Staphylococcus aureus Colonization and Strain Type at Various Body Sites among Patients with a Closed Abscess and Uninfected Controls at U.S. Emergency Departments

Abstract

d Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is a prevalent cause of skin and soft tissue infections (SSTI), but the association between CA-MRSA colonization and infection remains uncertain. We studied the carriage frequency at several body sites and the diversity of S. aureus strains from patients with and without SSTI. Specimens from the nares, throat, rectum, and groin of case subjects with a closed skin abscess (i.e., without drainage) and matched control subjects without a skin infection (n ‫؍‬ 147 each) presenting to 10 U.S. emergency departments were cultured using broth enrichment; wound specimens were cultured from abscess cases. Methicillin resistance testing and spa typing were performed for all S. aureus isolates. S. aureus was found in 85/147 (57.8%) of abscesses; 49 isolates were MRSA, and 36 were methicillin-susceptible S. aureus (MSSA). MRSA colonization was more common among cases (59/147; 40.1%) than among controls (27/147; 18.4%) overall (P < 0.001) and at each body site; no differences were observed for MSSA. S. aureus-infected subjects were usually (75/85) colonized with the infecting strain; among MRSA-infected subjects, this was most common in the groin. The CC8 lineage accounted for most of both infecting and colonizing isolates, although more than 16 distinct strains were identified. Nearly all MRSA infections were inferred to be USA300. There was more diversity among colonizing than infecting isolates and among those isolated from controls versus cases. CC8 S. aureus is a common colonizer of persons with and without skin infections. Detection of S. aureus colonization, and especially MRSA, may be enhanced by extranasal site culture. Staphylococcus aureus frequently causes invasive and life-threatening infections. While historically common in patients with significant health care exposure, community-associated methicillin-resistant S. aureus (CA-MRSA) has emerged as an important cause of disease (1). CA-MRSA is the most common cause of skin and soft tissue infections (SSTI) among people presenting to emergency departments (EDs) in much of the United States, most of which are caused by a single MRSA strain, pulsed-field type USA300 (2). S. aureus colonization with methicillin-susceptible S. aureus (MSSA) is common in the general population, especially in the anterior nares (3). Studies of MRSA pathogenesis in health care settings have demonstrated that nasal colonization typically precedes and is a risk factor for infection (4); therefore, prevention strategies in health care often involve decolonization, especially before invasive surgical procedures (5).Despite the increasing prevalence of CA-MRSA infections, nasal colonization with MRSA has been infrequently detected during CA-MRSA outbreaks or in nationally representative prevalence surveys (6, 7). One possible explanation for this observation is that CA-MRSA strains might preferentially colonize at nonnasal body sites. The throat and groin have been implicated as important sites of S. aureus and MRSA c...

The single-species metagenome: subtypingStaphylococcus aureuscore genome sequences from shotgun metagenomic data

“…Given the current growth in metagenomic sequence production, these could soon number in the hundreds of thousands to millions. Largescale analysis subtype would give a much richer insight into S. aureus biogeography and colonization preferences than we have been able to achieve through conventional microbial sampling alone, a method which has been traditionally focused on one body site (anterior nares) and rarely takes into account the within sample genetic mixture of the species [66] . The binstrain method, and/or alternative approaches described above, can be extended to species other than S. aureus , giving us more tools to explore the bacterial diversity of this planet.…”

Molecular Characterization of Nasal Methicillin-Resistant Staphylococcus aureus Isolates Showing Increasing Prevalence of Mupirocin Resistance and Associated Multidrug Resistance following Attempted Decolonization

“…Genotypic MDR is defined as the carriage of three or more of the following antibiotic/antiseptic resistance genes: MRSA (mecA), beta-lactamase (blaZ), mupirocin (ileS2), macrolides, lincosamides and streptogramin B (MLS B ) compounds [erm(C)], tetracycline [tet(K), tet(M)], streptothricin (sat), aminoglycosides (aacA-aphD, aadD, and aphA3), and qacA (resistance to quaternary ammonium compounds). As S. aureus infection is often endogenous (10,11), our study suggests that antimicrobial and antiseptic resistance gene profiles of the original colonizing isolate may inform stewardship and guide systemic prophylaxis and/or antimicrobial therapy. While MDR/mupirocin resistance association has been reported in isolates causing infection (including bloodstream infection) (12)(13)(14), our investigation revealed several MDR genes in addition to ileS2 and/or qacA among MR-MRSA colonizing isolates.…”

Amino acid polymorphisms in the fibronectin-binding repeats of fibronectin-binding protein A affect bond strength and fibronectin conformation

“…Staphylococcus aureus is a Gram-positive bacterium that has a symbiotic relationship with humans. Its primary reservoir is the nares (1), although other sites may be colonized, such as the throat, groin, and axillae (2,3). This microorganism also is an opportunistic pathogen and can cause serious endovascular infections if bacteria access the bloodstream (4,5).…”