A high-molecular-weight fraction of smooth lipopolysaccharide in Klebsiella serotype O1:K20 contains a unique O-antigen epitope and determines resistance to nonspecific serum killing.
The lipopolysaccharide (LPS) O-antigen side chains of Klebsiella serotype O1 have been studied by using mutants selected by resistance to a Klebsiella bacteriophage designated O1-A. Two classes of LPS mutants were identified. The major group (90%) synthesized rough LPS. The remaining 10% of the mutants produced a novel LPS profile that lacked the highest-molecular-weight O-substituted molecules (HMW-LPS) but still produced lower-molecular-weight O-substituted species (LMW-LPS). By using antisera raised against mutant Klebsiella strains and antiserum specific for Pasteurella haemolytica serotype 4, it was demonstrated that HMW-LPS and LMW-LPS contain shared epitopes. HMW-LPS also contained an epitope absent in LMW-LPS. This unique epitope was recognized by a monoclonal antibody (O1-52.6) and appears to be responsible for the serological cross-reaction between the O antigens of Klebsiella O1 and Escherichia coli O19. This HMW-LPS epitope was present in eight other Klebsiella O1 isolates which were examined. Electron microscopy demonstrated that HMW-LPS excluded overlying capsular polysaccharide for a distance of 25 to 40 nm. The distance was reduced to 10 to 18 nm in strains which synthesized only LMW-LPS and to zero in rough LPS strains. The HMW-LPS of Klebsiella O1 was shown to be an important virulence determinant, since this molecule was responsible for the resistance of the bacterium to nonspecific, complement-mediated serum killing.
McCallum
K L
KL
Department of Microbiology, College of Biological Sciences, University of Guelph, Ontario, Canada.
Schoenhals
G
G
Laakso
D
D
Clarke
B
B
Whitfield
C
C
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D001435:Bacteriophages / Q000254:growth & development; D001770:Blood Bactericidal Activity; D000939:Epitopes; D066298:In Vitro Techniques; D007711:Klebsiella pneumoniae / Q000145:classification / Q000276:immunology* / Q000648:ultrastructure; D008070:Lipopolysaccharides / Q000276:immunology*; D008854:Microscopy, Electron; D008970:Molecular Weight; D019081:O Antigens; D011817:Rabbits; D012703:Serotyping
D000942:Antigens, Bacterial; D000939:Epitopes; D008070:Lipopolysaccharides; D019081:O Antigens