The incidence of skin and soft tissue infections (SSTIs) has increased dramatically over the past decade, resulting in significant morbidity in millions of otherwise healthy individuals worldwide. Certain groups, like military personnel, are at increased risk for SSTI development. Although nasal colonization with Staphylococcus aureus is an important risk factor for the development of SSTIs, it is not clear why some colonized individuals develop disease while others do not. Recent studies have revealed the importance of microbial diversity in human health. Therefore, we hypothesized that the nasal microbiome may provide valuable insight into SSTI development. To examine this hypothesis, we obtained anterior-naris samples from military trainees with cutaneous abscesses and from asymptomatic (non-SSTI) participants. We also obtained samples from within abscess cavities. Specimens were analyzed by culture, and the microbial community within each sample was characterized using a 16S sequencingbased approach. We collected specimens from 46 non-SSTI participants and from 40 participants with abscesses. We observed a significantly higher abundance of Proteobacteria in the anterior nares in non-SSTI participants (P < 0.0001) than in participants with abscesses. Additionally, we noted a significant inverse correlation between Corynebacterium spp. and S. aureus (P ‫؍‬ 0.0001). The sensitivity of standard microbiological culture for abscesses was 71.4%. These data expand our knowledge of the complexity of the nasal and abscess microbiomes and potentially pave the way for novel therapeutic and prophylactic countermeasures against SSTI. Staphylococcus aureus is a leading pathogen in both community and hospital settings. Infections with S. aureus range from invasive disease such as bacteremia and pneumonia to generally less severe skin and soft tissue infections (SSTIs) (1-3). SSTIs, especially those caused by USA300 methicillin-resistant Staphylococcus aureus (MRSA), have emerged as a common, burdensome, and costly disease (4-6). Individuals in congregate settings (e.g., members of athletic teams, prison inmates, and military trainees) are at increased risk for SSTI (7-10).Given that approximately one-third of people may exhibit S. aureus carriage, it is unclear why some develop SSTI while others do not (11). While it is clear that host genetics, immune responses, and strain differences contribute (12-17), there are likely other important factors. As the anterior nares appear to be a critical S. aureus reservoir (1, 18, 19) and because antecedent nasal carriage increases the risk for infection (1, 20, 21), a better understanding of nasal microbial ecology may yield valuable clues regarding SSTI susceptibility.The anterior nares are a dynamic microbial battleground between pathogens and commensals (22,23). The concept that changes in the host microbiome may influence human health is well documented (24); however, few studies have investigated how the nasal microbiome is altered in response to human disease (25,26). Importantl...

NCT01105767.

cChlorhexidine has been increasingly utilized in outpatient settings to control methicillin-resistant Staphylococcus aureus (MRSA) outbreaks and as a component of programs for MRSA decolonization and prevention of skin and soft-tissue infections (SSTIs). The objective of this study was to determine the prevalence of chlorhexidine resistance in clinical and colonizing MRSA isolates obtained in the context of a community-based cluster-randomized controlled trial for SSTI prevention, during which 10,030 soldiers were issued chlorhexidine for body washing. We obtained epidemiological data on study participants and performed molecular analysis of MRSA isolates, including PCR assays for determinants of chlorhexidine resistance and high-level mupirocin resistance and pulsed-field gel electrophoresis (PFGE). During the study period, May 2010 to January 2012, we identified 720 MRSA isolates, of which 615 (85.4%) were available for molecular analysis, i.e., 341 clinical and 274 colonizing isolates. Overall, only 10 (1.6%) of 615 isolates were chlorhexidine resistant, including three from the chlorhexidine group and seven from nonchlorhexidine groups (P > 0.99). Five (1.5%) of the 341 clinical isolates and five (1.8%) of the 274 colonizing isolates harbored chlorhexidine resistance genes, and four (40%) of the 10 possessed genetic determinants for mupirocin resistance. All chlorhexidine-resistant isolates were USA300. The overall prevalence of chlorhexidine resistance in MRSA isolates obtained from our study participants was low. We found no association between extended chlorhexidine use and the prevalence of chlorhexidine-resistant MRSA isolates; however, continued surveillance is warranted, as this agent continues to be utilized for infection control and prevention efforts. Skin and soft-tissue infections (SSTIs), particularly those attributed to methicillin-resistant Staphylococcus aureus (MRSA), remain a persistent cause of morbidity in community settings. Over the past decade, ambulatory care and emergency department visits for SSTIs have nearly doubled (1, 2). The emergence of MRSA, especially strain USA300 (3), as a community pathogen is recognized as underlying this surge in SSTI rates (1, 4). Individuals in congregate settings, such as children in day care centers, athletes, inmates, and military personnel, are at increased risk for MRSA SSTIs (5-8).Chlorhexidine, a topical antiseptic, has had a longstanding role in infection prevention in health care settings (9) and has been increasingly utilized in outpatient settings (9). It has been an integral component of prevention and control measures during MRSA outbreaks (5, 10, 11). Additionally, chlorhexidine has been demonstrated to be effective against recurrent MRSA SSTIs (12) and in limiting the household spread of SSTIs (13) and is recommended when MRSA decolonization of individuals is a goal (14). In the absence of an effective S. aureus vaccine (15), chlorhexidine has also been employed as an SSTI prevention strategy among military trainees, a group known to be...

While it is evident that nasal colonization with S. aureus increases the likelihood of SSTI, there is a significant lack of information regarding the contribution of extranasal colonization to the overall risk of a subsequent SSTI. Furthermore, the impact of S. aureus colonization on bacterial community composition outside the nasal microbiota is unclear. Thus, this report represents the first investigation that utilized both culture and high-throughput sequencing techniques to analyze microbial dysbiosis at multiple body sites of healthy and diseased/colonized individuals. The results described here may be useful in the design of future methodologies to treat and prevent SSTIs.

We describe the selection of reduced chlorhexidine susceptibility during chlorhexidine use in a patient with two episodes of cutaneous USA300 methicillin-resistantStaphylococcus aureusabscess. The second clinical isolate harbors a novel plasmid that encodes the QacA efflux pump. Greater use of chlorhexidine for disease prevention warrants surveillance for resistance.