The Human Microbiome and Skin and Soft-Tissue Infections
Uniformed Services University of the Health Sciences Bethesda United States
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Skin and soft tissue infections SSTIs are among the most prevalent and complex infections observed in both the inpatient and outpatient settings. Clinically, SSTIs can range from mild ex. folliculitis to severe ex. necrotizing fasciitis and can present as either purulent ex. cutaneous abscess or non-purulent ex. cellulitis. Furthermore, SSTIs can be caused by a wide array of bacterial pathogens such as Staphylococcus aureus and beta-hemolytic Streptococci BHS. While SSTIs are frequently reported throughout the world, certain congregate populations, such as military trainees, are at increased risk for SSTI development. Indeed, the number of SSTI-related hospital admissions exceed even those for influenza and pneumonia during the first two years of service. Although nasal colonization with S. aureus is an established risk factor for SSTI development, it is still unclear why some colonized individuals develop disease while others do not. Given the recent association between the human microbiome and human health, we hypothesized that fluctuations in the nasal microbiome may be associated with SSTI development. Furthermore, given the variability in SSTI presentation, we set out to determine if specific risk factors andor microbial profiles were unique to either cutaneous abscess or cellulitis. Using a high-throughput sequencing approach, we found that the nasal microbiomes of trainees developed SSTI had significantly less Proteobacteria compared to trainees that did not harbor a SSTI. Additionally, we found that the abundance of S. aureus in the nares was inversely correlated with Corynebacterium. With respect to bacterial etiology, we found that while most cutaneous abscesses were dominated by S. aureus, polymicrobial infections were frequently observed. We also characterized a unique case of cutaneous abscess caused by a strain of S. aureus with decreased susceptibility to chlorhexidine.