Immunochemical Analysis of Human Oral Strains of Fusobacterium and Leptotrichia.

de Araujo, Wilson C. (National Institute of Dental Research, Bethesda, Md.), Eileen Varah, and Stephan E. Mergenhagen. Immunochemical analysis of human oral strains of Fusobacterium and Leptotrichia. J. Bacteriol. 86:837-844. 1963.-Lipopolysaccharides, isolated by phenol-water extraction of 27 strains of oral gram-negative bacteria conforming either to Fusobacterium polymorphum or Leptotrichia buccalis, were shown to be endotoxic by their ability to alter dermal reactivity to epinephrine and to be serologically specific by hemagglutination and hemagglutination-inhibition tests. Numerous serotypes of these organisms were detected by hemagglutination tests with purified lipopolysaccharides. A F. polymorphum lipopolysaccharide produced two visible precipitin bands in agar gel with antiserum prepared against the homologous organism. Each of the immunologically distinct components of the endotoxin, isolated by differential centrifugation, altered dermal reactivity to epinephrine and acted as a hapten in hemagglutination tests. Crude antigens from F. polymorphum strains, released in supernatant fluids of heat-killed bacterial suspensions, showed broad serological cross-reactivity with antiserum prepared against homologous and heterologous strains of F. polymorphum but not with antiserum prepared against L. buccalis strains. Broad serological cross-reactivity of these crude F. polymorphum antigens could be eliminated by prior treatment with phenol or trypsin, indicating that the common antigen or antigens in these organisms are protein. Double-diffusion tests in agar identified and differentiated type-specific lipopolysaccharide from other antigens extracted by heat from these organisms. Similarly prepared crude antigens from L. buccalis had broad serological activity with antiserum prepared against various strains of L. buccalis but not with F. polymorphum. In contrast to the crude antigens from F. polymorphum, this serological cross-reactivity could not be eliminated by treatment with phenol or trypsin.