Treatment of Staphylococcus aureus Colonization in Atopic Dermatitis Decreases Disease Severity

Staphylococcus aureus is a known complication of atopic dermatitis, and treatment of S aureus can improve this condition. Nasal swabbing with mupirocin ointment is somewhat effective in reducing nasal carriage of S aureus, and other methods of S aureus control on skin surfaces have been postulated.

Huang and colleagues conducted a randomized controlled trial of bathing in dilute bleach bath plus nasal mupirocin treatments over a 3-month period to determine whether this combination would reduce the severity of atopic dermatitis. The patients were 6 months to 17 years old and were recruited from a referral dermatology population (single site). Patients were randomly assigned equally to treatment or placebo, but both groups received a 2 week run-in treatment of oral cephalosporin to treat S aureus.

Patients in the treatment group bathed for 5-10 minutes twice a week in water that contained a half-cup of 6% bleach (ultimate concentration of bath water was 0.005% bleach). Patients in the placebo group bathed in a similar manner but with a half-cup of placebo solution (water) added to the bath. Patients and parents were instructed not to tell investigators of their suspicions regarding the assignment (the placebo did not have a smell) in order to preserve investigator blinding, and investigators did not confirm or deny patient and parent suspicions. The concentration of bleach in the water was such that the bath water did not produce a distinctive odor, allowing investigator blinding.

Both groups placed mupirocin (treatment) or petrolatum (placebo) ointments in their nares twice per day for 5 consecutive days, at least 1 cycle per month. All patients received topical emollient hydration and used topical anti-inflammatory agents. The primary outcome of interest was eczema severity, measured at the arms, legs, head/neck, and trunk and assessed by using an objective scale. The score also incorporated the degree of body surface area involved.

Swabs of nares and "worst-appearing" skin areas were obtained at enrollment (before cephalosporin was given), and at 1- and 3-month follow-up. The authors enrolled 31 patients (15 in treatment group); 25 provided data at 1 month and 22 at 3 months. At enrollment, the patients had atopic dermatitis on a mean of 33% of their body surface area. Although the differences were not statistically significant, the patients in the treatment group had higher severity index scores at enrollment than those in the placebo group (22.1 vs 16.6, respectively), and they had a higher percentage of body surface area affected (37.8% vs 28.1%).

Both groups experienced statistically significant improvement over baseline at both 1- and 3-month follow-up, but the improvement was much greater in the treatment group. For example, at 3 months, the average severity index score was 6.8 in the treatment group (down from 22.1 at baseline) compared with 13.4 in the placebo group (down from 16.6).

In a similar manner, the involved body surface area decreased by 23.7% in the treatment group and by 3% in the placebo group. Cultures changed very little; S aureus was isolated from more than 80% of nares and skin from patients in both groups before the intervention. Methicillin-resistant isolates were obtained from 4% of nares and 7% of skin samples. After the trial, 82% of the patients still had S aureus isolated.

The authors concluded that the use of intermittent nasal mupirocin along with twice-weekly baths in dilute bleach can improve the skin condition of patients with atopic dermatitis.

The authors noted that the patients did not improve in the head and neck areas, which were not submerged in the baths. This finding supports the idea that it was the bathing that produced the benefit, not some trial-specific monitoring or the 2 weeks of cephalosporin treatment. Bleach baths have been suggested as a treatment for children with repeat S aureus skin infections, especially given the surge in community-associated methicillin-resistant S aureus disease. However, this study shows a more "proximal" benefit of skin symptom improvement. A study demonstrating the "home run" outcome of a reduction in cellulitis or localized abscess after this process would require many more patients. These data offer suggestions of how one might proceed to treat certain patients, but the findings should not be generalized to patients with repeat abscesses from community-associated methicillin-resistant S aureus, not all of whom will have atopic dermatitis.

Written by: Huang JT, Abrams M, Tlougan B, Rademaker A, Paller AS
Pediatrics. 2009;123:e808-814

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