Staphylococcus aureus Antibiotic Susceptibility Patterns in Pediatric Atopic Dermatitis

To describe the Staphylococcus aureus strains found on patients with atopic dermatitis (AD) as a means to offer the best empirical antibiotic choices for skin infections in patients with AD.

The study included patients younger than 18 years of age with dermatology evaluated AD and a cutaneous aerobic bacterial culture from an infected site obtained during the study period of September 1, 2012 to August 31, 2017.

A retrospective cohort study of the study population seen at Saint Louis Children’s Hospital and associated dermatology clinics during a five-year period. Review of electronic medical records identified patients with AD seen for cutaneous infections and positive bacterial cultures. Within the study population, patient demographics and use of bleach baths was evaluated as a potential link to methicillin resistance. Patients with methicillin-resistant S. aureus (MRSA) infections were compared with those with methicillin-sensitive S. aureus (MSSA) infections. The data obtained from cutaneous bacterial cultures of these AD patients was also compared with pediatric patients seen from 2013 to 2015 for S. aureus skin abscess at the Saint Louis Children’s Hospital Emergency Department (ED).

During wthe study period a total of 182 cultures were obtained from 118 patients with skin infections. Of those cultures, S. aureus grew in 170 (93.4%) and the remainder grew different species. Among the cultures growing S. aureus, only MSSA grew in 130 (77.8%) and MRSA grew in 37 (22.2%), while 3 cultures were excluded for growing both MRSA and MSSA. None of the patient demographics of age, sex, or race varied in prevalence between MRSA compared with MSSA patients. Upper extremities were the most affected body site. MRSA prevalence was not significantly different in patients using dilute bleach baths during the study period to those that did not. Additionally, patients with AD had a lower prevalence of MRSA infections (22%) when compared with the prevalence of MRSA infections seen in the ED (44%). Patients with AD and MSSA skin infections were less susceptible to doxycycline (89.4%) compared with 97% of patients seen in the ED. Patients with AD growing only MRSA were likewise less susceptible to trimethoprim-sulfamethoxazole (92%) when compared with ED patients (98%).

The overwhelming majority (93%) of skin infections in study AD patients isolated S. aureus. Based on the culture results obtained in this study, the use of first-generation cephalosporins is appropriate. Empirical doxycycline, clindamycin or trimethoprim-sulfamethoxazole (TMP-SMX) should be considered in patients with a history of MRSA infection.

As physicians, we play a vital role in the plight against antibiotic resistance. Studies such as this one provide invaluable insight into the day-to-day decisions made by physicians in their practice. There are nonetheless limitations to the study given the retrospective, single-center manner in which the data were collected. Continuation of these type of studies are important to confirm the appropriateness of antibiotic choices.