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.
Staphylococcus aureus infections represent the most common cause of skin and soft tissue infections in the US with documented ethnic-based disparities in types of infecting strains and modes of acquisition. We aim to address this minority health disparity by understanding the roles of asymptomatic community carriage, pathogen genotypes and social interactions on the transmission of S. aureus. The eventual goal is to model and provide improved public health interventions that will reduce transmission rates and reinfection rates in populations.
