PHILADELPHIA — Community-associated methicillin-resistant Staphylococcus aureus skin infections occur significantly less often among children with atopic dermatitis than among other outpatients with skin and soft tissue infections, based on a retrospective study of 78 children.
Children with atopic dermatitis (AD) and Staphylococcus aureus skin infections seen at a pediatric and adolescent dermatology clinic had a relatively low incidence (14%) of methicillin resistance, much lower than the rate noted (45.5%) in other outpatient services during the same period (2007–2008), Dr. Catalina Matiz and her colleagues wrote in a poster presented at the annual meeting of the Society for Pediatric Dermatology.
Dr. Matiz, a postdoctoral fellow at Rady Children's Hospital in San Diego, and her coinvestigators conducted a retrospective chart study of 78 children with superinfected AD seen at the Rady pediatric and adolescent dermatology clinic between June 2007 and June 2008. The children had a positive skin culture for S. aureus.
The investigators compared these data with all skin and soft tissue infection outpatient samples sent to the hospital's microbiology lab during the same period, and also with those sent during January 2000 through January 2001 (excluding samples from the dermatology clinic). The CA-MRSA rate for samples from all outpatient services from 2000 to 2001 was 4% (192 S. aureus–positive cultures). The outpatient services rates for 2000–2001 and 2007–2008 highlight the sharp increase in CA-MRSA over the last several years.
The rate of community-associated methicillin-sensitive S. aureus (CA-MSSA) among patients with AD in the dermatology clinic from 2007 to 2008 was 86%. In comparison, the CA-MSSA rate for other outpatient services during that period was 55%. The CA-MSSA rate for all outpatient services from 2000 to 2001 was 96%.
They found that prior history of hospitalization, eczema severity, age, sex, and prior antibiotic treatment had no impact on the risk of methicillin resistance or sensitivity in these patients. For the patients with AD, positive S. aureus cultures were most common among patients aged 1–4 years (26%), followed by those aged 5–9 years (24%), and those less than a year old (23%).
The findings are striking. “It's absolutely counterintuitive because if you think of patients with AD as being more at risk for infection, you would think that at the very least they would have the same rate as that occurring in the regular population,” said Dr. Sheila Fallon Friedlander, a study coauthor and professor of pediatrics and medicine at the University of California, San Diego.
It may be that “because these kids are colonized already so much of the time with regular S. aureus, that it may exert sort of a protective effect against CA-MRSA,” Dr. Friedlander said.
In addition, patients with AD tend to present more often with multiple lesions. “That may also play a role in this. It may be that our atopic patients are presenting with secondarily infected lesions that are distinct from the abscesses and the folliculitis that we are seeing in the community,” she noted.
The findings “have informed the way that I prescribe medications for my patients,” she said. The results suggest that more standard antibiotic drugs with fewer side effects—like cephalosporins—can be used first, especially while waiting for culture results. This could not only reduce costs but also save patients from the more serious side effects of antibiotics used for resistant pathogens.
Disclosures: Dr. Matiz and Dr. Friedlander had no conflicts of interest related to this study.