Differences in virulence within the species Bacteroides gingivalis.

In order to gain insight into the relative importance of several virulence factors of Bacteroides gingivalis, 8 strains with a varying virulence were studied. The virulence of B. gingivalis was determined in a mouse model. Strains HG 66, HG 76 and HG 184 were very virulent causing phlegmonous abscesses with lesions and necrosis. The strains HG 405 and HG 462 caused phlegomonous abscesses with pus. Strains HG 91, HG 94 and HG 185 were less virulent and induced gravity abscesses. In vitro strains HG 66, HG 76 and HG 184 induced low amounts of chemiluminescence by polymorphonuclear leucocytes. All other strains including HG 405 and HG 462 caused a relatively high chemiluminescence. Most strains displayed a high sensitivity to the bactericidal activity of fresh serum except for the highly virulent strains HG 66, HG 76 and HG 184. No differences in extracellular proteolytic activity on Azocoll, production of volatile fatty acids and ammonia were found between the B. gingivalis strains studied. In conclusion, differences in virulence were shown within the species B. gingivalis; the relative importance of several virulence factors was investigated.