-
[show abstract]
[hide abstract]
ABSTRACT: Streptococcus mutans is recognised as a major aetiological agent of dental caries. One of its important virulence factors is its ability to form biofilms on tooth surfaces. The aim of this study was to evaluate the effects of the quorum sensing inhibitor furanone C-30 on biofilm formation by S. mutans and its luxS mutant strain. The effects of furanone C-30 on biofilms of both strains formed on 96-well microtitre plates at 37 °C were determined by a colorimetric technique (MTT assay). Different concentrations of furanone C-30 (0.0, 2.0 and 4.0 μg/mL) and different time points of biofilm formation (4, 14 and 24 h) were investigated. The structures and thickness of the biofilms were observed by confocal laser scanning microscopy (CLSM). Quorum sensing-related gene expression (ftf, smu630, brpA, gbpB, gtfB, vicR, comDE and relA) was investigated by real-time polymerase chain reaction (RT-PCR). The results showed that synthetic furanone C-30 can inhibit biofilm formation by S. mutans and its luxS mutant strain, although it does not affect the bacterial growth rate itself. The quantities of biofilm formed by both strains significantly decreased (P<0.05) and the biofilms became thinner and looser as revealed by CLSM with increasing concentrations of furanone C-30. Expression of the genes tested was downregulated in the biofilms by the addition of furanone C-30. These results revealed that synthetic furanone C-30 can effectively inhibit biofilm formation by S. mutans and its luxS mutant strain.
International journal of antimicrobial agents 05/2012; 40(1):30-5. · 3.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: AI-2-mediated quorum sensing has been identified in various bacteria, including both Gram-negative and Gram-positive species, and numerous phenotypes have been reported to be regulated by this mechanism, using the luxS-mutant strain. But the AI-2 production process confused this regulatory function; some considered this regulation as the result of a metabolic change, which refers to an important metabolic cycle named activated methyl cycle (AMC), caused by luxS-mutant simultaneously with the defect of AI-2. Herein we hypothesized that the quorum sensing system--not the metabolic aspect--is responsible for such a regulatory function. In this study, we constructed plasmids infused with sahH and induced protein expression in the luxS-mutant strain to make the quorum-sensing system and metabolic system independent. The biofilm-related genes were investigated by real-time polymerase chain reaction (PCR), and the results demonstrated that the quorum-sensing completed strain restored the gene expression of the defective strain, but the metabolically completed one did not. This evidence supported our hypothesis that the autoinducer-2-mediated, quorum-sensing system, not the AMC, was responsible for luxS mutant regulation.
Sensors 01/2012; 12(5):6155-75. · 1.74 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: DGGE of 16S rDNA is one of the most frequently used methods to study microbial communities. In this study, the DGGE profiles of different 16S rDNA regions of the periodontal pathogens Porphyromonas gingivalis, Fusobacterium nucleatum, and Prevotella nigrescens were investigated. The results suggested that V3-V5 and V6-V8 fragments may be suitable for community analysis of subgingival bacteria. Further analysis of subgingival samples with V3-V5 and V6-V8 regions as target fragments suggested that, in chronic periodontitis, re-colonization by periodontal bacteria with a population very similar to the baseline may occur by 6 weeks after mechanical debridement.
Microbiology and Immunology 11/2010; 54(11):702-6. · 1.30 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Pseudomonas aeruginosa is the major pathogen of chronic lung infections in individuals with cystic fibrosis (CF). Traditionally, it has been regarded as living in planktonic form, and as being able to perform only simple physiological activities. Recent studies in biofilm infections in CF patients, however, show that P. aeruginosa can perform many social behaviors, like cooperation and cheating. Based on the theory of "survival of the fittest", it may be presumed that every individual will take advantage of cheating instead of cooperation to increase its fitness, at the cost of group survival. In reality, however, a bacterial society can remain stable, even though cheaters arise frequently in the population. It is therefore possible that there are anti-cheating mechanisms in a bacterial society. The cheaters of P. aeruginosa will cause the loss or the decrease of the pathogenesis of the microorganism in the cystic fibrosis host. These defects in pathogenesis will be disadvantageous to bacterial colonization and compromise the resistance to host immunity. We therefore propose the hypothesis that the pathogenesis in cystic fibrosis lung infections could be one of the anti-cheating mechanisms that contribute to the hidden costs of the cheater strains. To test this hypothesis, we designed an experiment in an animal model of CF. If this hypothesis can be confirmed, it will illustrate that nontrivial analogies exist between microbial social behaviors and the social traits that are observed in the more traditional model systems for sociobiology. This will not only provide a genetic model for sociobiology research, but also cast light on the social control of chronic bacterial infections.
Medical Hypotheses 10/2010; 76(2):166-8. · 1.39 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To evaluate the in vitro cario-static effect of Galla chinesis with biofilm model.
A four-organism bacterial consortium was cultured in a biofilm model on hydroxyapatite (HA) discs in a continuous culture system and exposed to repeated solution pulsing. There were three groups with different solution pulsed in the model: negative control group was pulsed with distilled water, positive control group was pulsed with 100 mmol/L sucrose solution and experimental group was pulsed with 100 mmol/L sucrose solution containing 4.0 g/L Galla chinensis. During the experiment, the dynamic changes of pH were recorded. After 6 pulses, surface structure of the biofilm was observed with a scanning electron microscope and the population on the biofilm was enumerated.
Galla chinesis significantly inhibited the adherence of Actinomyces naelundii to HA disc compared with the control group and facilitated the removal of acid products. It was also found that the extra-cellular polysaccharide was reduced with the pulsing of Galla chinesis.
Galla chinesis in the biofilm model can partially reduce the cario-genic response of sucrose solution.
Hua xi kou qiang yi xue za zhi = Huaxi kouqiang yixue zazhi = West China journal of stomatology 11/2003; 21(5):389-91.
-
[show abstract]
[hide abstract]
ABSTRACT: To evaluate the Nidus vespae's cario-static effect on biofilm model in vitro.
A four-organism bacterial consortium was grown in a biofilm model on hydroxyapatite (HA) discs in a continuous culture system and exposed to repeated solution pulsing respectively. There were three parallel-connected flow cells in the model, so were the three groups with different solution pulsed in. Negative control group was pulsed with distilled water, positive control group was pulsed with 250 mmol/L sucrose solution as well. While 4.0 g/L Nidus vespae together with 250 mmol/L sucrose solution was pulsed in the experiment group. During the experiment, the pH responses against the pulses were recorded. After the 6 pulses, the biofilm surface structure was observed with a scan electron microscope and the population on the biofilm was enumerated.
Nidus vespae can significantly inhibit the adherence of Streptococcus mutans to HA discs compared with the control group of 250 mmol/L sucrose pulsed in, and can facilitate the remove of acid products. It is also found that the extra-cellular polysaccharide is reduced with the pulsing of Nidus vespae.
Nidus vespae in the biofilm model can partially decrease the cariogenic response of sucrose solution pulsed in.
Hua xi kou qiang yi xue za zhi = Huaxi kouqiang yixue zazhi = West China journal of stomatology 09/2003; 21(4):304-6, 317.
-
[show abstract]
[hide abstract]
ABSTRACT: To investigate the effects of traditional Chinese medicines on the preliminary adherence of Streptococcus mutans to salivary acquired pellicles.
The hydroxyapatites beads were coated by saliva to form S-HA, an in vitro model of experimental pellicle. Streptococcus mutans was chosen as the experiment strain, and radiolabeled with 3H-thymidine. Two parts of adherence inhibit study were carried on with medicines pretreated S-HA and medicines pretreated bacteria. The numbers of 3H-thymidine labeled bacteria attached to S-HA were counted by scintillation counting to indicate the amount of adherence.
It was found that most of the traditional Chinese medicines tested could inhibit the adherence to S-HA to different extent, especially the Galla Chinensis, which has significant inhibitory action.
Galla Chinensis may be a prospective medicine to inhibit the cariogenic bacteria's preliminary adherence to salivary acquired pellicles.
Sichuan da xue xue bao. Yi xue ban = Journal of Sichuan University. Medical science edition 02/2003; 34(1):135-7.
-
[show abstract]
[hide abstract]
ABSTRACT: To assess the effects of different natural medicines on the growth and acid production of Actinomyces viscosus, thus making preparations for screening an effective agent to mediate the balance of oral microflora.
Actinomyces viscosus ATCC 19246 was chosen as the experimental bacteria. 11 kinds of traditional Chinese medicine, such as Rhizoma Ligustici Chuanxiong, Sargentodoxa Cuneata and Galla Chinensis were extracted by means of maceration, percolation and reflux extraction. First, the values of MIC of various extracts were measured. Second, the experimental medium containing various extracts was prepared. The concentration of the extracts was lower than the MIC of the medicine, and the initial pH of the medium was 7.4. Then Actinomyces viscosus was cultured in the medium for 48 h, and finally the rest pH was measured.
When the concentration of the medicines was lower than or equal to 8.000 mg/ml, it was found that all kinds of medicine except Radix Notoginseng can inhibit the growth of Actinomyces viscosus effectively, especially Polistes mandarinus and Semen Arecae. Tea polyphenols, Radix Notoginseng, Radix et Rhizoma Rhei, Polistes mandarinus and Sargentodoxa cuneata can inhibit the acid production of Actinomyces viscosus effectively, but Radix Scutellariae, Rhizoma Ligustici Chuanxiong, Semen Arecae, Radix Angelicae Dahuricae, Galla Chinensis and Catechu have no preliminary effect on it.
Tea polyphenols, Radix et Rhizoma Rhei, Polistes mandarinus and Sargentodoxa cuneata can inhibit the growth and the acid production of Actinomyces viscosus effectively.
Hua xi yi ke da xue xue bao = Journal of West China University of Medical Sciences = Huaxi yike daxue xuebao / [bian ji zhe, Hua xi yi ke da xue xue bao bian wei hui] 05/2002; 33(2):253-5.
