Development and Evaluation of Capture Enzyme‐Linked Immunosorbent Assays for Detection of Immunoglobulin G and M Antibodies to Group A Streptococcal Antigens

Abstract

Capture enzyme-linked immunosorbent assays (ELISAs) were developed to detect immunoglobulin G and M antibodies to group A streptococcal (GAS) antigens, streptolysin O, streptokinase, and group A carbohydrate. The sensitivities and the specificities of the IgM capture ELISAs to each GAS antigen were high enough to distinguish the patients with GAS infections (diagnosed as GAS pharyngitis or scarlet fever) from the control groups (healthy people and patients with pharyngitis from whom GAS could not be isolated). On the other hand, the specificities of the IgG capture ELISAs were not very effective in diagnosis of GAS infections. When the capture ELISA and an indirect ELISA detecting IgM antibodies to group A carbohydrate were compared, false-positive reactions due to rheumatoid factor occurred in the indirect ELISA, but did not occur in the capture ELISA. These results indicate that the capture ELISA works better than the indirect ELISA in detecting the IgM antibody, and that the IgM capture ELISA to GAS antigen provides a rapid and highly reliable serodiagnosis for GAS infections employing only a single serum.

Fosfomycin Reduces CD15s-Related Antigen Expression ofStreptococcus pyogenes

“…When used to treat S. pyogenes biofilms in vitro, fosfomycin and its enantiomer at their sub-MICs reduced the level of antigen expression on the biofilm surface, although these agents did not cause significant morphological changes in the biofilm. High IgM and IgG titers against S. pyogenes surface antigens were observed in the sera of S. pyogenes-infected patients (8,10). CD15s-bearing glycolipids were quite abundant on neutrophils, with 2 ϫ 10 7 copies/cell (27) and a calculated density of CD15s-bearing glycolipids on the neutrophil surface of 44,000 molecules/m (5,22,28).…”