Human β-defensin 3 ( DEFB103) and its influence on Staphylococcus aureus nasal carriage

Abstract

The DEFB103 gene encodes human β-defensin 3, which has a high activity against Staphylococcus aureus. In the general population 20% are persistent nasal carriers of S. aureus, which is a problem for their general health. DEFB103 shows extensive variation in copy number. Copy number variations (CNVs) are believed to play a role in susceptibility to certain diseases. The possible associations between CNVs, mRNA, and nasal S. aureus carriage status were investigated. We used the pyrosequencing-based paralog ratio test to determine the DEFB103 copy number. Nasal swabs were collected for RNA and S. aureus determination. S. aureus genotypes were determined by spa typing, and real-time PCR was used to determine DEFB103 mRNA expression. The DEFB103 CNV varied from 2 to 8 copies per diploid genome. No significant difference in copy number was observed among the groups. We found 74% of the volunteers to be non-carriers, 20% to be persistent carriers, and 6% to be intermittent carriers. The S. aureus isolates linked to more than 16 clonal lineages. mRNA expression varied extensively, but no significant differences were observed between the groups. We did not find a linear correlation between CNV and mRNA expression. The results indicate that DEFB103 CNV does not influence S. aureus carrier status.