title: Further characterization of "promptly" and "delayed" human serum-sensitive strains of Serratia marcescens.
abstract: The kinetics of the bactericidal activity of 80 vol% of fresh human serum against representative 'delayed serum-sensitive' (DSS) and 'promptly serum-sensitive' (PSS) strains of Serratia marcescens were further examined with regard to various chemical and absorption procedures known to affect various components of the alternative and classical pathways of human complement activation. Inulin treatment of fresh human serum failed to diminish serum bactericidal activity against DSS and PSS assay strains. Fresh human serum that had been depleted of properdin (factor P) through absorption with zymosan, was as active as control serum against DSS strains of S. marcescens; however, PSS strains were killed in a 'delayed' fashion. Human serum that had been heat-inactivated at 50 degrees C for minutes (depletion of factor B), no longer killed DSS strains, whereas PSS strains of S. marcescens and the PSS control strain Escherichia coli C were killed in a slightly delayed fashion. Hydrazine-hydrate treatment (inactivation of C3 of the complement system) and exposure of fresh human serum to dithiothreitol completely abolished serum bactericidal activity. Bentonite-absorbed fresh human serum no longer killed DSS strains of S. marcescens; some PSS strains of S. marcescens were killed in a delayed manner, whereas control strain E. coli C was as PSS as before. Addition of Seitz-filtered fresh human serum, that lacked beta-lysin and was deficient in lysozyme, to bentonite-absorbed human serum restored bactericidal activity against DSS and PSS strains of S. marcescens; addition to heat-inactivated or Seitz-filtered, heat-inactivated human serum failed to do so. Therefore, bentonite absorption removed to a heat-labile component from fresh human serum clearly different from beta-lysin and lysozyme. Furthermore, human serum beta-lysin and lysozyme were not required for serum-mediated killing of S. marcescens strains of either serum susceptibility category.
mesh_terms: D000042:Absorption; D000328:Adult; D000368:Aged; D001546:Bentonite / Q000494:pharmacology; D001770:Blood Bactericidal Activity / Q000187:drug effects; D004229:Dithiothreitol / Q000494:pharmacology; D004926:Escherichia coli / Q000276:immunology; D006358:Hot Temperature; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D066298:In Vitro Techniques; D007444:Inulin / Q000494:pharmacology; D008297:Male; D012706:Serratia marcescens / Q000187:drug effects / Q000276:immunology*; D013045:Species Specificity; D015054:Zymosan / Q000494:pharmacology
chemical_list: D006834:Hydrazines; D001546:Bentonite; D007444:Inulin; D015054:Zymosan; D004229:Dithiothreitol