Topical Antimicrobial Treatments Can Elicit Shifts to Resident Skin Bacterial Communities and Reduce Colonization by Staphylococcus aureus Competitors

<jats:title>ABSTRACT</jats:title> <jats:p> The skin microbiome is a complex ecosystem with important implications for cutaneous health and disease. Topical antibiotics and antiseptics are often employed to preserve the balance of this population and inhibit colonization by more pathogenic bacteria. However, despite their widespread use, the impact of these interventions on broader microbial communities remains poorly understood. Here, we report the longitudinal effects of topical antibiotics and antiseptics on skin bacterial communities and their role in <jats:named-content content-type="genus-species">Staphylococcus aureus</jats:named-content> colonization resistance. In response to antibiotics, cutaneous populations exhibited an immediate shift in bacterial residents, an effect that persisted for multiple days posttreatment. By contrast, antiseptics elicited only minor changes to skin bacterial populations, with few changes to the underlying microbiota. While variable in scope, both antibiotics and antiseptics were found to decrease colonization by commensal <jats:named-content content-type="genus-species">Staphylococcus</jats:named-content> spp. by sequencing- and culture-based methods, an effect which was highly dependent on baseline levels of <jats:named-content content-type="genus-species">Staphylococcus</jats:named-content> . Because <jats:named-content content-type="genus-species">Staphylococcus</jats:named-content> residents have been shown to compete with the skin pathogen <jats:named-content content-type="genus-species">S. aureus</jats:named-content> , we also tested whether treatment could influence <jats:named-content content-type="genus-species">S. aureus</jats:named-content> levels at the skin surface. We found that treated mice were more susceptible to exogenous association with <jats:named-content content-type="genus-species">S. aureus</jats:named-content> and that precolonization with the same <jats:named-content content-type="genus-species">Staphylococcus</jats:named-content> residents that were previously disrupted by treatment reduced <jats:named-content content-type="genus-species">S. aureus</jats:named-content> levels by over 100-fold. In all, the results of this study indicate that antimicrobial drugs can alter skin bacterial residents and that these alterations can have critical implications for cutaneous host defense. </jats:p>