JMIR Publications

ABSTRACT

Background:

Healthcare-associated (HA) Staphylococcus aureus (S. aureus) infections are declining but remain common. Conversely, rates of community-associated (CA) infections have not decreased due to the inadequacy of public health mechanisms to control transmission in a community setting. Our long-term objective is to use risk-based information from empirical socio-cultural-biological evidence of carriage and transmission to inform intervention strategies that reduce S. aureus transmission in the community. Our immediate goals are to determine the extent to which asymptomatic carriage patterns reflect national trends and result in differential health disparities among different ethnic groups. Given the broad differences in social interactions due to cultural affiliation, travel, and residency patterns among ethnic groups, we aim to determine the role that social relationships and interactions have on S. aureus carriage and transmission, either as risk or as protective factors. We will simultaneously determine if clinical strains are representative of community-carriage strains and not due to the emergence of a few, highly fit lineages. The rationale for this work is that we will gain an understanding of underlying causes of this public health issue and gain further insights into important components of S. aureus transmission: community carriage, pathogen genotypes, and the impact of social interactions.

Objective:

Specific Aim #1. To characterize S. aureus carriage rates and compare circulating pathogen genotypes with those associated with disease isolated from local clinical specimens across resident groups, and across Hispanic and Non-Hispanic White ethnic groups. Specific Aim #2. To evaluate social network relationships and social determinants of health-based risk factors for their impact on carriage and transmission of S. aureus.

Methods:

Our research methods combine sociocultural survey approaches to population health sampling with S. aureus carriage and pathogen genomic analysis to infer transmission patterns. Whole genome sequences of S. aureus from community and clinical sampling will be phylogenetically compared to determine if the strains that cause disease (clinical samples) are representative of community genotypes. We expect to accumulate evidence that S. aureus populations do not differ between community and clinical samples or among ethnic groups, suggesting that genotypes are equally likely to cause disease and do not explain any ethnic based disparities in S. aureus infections. Phylogenetic comparisons of strains collected from participants within social groups can indicate possible transmission within the group. We can therefore combine transmission data with social determinants of health variables (socioeconomic status, health history, etc.) and social network variables (both ego-centric and relational) to determine the extent to which social relationships are associated with S. aureus transmission.

Results:

We conducted a first year pilot test and feasibility test of survey and biological data collection and analytic procedures based on the original funded design for this project (#NIH U54MD012388). That design resulted in survey data collection targeted 336 groups and 1337 individuals. The protocol, described below, is a revision based on data assessment, new findings for statistical power analyses, and refined data monitoring procedures.

Conclusions:

This study is designed to evaluate the ethnic-specific prevalence of S. aureus carriage in a US border community. The study will also examine the extent to which kin and non-kin social relationships are concordant with carriage prevalence in naturally occurring social groups. Genetic analysis of S. aureus strains will further distinguish putative transmission pathways across social relationship contexts and inform our understanding of the correspondence of S. aureus reservoirs across clinical and community settings. Basic community engaged non-probabilistic sampling procedures provide a rigorous framework for completion of this five year study of the social and cultural parameters of S. aureus carriage and transmission.