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Viridans group streptococci (VGS) are a common cause of infective endocarditis, and dental plaque is the major source of these bacteria. The present study examined the antibiotic resistance of 635 VGS isolates obtained from dental plaques. Isolates from supragingival plaques were identified using the rapid ID 32 Strep and mini API reader (bioMérieux, France), and minimal inhibitory concentrations (MICs) were determined by a broth microdilution method. High rates of resistance to ampicillin and tetracycline were detected among the isolates. The most resistant species were Streptococcus sanguinis and Streptococcus salivarius. Among the 635 isolates, 9.1% were resistant to erythromycin, and 20.6% to tetracycline. All isolates were sensitive to vancomycin. Resistance to amoxicillin was observed in 0.2% of all isolates. In this study, we showed the incidence of antimicrobial resistance and the susceptibility patterns among 635 VGS isolates from dental plaque.

Objective: Mitis-salivarius (MS) agar has been used widely in microbial epidemiological studies because oral viridans streptococci can be selectively grown on this medium. Even though the previous findings reported the limited selecting power of MS agar for streptococcus strains, the identities of non-streptococcal strains from human oral samples which can grow on this medium are not clear yet. In this study, we identified non-streptococcal organisms grown on MS agar plates by polymerase chain reaction (PCR) amplification and sequencing of the 16S ribosomal RNA (rRNA) gene., Design: Eighty bacterial colonies on MS plates were isolated from plaque samples, and bacterial identification was achieved with the rapid ID 32 Strep system and mini API reader. The bacterial colonies identified as non-streptococci by the API system were selected for further identification. The 16S rRNA gene was amplified by PCR and verified using DNA sequencing analysis for identification. Sequences were compared with those of reference organisms in the genome database of the National Center for Biotechnology Information using the Basic Local Alignment Search Tool (BLAST)., Results: Among the 11 isolated non-streptococcal strains on MS plates, 3 strains were identified as Actinomyces naeslundii, 7 strains were identified as Actinomyces oris and 1 strain were identified as Actinomyces sp. using Blastn., Conclusions: In this study, we showed that some oral Actinomyces species can grow on Streptococcus-selective MS agar plates., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Laminaria japonica is a brown alga, which is consumed widely in Korea, Japan, and China. This study investigated the antimicrobial activity of ethanol extracts of L. japonica against oral microbial species to assess the possible application of L. japonica extracts in dental care products. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined in culture medium using a microdilution method. The MICs of ethanol extracts of L. japonica with oral streptococci were 62.5-500 μg/ml and the MBCs were 125-1000 μg/ml. The MICs of Actinomyces naeslundii and Actinomyces odontolyticus were 250 and 62.5 μg/ml, respectively. The MBCs of A. naeslundii and A. odontolyticus were 500 and 250 μg/ml, respectively. The MICs were 250 and 62.5 μg/ml for Fusobacterium nucleatum and Porphyromonas gingivalis, respectively. The killing of Streptococcus mutans and P. gingivalis was dependent on the incubation time. The killing of S. mutans, A. odontolyticus, and P. gingivalis was significantly dependent on the extract concentration. Bacterial treatment with L. japonica extracts changed the cell surface texture of S. mutans, A. odontolyticus, and P. gingivalis. The results of this study suggest that L. japonica extracts may be useful for the development of antimicrobial agents to combat oral pathogens., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objective: To evaluate changes that occur in the subgingival microbiota after removal of fixed orthodontic appliances using polymerase chain reaction (PCR)., Materials and Methods: Thirty orthodontic patients (11 males and 19 females; aged 20 +/- 7.3 yr) were included in this study. Subgingival plaque samplings were gathered from the disto-buccal gingival crevice of the left upper central incisors and the left lower central incisors, and from the mesio-buccal gingival crevice of the left upper first molars and the left lower first molars, at two different times: 2 weeks before appliance removal (T1), and 3 months after appliance removal (T2). DNA was extracted from the samples and the 16S rRNA-based PCR detection method was used to determine the prevalence of Actinobacillus actinomycetemcomitans , Tannerella forsythia , Campylobacter rectus , Eikenella corrodens , Porphyromonas gingivalis , Prevotella intermedia , Prevotella nigrescens , and Treponema denticola , which are considered as putative periodontopathogens., Results: The frequency of positive sites at T1 and T2 was 65% and 43.3% for C. rectus , and 53.3% and 30.8% for E. corrodens , respectively. For the other bacteria, the frequency tended to be reduced between times., Conclusion: Periodontopathogens during orthodontic treatment were significantly reduced within 3 months of appliance removal. However, how long it takes to return to the preorthodontic composition of the subgingival microbiota and whether it happens at all remain to be seen.