title: Mammalian serum susceptibility of Serratia marcescens: detection of three human serum susceptibility categories.
abstract: A total of 65 strains of S. marcescens, including 36 currently employed O- and H-antigen reference strains, were examined for their susceptibility to the bactericidal activity of 80 vol % of fresh human serum. The majority of strains (57 = 87.6%) proved 'delayed serum-sensitive' (DSS); 4 strains (6.2%) were 'promptly serum-sensitive' (PSS), whereas 4 strains (6.2%) resisted (NSS) complement-mediated killing by human serum. Fresh sera obtained from 7 adult human volunteers yielded essentially identical kinetic killing data against representative NSS, DSS and PSS strains of S. marcescens. These observations were interpreted as further justification for the assignment of clinical isolates of S. marcescens to 3 categories of human serum susceptibility: DSS, PSS and NSS. Species differences among fresh sera from sheep, rabbits and guinea pigs, as contrasted with fresh human serum, were noted. In general, PSS strains of S. marcescens were killed in a slightly delayed fashion; DSS strains of S. marcescens were killed in an unpredictable kinetic pattern by sheep and rabbit sera, whereas fresh guinea pig serum entirely failed to kill selected DSS isolates of S. marcescens.
mesh_terms: D000328:Adult; D000818:Animals; D001770:Blood Bactericidal Activity; D004926:Escherichia coli / Q000276:immunology; D006168:Guinea Pigs / Q000097:blood; D006801:Humans; D011817:Rabbits / Q000097:blood; D012706:Serratia marcescens / Q000145:classification / Q000276:immunology*; D012756:Sheep / Q000097:blood; D013045:Species Specificity