Biomedical subjects

Mitsuko Seki

Publications and source records attributed to Mitsuko Seki.

6 recordsLinked to original sources

PubMed2005

Decreasing caries prevalence in Japanese preschool children is accompanied with a reduction in mutans streptococci infection.

OBJECTIVE: To evaluate the association between decreasing caries prevalence in Japanese preschool children and mutans streptococci (MS) infection. METHODS: The prevalence of caries and salivary MS was examined in 1- to 3-year-old preschool children in 1995 (n = 135) and 2000 (n = 118). RESULTS: The caries prevalence for 3-year-old subjects significantly declined from 65.1% to 37.5% (p < 0.01), reflecting the data seen in Japanese national oral health surveys in 1993 and 1999. Salivary MS detection for 3-year-old subjects significantly declined from 68.3% to 37.5% (p < 0.05). On the other hand, the decrease in the prevalence of caries and salivary MS was not significant in 1- and 2-year-olds. The correlation between caries experience (dft) and the salivary MS score for 3-year-old subjects with low caries prevalence in the later examination (r(s) = 0.479, p < 0.001) was comparable with that in 1995 (r(s) = 0.462, p = 0.001). CONCLUSIONS: The recent decrease in decay in Japan is accompanied with a reduction in MS infection in the deciduous dentition. MS levels are closely related to caries prevalence in preschool children regardless of the extent of caries.

Child, Preschool↗

PubMed2005

Loop-mediated isothermal amplification method targeting the lytA gene for detection of Streptococcus pneumoniae.

It is difficult to separate Streptococcus pneumoniae from the genotypically similar species Streptococcus mitis and Streptococcus oralis, which are commensals of the human oral cavity. A novel nucleic acid amplification technique, loop-mediated isothermal amplification (LAMP), which amplifies DNA under isothermal conditions (63 degrees C) with high specificity, efficiency, and rapidity, was examined regarding its applicability for detecting S. pneumoniae. An S. pneumoniae-specific LAMP primer targeting the lytA gene was designed. The primer specificity was validated using 10 Streptococcus and 7 non-Streptococcus species. Within 60 min, the assay could detect 10 or more copies of purified S. pneumoniae DNA with a sensitivity 1,000 times that of conventional PCR. Clinical isolates of 21 other strains (3 S. oralis, 17 S. mitis, and 1 Streptococcus species) that harbor virulence-factor-encoding genes (lytA or ply) were tried to differentiate S. pneumoniae. The detection of S. pneumoniae in clinical isolates was more selective using the LAMP method than using conventional PCR. Therefore, LAMP appears to be a sensitive and reliable means of diagnosing S. pneumoniae infection.

Bacterial Typing Techniques↗

PubMed2005

Discrimination of Streptococcus pneumoniae from viridans group streptococci by genomic subtractive hybridization.

Two oligonucleotide primer sets for the discrimination of Streptococcus pneumoniae from "pneumococcus-like" oral streptococcal isolates by PCR were developed. Genomic subtractive hybridization was performed to search for differences between Streptococcus pneumoniae strain WU2 and the most closely related oral streptococcus, Streptococcus mitis strain 903. We identified 19 clones that contained S. pneumoniae-specific nucleotide fragments that were absent from the chromosomal DNA of typical laboratory strains of S. mitis and other oral bacteria. Subsequently, oligonucleotide PCR primers for the detection of S. pneumoniae were designed from the sequences of the subtracted DNA fragments, and the specificities of the 19 primer sets were evaluated by PCR using chromosomal DNAs extracted from four S. pneumoniae clinical isolates and from 20 atypical organisms classified as S. mitis or S. oralis, which harbored genes encoding the pneumococcal virulence factors autolysin (lytA) or pneumolysin (ply), as templates. Of the 19 primer sets, two (Spn9802 and Spn9828) did not amplify PCR products from any of the pneumococcus-like streptococcal strains that we examined. The genes containing the Spn9802 and Spn9828 sequences encoded proteins of unknown function that did not correspond to any previously described proteins in other bacteria. These new oligonucleotide primers may be very useful for early and correct diagnosis of S. pneumoniae infections.

Bacterial Proteins↗

PubMed2003

Analysis of loci required for determination of serotype antigenicity in Streptococcus mutans and its clinical utilization.

We recently identified the genes responsible for the serotype c-specific glucose side chain formation of rhamnose-glucose polysaccharide (RGP) in Streptococcus mutans. These genes were located downstream from the rgpA through rgpF locus that is involved in the synthesis of RGP. In the present study, the corresponding chromosomal regions were isolated from serotype e and f strains and characterized. The rgpA through rgpF homologs were well conserved among the three serotypes. By contrast, the regions downstream from the rgpF homolog differed considerably among the three serotypes. Replacement of these regions in the different serotype strains converted their serotypic phenotypes, suggesting that these regions participated in serotype-specific glucose side chain formation in each serotype strain. Based on the differences among the DNA sequences of these regions, a PCR method was developed to determine serotypes. S. mutans was isolated from 198 of 432 preschool children (3 to 4 years old). The serotypes of all but one S. mutans isolate were identified by serotyping PCR. Serotype c predominated (84.8%), serotype e was the next most common (13.3%), and serotype f occured rarely (1.9%) in Japanese preschool children. Caries experience in the group with a mixed infection by multiple serotypes of S. mutans was significantly higher than that in the group with a monoinfection by a single serotype.

Child, Preschool↗

PubMed2003

Does a clinical evaluation of oral cleanliness correlate with caries incidence in preschool children? Findings from a cohort study.

The aim of this study was to assess whether a clinical evaluation of oral cleanliness reflects subsequent caries incidence. Oral examination of 180 children (1- to 4-year-olds) was carried out twice in a six-month period. Caries prevalence at baseline (dfs) in 1- to 2-year-olds (group A) and 3- to 4-year-olds (group B) correlated significantly with oral cleanliness as well as salivary mutans streptococci count (MS). Caries increment (delta(dfs)) correlated significantly with oral cleanliness in group A but not in group B, while delta(dfs) significantly correlated with MS in group B and slightly correlated with that in group A. ANCOVA revealed that dfs was significantly higher at the second examination than at baseline in group B, even after adjusting for oral cleanliness. This finding was confirmed by Wilcoxon test when group B was divided in three categories (low, middle and high) based on oral cleanliness. This suggests that the relationship between delta(dfs) and oral cleanliness decreased with age and that the significant positive correlation found in group B by our point-prevalence survey is derived from the remainder of the positive correlation that occurred at a younger age.

Age Factors↗

PubMed2002

An improved method for detecting mutans streptococci using a commercial kit.

The improved detection of mutans streptococci (MS) in individuals was investigated using several modifications to a commercially available kit, Dentocult SM. Significantly better detection of MS was achieved using plaque from the four approximal surfaces at two interdental spaces than with saliva (P < 0.001). Furthermore, the MS estimates for approximal surfaces at the same interdental space were similar (kappa = 0.654) suggesting that differentiating the two surfaces does not improve the detection of MS, and that increasing the number of interdental spaces sampled is a more effective option. This study also evaluated a modification to the standard Dentocult SM site strip method in which two strips were incubated per broth vial so that plaque from eight interdental spaces could be tested at the same time (new method). The results were compared to those obtained when one strip was incubated per broth vial (standard method). Although the MS estimates by the new and standard methods were comparable (kappa = 0.721), the efficiency of MS detection was improved significantly by increasing the number of sites used for MS estimates (P = 0.01). In conclusion, MS detection at eight interdental spaces is recommended using the new Dentocult SM method.

Adult↗