The Cutaneous Microbiome in Outpatients Presenting With Acute Skin Abscesses

Patients commonly present to emergency departments with skin abscesses, and the incidence appears to be increasing [1]. While many factors contribute to the development of infection with community-acquired methicillin-resistant Staphylococcus aureus (MRSA), such as participation in contact sports, incarceration, injection drug use, and, for men, having sex with men, the strongest risk factors are having a household contact with MRSA infection and having a history of recent antibiotic use [2]. Systemic antibiotics, as well as topical agents, including antibacterial soaps and cleansers, can suppress or eliminate normal skin bacteria [3]; antibiotic use may alter the indigenous microbiota for several weeks or longer [3]. Among patients presenting to the emergency department with skin abscesses due to MRSA, antibiotic use within the prior month has been associated with an increased risk [2]. The composition of the normal cutaneous microbiota is complex; analysis of skin bacteria indicates multiple species, with particular compositions depending on body site [4–10]. The skin microbiome can be divided into dry, moist, and sebaceous sites [6]. As at other sites, the residential bacteria may play a role in defenses against pathogenic bacteria [3]. Our hypothesis is that the perturbation of the normal protective bacterial population predisposes individuals to contracting MRSA and developing skin abscesses. We tested this hypothesis by comparing the microbiota in patients with skin abscesses to the microbiota in control patients without abscesses. We hypothesized that, compared with controls, individuals who developed skin abscesses would have an abnormal microbiota, either at sites adjacent to the abscess, indicating a local diathesis, or more distantly, consistent with a more generally perturbed microbiota.