Infect Immun. monoclonal antibody (MAb) (26) reacted with a cell surface antigen of (11). The role of the CD15s-related antigen in the pathogenesis of has not been studied in detail. The expression on of an antigen that mimics the host structure may camouflage after infection (16, 19), thereby aiding survival and successful colonization. possesses multiple adhesins: lipoteichoic acid, fibronectin-binding protein, M protein, vitronectin-binding protein, and C carbohydrate (9). In addition, CD15s on the streptococcal surface may act as an adhesin to the selectin family expressed on host cells such as endothelial cells and neutrophils. Infection with a bacterium expressing CD15s-related antigen possibly induces antibody specific for CD15s, which has a potential role in autoimmunity, as suggested for and (1, 29). Brook et al. (2) reported that sub-MICs of penicillin and clindamycin reduce the level of expression of the capsule. However, the effects of antibiotics on CD15s-related antigen expression have not been studied. In this study, therefore, the effects of sub-MICs of antibiotics on CD15s-related antigen expression by and on Rabbit Polyclonal to IKK-gamma (phospho-Ser31) biofilms were determined by an enzyme-linked immunosorbent assay (ELISA) and laser scanning fluorescence microscopy. The morphological changes in biofilms as a result of treatment Darenzepine with antibiotics at sub-MICs were studied by scanning electron microscopy. MATERIALS AND METHODS Bacterial strains and culture conditions. ATCC 19615 was isolated Darenzepine from a patient with a sore throat. TDP-1 (M type 1), TDP-3 (M type 3), and TDP-4 (M type 12) are isolates from children with acute glomerulonephritis (11). TDP-11 (M type 6) is an isolate from an upper pharynx tumor. A374 (M type 12) is an isolate from a patient with poststreptococcal glomerulonephritis (24). Serotypes M1 Darenzepine and M3 are reported to be particularly associated with invasive disease and fatal infections (4, 17), and M6 and M12 are potentially nephritogenic types (7). All strains were cultured in brain heart infusion broth (BHI; Difco, Detroit, Mich.) supplemented with 0.5% glucose for 18 h at 37C. Antibiotics and MIC determination. The antibiotics used in this study were fosfomycin (1whole-cell suspension was added to 100 l of a serial twofold dilution of antibiotics in Anaerobe Broth MIC (Difco) in wells of a microtiter plate to achieve a final concentration of 106 organisms per ml. The plate was incubated overnight at 37C in an atmosphere of 5% CO2. The MIC was the lowest concentration of antibiotic which yielded no bacterial growth. Whole-cell ELISA. CD15s expression on bacterial surfaces was measured as described previously (11). CD15s-polyacrylamide polymer (CD15s-PA; monosaccharide composition; Neu5Ac, 9.3 mol%; Fuc, 10.1 mol%; Gal, 9.6 mol%; GlcNAc, 9.5 mol%; Seikagaku Kogyo, Tokyo, Japan) was used as a positive control. Briefly, 50 l of the whole-cell suspension system (2.0 108 CFU/ml) or Compact disc15s-PA suspension was split into aliquots, and each aliquot was placed into specific wells of the ELISA dish (MS-8696F; Sumitomo Bakelite Co., Ltd., Tokyo, Japan) and permitted to dried out over night at 37C. The wells had been pretreated Darenzepine with 1% bovine serum albumin in 0.01 M phosphate-buffered saline (PBS; pH 7.2) for 1 h in space temperature. After cleaning 3 x with PBS, anti-CD15s MAb SNH-3 (diluted to at least one 1:200; Wako Pure Chemical substance, Osaka, Japan) (24) was put into each well as well as the dish was permitted to stand at space temp for 1 h. The dish was cleaned as referred to above, horseradish peroxidase-labeled goat anti-mouse immunoglobulin M (IgM; diluted to at least one 1:2,000; string; Cappel Research Items,.