Kazuhiko Nakano, Atsuo Amano and Takashi Ooshima
54
focus on intrafamilial transmission [55]. On the other hand, PCR methods using the bacterial
DNA extracted from the oral specimens can readily identify organisms in children and their
mothers. Thus, we decided to compare the distribution of oral bacteria in children and their
mothers in order to understand which periodontal bacterial species are transmitted from
mothers to their children.
Saliva specimens were collected from 113 pairs of children (61 boys and 52 girls) aged 2-
12 years and their mothers aged 24-49 years [72]. PCR detectionidentifies the species
estimated to be involved in mother-to-child transmission based on the results of the detection
rates in both groups.
T. denticola
was detected most frequently (83%) in children whose
mothers possessed the same pathogen and was shown to be significantly higher than that in
children whose mothers did not harbor the spirochete.In addition to
T. denticola
,
C. sputigena
,
A. actinomycetemcomitans
, and
E. corrodens
showed this same tendency for which the odds
ratiosare shown in Figure 23. These resultssuggest that a correlation between the presence of
periodontal bacteria in children and their mothers, and the presence of RC bacteria in children
was shown to be highly associated with the prevalence in their mothers. As for the other
species, the detection rates for
C. sputigena
and
A. actinomycetemcomitans
were relatively
high in both mothers and children. Thus, the presence of these species in the mother-child
pairs might have been coincidental and were not statistically analyzed. In addition, the
numbers of children with
P. gingivalis
were too low in the present study to estimate
transmission from mother to child. However, another study demonstrated a tendency for
detection of
P. gingivalis
in children whose mothers were also positive for this organism[64].
In addition, the genotypes of
P. gingivalis
fimbriae genesfor mother-child pairs were shown
to be consistent which led us to speculate that
P. gingivalis
is also one of the species
transmitted from mothers to children. An additional study analyzing 56 Japanese children and
adolescents aged 1-15 years and their parents suggested that
P. intermedia
,
P. nigrescens
, and
T. forsythia
were transmitted in an intrafamilial manner [73].
Figure 23. Odds ratios of the species with estimated mother-to-child transmission based on the
distribution of the species in children and their mothers.
As described above, RC species are reportedly associated with gingival inflammation
based on studies of Japanese teenagers [59, 60].
In our study, approximately 40% of
the saliva
specimens taken from mothers were shown to possess RC species and their total number of
Periodontal Diseases in Children and Adolescents …
55
periodontal bacteria was significantly higher than in those without RC species [64]. The
detection rate of the RC species in children whose mothers possessed the same species was
shown to be significantly higher than in those whose mothers did not (odds ratio 7.4). A
similar study conducted in the United States demonstrated that children whose parents were
colonized by RC species were 9.8 times more likely to be colonized by the same species [74].
In addition, the total number of bacterial species in children whose mothers possessed the RC
species was shown to be significantly greater than in those whose mothers did not. Taken
together, the present data suggested that mothers should be careful not only regarding the
current periodontal condition of their children but also their own periodontal
health in order to
prevent the early subsequent onset of periodontitis in their children.
6)
Porphyromonas gingivalis
Fimbriae
P. gingivalis
is considered to be one of the most important pathogens in periodontal
disease. This pathogen expresses fimbriae, filamentous appendages on the bacterial surface,
which are thought to play a significant role in colonization and invasion of periodontal tissues
[75]. FimA, a subunit protein of the major fimbriae, is encoded by the
fimA
gene which is
classified into six variants (types I through V and Ib) [76-78]. Table 5 lists the primer sets for
identification of
fimA
genotypes in the clinical specimens. A majority of the
P. gingivalis
organisms isolated from marginal periodontitis patients are reported to belong to type II,
followed by type IV, while type I tends to be prevalent in periodontally healthy adults [79]. In
fact, several other studies conducted in different countries also support our findings that type
II
fimA
organisms are strongly correlated with the development of periodontitis [80-82].
These findings suggest the existence of disease-associated and non-associated
P. gingivalis
.
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