PREVALENCE AND DISTRIBUTION OF 6 CAPSULAR SEROTYPES OF PORPHYROMONAS-GINGIVALIS IN PERIODONTITIS PATIENTS

Previous reports have described six serotypes based on K antigens in P orphyromonas gingivalis strains. The purpose of the present study was to investigate the prevalence and distribution of these serotypes in 1 85 patients with P. gingivalis-associated periodontitis. Polyclonal ra bbit antisera, raised against each of the different type strains, were used in double-immunodiffusion and immunoelectrophoresis assays. In a ddition, a subset of 76 strains was investigated for the presence of c apsular structures by means of the India ink and Bruce White staining techniques. These strains were also tested for auto-aggregation in pho sphate-buffered saline (PBS). All six K serotypes were present in the study sample. In total, 84 (45.4%) patients were colonized with a K-ty peable P. gingivalis strain with a predominance of types K5 (12%) and K6 (23.2%). A correlation was found between arbitrary age categories a nd the prevalence of currently known K serotypes, which were found in 60% of patients aged 12 to 30 years, in 49% of patients aged 31 to 50, and in 25% of patients aged 51 to 70 years. In the subset of 76 P. gi ngivalis strains, 32 (42.1%) were K-typeable. Fifty-three strains (69. 7%) showed microscopic evidence of encapsulation, suggesting the exist ence of K serotypes other than K1 to K6. Twenty-one strains (27.6%) au to-aggregated in PBS and were not K-typeable, nor did they show any ev idence of encapsulation. It was concluded that the majority of clinica l P. gingivalis isolates is encapsulated and that encapsulation is ass ociated with the presence of a K antigen. Auto-aggregation seems to be associated with the absence of a capsular structure and, consequently , the absence of a K antigen.