NOVEL POLYSACCHARIDE CAPSULAR SEROTYPES IN PORPHYROMONAS-GINGIVALIS

Recently van Winkelhoff et al. (1) described 3 novel serotypes in viru lent Porphyromomas gingivalis strains, which were based on different p olysaccharide antigens. These antigens probably represent capsular str uctures and have been designated K1, K2 and K3. In the present study w e report on 3 novel capsular serotypes, which are represented by P. gi ngivalis strains ATCC 39417, HG 1690 and HG 1691. The strains, isolate d from patients with periodontitis, showed obvious encapsulation in we t India ink preparations. Thermostable antigens could be detected in t he supernatant fractions of autoclaved cells. These antigens appeared to be negatively charged, sensitive to periodate degradation, and resi stant to proteinase K treatment. On the basis of these characteristics are conclude that the antigens are probably extra-cellular polysaccha rides representing a bacterial capsular structure. These K-antigens di d not cross-react with K1, K2 or K3 immunesera of P. gingivalis, with the exception of the K2 antiserum, which partially recognized K5- and K6-antigens. In contrast, K5 and K6 antisera did not react with the K2 -antigen. After absorbtion of the K2 antiserum with cells of strains H G 1690 (K5) and HG 1691 (K6) cross-reactivity was no longer present. W e propose these novel serotypes to be designated: K3 (ATCC 49417), K5 (HG 1960) and K6 (HG 1691).