VIRULENCE OF 6 CAPSULAR SEROTYPES OF PORPHYROMONAS-GINGIVALIS IN A MOUSE MODEL

Capsular structures of Porphyromonas gingivalis have been correlated t o the pathogenicity in animal models. Six polysaccharide capsular sero types have recently been described in P. gingivalis. In the present st udy, virulence of the P. gingivalis strains of the six capsular seroty pes was compared with strains of the non-capsular serotype of P. gingi valis in a mouse model. All 18 encapsulated strains caused a spreading type of infection with exudate, often accompanied by ulceration and n ecrosis of the skin and a significant loss of body weight. All three n on-encapsulated strains tested induced localized abscesses, although a spreading type of infection was occasionally observed. Illness of the mice was almost always associated with recovery of encapsulated P. gi ngivalis from blood, kidneys, lungs and spleens. A statistically signi ficant contrast was found in the average weight change during the expe riment between the mice infected with the K- serotype strains and the mice infected with the encapsulated P. gingivalis strains. Differences in severity of illness and the recovery of P. gingivalis from mouse t issues were recorded between strains of the same serotype. The differe nces in virulence within a capsular serotype suggest that the capsule is an important but not the only determining virulence factor for P. g ingivalis.