Pseudomonas Folliculitis

Background

Pseudomonas folliculitis is a community-acquired skin infection that results from bacterial colonization of hair follicles after exposure to contained contaminated water^{[1, 2]} (eg, in whirlpools,^{[3, 4]}  swimming pools,^[5]  water slides, bathtubs, or flotation tanks^[6] ). Pseudomonas is one of the top three pathogens associated with recreational water use.^[7] First reported in 1975 in association with whirlpool contamination, Pseudomonas folliculitis is caused by strains of Pseudomonas aeruginosa that are acquired secondary to skin contamination.

The rash of Pseudomonas folliculitis has also been described following the use of diving suits in both seawater and freshwater immersion^[8] and, less commonly, following the use of contaminated bathing objects (eg, synthetic and natural sponges) or inflatable swim toys.^{[9, 5]} Pseudomonas folliculitis has occurred after skin depilation and with no obvious recreational exposure.

Pseudomonas folliculitis also rarely occurs as a perioral acneiform eruption in patients on long-term antibiotic (eg, tetracycline) therapy for acne.^[10]

Generally, no treatment is necessary, and most cases of Pseudomonas folliculitis resolve without any adverse reactions. For symptomatic relief, acetic acid 5% compresses may be helpful.

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Pathophysiology

The ubiquitous gram-negative bacterial organism P aeruginosa, found in soil and fresh water, gains entry through hair follicles or via breaks in the skin. Bacterial serotype O:11 is the most commonly reported isolate for water-associated Pseudomonas folliculitis, but other serotypes that have been reported include O:1, O:3, O:4, O:6, O:7, O:9, O:10, and O:16. Serotype O:11 is possibly more invasive or better adapted to survive in halogenated water.

Minor trauma from wax depilation or vigorous rubbing with sponges may facilitate the entry of organisms into the skin, and a dose-response relation exists with respect to the degree of water contamination.^{[11, 12]} Hot water, high pH (>7.8), and low chlorine level (< 0.5 mg/L) all predispose to infection.

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Etiology

The following three primary environmental conditions are known to be associated with outbreaks of Pseudomonas folliculitis^{[13, 14]} :

• Prolonged water exposure
• Excessive numbers of bathers
• Inadequate pool or hot tub care^{[14, 15]}

Risk factors for Pseudomonas folliculitis include the following^[16] :

• Crowding
• Youth
• Wearing of snug bathing suits
• Frequent and extended exposure

Pseudomonas folliculitis outbreaks have been associated with waterslides and similar water attractions.^{[16, 17]} Superchlorinated water has been advised to decrease the incidence of outbreaks. Inflatable pool toys have also been implicated as a source of infection.^{[5, 18]}

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Epidemiology

Because of the transient nature of the bather population, the actual incidence of Pseudomonas folliculitis is difficult to assess.^[19]

Pseudomonas folliculitis may occur at any age; even congenital disease has been described.^[20]  No sexual differences in incidence are known, and no racial differences in incidence have been defined.

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History

Pseudomonas folliculitis is characterized by a rash that is described as a dermatitis or a folliculitis. The onset of the rash usually occurs within 48 hours (range, 8 hr to 5 d) after exposure to contaminated water, but it can occur as long as 14 days after exposure.^[21]

Lesions begin as pruritic erythematous macules that progress to papules and pustules. Lesions are most prevalent in intertriginous areas or under bathing suits. The rash usually clears spontaneously in 2-10 days, rarely recurs, and heals without scarring, but it may cause desquamation or leave hyperpigmented macules. Pseudomonas may be cultured in patients with epidermal growth factor inhibitor (EGFR)-related folliculitis.^[22]

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Physical Examination

The predominant manifestation of Pseudomonas folliculitis is dermatitis (79%).

Pseudomonas folliculitis is characterized by follicular papules, vesicles, and pustules, which may be crusted. Lesions involve exposed skin, but they usually spare the face, the neck, the soles, and the palms. Lesions progress to erythematous papulopustules that range from 2 to 10 mm in diameter, with a pinpoint central pustule. (See the images below.) The rash is not unique in appearance and is most often confused with insect bites.

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Erythematous papulopustules of pseudomonas folliculitis. Image from Mark Welch, MD.

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Erythematous papulopustules of pseudomonas folliculitis, with significant perilesional flare. Image from Andy Montemarano, MD.

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Pseudomonas folliculitis. Image from Hon Pak, MD.

Other systemic signs of Pseudomonas folliculitis that can occur with the rash include the following:

• Low-grade fever (4%), often accompanied by headache (15%) or malaise/fatigue (19%)
• Otitis media and otitis externa^[23]
• Breast tenderness in both women and men - The glands of Montgomery on the nipple may become infected or may involve frank mastitis (11%)
• Painful lymphadenopathy
• Conjunctivitis
• Rhinitis
• Pneumonia (rare)
• Urinary tract infection (UTI; rare)^[24]

Rarely, lesions may progress to chronically draining subcutaneous nodules.

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Laboratory Studies

The diagnosis of Pseudomonas folliculitis is best verified by results of bacterial culture growth from either a fresh pustule or a sample of contaminated water. Gram staining of a Pseudomonas folliculitis pustule may also be performed.

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Histologic Findings

Standard hematoxylin and eosin (H&E) preparation displays a severe follicular epithelial inflammatory response, which may result in follicular distention and rupture. The pilar canal is filled with a dense polymorphonuclear leukocytic infiltrate, often accompanied by a brisk perifollicular lymphocytic infiltration. Both the epidermis and the infected apocrine glands remain intact.

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Medical Care

P aeruginosa infection is usually self-limited, clearing in 2-10 days. Despite the discomfort caused by the Pseudomonas folliculitis rash, no treatment is necessary. Systemic spread is typically not observed. P aeruginosa is resistant to nearly all common topical and oral antibiotics, and no indication exists that the course of the skin condition is altered with treatment.

Symptomatic relief of Pseudomonas folliculitis may be achieved through the use of acetic acid 5% compresses for 20 minutes two to four times a day.

In Pseudomonas folliculitis patients with associated mastitis, those with persistent infections, and those who are immunosuppressed, a course of ciprofloxacin (500 or 750 mg PO q12hr) is advised.

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Prevention

Proper maintenance and chlorination of pools, hot tubs, whirlpools, and spas are essential to decrease the population of Pseudomonas species. The Centers for Disease Control and Prevention (CDC) has recommended a free chlorine concentration of 1 mg/L (for home pools) or 3 mg/L (for hot tubs) and a pH of 7.0-7.8.^[2] However, P aeruginosa has been recovered from adequately chlorinated water containing 2 mg/L of free chlorine. Bromine is considered an acceptable alternative to chlorine and is considered more effective in hot water, with a longer period of activation.

Complete drying of sponges between uses is essential because P aeruginosa does not survive drying.

Showering after exposure to contaminated water does not seem to prevent Pseudomonas folliculitis.

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Medication Summary

Systemic antibacterials for uncomplicated Pseudomonas folliculitis infections have shown no benefit. Persistent infections may benefit from a standard 7- to 10-day course of ciprofloxacin.

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Ciprofloxacin (Cipro)

• Dosing, Interactions, etc.

Clinical Context:  Ciprofloxacin is a member of the fluoroquinolone family of synthetic, broad-spectrum antibacterials. It contains a piperazine moiety responsible for antipseudomonal activity. Ciprofloxacin interferes with DNA gyrase normally needed for synthesis of bacterial DNA.

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Class Summary

Bactericidal antibacterials inhibit bacterial growth and proliferation.

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