Genetic diversity of Porphyromonas gingivalis and its possible importance to pathogenicity

During recent years much effort has been put into understanding the genetic composition of the oral populations of black-pigmented anaerobic bacteria. One of them, Porphyromonas gingivalis, is a putative periodontopathogenic organism considered to be particularly relevant in the etiology of adult pe riodontitis. It has been shown in studies using molecular typing methods th at most bacterial populations consist of numerous genetic clones, and that only a small proportion of these clones cause disease. Elucidation of a pos sible association of genotypic profiles with either disease or clinical hea lthy condition is important for understanding the pathogenic characteristic s of bacteria. Studies addressing this issue as it relates to P. gingivalis are reviewed in the present article. Genotypic characterization of P. ging ivalis strains has revealed extensive heterogeneity in natural populations of this bacterium. Some of the potential virulence factors of P. gingivalis have been purified and cloned and methods have been established to identif y their genes. Although no studies have clearly defined the relationship be tween a specific genotype of P. gingivalis and periodontal status of the ho st, it seems that molecular typing tools, which are undergoing rapid improv ements, will allow us to distinguish between virulent and avirulent strains of the same species in the near future.