Healthcare-associated (HA) Staphylococcus aureus infections are common but declining. Conversely,
community-associated (CA) infections have not decreased. A lack of knowledge about carriage, carriage
disparities, and transmission, has translated into inadequate mechanisms to control the spread of S. aureus in
our communities. Few studies have addressed risk of S. aureus infections among ethnic minorities. For Native
Americans, hospitalization rates are increasing, especially in the southwest. Infections are more likely to be CA
and due to methicillin resistant S. aureus (MRSA). For Hispanics, infections are also more likely to be due to
MRSA although colonization rates are lower compared to other ethnicities. In Flagstaff Arizona, S. aureus
infections are more likely among Native Americans than Hispanics and non-Hispanic whites. Causes of this
disparity are unknown. These, and our proof of concept research 1, strongly suggest the need and utility of
baseline and comparative population data to establish models that identify differences in carriage and
transmission based on sociocultural conditions. Our long term objective is to use risk-based information founded
upon empirical evidence of transmission to inform intervention strategies that reduce transmission and
prevalence in the community. Our immediate goals are to determine whether the observed clinical disparity is
reflected in the community via asymptomatic carriage. Given broad cultural differences, we also aim to determine
roles of social relationships and interactions on S. aureus transmission. This work, will provide an understanding
of underlying causes of this health disparity and gain further insights into important components of S. aureus
transmission: community carriage, pathogen genotypes, and social interactions.
Specific Aim #1. Carriage: Determine if and why there is an ethnic based S. aureus carriage disparity
among Native Americans, Hispanics and non-Hispanic whites in Flagstaff Arizona. Using theoretically
driven community sampling for S. aureus, data on social determinant variables, genome sequencing, and
phylogenetic comparison, we predict significant ethnic based carriage differences driven by key social
determinants of health, but no clustering of pathogen genotypes by ethnicity, excluding genotype as a possible
explanation of ethnic based disparities in S. aureus colonization. Specific Aim #2. Transmission: Identify key
social determinants and social network based risk factors for transmission of S. aureus in Flagstaff.
Enrollement will target social groups (family, friends, and coworkers) to 1) obtain data on direct and indirect
physical contact within groups, 2) characterize nasal, oral, and hand microbiomes as estimators of contact and
proximity resulting in transmission of commensal species, and 3) assess phylogenomic relationships among
positive S. aureus samples to confirm or refute dyadic transmission. Assessments of transmission will be
compared to physical and social contact metrics, sociodemographic data, health status, and social integration,
all stratified by ethnicity, to determine their importance in predicting transmission.
