Evaluating genetic susceptibility to Staphylococcus aureus bacteremia in African Americans using admixture mapping

Abstract

The incidence of Staphylococcus aureus bacteremia (SAB) is significantly higher in African American (AA) than in European-descended populations. We used admixture mapping (AM) to test the hypothesis that genomic variations with different frequencies in European and African ancestral genomes influence susceptibility to SAB in AAs. A total of 565 adult AAs (390 cases with SAB; 175 age-matched controls) were genotyped for AM analysis. A case-only admixture score and a mixed χ 2 (1df) score (MIX) to jointly evaluate both single-nucleotide polymorphism (SNP) and admixture association (P<5.00e-08) were computed using MIXSCORE. In addition, a permutation scheme was implemented to derive multiplicity adjusted P-values (genome-wide 0.05 significance threshold: P<9.46e-05). After empirical multiplicity adjustment, one region on chromosome 6 (52 SNPs, P=4.56e-05) in the HLA class II region was found to exhibit a genome-wide statistically significant increase in European ancestry. This region encodes genes involved in HLA-mediated immune response and these results provide additional evidence for genetic variation influencing HLA-mediated immunity, modulating susceptibility to SAB.