Persistence, Discordance and Diversity of Staphylococcus aureus Nasal and Oropharyngeal Colonization in School-aged Children.

Background: The anterior nares are regarded as the primary site for Staphylococcus aureus colonization, although studies have highlighted the potential importance of colonization at extra-nasal sites, including the oropharynx. Accordingly, the aims of this study were to assess the prevalence, persistence and molecular epidemiology of S. aureus colonization in the nares and oropharynx of Māori and Pacific children, a population with strikingly high rates of S. aureus infection.

Methods: A cross-sectional study of predominantly Māori and Pacific school-aged children in Auckland, New Zealand was performed in October 2013, and swabs were taken from the nares and oropharynx. Sampling was repeated from the same schools in October 2014. All S. aureus isolates underwent antimicrobial susceptibility testing and spa typing.

Results: Overall, 506/893 (56.7%) children were colonized with S. aureus, and the colonization prevalence was significantly higher in the oropharynx than nares (41.1% vs. 31.5%; P < 0.001). Longitudinal colonization was significantly higher in the oropharynx than the nares, and children with longitudinal oropharyngeal colonization were more likely to be colonized with the same spa type than those colonized in the nares (67.6% vs. 37.0%; P = 0.01). Approximately 40% of children had discordant spa types at the nares and oropharynx.

Conclusions: Oropharyngeal S. aureus colonization represents a significant reservoir of S. aureus and it is possible that the oropharynx may represent a protected anatomical niche, enabling persistent colonization with the same S. aureus strain. Future study should attempt to better understand the determinants of oropharyngeal carriage.