FOSFOMYCIN REDUCES CD15S-RELATED ANTIGEN EXPRESSION OF STREPTOCOCCUS-PYOGENES

We have previously shown the immunological mimicry of human sialyl-Lew is(x) (CD15s) by a surface antigen of Streptococcus pyogenes, This mim icking surface antigen may act as a ligand to the selectin family and may induce antibody production against CD15s on host cells, suggesting a possible role in the pathogenesis of S. pyogenes, In this study, th e effects of antibiotics on the CD15s-related antigen expression of S. pyogenes were examined at a concentration below the MIC (sub-MIC). Th e amounts of CD15s on the surfaces of S. pyogenes cells and on the sur faces of S. pyogenes biofilms were determined by a whole-cell enzyme-l inked immunosorbent assay and by laser scanning fluorescence microscop y, respectively, by using an anti-CD15s monoclonal antibody. At the su b-MICs, fosfomycin (1R,2S-1,2-epoxypropyl phosphonic acid), its enanti omer (1S,2R-1,2-epoxypropyl phosphonic acid), and benzylpenicillin sig nificantly inhibited the CD15s expression of all strains studied. The effects of fosfomycin and its enantiomer on biofilms were also observe d by scanning electron microscopy, Incubation of S. pyogenes with the sub-MIG of fosfomycin or its enantiomer, which has no antibacterial ac tivity, reduced the amount of CD15s on the biofilm surface and made it smooth. These results suggest that fosfomycin or its enantiomer might be useful for preventing S. pyogenes adherence to human CD15s recepto rs and the resulting immunological pathogenicity.