Growing threat: MRSA emergence poses infection problem for patients with AD

Available data indicates that the number of MRSA infections is increasing in both AD patients and the general population, an expert says. Understanding innate immunity and antimicrobial peptide production may lead to new treatment modalities.

Key Points

"Patients with AD have an increased susceptibility to infections, especially with S. aureus, and S. aureus superantigens can exacerbate AD through several mechanisms.

"Now, with the emergence of MRSA, the importance of judicious antibiotic prescribing for treating S. aureus infections, a need for new therapeutic modalities, and use of non-antibiotic techniques to decrease colonization may be even more critical," Dr. Paller tells Dermatology Times.

There is also solid evidence showing a correlation between the severity of AD and the skin-surface bacterial load.

"There are few studies about MRSA and AD, but available data indicates that the numbers of MRSA infections is increasing in both patients with AD and the general population," Dr. Paller says.

Non-antibiotic decolonization

Dilute bleach baths are often recommended for reducing S. aureus colonization in patients with AD, and results from a single-center, randomized, investigator-blind, placebo-controlled study undertaken by Dr. Paller and colleagues indicate there are benefits for this strategy.

The study enrolled pediatric patients who had moderate-to-severe AD based on the Investigator's Global Assessment (IGA) rating along with clinical signs of S. aureus infection.

After treatment with an initial course of antibiotics, they were randomized into two groups to use: 1) 1/2 cup 0.005 percent sodium hypochlorite added to a full, standard tub of water for bathing at least twice a week plus intranasal mupirocin ointment twice a day for five days out of the month; or 2) water added to the tub and vehicle ointment in the nose.

Use of bleach baths and intranasal mupirocin did not eradicate the S. aureus, although quantitative cultures were not done to assess changes in bacterial load.

The bleach baths were well tolerated, even when done daily, and their use with intermittent intranasal mupirocin was associated with better disease control based on assessments of changes in the Eczema Area and Severity Index, percent body surface area of involvement, and the IGA, Dr. Paller says.

Specialized clothing

Use of special antibacterial clothing manufactured from silver-coated textiles or silk fabric with antimicrobial activity may be another viable strategy for reducing bacterial skin colonization and controlling AD.

For example, in a split-side comparative study, investigators found similar disease improvement among patients who wore antimicrobial silk fabric on one side of the body and used a topical corticosteroid on the other side.

With a focus on minimizing bacterial colonization, physicians should also be aware that the topical products patients are using may be a source for bacterial exposure.

Contamination

In a study from Dr. Michael Cork's group in England that examined contamination of topical medications and emollients, more than half of the products being used by patients with AD grew positive cultures, and one-fourth were contaminated with S. aureus.

"These findings provide a warning to counsel patients on strategies for minimizing product contamination, including using a clean utensil for scooping out emollients from jars and storing products in the refrigerator," Dr. Paller says.

Future pathways

Emerging understanding of alterations in the innate immune response and antimicrobial peptide production in patients with AD may point to novel strategies for preventing and controlling infections.

Possibilities include the development of topical antimicrobial peptides or of targeted biologics for the TH2 cytokines, interleukin-4 (IL-4) and IL-13 and IL-10. These approaches may also be helpful in controlling viral infections in AD patients, Dr. Paller says.

"In addition to S. aureus, AD patients have increased susceptibility to infection with herpes simplex, vaccinia and molluscum.

"Innate immunity is important in controlling these viral infections, but AD patients have decreased innate immune responses with upregulation of IL-4 and IL-13, and decreased expression of natural antimicrobial peptides," Dr. Paller says.

Disclosure: Dr. Paller has no financial interests relevant to any of the material she discussed.