Fimbria encoded by the gene fimA is considered one of the main factors in the colonization of the oral cavity by Porphyromonas gingivalis. Allelic variation in fimA led to the classification of strains of P. gingivalis into six genotypes. The occurrence of P. gingivalis was determined by polymerase chain reaction using 16S rRNA primers in 302 subgingival samples obtained from 102 Brazilian subjects exhibiting different periodontal conditions. Distribution of fimA genotypes was assessed in 146 P. gingivalis positive samples by polymerase chain reaction using primers pairs homologous to the different fimA genes. P. gingivalis was detected in 51 of 57 (89.4%) patients with periodontal attachment loss, in six of 20 gingivitis patients (30.0%) and in two of 25 (8.0%) subjects with a healthy periodontium. Variant type II was the only type detected in 53 sites (39.3%), distributed among 19 periodontitis patients (37.3%) and in one patient with no periodontal destruction. Type Ib was the second most prevalent genotype in periodontitis patients (19.6%). Genotype V was not detected in the studied population. Type IV was the most commonly type found among gingivitis patients, either alone or in combination with other genotypes. Multiple genotypes were detected in nine sites (6.1%). A fimA genotype was not identified in 26 sites (17.8%) of 146 sites positive for P. gingivalis, suggesting that other alleles of fimA not yet sequenced may be prevalent in this population. These data demonstrated that P. gingivalis type II strains followed by type Ib are more prevalent in periodontitis patients from a multiracial population in Brazil, suggesting an increased pathogenic potential of these types.

Adhesion to and invasion of epithelial cells by the periodontopathogen Porphyromonas gingivalis is promoted by the major fimbriae, encoded by fimA. The microorganism can be classified in six genotypes, based on fimA sequence, and genotype II strains are more prevalent than others in periodontitis patients. This study aimed to determine the adhesive and invasive abilities on KB cells of different fimA allelic variants of P. gingivalis isolates. Twenty-two isolates and six reference strains representing the six fimA genotypes and non-typeable strains were screened for their adhesion and invasion abilities on KB cells, using standard methods. All strains were able to adhere and, except for one, to invade KB cells. However, these properties were not homogeneous among strains belonging to the same genotype. There was no correlation between adhesion and invasion efficiencies. Isolate KdII 865 (fimA genotype II) was the most invasive and the second most adhesive strain, whereas reference strain ATCC 33277 (fimA I) showed a low adhesion ability but was highly invasive. These data indicated that fimA genotypes of P. gingivalis are not related to the adhesion and invasion abilities on KB cells, suggesting that the increased prevalence and proportion of certain genotypes may be attributed to other characteristics besides FimA variation.