Distribution of Porphyromonas gingivalis strains with fimA genotypes in periodontitis patients

Fimbriae (FimA) of Porphyromonas gingivalis are filamentous components on t he cell surface and are thought to play an important role in the colonizati on and invasion of periodontal tissues. We previously demonstrated that fim A can be classified into four variants (types I to IV) On the basis of the nucleotide sequences of the fimA gene. In the present study, we attempted t o detect the four different fimA genes in saliva and plaque samples isolate d from patients with periodontitis using the PCR method. Four sets of fimA type-specific primers were designed for the PCR assay. These primers select ively amplified 392-bp (type I), 257-bp (type II), 247-bp (type III), and 2 51-bp (type IV) DNA fragments of the fimA gene. Positive PCR results were o bserved with reference strains of P. gingivalis in a type-specific manner. All other laboratory strains of oral and nonoral bacteria Save negative res ults. The sensitivity of the PCR assay for fimA type-specific detection was between 5 and 50 cells of P, gingivalis. Clinical samples were obtained fr om saliva and subgingival plaque from deep pockets (greater than or equal t o 4 mm) of 93 patients with periodontitis. Bacterial genomic DNA was isolat ed from the samples, and the targeted fragments were amplified by PCR The p resence of P. gingivalis was demonstrated in 73 patients (78.5%), and a sin gle fimA gene Has detected in most patients, The distribution of the four f imA types among the P. gingivalis-positive patients was as follows: type I, 5.4%; type II, 58.9%; type III, 6.8%; type IV, 12.3%; types I and II, 6.8% ; types II and IV: 2.7%; and untypeable, 6.8%. P, gingivalis with type II f imA was detected more frequently in the deeper pockets, and a significant d ifference of the occurrence was observed between shallow (4 mm) and deep (g reater than or equal to 8 mm) pockets. These results suggest that P. gingiv alis strains that possess type II fimA. are significantly more predominant in periodontitis patients, and we speculate that these organisms are involv ed in the destructive progression of periodontal diseases.