Diversity of Staphylococcus aureus strains colonizing various niches of the human body

Abstract

Objectives: As individuals may be colonized with multiple strains of Staphylococcus aureus at different body sites, the objectives of this study were to determine whether S. aureus polyclonal colonization exists within one body niche and the optimal sampling sites and culture methodology to capture the diversity of S. aureus strains in community-dwelling individuals.

Methods: Swabs were collected from the nares, axillae, and inguinal folds of 3 children with community-associated S. aureus infections and 11 household contacts, all with known S. aureus colonization. S. aureus isolates were recovered from each body niche using 4 culture methods and evaluated for polyclonality using phenotypic and genotypic strain characterization methodologies.

Results: Within individuals, the mean (range) number of phenotypes and genotypes was 2.4 (1-4) and 3.1 (1-6), respectively. Six (43%) and 10 (71%) participants exhibited phenotypic and genotypic polyclonality within one body niche, respectively. Broth enrichment yielded the highest analytical sensitivity for S. aureus recovery, while direct plating to blood agar yielded the highest genotypic strain diversity.

Conclusions: This study revealed S. aureus polyclonality within a single body niche. Culture methodology and sampling sites influenced the analytical sensitivity of S. aureus colonization detection and the robustness of phenotypic and genotypic strain recovery.

Keywords: Broth enrichment; Polyclonal colonization; Staphylococcus aureus; Strain diversity.

Figure 1

Four separate culture methods were compared: 1) direct plating to blood agar plate (BAP), 2) direct plating to Spectra MRSA, 3) broth enrichment with subculture to BAP, and 4) broth enrichment with subculture to Spectra MRSA.