title: Effect of subinhibitory concentrations of josamycin on the expression of M protein by group A streptococci.
abstract: In an attempt to inhibit the biosynthesis of the type-specific M protein usually expressed on surface fimbriae group A Streptococcus pyogenes delta 2305 was cultivated in Todd-Hewitt broth containing 10% human serum and subinhibitory concentrations of either josamycin, erythromycin or clindamycin. Electron microscopy revealed that the antibiotic-pretreatment had little visible effect on the surface structures of the streptococci. However, josamycin and clindamycin-pretreated bacteria adhered less to hydrophobic gels than erythromycin-pretreated or untreated control cultures. Due to the decrease in surface hydrophobicity, the drug-pretreated bacteria also activated complement more readily and fixed more C3 on their surface. Consequently the killing of josamycin and clindamycin-pretreated bacteria by polymorphonuclear leucocytes was significantly enhanced. Similar findings were obtained when the M protein was removed from the bacteria by digestion with trypsin. These results suggest that josamycin, like clindamycin, reverses the capacity of group A streptococci to resist opsonization by normal human serum and interferes with the adhesion of the organisms to host epithelial cell surfaces.
mesh_terms: D000268:Adhesiveness; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000502:physiology; D002352:Carrier Proteins; D002981:Clindamycin / Q000494:pharmacology; D003176:Complement C3 / Q000378:metabolism; D003168:Complement Fixation Tests; D004917:Erythromycin / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006801:Humans; D007933:Leucomycins / Q000494:pharmacology*; D009504:Neutrophils / Q000276:immunology; D009895:Opsonin Proteins / Q000276:immunology; D010587:Phagocytosis; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D014357:Trypsin
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D003176:Complement C3; D007933:Leucomycins; D009895:Opsonin Proteins; C014689:streptococcal M protein; D002981:Clindamycin; D004917:Erythromycin; D014357:Trypsin