Kazuhiko Nakano, Atsuo Amano and Takashi Ooshima
56
and Ib. Figure 24 illustrates the odds ratios showing the relationship between
P. gingivalis
fimA
genotypes and development of periodontitis in the subjects. Type II was the highest,
followed by types IV and Ib, all of which are regarded as highly virulent groups, whereas
types I, III and V are considered to be low virulence groups. In addition, the results of
in vitro
analyses using gingival epithelial cells as well as a mouse model of abscess formation
supported this suggestion [83, 84]. Specifically, it was interesting to observe that a mutant
with a substitution of the type I
fimA
gene with that of type II showed enhanced bacterial
adhesion/invasion to epithelial cells, whereas that with substitution of type II
fimA
with type I
resulted in diminished adhesion/invasion [85]. These results suggest that it is possible to
estimate the risk of subjects for periodontitis by analyzing the types of
P. gingivalis fimA
genes in oral specimens.
Figure 24. Odds ratios of the
P. gingivalis fimA
genotypes and marginal periodontitis based on the
fimA
genotypes distribution in marginal periodontitis patients.
A total of 650 saliva specimens were isolated from 464 children (3 to 18 years of age)
were analyzed, and PCR detection showed that only 15 (3.23%) subjects were
P. gingivalis
-
positive [72] (Figure 25). The detection ratesfor
P. gingivalis
and the ages of the subjects were
similar to those in a previous study [47, 48] which supports the suggestion that
P. gingivalis
tended to be more frequently detected in older subjects. It should be noted that
P. gingivalis
is
regarded as a transient species in children and adolescents and the detection rates for
P.
gingivalis
at different times was shown to be 25-67% in
P. gingivalis
-positive subjects [48].
Therefore, multiple specimens at different times are required to identify
P. gingivalis
-positive
subjects. Furthermore, additional assaysof these specimens to discriminate between the
fimA
genotypes demonstrated that none of these showed a positive reaction to the type II
fimA
-
specific primers, while 4, 1, and 2 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. It should be noted that one-third of the
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