BACKGROUND: Porphyromonas gingivalis produces outer membrane-attached proteins 
that include the virulence-associated cysteine proteinases RgpA and RgpB 
(Arg-gingipains) and Kgp (Lys-gingipain). The gingipains provide P. gingivalis 
with a general proteolytic tool for degradation of proteinaceous nutrients for 
growth. They are also essential for the processing and maturation of the major 
fimbriae (FimA) which are important in facilitating bacterial adhesion to host 
tissues. FimA has been characterized as an important virulence factor for P. 
gingivalis, and many studies, both animal experiments and clinical 
investigations, have characterized fimA genotypes II, Ib, and IV to be 
associated with disease (periodontitis and cardiovascular disease) while 
genotypes I, III, and V represent avirulent strains. The relationship between 
virulence and gene variation of the rgpB gene has not been investigated 
extensively. However, nucleotide variations of the rgpB gene result in four 
amino acid substitutions in the catalytic domain identifying five different rgpB 
genotypes. They are named according to the different amino acid sequences in the 
primary protein structure of RGPB and named NYPN, NSSN, NSSK, NYPK, and DYPN 
(Beikler et al. 2005).
AIM: The aim of the present study is to elucidate a possible relationship 
between fimA virulent and avirulent genotypes to the corresponding rgpB 
genotypes.
METHODS: The total length of the rgpB (2212 bp) and fimA genes (1140 bp) from 20 
clinical isolates was sequenced. Primers for pcr and sequencing of the genes 
were selected according to earlier investigations.
RESULTS: The rgpB genotypes, NSSN and NYPN (n=2 and 6, respectively), were 
detected in the fimA II genotypes of P. gingivalis, while NSSK was detected in 
one fimA Ib genotype in the population. For the eight fimA IV genotypes, five 
NSSK and three NSSN rgpB genotypes were detected. In two fima I genotypes were 
detected one DYPN and one NYPN of the rgpB variants, while one fimA III genotype 
was associated with NSSK.
CONCLUSION: The rgpB genotypes NSSN, NYPN, NSSK of P. gingivalis may be 
associated with the virulent fimA genotypes II, Ib and IV, indicating a possible 
connection to their virulent properties.