Effect of Lactobacillus rhamnosus strain GG (ATCC 53103) on the growth of Streptococcus sobrinus in vitro

Lacticaseibacillus rhamnosus inhibits the development of dental caries in rat caries model and in vitro

OBJECTIVES

Dental caries result from a microbial imbalance in the oral cavity. Probiotics ecologically modulate the oral microflora to prevent caries. This study evaluated the anti-cariogenic effects of two Lacticaseibacillus rhamnosus strains in vitro and in vivo to provide a more theoretical basis for its clinical applications in caries prevention.

METHODS

In the study, cariogenic biofilms were grown with L. rhamnosus (LGG) or L. rhamnosus ATCC 7469 and analyzed. Quantitative real-time PCR (qPCR), Scanning Electron Microscope (SEM), and Confocal laser scanning microscope (CLSM) were used to detect the changes in the composition and architectures; cariogenic activity was measured by the lactic acid production and Transverse Microradiography (TMR). The effects of LGG on the 12 Sprague-Dawley rat caries model were assessed using Keyes scores and micro-CT analysis. Oral microbiome changes were evaluated through 16S rRNA gene high-throughput sequencing.

RESULTS

L. rhamnosus can reduce cariogenic bacteria in biofilm by 14.7 % to 48.9 %, with LGG exhibiting more potent inhibitory effects. Both strains of L. rhamnosus can adhere to the surface of biofilms, reduce the extracellular polysaccharides (EPS) matrix, and loosen the biofilm structure. L. rhamnosus inhibited cariogenic activity by reducing the lactic acid production in biofilms. The bovine enamel blocks presented lower mineral loss values and lesion depth values in the group Core+L.rh and Core+LGG. LGG-ingested rats had significantly lower levels of moderate dentin lesions and higher mineral density than the control group. The 16 s rRNA gene sequencing revealed that LGG regulated the beta diversity of the oral microbial community in the rat dental caries model.

CONCLUSIONS

This study revealed the promising potential of L. rhamnosus, especially the LGG strain, in the ecological prevention of dental caries.

CLINICAL SIGNIFICANCE

Probiotics may provide a strategy for preventing caries by regulating the oral microecological balance. The study revealed the promising anti-caries potential of the LGG probiotic strain in vivo and in vitro. It is expected that LGG could be used as an oral probiotic for the clinical prevention and treatment of caries.

A comprehensive review of the application of probiotics and postbiotics in oral health

Oral diseases are among the most common diseases around the world that people usually suffer from during their lifetime. Tooth decay is a multifactorial disease, and the composition of oral microbiota is a critical factor in its development. Also, Streptococcus mutans is considered the most important caries-causing species. It is expected that probiotics, as they adjust the intestinal microbiota and reduce the number of pathogenic bacteria in the human intestine, can exert their health-giving effects, especially the anti-pathogenic effect, in the oral cavity, which is part of the human gastrointestinal tract. Therefore, numerous in vitro and in vivo studies have been conducted on the role of probiotics in the prevention of tooth decay. In this review, while investigating the effect of different strains of probiotics Lactobacillus and Bifidobacteria on oral diseases, including dental caries, candida yeast infections, periodontal diseases, and halitosis, we have also discussed postbiotics as novel non-living biological compounds derived from probiotics.

Efficacy of probiotics against dental caries in children: a systematic review and meta-analysis

Dental caries causes serious consequences and the financial burden of society especially in children with high morbidity rate. Here we carried out a meta-analysis to systematically evaluate the efficacy of probiotics against dental caries in children. Forty-three RCTs were eligible for this meta-analysis after searching the PubMed, Cochrane and Web of Science from the inception through October 2021. Pooled estimates demonstrated that treatment with probiotics significantly reduced noncavitated (dicdas2-6mft) (SMD = -0.18, 95% CI: -0.3 to -0.06, p = 0.002) and cavitated (dicdas5-6mft) carious lesions in children (SMD = -0.32, 95% CI: -0.5 to 0.14, p = 0.0004). Probiotics also reduced prevalence of noncavitated (dicdas2-6mft) carious lesions (RR = 0.8, 95% CI: 0.67 to-0.97, p = 0.02). Salivary Streptococcus mutans was declined after intervention (SMD = -1.17, 95% CI: -1.85 to -0.5, p = 0.0007), while Lactobacillus counts were upregulated (SMD = 1.19, 95% CI: 0.46-1.92, p = 0.001). However, no significant effects in total bacteria counts and salivary pH were observed. Our findings suggest that probiotics especially Lactobacillus could be a promising therapeutic strategy for clinical applications in children dental caries.

Probiotics: Dawn of a new era in dental caries management

Dental caries is considered to be the most common pathology of the oral cavity. The pathogenesis of dental carries is believed to be because of imbalance in the microbiological niche creating an ecological pressure. Probiotics are living microorganisms which when dispensed in appropriate amounts can benefit the health of the host. They have posed as a promising replacement to antibiotics that can aid in solving dental issues like dental caries. There are numerous Randomized control trials to validate this fact. There are also various modes through which a probiotic can be delivered against dental caries. Numerous new avenues like effector strains and synbiotics are also explored nowadays. The present review is about the significance of probiotics in the management of dental caries.

Salivary microbial community alterations due to probiotic yogurt in preschool children with healthy deciduous teeth

Probiotics are considered valuable to human health since they improve intestinal microbial balance. Probiotics are orally taken and affect the oral microbiota, which is one of the most important parts of the human microbial community. However, there is little information on the effects of probiotics on the oral microbiota. Caries-free preschool children (N = 6) with complete deciduous dentition were enrolled and given 100 g probiotic yogurt daily for 1 year. Salivary samples were collected every 6 months and then sequenced by Illumina MiSeq system based on 16S rDNA V3-V4 hypervariable regions. The data were analyzed to obtain the changes in microbiota profiles before and after the probiotic yogurt consumption. The α diversity analysis showed that salivary microbial diversity and richness were similar between the groups. The β diversity analysis showed that salivary microbial community structure changed with the consumption of probiotic yogurt. The variation of the microbial community composition was mainly due to 9 genera; for 7 genera (Campylobacter, Haemophilus, Lautropia, Bacillus, Catonella, Lactococcus, and Solibacillus) increased, while 2 genera (Gemella, and Streptococcus) decreased. The variation of salivary microbiota structure and composition with the consumption of probiotic yogurt was revealed. This expands overall insights on the effects of probiotic products on oral microecology. It further provides a basis for predicting possible relations between probiotic interventions and oral health in preschool children.

Effect of Lactobacillus rhamnosus on Physicochemical Properties of Fermented Plant-Based Raw Materials

Texture and flavor are currently the main challenges in the development of plant-based dairy alternatives. To overcome them, the potential of microorganisms for fermentation of plant-based raw materials is generating great interest in the food industry. This study examines the effect of Lactobacillus rhamnosus, LGG® (LGG® is a trademark of Chr. Hansen A/S) on the physicochemical properties of fermented soy, oat, and coconut. LGG® was combined with different lactic acid bacteria (LAB) strains and Bifidobacterium, BB-12® (BB-12® is a trademark of Chr. Hansen A/S). Acidification, titratable acidity, and growth of LGG® and BB-12® were evaluated. Oscillation and flow tests were performed to analyze the rheological properties of fermented samples. Acids, carbohydrates, and volatile organic compounds in fermented samples were identified, and a sensory evaluation with a trained panel was conducted. LGG® reduced fermentation time in all three bases. LGG® and BB-12® grew in all fermented raw materials above 107 CFU/g. LGG® had no significant effect on rheological behavior of the samples. Acetoin levels increased and acetaldehyde content decreased in the presence of LGG® in all three bases. Diacetyl levels increased in fermented oat and coconut samples when LGG® was combined with YOFLEX® YF-L01 and NU-TRISH® BY-01 (YOFLEX® and NU-TRISH® are trademarks of Chr. Hansen A/S). In all fermented oat samples, LGG® significantly enhanced fermented flavor notes, such as sourness, lemon, and fruity taste, which in turn led to reduced perception of the attributes related to the base. In fermented coconut samples, gel firmness perception was significantly improved in the presence of LGG®. These findings suggest supplementation of LAB cultures with LGG® to improve fermentation time and sensory perception of fermented plant-based products.

Synbiotics in caries prevention: A scoping review

The scoping review aimed to examine the evidence on the role of synbiotics in caries prevention. PubMed, SCOPUS, and Web of Science databases search were performed. Any in vitro study, clinical trial, systematic review with/without meta-analysis, umbrella review/meta-evaluation, narrative review addressing the role of synbiotics in caries prevention were included in the scoping review. Data were extracted from the included studies using pre-approved registered protocol. Twenty-eight records were identified, of which 5 in vitro studies, 1 quasi-experimental clinical trial and 1 narrative review were included in the present review. No controlled clinical trials or systematic reviews on the role of synbiotics in caries prevention could be identified. Except 1, all in vitro studies examined the combined effect of saccharides and lactobacilli spp. as potential synbiotics on the growth of Streptococcus mutans. However, the proposed synbiotics in 4 in vitro studies either did not qualify or remained ambiguous of its eligibility as a potential synbiotic for caries prevention. One recent in vitro study explored the possibility of L-arginine and Lactobacillus rhamnosus GG synbiotic for caries prevention. The quasi-experimental clinical study without a control arm did not explicitly mention the intervention composition and thus, its synbiotic potential remains unclear. A narrative review highlighted the potential of combining arginine (prebiotic) with arginolytic bacteria (probiotic) as a synbiotic, which appears promising for caries prevention. The eligibility of the proposed synbiotics as a true synbiotic needs to be carefully addressed. Due to a lack of controlled clinical studies on synbiotics for caries prevention, evidence on their caries-preventive potential is weak. Future studies are needed to examine the combination of amino acids (esp. arginine) with probiotics as a potential synbiotic against cariogenic pathogens.

Effect of a novel synbiotic on Streptococcus mutans

We examined the effect of L-arginine - (i) on the growth of L. rhamnosus GG (LrG) and (ii) combined LrG synbiotic on the growth of cariogenic S. mutans. Viability of LrG was assessed using MTT/XTT assays, confocal imaging with ADS activity measurement. The effect of L-arginine (0.5%/1%/2%) (2×/24 h) with LrG on S. mutans was evaluated by measuring the colony forming units, biofilm biomass, real-time qPCR and confocal imaging. The pH of the spent media was measured immediately and 24 h post-treatment with assessment of lactic acid. The LrG viability was highest with 2% L-arginine (p < 0.001). Confocal imaging showed that 2% L-arginine increased biofilm thickness of LrG. The 2% L-arginine and LrG synbiotic significantly inhibited the growth of S. mutans (p < 0.001) reducing the viable counts (p = 0.002) and biofilm biomass (p < 0.001). The pH of spent media was the highest when treated with 2% L-arginine and LrG synbiotic (p < 0.001) with no difference between post-treatment and 24 h post-treatment (p > 0.05). Conversely, the 2% L-arginine and LrG synbiotic showed the lowest lactic acid production (p < 0.001). This study demonstrated that L-arginine enhanced the growth of LrG. The 2% L-arginine and LrG synbiotic synergistically inhibits the growth of S. mutans with significant potential to develop as an anti-caries regimen.

Investigating the antibacterial effects of some Lactobacillus, Bifidobacterium and acetobacter strains killed by different methods on Streptococcus mutans and Escherichia coli

Although there are many health advantages assigned to different live bacteria such as probiotics, some health threatening effects have also been reported. For example, live bacteria can transfer antibiotic resistance genes to other commensal and opportunistic bacteria of gastrointestinal tract. Recently, it was shown that using killed bacteria have some advantages over live ones. In this research, heat, paraformaldehyde and ozone killing methods were used to kill the bacteria. Acetobacter cerevisiae, Lactobacillus acidophilus, Bifidobacterium lactis and traditional vinegar and fermented dairy product (Kumeh) derived bacteria were killed and their antibacterial activity against Streptococcus mutans and Escherichia coli was investigated. To identify the bacteria isolated from the traditional products, 16S rDNA gene was partially sequenced. The gene analysis showed vinegar and Kumeh derived bacteria were Acetobacter pasteurianus and Lactobacillus crustorum (LcK) strains respectively. The S. mutans growth inhibition was detected in the all concentrations of all killed samples. However, generally, E. coli showed more resistant to the killed bacteria than S. mutans and the antibacterial effect of heat-killed bacteria against E. coli was not observed in the all concentrations for some killed bacteria. Among the pathogenic bacteria, S. mutans was the most sensitive one to the killed bacteria with 70% of reduction in its viability. In conclusion, this research showed that different killed bacteria had different effects on other bacteria and the killing method showed an impact on these effects. Overall, paraformaldehyde-killed L.crustorum (LcK) showed the best antibacterial activity against S. mutans; about 70% decrease in bacterial viability.

Impact of probiotics on development and behaviour in Drosophila melanogaster - a potential in vivo model to assess probiotics

In vitro models are frequently used in probiotic research. However, such models often fail to predict in vivo functionality and efficacy. This fact complicates the screening process for selecting the most suitable strains, prior to accomplish expensive animal studies and clinical intervention trials. Therefore, additional sensitive, discriminating and cost-effective models are needed to conduct preliminary assays before undertaking human intervention studies definitely proving efficacy. With this purpose in mind, we explored the potential of axenic Drosophila melanogaster populations as well as of these axenic flies treated with probiotic microbial strains as a model to test the effects of probiotics on a subset of developmental and behavioural traits. An axenic D. melanogaster progeny from the wild-type Canton S strain was obtained and its eggs were further developed until pupae eclosion occurred in growth medium containing either of two probiotic strains: Bifidobacterium animalis subsp. lactis Bb12 or Lactobacillus rhamnosus GG. Whereas B. animalis Bb12 colonised the flies, the capacity of L. rhamnosus LGG to colonise was considerably lower in our experimental conditions. Regarding the influence of microbial load on the flies' development, the axenic condition caused a decrease in egg survival, and lowered adults' average weight with respect to wild-type flies. Both probiotics were able to counteract these effects. An earlier emergence of adults was observed from eggs treated with L. rhamnosus GG in comparison to the other fly populations. The axenic condition did not influence negative geotaxis behaviour in Drosophila; however, flies mono-associated with B. animalis Bb12 moved faster than wild-type. Our results suggest that the use of axenic/probiotic-treated D. melanogaster populations may be an affordable model for preliminary testing of the effects of probiotics on developmental or behavioural aspects.

Inhibitory effects of tea catechin epigallocatechin-3-gallate against biofilms formed from Streptococcus mutans and a probiotic lactobacillus strain

OBJECTIVE

Effects of tea catechin epigallocatechin-3-gallate (EGCG) against biofilm formation by Streptococcus mutans and probiotic Lactobacillus casei in Yakult^® (LcY) were examined.

DESIGN

Biofilms were formed by S. mutans alone (Sm) and co-culture of S. mutans and LcY (Sm + LcY) in the absence or presence of EGCG. The biomass of biofilms, which were sonicated or not, was measured by the crystal violet assay. Biofilm morphology was observed by scanning electron microscopy. Bacterial viability and extracellular polysaccharides were determined by SYTO9/propidium iodide and dextran-conjugated fluorescein staining, respectively, and confocal microscopy. Gene expression of glucosyltransferase was determined by quantitative polymerase chain reaction.

RESULTS

While 250 μg/ml EGCG significantly decreased the biomass and acid production of Sm biofilms, 500 μg/ml EGCG was required to inhibit Sm + LcY biofilm formation and acid production. EGCG decreased the amount of live bacteria present in both Sm and Sm + LcY biofilms. The level of dead bacteria in Sm + LcY biofilms was higher than in Sm biofilms when formed in the presence of 250 μg/ml EGCG. EGCG decreased levels of extracellular polysaccharides in Sm and Sm + LcY biofilms. The extent of biofilm removal by sonication was not different between Sm and Sm+LcY biofilms formed in the absence or presence of 62.5 or 125 μg/ml EGCG. The level of Sm gtfB and gtfD expression in Sm + LcY biofilms was higher than those in the Sm biofilms when formed in the presence of EGCG at 250 μg/ml.

CONCLUSION

The results indicated that LcY might interfere the inhibitory effects of EGCG against biofilm formation by S. mutans.

Lactobacillus rhamnosus GG in Experimental Oral Biofilms Exposed to Different Carbohydrate Sources

Probiotic administration may favour caries prevention, as recent research has shown. This in vitro study aimed to investigate the growth of Lactobacillus rhamnosus GG (LGG) in experimental biofilms exposed to various carbohydrates, and also to assess its cariogenic potential. Multispecies experimental oral biofilms with or without LGG were grown with a sole-carbohydrate source (fructose/glucose/lactose/sorbitol/sucrose). The viable cells of LGG and structure of the biofilms were examined after 64.5 h of incubation, and pH values of spent media were measured at 16.5, 40.5, and 64.5 h. Fermentation profiles of LGG in biofilm media were assessed with study carbohydrate as the sole energy source. Our results showed that LGG reached higher viable cell numbers with glucose and sucrose in 64.5-h multispecies experimental oral biofilms compared to other carbohydrates. When LGG was incorporated in biofilms, no distinct pH changes at any time points were observed under any of the carbohydrates used; the pH values of spent media at each time point were lower when lactose was used, compared to other carbohydrates. The fermentation profiles of LGG in biofilm media were similar to its growth in MRS (no obvious growth with lactose or sucrose). In conclusion, LGG in our in vitro multispecies experimental oral biofilms was capable of surviving and growing well in each carbohydrate source. LGG might not have harmful effects on dental hard tissues. Another finding from our study was that the lowest pH values were observed in the presence of lactose, and the thickest biofilms were in sucrose.

Inhibition of Streptococcus mutans Growth and Biofilm Formation by Probiotics in vitro

To exert anticaries effects, probiotics are described to inhibit growth and biofilm formation of cariogenic bacteria such as Streptococcus mutans (SM). We screened 8 probiotics and assessed how SM growth or biofilm formation inhibition affects cariogenicity of probiotic-SM mixed-species biofilms in vitro. Growth inhibition was assessed by cocultivating probiotics and 2 SM strains (ATCC 20532/25175) on agar. Probiotics were either precultured before SM cultivation (exclusion), or SM precultured prior to probiotic cultivation (displacement). Inhibition of SM culture growth was assessed visually. Inhibition of SM biofilm formation on bovine enamel was assessed using a continuous-flow short-term biofilm model, again in exclusion or displacement mode. The cariogenicity of mixed-species biofilms of SM with the most promising growth and biofilm formation inhibiting probiotic strains was assessed using an artificial mouth model, and enamel mineral loss (ΔZ) was measured microradiographically. We found limited differences in SM growth inhibition in exclusion versus displacement mode, and in inhibition of SM 20532 versus 25175. Results were therefore pooled. Lactobacillus acidophilus LA-5 inhibited significantly more SM culture growth than most other probiotics. L. casei LC-11 inhibited SM biofilm formation similarly to other alternatives but showed the highest retention of probiotics in the biofilms (p < 0.05). Mineral loss from SM monospecies biofilms (ΔZ = 9,772, 25th/75th percentiles: 6,277/13,558 vol% × µm) was significantly lower than from mixed-species SM × LA-5 biofilms (ΔZ = 24,578, 25th/75th percentiles: 19,081/28,768 vol% × µm; p < 0.01) but significantly higher than from SM × LC-11 biofilms (ΔZ = 4,835, 25th/75th percentiles: 263/7,865 vol% × µm; p < 0.05). Probiotics inhibiting SM culture growth do not necessarily reduce the cariogenicity of SM-probiotic biofilms. Nevertheless, SM biofilm formation inhibition may be relevant in the reduction of cariogenicity.

Mulberry anthocyanin biotransformation by intestinal probiotics

This study was designed to evaluate mulberry anthocyanins bioconversion traits for intestinal probiotics. Five intestinal beneficial bacteria were incubated with mulberry anthocyanins under anaerobic conditions at 37°C, and bacterial β-glucosidase activity and anthocyanin level were determined. Results demonstrated that all strains could convert mulberry anthocyanins to some extent. With high β-glucosidase production capacity, Streptococcus thermophiles GIM 1.321 and Lactobacillus plantarum GIM 1.35 degraded mulberry anthocyanins by 46.17% and 43.62%, respectively. Mulberry anthocyanins were mainly biotransformed to chlorogenic acid, crypto-chlorogenic acid, caffeic acid, and ferulic acid during the anaerobic process. Non-enzymatic deglycosylation of anthocyanins also occurred and approximately 19.42% of the anthocyanins were degraded within 48h by this method.

Effect of the Probiotic Lactobacillus rhamnosus LB21 on the Cariogenicity of Streptococcus mutans UA159 in a Dual-Species Biofilm Model

Despite promising results using probiotics, evidence of the preventive effect on enamel demineralization is insufficient and the cariogenic potential of probiotics is still controversial. Probiotics could affect biofilm formation and interfere with adherence, growth or coaggregation with Streptococcus mutans in biofilms. However, most of the studies have been conducted using planktonic bacteria. Hence, the aim of the study was to assess the effect of probiotic bacteria on the cariogenicity of S. mutans using an in vitro biofilm caries model on enamel. Single-species biofilms (S. mutans UA159, SM or Lactobacillus rhamnosus LB21, LB) or dual-species biofilms simultaneously inoculated (SM + LB) or LB inoculated 8 h after SM (SM x2192; LB) were grown for 96 h. Biofilms were formed on bovine enamel saliva-coated slabs of known surface hardness (SH) and immersed in culture media. Biofilms were exposed 8 times per day to 10% sucrose. Medium pH was monitored twice daily as a biofilm acidogenicity indicator. After 96 h, biofilms were collected to determine biomass and bacteria viability. Slab demineralization was calculated as percentage of SH loss (%SHL). Additionally, the model was tested with different concentrations of the initial inoculum (103, 106, 108 cells/ml) and different adhesion times (2 or 8 h). The dual-species biofilm revealed no LB effects on SM cariogenicity, without changes in acidogenicity or %SHL among groups (p > 0.05, n = 12). Lack of activity of LB on SM cariogenicity persisted even when 105 times higher concentration of the probiotic was tested. Coaggregation was not observed. In conclusion, findings suggest that LB does not reduce cariogenicity of SM in a validated experimental caries model.

The magic of magic bugs in oral cavity: Probiotics

The aim of this review is to present an update about the current status of probiotics in the field of dentistry. Oral infections are the most common forms of infections. It is necessary to understand the role of the ecology and microbiology of the oral cavity in better understanding of the pathogenesis of various oral diseases. The concept of bacteriotherapy has been an emerging field in dentistry. The use of health-beneficial micro-organisms to heal diseases or support immune function was first introduced in the beginning of the 20^th century. Probiotics are dietary supplements containing potentially beneficial bacteria or yeasts and it has been found to be beneficial to the host health. In medicine, probiotics are used mainly in support therapy for gastro-intestinal diseases. In recent years, probiotics have been used as a treatment to promote oral health. This approach has shown promising results in the oral cavity with respect to control of chronic diseases such as dental caries, periodontitis, and recurring problems such as halitosis and candidal infections. Despite the immense potential of probiotics, data are still deficient on the probiotic action in the oral cavity, which further mandates randomized trials before any concrete clinical recommendations can be arrived.

Enhancement of salivary human neutrophil peptide 1-3 levels by probiotic supplementation

Background

Probiotic supplementation can reduce mutans streptococci (MS) numbers. One of its proposed mechanisms is immunomodulation. Salivary human neutrophil peptide 1–3 (HNP1-3) levels have previously been demonstrated to be higher in caries-free than in caries-susceptible children, suggesting their preventive role against caries. We aimed to compare salivary HNP1-3 levels between an intervention group with probiotics and a control group.

Methods

A randomized double-blinded clinical trial was conducted. Sixty schoolchildren were equally allocated to either an intervention or control group. The use of a probiotic strain, Lactobacillus paracasei SD1, has shown to reduce MS numbers in volunteers. In unstimulated whole saliva, HNP1-3 levels were assayed by ELISA, and MS and lactobacilli counts were assayed by colony counting at baseline (T0) and at 3 (T3), 6 (T6), and 12 months (T12). The International Caries Detection and Assessment system was used to assess caries status.

Results

In the intervention group, salivary HNP1-3 levels were significantly greater than those in the control group at T3 and T6 (p < 0.001), whereas MS counts were significantly decreased (p < 0.01). In the intervention group, positive and negative correlations were found between HNP1-3 levels and lactobacilli counts and between MS and lactobacilli counts, respectively. However, there was no significant correlation between enhanced HNP1-3 levels and decreased MS numbers. The caries increment for the pit and fissure surface, but not for the smooth surfaces, was significantly decreased in the intervention group compared with the control group (p = 0.01).

Conclusions

Probiotics can temporarily enhance salivary HNP1-3 levels; however, their action to reduce new pit and fissure caries probably involves microbial interactions.

Trial registration

TCTR20130904001 (registration date: September 04, 2013).

Electronic supplementary material

The online version of this article (doi:10.1186/s12903-015-0003-0) contains supplementary material, which is available to authorized users.

A comparative study of the effect of probiotics on cariogenic biofilm model for preventing dental caries

Dental caries is induced by oral biofilm containing Streptococcus mutans. Probiotic bacteria were mainly studied for effect on the gastrointestinal tract and have been known to promote human health. However, the information of probiotics for oral health has been lack yet. In this study, we investigated influence of various probiotics on oral bacteria or cariogenic biofilm and evaluated candidate probiotics for dental caries among them. The antimicrobial activity of the spent culture medium of probiotics for oral streptococci was performed. Probiotics were added during the biofilm formation with salivary bacteria including S. mutans. The oral biofilms were stained with a fluorescent dye and observed using the confocal laser scanning microscope. To count bacteria in the biofilm, the bacteria were plated on MSB and BHI agar plates after disrupting the biofilm and cultivated. Glucosyltransferases (gtfs) expression of S. mutans and integration of lactobacilli into the biofilm were evaluated by real-time RT-PCR. Among probiotics, Lactobacillus species strongly inhibited growth of oral streptococci. Moreover, Lactobacillus species strongly inhibited formation of cariogenic biofilm model. The expression of gtfs was significantly reduced by Lactobacillus rhamnosus. The integration of L. rhamnosus into the biofilm model did not exhibit. However, L. acidophilus and L casei integrated into the biofilm model. These results suggest that L. rhamnosus may inhibit oral biofilm formation by decreasing glucan production of S. mutans and antibacterial activity and did not integrate into oral biofilm, which can be a candidate for caries prevention strategy.

Lactobacillus acidophilus modulates the virulence of Clostridium difficile

Clostridium difficile is a spore-forming, toxin-producing, anaerobic bacterium that colonizes the human gastrointestinal tract. This pathogen causes antibiotic-associated diarrhea and colitis in animals and humans. Antibiotic-associated diseases may be treated with probiotics, and interest is increasing in such uses of probiotics. This study investigated the effect of Lactobacillus strains on the quorum-sensing signals and toxin production of C. difficile. In addition, an in vivo experiment was designed to assess whether Lactobacillus acidophilus GP1B is able to control C. difficile-associated disease. Autoinducer-2 activity was measured for C. difficile using the Vibrio harveyi coupled bioluminescent assay. Cell extract (10μg/mL) of L. acidophilus GP1B exhibited the highest inhibitory activity among 5 to 40μg/mL cell-extract concentrations. Real-time PCR data indicated decreased transcriptional levels in luxS, tcdA, tcdB, and txeR genes in the presence of 10μg/mL of cell extract of L. acidophilus GP1B. Survival rates at 5d for mice given the pathogen alone with L. acidophilus GP1B cell extract or L. acidophilus GP1B were 10, 70, and 80%, respectively. In addition, the lactic acid-produced L. acidophilus GP1B exhibits an inhibitory effect against the growth of C. difficile. Both the L. acidophilus GP1B and GP1B cell extract have significant antipathogenic effects on C. difficile.

Effect of Probiotics Containing Lactobacillus paracasei SD1 on Salivary Mutans Streptococci and Lactobacilli in Orthodontic Cleft Patients: A Double-Blinded, Randomized, Placebo-Controlled Study

Objective

(1) To investigate the effect of probiotic bacterium Lactobacillus paracasei SDA on the level of salivary mutans streptococci and lactobacilli, and (2) the oral persistence of L. paracasei SD1 in orthodontically treated nonsyndromic cleft lip and palate patients.

Design

Double-blinded, randomized, placebo-controlled study.

Participants

A total of 30 orthodontically treated nonsyndromic cleft lip and palate patients (aged 19.22 ± 3.66 years): 15 in the intervention group (A) and 15 in the control group (B).

Interventions

Milk with or without L. paracasei SD1. Average daily consumption of milk in both groups was 50 mL for 4 weeks.

Main Outcome Measures

Salivary mutans streptococci and lactobacilli were enumerated using a quantitative differential culture at baseline and once a week after the end of the administration period for 4 weeks. The persistence of L. paracasei SD1 was traced using arbitrarily primed polymerase chain reaction of the DNA fingerprinting.

Results

A statistically significant reduction in mutans streptococci counts occurred in group A, in contrast to group B ( P < .001). A significant increase of lactobacilli numbers was found in group A ( P < .001), and L. paracasei SD1 could be detected up to 4 weeks following cessation of dosing.

Conclusions

The probiotic milk powder containing L. paracasei SD1 could reduce mutans streptococci counts and was apparently able to colonize the oral cavity of the orthodontically treated cleft lip and palate patients. However, the potentially beneficial influence of the probiotic milk on the complex oral microflora justifies further studies with a larger group of volunteers.

Cell-free preparations of Lactobacillus acidophilus strain La-5 and Bifidobacterium longum strain NCC2705 affect virulence gene expression in Campylobacter jejuni

Campylobacter spp. are among the most commonly reported bacterial causes of acute diarrheal disease in humans worldwide. Potential virulence factors include motility, chemotaxis, colonization ability, adhesion to intestinal cells, invasion and epithelial translocation, intracellular survival, and formation of toxins. Probiotic Lactobacillus and Bifidobacterium strains are known to have an inhibitory effect against the growth of various foodborne pathogens. The objective of this study was to investigate the effect of Lactobacillus acidophilus strain La-5 and Bifidobacterium longum strain NCC2705 cell-free spent media (CFSM) on the expression of virulence genes (cadF, cdtB, flaA, and ciaB) of Campylobacter jejuni strain 81-176 and a luxS mutant, using real-time PCR. Our results demonstrated that the CFSM of both probiotic strains were able to down-regulate the expression of ciaB (ratio of -2.80 and -5.51, respectively) and flaA (ratio of -7.00 and -5.13, respectively) in the wild-type Campylobacter strain. In the luxS mutant, where the activated methyl cycle is disrupted, only the ciaB gene (ratio -7.21) was repressed in the presence of La-5 CFSM. A supplementation of homocysteine to restore the disrupted cycle was able to partially reestablish the probiotic effect of both strains. luxS and the activated methyl cycle might play an active role in the modulation of virulence of C. jejuni by probiotic extracts.

Bifidobacterium spp. influences the production of autoinducer-2 and biofilm formation by Escherichia coli O157:H7

The effect of Bifidobacterium spp. on the production of quorum-sensing (QS) signals and biofilm formation by enterohemorrhagic Escherichia coli (EHEC) O157:H7 was investigated. In an AI-2 bioassay, cell extracts of Bifidobacterium longum ATCC 15707 resulted in a 98-fold reduction in AI-2 activity in EHEC O157:H7 as well as in the Vibrio harveyi reporter strain, even though they did not inhibit the growth of EHEC O157:H7. In addition, they resulted in a 36% reduction in biofilm formation by the organism. Consistently, the virulence of EHEC O157:H7 was significantly attenuated by the presence of cell extracts of B. longum ATCC 15707 in the Caenorhabditis elegans nematode in vivo model. By a proteome analysis using two dimensional electrophoresis (2-DE), we determined that seven proteins including formation of iron-sulfur protein (NifU), thiol:disulfide interchange protein (DsbA), and flagellar P-ring protein (FlgI) were differentially regulated in the EHEC O157:H7 when supplemented with cell extracts of B. longum ATCC 15707. Taken together, these findings propose a novel function of a dairy adjunct in repressing the virulence of EHEC O157:H7.

Probiotics as oral health biotherapeutics

INTRODUCTION

Oral health is affected by its resident microorganisms. Three prominent oral disorders are dental caries, gingivitis and periodontitis, with the oral microbiota playing a key role in the initiation/progression of all three. Understanding the microbiota and the diseases they may cause is critical to the development of new therapeutics. This review is focused on probiotics for the prevention and/or treatment of oral diseases.

AREAS COVERED

This review describes the oral ecosystem and its correlation with oral health/disease. The pathogenesis and current prevention/treatment strategies of periodontal diseases (PD) and dental caries (DC) are depicted. An introduction of probiotics is followed by an analysis of their role in PD and DC, and their potential role(s) in oral health. Finally, a discussion ensues on the future research directions and limitations of probiotics for oral health.

EXPERT OPINION

An effective oral probiotic formulation should contribute to the prevention/treatment of microbial diseases of the oral cavity. Understanding the oral microbiota's role in oral disease is important for the development of a therapeutic to prevent/treat dental diseases. However, investigations into clinical efficacy, delivery/dose optimization, mechanism(s) of action and other related parameters are yet to be fully explored. Keeping this in mind, investigations into oral probiotic therapies are proving promising.

Can early exposure to probiotics in children prevent dental caries? A current perspective

BACKGROUND

Probiotics are supplements or foods that contain viable microorganisms which cause alterations of the microflora of the host. Probiotics have already been established in the treatment and prevention of various gastrointestinal system. Recently, role of probiotics has become an important issue for research in dentistry in the era of increased antibiotic resistance.

MATERIALS AND METHODS

The basis of the paper is the clinical studies and research done in relation to probiotics on oral health using PUBMED search database.

RESULTS AND CONCLUSIONS

Although many clinical studies have demonstrated positive outcome in preventing caries and periodontal diseases, the data is still scarce in recommending probiotics for the oral health. Moreover, since initial colonization of oral cavity of the newborn is very important for developing immunity and prevention of future diseases. Hence, measures should be directed towards its preventive use in infants and children. The formulations produced for oral cavity should also be within reach of common man especially in underdeveloped and developing countries. This review endeavors to compile the research of probiotics on oral cavity and throws a light on its evolving status in developing countries. It also evaluates its use in children for a long-term benefit.

The effect of a probiotic strain (Lactobacillus acidophilus) on the plaque formation of oral Streptococci

The objective of this study was to investigate the ability of biofilm formation among mutans and non mutans oral streptococci and to determine the effect of Lactobacillus acidophilus DSM 20079 as a probiotic strain on the adhesion of selected streptococcal strains on the surfaces. The sample comprised 40 isolates of oral streptococci from dental plaque and caries of volunteer persons. Streptococcus mutans ATCC35668 (no24) was as an standard strain. The probiotic strain was Lactobacillus acidophilus DSM 20079. The ability of biofilm formation was investigated with colorimetric method and the strongest isolates were selected. Then the effect of probiotic strain on the adhesion of streptococci isolates was determined in polystyrene microtiter plate simultaneously and 30 minutes before streptococci entrance to the system. The results showed that 42% of mutans streptococci were strongly adherent (SA) and in non mutans streptococci, only 23.5% of isolates were found strongly adherent. The strong biofilm forming bacterium isolated was Streptococcus mutans strain22. In the next step, in the presence of probiotic strain the streptococcal adhesion were reduced, and this reduction was non significantly stronger if the probiotic strain was inoculated to the system before the oral bacteria. The Lactobacillus acidophilus had more effect on adherence of mutans streptococci than non mutans streptococci with significant difference (p < 0.05). Adhesion reduction is likely due to bacterial interactions and colonization of adhesion sites with probiotic strain before the presence of streptococci. Adhesion reduction can be an effective way on decreasing cariogenic potential of oral streptococci.

Effects of Lactobacillus rhamnosus GG on saliva-derived microcosms

OBJECTIVE

The probiotic strain Lactobacillus rhamnosus GG (LGG) is shown to hamper the presence of mutans streptococci in saliva and may have positive effects on oral health. We investigated the effects of LGG on the cariogenic potential and microbial composition of saliva-derived microcosms.

DESIGN

Single and dual species biofilms of LGG and Streptococcus mutans, and saliva-derived microcosms with or without LGG were grown in an Active Attachment Biofilm model. The microcosms were grown on bovine dentin/enamel discs in the presence or absence of sucrose (suc+/suc-). The presence of LGG was determined by multiplex ligation-dependent probe amplification (MLPA) and real-time PCR. Mutans streptococci (MS) and total viable counts, pH of the spent medium, capacity of lactate formation and integrated mineral loss in dentin was assessed. MLPA was used for identification and relative quantification of 20 oral microorganisms in the microcosms. Principal Component Analysis was applied to MLPA data.

RESULTS

LGG inhibited the growth of S. mutans in dual species biofilms and did not affect the pH. LGG established in saliva-derived microcosms and reduced MS counts significantly, but did not affect pH or dentin demineralization. Simultaneous growth of the microcosms with LGG under heavy cariogenic conditions (suc+) introduced a compositional shift in the microbial community. The CFU, real-time PCR and MLPA data correlated significantly.

CONCLUSION

We conclude that LGG established into and inhibited the growth of MS in complex saliva-derived biofilms, but this had no significant effect on cariogenic potential of the microcosms. This suggests that other microorganisms besides MS were responsible for increased cariogenicity of sucrose-exposed biofilms.

Competition between yogurt probiotics and periodontal pathogens in vitro

OBJECTIVE

To investigate the competition between probiotics in bio-yogurt and periodontal pathogens in vitro.

MATERIAL AND METHODS

The antimicrobial activity of bio-yogurt was studied by agar diffusion assays, using eight species of putative periodontal pathogens and a 'protective bacteria' as indicator strains. Four probiotic bacterial species (Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, and Bifidobacterium) were isolated from yogurt and used to rate the competitive exclusion between probiotics and periodontal pathogens.

RESULTS

Fresh yogurt inhibited all the periodontal pathogens included in this work, showing inhibition zones ranging from 9.3 (standard deviation 0.6) mm to 17.3 (standard deviation 1.7) mm, whereas heat-treated yogurt showed lower antimicrobial activity. In addition, neither fresh yogurt nor heat-treated yogurt inhibited the 'protective bacteria', Streptococcus sanguinis. The competition between yogurt probiotics and periodontal pathogens depended on the sequence of inoculation. When probiotics were inoculated first, Bifidobacterium inhibited Porphyromonas gingivalis, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, Porphyromonas circumdentaria, and Prevotella nigrescens; L. acidophilus inhibited P. gingivalis, A. actinomycetemcomitans, P. circumdentaria, P. nigrescens, and Peptostreptococcus anaerobius; L. bulgaricus inhibited P. gingivalis, A. actinomycetemcomitans, and P. nigrescens; and S. thermophilus inhibited P. gingivalis, F. nucleatum, and P. nigrescens. However, their antimicrobial properties were reduced when both species (probiotics and periodontal pathogens) were inoculated simultaneously. When periodontal pathogens were inoculated first, Prevotella intermedia inhibited Bifidobacterium and S. thermophilus.

CONCLUSIONS

The results demonstrated that bio-yogurt and the probiotics that it contains are capable of inhibiting specific periodontal pathogens but have no effect on the periodontal protective bacteria.

Probiotic Lactobacillus paracasei effect on cariogenic bacterial flora

Lactobacillus paracasei has been demonstrated to inhibit the growth of many pathogenic microbes such as Streptococcus mutans, in vitro. However, its clinical application remains unclear. Here, we examined whether a novel probiotic L. paracasei GMNL-33 may reduce the caries-associated salivary microbial counts in healthy adults. Seventy-eight subjects (aged 20 to 26) had completed this double-blinded, randomized, placebo-controlled study. A probiotic/test (n = 42) and a control group (n = 36) took a L. paracasei GMNL-33 and a placebo oral tablet three times per day for 2 weeks, respectively. Bacterial counts of salivary S. mutans, lactobacilli, and salivary buffer capacity were measured with chair-side kits at the beginning (T1), the completion (T2) of medication, and 2 weeks after medication (T3). The results did not show differences in the counts of S. mutans and lactobacilli between probiotic and control groups at T1, T2, and T3. Nevertheless, within the probiotic group, an interesting probiotic effect was noticed. Between T1 and T2, no inhibitory effect against S. mutans was observed. However, a significant count reduction in the salivary S. mutans was detected between T2 and T3 (p = 0.016). Thus, a 2-week period of medication via oral administration route may be needed for L. paracasei GMNL-33 to be effective in the probiotic action.

Final pH affects the interference capacity of naturally occurring oral Lactobacillus strains against mutans streptococci

OBJECTIVES

To establish the effects of three factors: previous caries experience; colonization of Streptococcus mutans; and final pH on autologous lactobacilli-mediated inhibition against a panel of mutans streptococci in young subjects with different caries experiences.

DESIGN

The inhibition capacity was determined by the use of the agar overlay method and the final pH in culture medium was measured after 20 h. Using a logistic regression model, the risk of having an incomplete lactobacilli-mediated inhibition was calculated.

RESULTS

All three factors significantly influenced the interference outcome in the order; final pH of the Lactobacillus strains, oral colonization of autologous S. mutans and caries experience. A high risk occurred at a lower pH and at a wider pH range for individuals with previous caries experience and autologous colonization of S. mutans compared with caries-free subjects who were not colonized. At a final pH of 4.0, this risk was approximately eight times higher than that of the latter group. Two mutans Streptococcus strains in the test panel demonstrated high individual predictive values of inhibition mediated by oral lactobacilli.

CONCLUSIONS

Generation of a low pH either directly via organic acid production and/or production of bacteriocins or metabolites at a low pH may promote mutans Streptococcus growth inhibition, in vitro. Furthermore, a shift of pH range for the risk of incomplete inhibition of mutans streptococci suggests a less effective inhibition at a wider pH range for naturally occurring lactobacilli from individuals with earlier caries experience containing own S. mutans.

The effect of probiotics and organic acids on Shiga-toxin 2 gene expression in enterohemorrhagic Escherichia coli O157:H7

Probiotics are known to have an inhibitory effect against the growth of various foodborne pathogens, however, the specific role of probiotics in Shiga-toxin-producing Escherichia coli (STEC) virulence gene expression has not been well defined. Shiga toxins are members of a family of highly potent bacterial toxins and are the main virulence marker for STEC. Shiga toxins inhibit protein synthesis in eukaryotic cells and play a role in hemorrhagic colitis and hemolytic uremic syndrome. STEC possesses Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2), both of which have A and B subunits. Although STEC containing both Stx1 and Stx2 has been isolated from patients with hemorrhagic colitis, Stx2 is more frequently associated with human disease complications. Thus, the effect of Lactobacillus, Pediococcus, and Bifidobacterium strains on stx2A expression levels in STEC was investigated. Lactic acid bacteria and bifidobacteria were isolated from farm animals, dairy, and human sources and included L. rhamnosus GG, L. curvatus, L. plantarum, L. jensenii, L. acidophilus, L. casei, L. reuteri, P. acidilactici, P. cerevisiae, P. pentosaceus, B. thermophilum, B. boum, B. suis and B. animalis. E. coli O157:H7 (EDL 933) was coincubated with sub-lethal concentrations of each probiotic strain. Following RNA extraction and cDNA synthesis, relative stx2A mRNA levels were determined according to a comparative critical threshold (Ct) real-time PCR. Data were normalized to the endogenous control glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the level of stx2A expression between treated and untreated STEC was compared. Observed for all probiotic strains tested, stx2A was down-regulated, when compared to the control culture. Probiotic production of organic acids, as demonstrated by a decrease in pH, influenced stx2A gene expression.

Probiotics and oral health effects in children

BACKGROUND

Probiotics are living micro-organisms added to food which beneficially affect the host by improving its intestinal microbial balance.

OBJECTIVE

This paper aims to present a general background on probiotics and its health effects in children, and to examine the evidence for oral colonization and the possible impact on oral health in children and young adults.

METHODS

For delivery and general health effects, recent systematic reviews, meta-analyses, and other relevant papers were used. Concerning oral installation and oral effects, a broad search for publications in English was conducted through February 2007 in PubMed. Studies describing an installation or intervention trial in humans with a controlled design and an oral endpoint measure were considered. Fourteen papers with dental focus were identified, of which two were narrative reviews.

RESULTS

Only one study of dental interest was conducted in children. Four papers dealt with oral installation of probiotic bacteria, and although detectable levels were found in saliva shortly after intake, the studies failed to demonstrate a long-term installation. Seven papers evaluated the effect of lactobacilli- or bifidobacteria-derived probiotics on the salivary levels of caries-associated bacteria in placebo-controlled designs. All but one reported a hampering effect on mutans streptococci and/or yeast. The single study carried out in early childhood reported a significant caries reduction in 3- to 4-year-old children after 7 months of daily consumption of probiotic milk.

CONCLUSION

Bacteriotheraphy in the form of probiotic bacteria with an inhibitory effect on oral pathogens is a promising concept, especially in childhood, but this may not necessarily lead to improved oral health. Further placebo controlled trials that assess carefully selected and defined probiotic strains using standardized outcomes are needed before any clinical recommendations can be made.

Lactobacillus-mediated interference of mutans streptococci in caries-free vs. caries-active subjects

In order to assess whether naturally occurring oral lactobacilli have probiotic properties, lactobacilli were isolated from saliva and plaque from children and adolescents, with or without caries lesions. The interference capacities of these lactobacilli were investigated against a panel of 13 clinical isolates and reference strains of Streptococcus mutans and Streptococcus sobrinus, as well as against the subject's autologous mutans streptococci, using the agar-overlay technique. Lactobacillus-mediated inhibition differed significantly between the three subject groups (no caries, arrested caries, or active caries), demonstrating increased inhibition in subjects without present or previous caries experience compared to subjects with arrested caries or subjects presenting with frank lesions. Lactobacilli from subjects lacking S. mutans inhibited the growth of the test panel of mutans streptococci significantly better than lactobacilli from subjects who were colonized. Furthermore, subjects without caries experience harbored lactobacilli that more effectively repressed the growth of their autologous mutans streptococci. Twenty-three Lactobacillus spp. completely inhibited the growth of all mutans streptococci tested. Species with maximum interference capacity against mutans streptococci included Lactobacillus paracasei, Lactobacillus plantarum, and Lactobacillus rhamnosus. Naturally occurring oral lactobacilli significantly inhibited the growth of both test strains of mutans streptococci and the subject's autologous mutans streptococci in vitro, and this effect was more pronounced in caries-free subjects.

Oral adhesion and survival of probiotic and other lactobacilli and bifidobacteria in vitro

INTRODUCTION

Most probiotic products are consumed orally and hence it is feasible that the bacteria in these products may also attach to oral surfaces; however, the effects of these bacteria on the oral ecosystem are mostly unknown. Our aim was to evaluate the oral colonization potential of different probiotic, dairy, and fecal Lactobacillus and Bifidobacterium strains in vitro.

METHODS

The binding of 17 Lactobacillus and seven Bifidobacterium strains to hydroxyapatite and microtitre wells coated with human saliva was tested. Binding of selected strains to human buccal epithelial cells and co-adherence with Fusobacterium nucleatum were also investigated. In addition, the survival in sterilized human whole saliva was examined.

RESULTS

There was a large variation in binding to saliva-coated surfaces and buccal epithelial cells but all strains survived in saliva. The binding pattern of the probiotics did not differ from the binding of the fecal strains. F. nucleatum altered the binding of both the low-binding bifidobacteria and the high-binding lactobacilli.

CONCLUSION

The differences in binding in vitro may indicate that there are also differences in the persistence of the different probiotic strains in the oral cavity in vivo.

Probiotics: do they have a role in oral medicine and dentistry?

This review describes current knowledge on probiotic bacteriotherapy from the oral health perspective. Recent experimental studies and results from randomized controlled trials have shown that certain gut bacteria, in particular species of Lactobacillus and Bifidobacterium, may exert beneficial effects in the oral cavity by inhibiting cariogenic streptococci and Candida sp. Probiotics have been successfully used to control gastro-intestinal diseases. They also appear to alleviate symptoms of allergy and diseases with immunological pathology. The mechanisms of probiotic action appear to link with colonization resistance and immune modulation. Lactic acid bacteria can produce different antimicrobial components such as organic acids, hydrogen peroxide, carbon peroxide, diacetyl, low molecular weight antimicrobial substances, bacteriocins, and adhesion inhibitors, which also affect oral microflora. However, data is still sparse on the probiotic action in the oral cavity. More information is needed on the colonization of probiotics in the mouth and their possible effect on and within oral biofilms. There is every reason to believe that the putative probiotic mechanisms of action are the same in the mouth as they are in other parts of the gastrointestinal tract. Because of the increasing global problem with antimicrobial drug resistance, the concept of probiotic therapy is interesting and pertinent, and merits further research in the fields of oral medicine and dentistry.

Bacteriotherapy and probiotics’ role on oral health

Oral infections constitute some of the most common and costly forms of infections in humans. The concept of microbial ecological change as a mechanism for preventing dental disease is an important one while altered microbial ecology may lead to dental disease. New methods such as probiotic approaches (i.e. whole bacteria replacement therapy) to eliminate pathogenic members of the microbiota can be investigated. Bacteriotherapy is an alternative and promising way to combat infections by using harmless bacteria to displace pathogenic microorganisms. Probiotics are one of these new agents which are widely used for their therapeutic action. Limited research is available showing that some probiotic cultures may help dental improvement. Present paper focuses on possible oral benefits of probiotics.

Rapid determination of vitamin B2 secretion by bacteria growing on solid media

AIMS

Development of an agar-diffusion assay to measure vitamin B2 in biological samples and application of the method to determine the amount of vitamin B2 secreted by bacteria.

METHODS AND RESULTS

A riboflavin-auxotrophic mutant of Bacillus cereus was generated by mini-Tn10 insertion in the ribD gene. ribD mutant sensitivity to exogenous vitamin B2 was investigated by turbidimetric and agar-diffusion assays. In turbidimetric assays, the B. cereus mutant displayed a similar level of sensitivity to vitamin B2 to that of Lactobacillus casei ATCC 7469, the reference organism used for microbiological vitamin B2 quantification. However, only the ribD mutant could be used as an indicator organism in agar-diffusion assays. A total of eight probiotic strains, from five different probiotic formulations, were analysed by the ribD mutant-based assay on agar plates in order to determine their ability to secrete vitamin B2 during growth.

CONCLUSION

The agar diffusion method with the ribD mutant of B. cereus is highly reproducible, sensitive, rapid, inexpensive, and can be applied to measure the amount of vitamin B2 in different samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

The method developed in this study appears to be a good candidate for the screening of vitamin B2 secretion by bacteria growing on solid media.

Short-term consumption of probiotic-containing cheese and its effect on dental caries risk factors

Cheese is known to contain compounds that reduce the risk of dental caries. The long-term consumption of milk containing Lactobacillus rhamnosus GG, ATCC 53103 (LGG), has been shown to reduce caries risk in children. The aim of the present study was to examine whether short-term consumption of cheese containing LGG and Lactobacillus rhamnosus LC 705 would diminish caries-associated salivary microbial counts in young adults. Altogether, 74 18-35 year-old subjects completed this double-blinded, randomised, placebo-controlled study. During the 3 week intervention, the subjects ate 5 x 15 g cheese per day. Oral examinations were made before and after the study. Stimulated salivary secretion rates, buffer capacity and counts of salivary Streptococcus mutans, yeast and lactobacilli were evaluated before and after the intervention and after a 3 week post-treatment period. The results showed no statistically significant difference between the groups in Streptococcus mutans counts after the intervention, but during the post-treatment period there was a significantly greater reduction in these counts in the intervention group compared to the control group (P=0.05). However, Streptococcus mutans counts decreased in 20% (P=0.01) and yeast counts in 27% (P=0.005) of all the subjects, regardless of the intervention group. Results from logistic regression showed a trend indicating that probiotic intervention might reduce the risk of the highest level of Streptococcus mutans (OR=0.37, 95% CI 0.08-1.75, P=0.21) and salivary yeasts (OR=0.40, 0.09-1.71, P=0.22).

Stability and activity of specific antibodies against Streptococcus mutans and Streptococcus sobrinus in bovine milk fermented with Lactobacillus rhamnosus strain GG or treated at ultra-high temperature

Passive local immunization against dental caries is a promising approach to its prevention, as clinical evidence of active oral or nasal immunization is still limited and controversial. By means of systemic immunization of pregnant cows with a multivalent vaccine, high titres of IgG antibodies against human cariogenic bacteria, Streptococcus mutans and Streptococcus sobrinus, were produced in bovine colostrum. The purified immune product (IP) of this preparation has a number of anticariogenic properties, such as inhibition of streptococcal adherence to saliva-coated hydroxyapatite and inhibition of glucosyltransferase enzymes. This study investigated whether IP antibodies remained active and functional when added to ultra-high temperature (UHT)-treated milk or to Lactobacillus rhamnosus GG (LGG)-fermented milk stored for an extended time. LGG was chosen because of its widely known health benefits in humans and animals. A commercial UHT toddler's milk was supplemented with IP and stored for 2 months at 5, 21 and 30 degrees C. The antistreptococcal titres in UHT milk did not decline at any temperature during storage, and UHT-IP inhibited the adherence of S. mutans for up to 2 months. This was not the case with UHT toddler's milk without IgG antibodies. Milk was fermented with live LGG cells in the presence or absence of 5% IP. The antistreptococcal titres declined to about 30% of the original titres after storage. Fresh milk alone slightly enhanced streptococcal adhesion but fresh milk with IP inhibited the adherence of S. mutans by over 50%. LGG-positive fermented milk without antibodies also inhibited (P < 0.05) the adhesion by about 40%. In both LGG-fermented and UHT immune milk, the activity of antibodies against cariogenic streptococci was maintained during the expected shelf-life of these products. From the anticariogenic point of view it may be beneficial to add bovine-specific antibodies against mutans streptococci to probiotic LGG-containing milk products.

A randomized clinical trial of the effect of yoghurt on the human salivary microflora

Yoghurt is active against some human pathogens, so this experiment tested whether it is also active against the salivary microflora. A clinical trial was designed, with volunteers aged between 23 and 37 years. Initially, for 8 weeks, they consumed neither yoghurt nor casein-free soybean ice cream (phase 1). They were then split randomly into test (yoghurt) and control (ice cream) groups and required to consume 125 g of these foods twice daily for 8 weeks (phase 2) and then to avoid them for the following 2 weeks (phase 3). Many potential sources of microbial fluctuation were standardized. Salivary samples were then collected at regular intervals of 2 weeks. For each group and phase, the mean logarithms of the salivary counts for total viable flora, oral streptococci, mutans streptococci, lactobacilli and Candida were calculated. The prevalence of Streptococcus thermophilus and Lactobacillus bulgaricus was also assessed. Twenty test and 22 control participants completed the study. At phase 2, the mean for mutans streptococci was lower in the test than in the control group (3.6 vs. 4.0 log colony-forming units/ml; P=0.02). Moreover, the mean had decreased in all test participants with high phase 1 means for lactobacilli as compared to only 36.4% of those with low phase 1 means (P=0.01). L. bulgaricus was transiently detected in three test participants during phase 2. These results suggest that yoghurt does have some activity against the salivary microflora, but this does not seem to be due to the installation of yoghurt microorganisms in the mouth.

Fermentations of fructo-oligosaccharides and their components by Bifidobacterium infantis ATCC 15697 on batch culture in semi-synthetic medium

AIMS

To compare the physiological behaviour of Bifidobacterium infantis ATCC 15697 growing on synthetic oligofructose or its components.

METHODS AND RESULTS

The studies were carried out in regulated or non-regulated batch cultures on semi-synthetic media. Differences between the carbohydrate utilization patterns with glucose, fructose, sucrose and fructo-oligosaccharides (FOS) were determined. Glucose was the preferred substrate for growth and biomass production, whereas fructose was the best for lactate and acetate production. With sucrose, biomass production reached the level obtained with glucose, whereas with FOS, more metabolites were produced, as with fructose. In a mixture of FOS, the shorter saccharides were used first and fructose was released in the medium. Fructofuranosidase, an enzyme necessary to hydrolyse FOS, was inducible by fructose.

CONCLUSION

Glucose contained in FOS and sucrose might sustain growth and cell production, while fructose might enable the production of major metabolites.

SIGNIFICANCE AND IMPACT OF THE STUDY

A better understanding of the bifidogenic nature of oligofructose has been gained.