Pseudomonas Folliculitis

Background

Pseudomonas folliculitis is a community-acquired skin infection, which results from the bacterial colonization of hair follicles after exposure to contained, contaminated water (eg, whirlpools,^{[1, 2, 3, 4, 5, 6]} swimming pools,^[7] water slides, bathtubs). Pseudomonas is one of the top three pathogens associated with recreational water use.^[8] 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 fresh water immersion,^{[9, 10]} and, less commonly, following the use of contaminated bathing objects (eg, synthetic and natural sponges) or inflatable swim toys.^{[11, 12, 13, 14]} 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.^[15]

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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 relationship exists in relation to the degree of water contamination.^{[11, 12, 16, 17]} 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^{[18, 19, 20]} :

• Prolonged water exposure
• Excessive numbers of bathers
• Inadequate pool or hot tub care^{[20, 21, 22]}

Risk factors for Pseudomonas folliculitis include the following^[23] :

• Crowding
• Youth
• Wearing of snug bathing suits
• Frequency and duration of exposure

Pseudomonas folliculitis outbreaks have been associated with waterslides and similar water attractions.^[24] Superchlorinated water has been advised to decrease the incidence of outbreaks. Inflatable pool toys have also been implicated as a source of infection.^[25]

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Epidemiology

Frequency

The actual incidence of Pseudomonas folliculitis is difficult to assess because of the transient nature of the bather population.^[26]

Race

No racial differences in incidence are known for Pseudomonas folliculitis.

Sex

No sexual differences in incidence are known for Pseudomonas folliculitis.

Age

It may occur at all ages, and even congenital disease has been described.^[27]

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Prognosis

Most cases of Pseudomonas folliculitis resolve without any adverse reactions.

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History

Pseudomonas folliculitis is characterized by a rash, described as a dermatitis or a folliculitis. The rash onset is usually 48 hours (range, 8 h to 5 d) after exposure to contaminated water, but it can occur as long as 14 days after exposure.^[28]

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.

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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 in size from 2-10 mm in diameter, with a pinpoint central pustule. The rash is not unique in appearance and is most often confused with insect bites. See the images below.

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Erythematous papulopustules of pseudomonas folliculitis. Courtesy of Mark Welch, MD.

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

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Pseudomonas folliculitis. Courtesy of 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%) and malaise/fatigue (19%)
• Otitis media and otitis externa^[29]
• 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)^[30]

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 stain of a Pseudomonas folliculitis pustule may also be performed.

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Histologic Findings

Standard hematoxylin and eosin 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 is usually a self-limited infection, 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 twice a day to 4 times a day.

In Pseudomonas folliculitis patients with associated mastitis, in those with persistent infections, or in those who are immunosuppressed, a course of ciprofloxacin (500 or 750 mg PO bid) 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 recommend a free chlorine concentration of 1-3 mg/L and a pH of 7.2-7.8.^[31] 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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