Clonal stability of Porphyromonas gingivalis in untreated periodontitis

The objective of the present investigation was to study the clonal stability of Porphyromonas gingivalis in a population of Indonesian subjects, deprived of dental care and with varying degrees of periodontitis over a period of 8 years.

In 1994, 105 subjects and in 2002, 103 subjects were P. gingivalis culture positive. Multiple isolates from each of these subjects were used for amplified fragment length polymorphism (AFLP) typing.

Sixty-six individuals were P. gingivalis culture positive at both time points. In 31 subjects (47%) an exact identical P. gingivalis genotype distribution was found in 1994 and in 2002. In 26 of these subjects one genotype, in eight subjects two identical genotypes were found at both time points. In 70% of the subjects at least one P. gingivalis genotype was found in 1994 and 2002, whereas other genotypes were either newly detected or were no longer detectable. Identical genotypes were found in 26% of the sibships. Clonal stability in siblings was 39%. Horizontal transmission of P. gingivalis was only found in 2002 and was low (11%). In total, 56 P. gingivalis genotypes were identified in 1994 and 61 in 2002. Twenty-four appeared unique, whereas other genotypes were found in multiple subjects within as well as without families. One genotype occurred in 11 different subjects.

The clonal stability of P. gingivalis under natural conditions is high. Complete different genotype distribution was found in only 27% of the subjects. Transmission of P. gingivalis occurred frequently among siblings but not among spouses.