Occurrence and serotype distribution of Aggregatibacter actinomycetemcomitans in subjects without periodontitis in Turkey
Introduction
Gram-negative, nonmotile, facultative Aggregatibacter actinomycetemcomitans is a major etiologic agent of aggressive periodontitis and an occasional cause of non-oral infections (Asikainen and Chen, 1999, Slots and Ting, 1999, van Winkelhoff and Slots, 1999). The natural population structure of the species is clonal and comprises genetically distinct strains distinguished by serotypes (Kaplan, Schreiner, Furgang, & Fine, 2002; Kilian, Frandsen, Haubek, & Poulsen, 2006).
The clonal population structure of bacterial species is a consequence of recombination barriers between clonal lineages. Over time, individual lineages may diverge and acquire different biological properties via gain and loss of genes and also exhibit heterogeneity in virulence. For example, serotype b strains have been found to be more frequently detected in periodontitis than in periodontal health (Asikainen, Lai, Alaluusua, & Slots, 1991). Presumably strains of serotype b may possess unique virulence determinants, and the detection of specific serotype b strains may be indicative of a greater risk for periodontal disease progression. However, the associations between specific serotypes and disease must be interpreted in the context of the distribution of serotypes in the general population. If serotype b is also found to be the dominant serotype among subjects without periodontitis, the association between serotype b and disease is merely an extraneous finding.
Indeed, the distribution patterns of different serotypes of A. actinomycetemcomitans vary among geographical locations and race/ethnicity of the subjects (Chen, Wang, & Chen, 2010; Fine et al., 2007; Mombelli, Gmur, Lang, Corbert, & Frey, 1999; Saarela et al., 1992; Yang, Huang, Chan, & Chou, 2005). More pertinent to this study, serotype c of A. actinomycetemcomitans has been reported to be associated with subjects with periodontitis in Turkey (Doğan et al., 2003). It was postulated that serotype c represents the dominant pathogenic clone of A. actinomycetemcomitans in the Turkish population. To further explore the implication of this finding, this study was undertaken to determine the occurrence and serotype distribution of A. actinomycetemcomitans in Turkish students with healthy periodontium.
Section snippets
Study subjects
The study design was approved by the Ethics Committee of Medical Faculty, Marmara University (MAR-YÇ-2009-0064). Fig. 1 provides an overview of the subject recruitment process. The study subjects were recruited from dental students attending Marmara University, Faculty of Dentistry, Turkey. The students were informed that the participation in this study was voluntary. Full-mouth periodontal and panoramic radiographic examinations were carried out by a single examiner (S.Y.Ç.). For the
Results
A summary of the clinical parameters of the study subjects is provided in Table 2. In agreement with the diagnosis of non-disease, the subjects exhibited shallow pocket depths and minimal clinical attachment loss (whole mouth or sample sites). However, there was a wide range of variation in PI, GI, and BOP.
The detection limit of A. actinomycetemcomitans was determined based on PCR analysis of serially diluted DNA from genomic DNA of the sequenced strains held in our lab (data not shown). The
Discussion
This study aimed to address two issues, the first being the frequency of A. actinomycetemcomitans colonization in periodontally healthy individuals and the second being the distribution pattern of different serotypes of A. actinomycetemcomitans among healthy subjects colonized by this organism. To address these issues, we examined by PCR the presence of distinct serotypes of A. actinomycetemcomitans in subgingival plaque of periodontally healthy subjects.
In this study the detection limit of A.
Conclusion
Serotype a is the dominant serotype of A. actinomycetemcomitans found in young Turkish dental students. The result is consistent with the hypothesis that the distribution patterns of A. actinomycetemcomitans serotypes among human subjects may vary according to geographic locations and periodontal status of the study subjects.
Conflicts of interest
None.
Funding
This work was supported by grants from Marmara University Scientific Research Project CouncilSGA-A-300609-0215 (Başak Doğan) and NIHR01 DE012212 (Casey Chen).
Author’s contributions
Başak Doğan and Casey Chen designed and implemented the research protocol, performed data analysis, and prepared the manuscript for submission. Jason Chen, and Jonathan Huang processed the DNA samples and performed PCR analysis. Sinem Yıldız Çiftlikli, examined the subjects and collected the samples. Tanju Kadir, and Anıl Kınacı Alnıak organized the study subjects, calculated clinical parameter of each subject and put these data into the computer.
Ethical approval
The study design was approved by the Ethics Committee of Medical Faculty, Marmara University (MAR-YÇ-2009-0064).
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