Antimicrobial activity of commonly used topical moisturizers on the survival of methicillin-resistant Staphylococcus aureus USA300

Summary: Abstract Body: Patients with atopic dermatitis (AD), who are frequently colonized with Staphylococcus aureus (S. aureus), are often advised to use moisturizers to protect their skin barrier, though the effects of these products on the skin microbiome remains under exploration. This cell culture study investigates the impact of commonly used topical moisturizers on the survival of community-associated Staphylococcus aureus USA300, one of the dominant community-associated methicillin-resistant strains known to produce superantigens that impact barrier function. Commercially available products were inoculated with USA300, incubated at 30°C, and sampled in triplicate at 0, 1, 3, 5, 12 and 24 hours before agar plate analysis for colony-forming units (CFU). Results demonstrated differential effects among the moisturizers on USA300 survival. Cetaphil Eczema Restoraderm and Curel inhibited USA300 by the 5-hour timepoint, whereas Cerave Moisturizing Cream and Cerave Daily Moisturizing Lotion inhibited it at the 12-hour timepoint. In contrast, other tested moisturizers did not significantly inhibit and instead sustained methicillin-resistant S. aureus USA 300 survival to the 24-hour timepoint. These differences may contribute to the variable efficacy of these moisturizers in alleviating AD. Further studies will need to be performed to identify the factors influencing the survival of USA300 and other key bacteria involved in AD dysbiosis. This study highlights notable differences in the ability of common moisturizers to influence pathogenic S. aureus USA300 survival, highlighting the need for studies investigating the therapeutic potential of moisturizers in modulating the skin microbiome in atopic dermatitis. Victoria Li¹, Julia L. Gao¹, Richard N. Levy¹, Katie Dung¹, Richard L. Gallo¹, Teruaki Nakatsuji¹, Tissa Hata¹ 1. Dermatology, University of California San Diego, San Diego, CA, United States. Translational Studies: Preclinical