Differential Regulation of Virulence-Associated Proteins in Methicillin-Resistant Staphylococcus epidermidis Under Plasma Stress

Staphylococcus epidermidis encodes a variety of virulence- and pathogenicity-associated factors. These factors are insufficiently characterized owing to the absence of clearly defined criteria distinguishing clinically relevant S. epidermidis from commensals. The study analyzed the virulence-associated proteomic response of three S. epidermidis isolates of bacteremia patients of age 1 day to 5 months and three S. epidermidis isolates from healthy children skin. Isolates were characterized for pathogenicity marker mecA and commensalism marker fdh. One set of S. epidermidis isolates was exposed by growing in the presence of 10% human blood plasma, while another set was grown in nutrient broth only. Whole-cell proteins were analyzed through LC-MS/MS analysis (ESI-nano). In clinical isolates and in community isolates, 266 and 232 upregulated proteins were identified, respectively. Through in silico analysis, selectively expressed virulence-associated proteins were identified as being involved in stress responses, virulence regulation, toxin, and stress-associated metabolic pathways. This study concluded that S. epidermidis is selectively adapted to changing conditions. Clinically relevant isolates selectively expressed protein markers of virulence and pathogenicity, and therefore exhibit a distinct proteomic signature to understand virulence and pathogenicity of S. epidermidis. This study may provide insight into the virulence transition of S. epidermidis from a commensal background.