Risk factors for non-invasive (skin and soft tissue) and invasive Staphylococcus aureus infections among children and adults living in southeastern USA: a retrospective cohort study

OBJECTIVE: To characterise individual and area-level risks associated with invasive or skin and soft tissue (SSTIs) Staphylococcus aureus infections comparing methicillin-resistant S. aureus (MRSA) with methicillin-sensitive S. aureus (MSSA); and highlight differences between children and adults. SETTING: A population-based study from 21 reporting laboratories located in Georgia Health District 3 (HD3), an eight-county catchment area around metro Atlanta. PARTICIPANTS: A case is a resident of HD3 from whom S. aureus had been isolated in 2017. PRIMARY OUTCOME: Culture-confirmed S. aureus infections, classified as skin and soft tissue (proxy for non-invasive) or invasive, by methicillin-sensitivity status. RESULTS: The incidence of SSTIs was 19.7/100 000, compared with 5.2/100 000 for invasive infections. Adults experienced higher rates of SSTIs (22.3/100 000) and invasive infections (6.7/100 000) compared with children with SSTIs (13.0/100 000) and invasive infections (1.3/100 000). Risks of MRSA versus MSSA SSTIs were similar for children and adults. Black individuals with SSTIs were more likely to have MRSA than white individuals (children (OR 1.43, 95% CI 1.16 to 1.76); adults (OR 1.24, 95% CI 1.08 to 1.42)). Adults with invasive MRSA were more likely to be black (adjusted OR 1.69, 95% CI 1.25 to 2.29) compared with those with invasive MSSA. Children with invasive MRSA were more likely from a racial-ethnic concentrated area (OR 4.66, 95% CI 1.85 to 11.71). Hotspots of MRSA were found in crowded areas with higher rates of black populations. CONCLUSIONS: The risk of MRSA infections in children and adults can be defined by unique area-level sociodemographic characteristics which were distinct for those areas associated with MSSA infections. Place-based risks of MRSA or MSSA can be used to develop target public health interventions to decrease transmission and incidence.