Distribution of Porphyromonas gingivalis fimA Genotypes in Japanese Children and Adolescents

Abstract

Porphyromonas gingivalis is considered to be one of the most important pathogens in periodontal disease and its fimA genes have been classified into six variants (types I through V and Ib). A majority of the P. gingivalis organisms isolated from periodontitis patients are type II, followed by type IV, while type I is prevalent in healthy adults. A total of 650 saliva samples were taken from 464 children (3 to 18 years of age), who visited Osaka University Dental Hospital. Genomic DNA was extracted from each sample and analyzed using a polymerase chain reaction (PCR) method with P. gingivalis-specific primers, followed by an additional PCR assay to determine the fimA genotypes for P. gingivalis- positive subjects. Fifteen (3.23%) of the subjects were P. gingivalis-positive and none of those samples showed a positive reaction to the type II fimA-specific primers, while four, one, and two subjects were shown to be positive for the type I, Ib, and III genotypes, respectively. In addition, the type IV genotype was detected in three subjects in the older age group. Our findings suggest that a limited number of children harbor P. gingivalis, and that the distribution of type II and IV fimA genotypes is extremely low. Further, some adolescents were found to possess the type IV fimA genotype which has been shown to be possibly related to adult periodontitis, in contrast to types I, III, and V.