The role of Staphylococcal carotenogenesis in resistance to host defense peptides and in vivo virulence in experimental endocarditis model.

The defining hallmark of the newly described species, Staphylococcus argenteus, in comparison to its sister species, S. aureus and S. schweitzeri, is the absence of production of the carotenoid pigment, staphyloxanthin. Staphylococcus argenteus lacks the responsible genetic locus crtOPQMN. We examined the impact of carotenoid synthesis in two non-pigmented S. argenteus strains, MSHR1132 and SCC1165. Following complementation with a plasmid containing the carotenoid operon (pTX-crtOPQMN), compared to wild type, both complemented strains showed substantial carotenoid production, with a resultant increase in cell membrane rigidity. Surprisingly, both crtOPQMN-complemented strains exhibited increased susceptibility to the host defense peptides, LL-37 and hNP-1 in vitro, and reduced virulence in an experimental rabbit endocarditis model.