Colonization resistance of defined bacterial plaques to Streptococcus mutans implantation on teeth in a model mouth

We investigated the ability of Streptococcus mutans C67-1 to colonize simple bacterial plaques and the effects of age and stability of the pre-formed plaque on colonization resistance. Mixed-plaques of Actinomyces viscosus WVU627, 'Streptococcus mitior' LPA-1, and Veillonella dispar OMZ193 were grown on tooth segments, mounted back to back for simulation of approximal sites in a model mouth for 66 h. S. mutans C67-1 was either included in the original inoculum or super-inoculated onto the developing plaque. Inclusion of S. mutans C67-1 did not alter the total viable counts, but the proportional composition changed due to inter-species interactions. Colonization resistance of the mixed-plaque samples developed within 24 h, although S. mutans C67-1 was always able to colonize these stagnation sites. Colonization resistance of 24-hour plaque against a fresh isolate, S. mutans CP3, was also studied. There was greater colonization resistance by the basic plaque to this organism, compared with S. mutans C67-1, although the reasons for this were not clear. These initial experiments demonstrate the way in which the factors involved in bacterial colonization resistance in microbial films on teeth can be studied under controlled conditions.     

Monobacterial and mixed bacterial plaques of Streptococcus mutans and Veillonella alcalescens in an artificial mouth: development, metabolism, and effect on human dental enamel

To gain greater understanding of the role of Streptococcus mutans and Veillonella in the caries process, studies of both aerobically and anaerobically grown plaques of S. mutans C67-1 and V. alcalescens V-1 on human enamel slabs were carried out in an artificial mouth. Plaque development, acid production, and demineralization were measured. Early plaque development of monobacterial and mixed bacterial plaques started from randomly adhering cells on day 1 to confluent multilayered microcolonies on day 4. Differences were observed in viable cell counts, total cell mass, and in acid production. In most cases CFU, DNA and acid production were higher in the mixed bacterial plaque, especially in the anaerobic mixed plaque. Lactic acid was the predominant acid in all cases following the supply of sucrose to the plaque. No decisive role could be found for acetic, formic, and propionic acid. No inhibition of demineralization was observed in the enamel slabs inoculated with both aerobic and anaerobic mixed plaques. Demineralization ranged from the more classical picture of lesion development in the aerobic monobacterial plaque-treated samples to an aggressive etching of the enamel surface in the anaerobically mixed treated slabs.     

Effects of chlorhexidine and iodine on in vitro plaques of Streptococcus mutans and Streptococcus sanguis

Abstract – Both chlorhexidine and iodine showed greater antimicrobial effect on in vitro grown S. mutans plaque than on plaque composed of S. sanguis . One treatment with iodine for 8 min inhibited the acid production of S. mutans plaque whereas S. sanguis plaque required 20 min to be similarly affected. In contrast one treatment with chlorhexidine for up to 20 min did not completely inhibit the acid production of plaque of either microorganism. Repeated short term exposures increased the bactericidal effect of chlorhexidine but not that of iodine. The difference in antimicrobial effect between chlorhexidine and that of iodine on S. mutans and S. sanguis should be investigated in persons heavily infected by S. mutans .     

洗必泰涂料系统对窝沟菌斑中变形链球菌的影响

为了观察洗必泰涂料的防龋效果，本研究以一种天然树胶山达脂为基质，配制１０％、２０％及４０％醋酸洗必泰涂料以及一种缓释剂，构成洗必泰涂料系统。体外测试其中洗必泰释放率，临床观察涂料系统对窝沟菌斑中变形链球菌及微生态系的影响。结果显示，洗必泰山达脂涂料能选择性抑制窝沟菌斑中变形链球菌的生长，而对血链球菌无影响。缓释剂起到缓释涂料中洗必泰的作用，延长了涂层与菌斑之间的相互作用时间。提示本涂料系统具有防龋功效，同时能维持口腔菌系平衡。     

Effect of a chlorhexidine varnish on Streptococcus mutans in saliva

The aim of the present work was to evaluate the effect of a thymol/chlorhexidine varnish at 1% on Streptococcus mutans (S. mutans) in saliva applied after teaching and evaluating an oral hygiene technique and dressing the cavities to reduce the bacterial load. Streptococcus mutans levels in saliva samples and dental status were evaluated in 38 girls between 6 and 13 years of age with high risk of caries. The girls were then trained and assessed in oral hygiene. On day seven, oral hygiene assessment was repeated and supragingival plaque control was performed. After 15 days (day 21) another culture was performed and the level of S. mutans in saliva samples was determined. Evaluation and reinforcement of the oral hygiene technique were repeated and the cavities were dressed to reduce the bacterial load. At 36 days from the onset of the experiment, culture S. mutans counts were performed; evaluation and reinforcement of the oral hygiene technique were undertaken and the girls were divided randomly into two groups: 1 The teeth of the experimental group were painted with a varnish containing 1% chlorhexidine and thymol. 2 The teeth of the control group were painted with a placebo varnish containing only thymol. After a further 15 days (day 51), another culture and S. mutans counts were performed. The results showed a gradual reduction in the S. mutans counts in saliva in each subsequent experimental period analyzed. Significant differences between the experimental group and the control group were recorded after treatment. It can be concluded that the levels of S. mutans decreased in each subsequent experimental period and that the application of a 1% chlorhexidine varnish elicited a significant reduction in S. mutans levels.     

Effect of a fluoride-containing varnish on Streptococcus mutans in plaque and saliva

Abstract – The effect of topical application of a fluoride-containing varnish, Duraphat®, on the level of Streptococcus mutans in saliva and in dental plaque was investigated in schoolchildren. Samples of saliva and pooled buccal plaque were taken before varnish application and 4, 10 and 21 d after treatment. Fluoride varnish treatment with or without a preceding dental prophylaxis had no significant effect on the plaque and salivary levels of S. mutans. The findings suggest that the caries-reducing effect of fluoride varnish cannot be explained by an alteration of the incidence of 5. mutans in dental plaque or in saliva.     

Efficacy of two mouth rinse sprays in inhibiting Streptococcus mutans growth on toothbrush bristles

Objective

To compare the efficacy of two types of mouth rinse sprays (Periogard and Plax) in inhibiting the growth of Streptococcus mutans (S. mutans) on toothbrush bristles used by children.

Studies on the bacterial components which bind Streptococcus sanguis and Streptococcus mutans to hydroxyapatite.

Experiments utilizing radio labelled oral streptococci in an in-vitro assay system have demonstrated the selective ability of certain species of these bacteria preferentially to adhere to saliva-coated and dextran-coated hydroxyapatite (HA). Pretreatment of Streptococcus sanguis and Streptococcus mutans with the proteolyic enzymes trypsin and pronase greatly reduced their ability to adhere to saliva or dextran-coated HA respectively. Pretreatment of Strep. sanguis with lipase increased its adsorption to saliva-coated HA and stearic acid-blocked adsorption. Cell walls isolated from Strep. sanguis proved effective in blocking Strep. sanguis adsorption to salivacoated apatite. Cells of Strep. mutans after treatment with dextranase or low molecular weight dextrans did not adhere well to dextran-coated HA.     

Oral implantation of Streptococcus mutans in man with and without prior chlorhexidine mouthrinses

Abstract — Oral implantation of streptomycin resistant S. mutans was enhanced when chlorhexidine mouthrinses were applied before implantation. The difference in recovery of implanted bacteria between implantations with and without prior chlorhexidine mouthrinses was significant 9 days ( P<0.05 ), 15 days ( P <0.05) and 28 days ( P <0.01) after implantation. After 28 days implanted bacteria were no longer detected in any of the 20 test subjects when chlorhexidine was not used prior to implantation, but persisted in 11 subjects when chlorhexidine was used.     

Suppression of Streptococcus sobrinus 6715 (g) in plaques by Streptococcus mutans 32K (c)

The dental plaque of 96 healthy donors was screened for the production of such antibacterial substances as mutalipocin and bacteriocin and 192 strains of mutans streptococci isolated: 28 produced mutalipocin and 22 produced bacteriocin. Mutalipocin produced by these 28 S. mutans strains possessed similar biochemical and biological characteristics of well-characterized mutalipocin-producing strain S. mutans 32K (serotype c). When equal amounts of S. mutans 32K and S. sobrinus 6715 (g) were cultured together, cells of S. sobrinus 6715 were completely killed in 18 h. In addition, S. mutans 32K inhibited in vitro plaque formation by S. sobrinus 6715, and S. mutans 32K also eliminated in vitro plaque preformed by S. sobrinus 6715. In rat experiments, S. mutans 32K could preemptively colonize in plaque preformed by S. sobrinus 6715. On the other hand, S. sobrinus 6715 could not colonize in plaque preformed by S. mutans 32K. The results indicate that S. mutans serotype c which produces antibacterial substances is able to invade denatl plaque and replace the other mutans streptococci. This investigation offers one of the possible explanation why S. mutans serotype c is a predominant species among mutans streptococci in human plaque.     

Suppression of Streptococcus sobrinus 6715 (g) in plaques by Streptococcus mutans 32K (c)

The dental plaque of 96 healthy donors was screened for the production of such antibacterial substances as mutalipocin and bacteriocin and 192 strains of mutans streptococci isolated: 28 produced mutalipocin and 22 produced bacteriocin. Mutalipocin produced by these 28 S. mutans strains possessed similar biochemical and biological characteristics of well-characterized mutalipocin-producing strain S. mutans 32K (serotype c). When equal amounts of S. mutans 32K and S. sobrinus 6715 (g) were cultured together, cells of S. sobrinus 6715 were completely killed in 18 h. In addition, S. mutans 32K inhibited in vitro plaque formation by S. sobrinus 6715, and S. mutans 32K also eliminated in vitro plaque preformed by S. sobrinus 6715. In rat experiments, S. mutans 32K could pre-emptively colonize in plaque preformed by S. sobrinus 6715. On the other hand, S. sobrinus 6715 could not colonize in plaque preformed by S. mutans 32K. The results indicate that S. mutans serotype c which produces antibacterial substances is able to invade dental plaque and replace the other mutans streptococci. This investigation offers one of the possible explanation why S. mutans serotype c is a predominant species among mutans streptococci in human plaque.     

Oral implantation of Streptococcus mutans in man with and without prior chlorhexidine mouthrinses

Oral implantation of streptomycin resistant S. mutans was enhanced when chlorhexidine mouthrinses were applied before implantation. The difference in recovery of implanted bacteria between implantations with and without prior chlorhexidine mouthrinses was significant 9 days (P less than 0.05), 15 days (P less than 0.05) and 28 days (P less than 0.01) after implantation. After 28 days implanted bacteria were no longer detected in any of the 20 test subjects when chlorhexidine was not used prior to implantation, but persisted in 11 subjects when chlorhexidine was used.     

Effect of nicotine on growth and metabolism of Streptococcus mutans

Streptococcus mutans is a key contributor to dental caries. Smokers have a higher number of caries-affected teeth than do nonsmokers, but the association among tobacco, nicotine, caries, and S. mutans growth has not been investigated in detail. Seven S. mutans strains--UA159, UA130, 10449, A32-2, NG8, LM7, and OMZ175--were used in the present study. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), planktonic cell growth, biofilm formation, metabolism, and structure (determined using scanning electron microscopy) of the seven strains treated with different concentrations of nicotine (0-32 mg ml(-1)) were investigated. The MIC, MBC, and MBIC were 16 mg ml(-1) (0.1 M), 32 mg ml(-1) (0.2 M), and 16 mg ml(-1) (0.1 M), respectively, for most of the S. mutans strains. Growth of planktonic S. mutans cells was significantly repressed by 2.0-8.0 mg ml(-1) of nicotine. Biofilm formation and metabolic activity of S. mutans was increased in a nicotine-dependent manner up to 16.0 mg ml(-1) of nicotine. Scanning electron microscopy revealed that S. mutans treated with a high concentration of nicotine a had thicker biofilm and more spherical bacterial cells. In summary, nicotine enhances S. mutans biofilm formation and biofilm metabolic activity. These results suggest that smoking can increase the development of caries by fostering increased formation of S. mutans biofilm on tooth surfaces.