflamed nodules and large, painful pus-filled cysts that can leave scars. |
| Pseudomonas flare | Caused by overgrowth of Pseudomonas aeruginosa, usually producing scattered pustules with a stinging sensation on the face and neck. |
