Investigation of probiotic bacteria as dental caries and periodontal disease biotherapeutics

Manipulating the diseased oral microbiome: the power of probiotics and prebiotics

Dental caries and periodontal disease are amongst the most prevalent global disorders. Their aetiology is rooted in microbial activity within the oral cavity, through the generation of detrimental metabolites and the instigation of potentially adverse host immune responses. Due to the increasing threat of antimicrobial resistance, alternative approaches to readdress the balance are necessary. Advances in sequencing technologies have established relationships between disease and oral dysbiosis, and commercial enterprises seek to identify probiotic and prebiotic formulations to tackle preventable oral disorders through colonisation with, or promotion of, beneficial microbes. It is the metabolic characteristics and immunomodulatory capabilities of resident species which underlie health status. Research emphasis on the metabolic environment of the oral cavity has elucidated relationships between commensal and pathogenic organisms, for example, the sequential metabolism of fermentable carbohydrates deemed central to acid production in cariogenicity. Therefore, a focus on the preservation of an ecological homeostasis in the oral environment may be the most appropriate approach to health conservation. In this review we discuss an ecological approach to the maintenance of a healthy oral environment and debate the potential use of probiotic and prebiotic supplementation, specifically targeted at sustaining oral niches to preserve the delicately balanced microbiome.

Mechanism of Action of Streptococcus downii, a New Bacterial Species with Probiotic Potential

Streptococcus downii is a recently reported bacterial species of oral origin, with inhibitory capacity against Streptococcus mutans, Actinomyces naeslundii, Veillonella parvula and Aggregatibacter actinomycetemcomitans, which confers upon it the potential of being an oral probiotic. The aim of the present study was to identify the potential mechanisms by which S. downii exerts its inhibitory effect on S. mutans. To this end, the study assessed the consumption of glucose and proteins available in the culture medium, the modification of the pH, the production of short-chain fatty acids, the changes in the protein panel of the inhibition halo, the production of hydrogen peroxide and the effect of proteinase K. There were no differences in the glucose values or in the protein content of the medium, but there was a reduction in pH (with no effect on the growth of S. mutans). Significant increases were detected in the levels of lactic and formic acid (with no effect on the growth of S. mutans), as well as changes in the peptide panel (with no effect on the growth of S. mutans). The inhibitory effect was maintained in the presence of peroxidase but disappeared after adding proteinase K. Based on these results, it is suggested that the main mechanism of inhibition of S. downii against S. mutans is the production of bacteriocins.

Lactobacillus reuteri for chronic periodontitis: focus on underlying mechanisms and future perspectives

Chronic periodontitis is a common oral disorder caused by pathogenic bacteria. Despite the wide use of antibiotics as the conventional adjunctive treatment, the challenges of increased antibiotic resistance and limited therapeutic effect receive considerable attention and the developments of alternative treatments gain increasing consideration. Growing evidence showed that Lactobacillus reuteri (LR) may represent a promising alternative adjunct for chronic periodontitis. It can attenuate inflammation and reduce tissue disruption. LR-assisted treatment has been shown to be effective and relatively safe in multiple clinical trials, and accumulating evidence suggests its significant biological roles. In the current review, we focus on capturing the underlying mechanisms of LR involved in chronic periodontitis, thereby representing a scientific foundation for LR-assisted therapy. Furthermore, we point out the challenges and future directions for further clinical trials to improve the clinical applicability for LR.

In it together: Candida-bacterial oral biofilms and therapeutic strategies

Under natural environmental settings or in the human body, the majority of microorganisms exist in complex polymicrobial biofilms adhered to abiotic and biotic surfaces. These microorganisms exhibit symbiotic, mutualistic, synergistic, or antagonistic relationships with other species during biofilm colonization and development. These polymicrobial interactions are heterogeneous, complex and hard to control, thereby often yielding worse outcomes than monospecies infections. Concerning fungi, Candida spp., in particular, Candida albicans is often detected with various bacterial species in oral biofilms. These Candida-bacterial interactions may induce the transition of C. albicans from commensal to pathobiont or dysbiotic organism. Consequently, Candida-bacterial interactions are largely associated with various oral diseases, including dental caries, denture stomatitis, periodontitis, peri-implantitis, and oral cancer. Given the severity of oral diseases caused by cross-kingdom consortia that develop hard-to-remove and highly drug-resistant biofilms, fundamental research is warranted to strategically develop cost-effective and safe therapies to prevent and treat cross-kingdom interactions and subsequent biofilm development. While studies have shed some light, targeting fungal-involved polymicrobial biofilms has been limited. This mini-review outlines the key features of Candida-bacterial interactions and their impact on various oral diseases. In addition, current knowledge on therapeutic strategies to target Candida-bacterial polymicrobial biofilms is discussed.

The rationale and potential for using Lactobacillus in the management of periodontitis

Periodontitis refers to a wide range of the inflammatory conditions of supporting dental structures. For some patients with periodontitis, antibacterial agents are needed as an adjuvant to mechanical debridement treatments and oral hygiene maintenance. However, the widespread use of broad-spectrum antibiotics for the prophylaxis and treatment of periodontal infections results in the emergence of resistant pathogens. Therefore, probiotics have become markedly interesting to researchers as a potentially safe alternative to periodontal treatment and maintenance. Probiotics have been used in medicine for decades and extensively applied to the treatment of inflammatory diseases through the modulation of microbial synergy and other mechanisms. A growing amount of evidence has shown that using Lactobacillus strains for oral cavity maintenance could improve periodontal health. In this study, we reviewed studies showing proof of the inhibitory effects of Lactobacillus species on periodontal inflammation. We also explored the rationale and potential for using Lactobacillus species in the management of periodontitis.

What do we know about the mechanisms of action of probiotics on factors involved in the pathogenesis of periodontitis? A scoping review of in vitro studies

OBJECTIVE

Probiotics are increasingly used in oral prevention and treatment conditions, but little is known about their abilities. The aim of this review is to clarify, summarize and disseminate current knowledge about the mode of action of in vitro probiotics on factors involved in the pathogenesis of periodontitis.

METHOD

2495 articles were identified in three databases (Medline, Web of Science, SpringerLink) and 26 studies included in this scoping review.

RESULTS

Twenty-three probiotic species were identified, the majority of which were Lactobacilli or Bifidobacteria. Lactobacillus rhamnosus (30.8 %) and Lactobacillus reuteri (42.3 %) were found to be the two predominantly studied probiotic species and three main mechanisms of action of probiotics could be classified as: (i) modulation of the immuno-inflammatory response, (ii) direct actions of probiotics on periodontopathogens by adhesion or nutritive competitions and/or the secretion of antimicrobial molecules and (iii) indirect actions through environmental modifications. A combination of several probiotic strains seems to be beneficial via synergistic action amplifying the functions of each strain used. However, heterogeneity of the methodologies and probiotic species included in studies leads us to consider the following avenues for future research: (i) implementation of standardized periodontal models as close as possible to in vivo periodontal conditions to identify the functions of each strain for appropriate medication, (ii) updating data about interactions within oral biofilms to identify new candidates and to predict then analyze their behavior within these biofilms.

CONCLUSION

Probiotics may have their place in the response to inter-individual variability in periodontitis, provided that the choice of the probiotic strain or combination of them will be personalized and optimal for each patient.

Effects of Probiotic Culture Supernatant on Cariogenic Biofilm Formation and RANKL-Induced Osteoclastogenesis in RAW 264.7 Macrophages

Postbiotics are a promising functional ingredient that can overcome the limitations of viability and storage stability that challenge the production of probiotics. To evaluate the effects of postbiotics on oral health, eight spent culture supernatants (SCSs) of probiotics were prepared, and the effects of SCSs on Streptococcus mutans-induced cariogenic biofilm formation and the receptor activator of the nuclear factor κB ligand (RANKL)-induced osteoclastogenesis were evaluated in RAW 264.7 macrophages. SCS of Lactobacillus salivarius MG4265 reduced S. mutans-induced biofilm formation by 73% and significantly inhibited tartrate-resistant acid phosphatase (TRAP) activity, which is a biomarker of mature osteoclasts in RAW 264.7 macrophages. The suppression of RANKL-induced activation of mitogen activated the protein kinases (c-Jun N-terminal kinase, extracellular signal-regulated kinase, and p38) and nuclear factor κB pathways, as well as the upregulation of heme oxygenase-1 expression. The suppression of RANK-L-induced activation of mitogen also inhibited the expression of transcriptional factors (c-fos and nuclear factor of activated T cells cytoplasmic 1) and, subsequently, osteoclastogenesis-related gene expression (tartrate-resistant acid phosphatase-positive (TRAP), cathepsin K, and matrix metalloproteinase-9).Therefore, SCS of L. salivarius MG4265 has great potential as a multifunctional oral health ingredient that inhibits biofilm formation and suppresses the alveolar bone loss that is associated with periodontitis.

Lactobacillus Plantarum 108 Inhibits Streptococcus mutans and Candida albicans Mixed-Species Biofilm Formation

Streptococcus mutans is the principal biofilm forming oral pathogen associated with dental caries. Studies have shown that Candida albicans, a commensal oral fungus is capable of forming pathogenic mixed-species biofilms with S. mutans. The treatment of bacterial and fungal infections using conventional antimicrobial agents has become challenging due to the antimicrobial resistance of the biofilm mode of growth. The present study aimed to evaluate the efficacy of secretory components of Lactobacillus plantarum 108, a potentially promising probiotic strain, against S. mutans and C. albicans single and mixed-species biofilms. L. plantarum 108 supernatant inhibited S. mutans and C. albicans single-species biofilms as shown by XTT reduction assay, crystal violet assay, and colony forming units counting. The probiotic supernatant significantly inhibited the S. mutans and C. albicans mixed-species biofilm formation. The pre-formed mixed-species biofilms were also successfully reduced. Confocal microscopy showed poorly developed biofilm architecture in the probiotic supernatant treated biofilms. Moreover, the expression of S. mutans genes associated with glucosyltransferase activity and C. albicans hyphal specific genes (HWP1, ALS1 and ALS3) were down-regulated in the presence of the probiotic supernatant. Altogether, the data demonstrated the capacity of L. plantarum 108 supernatant to inhibit the S. mutans and C. albicans mixed-species biofilms. Herein, we provide a new insight on the potential of probiotic-based strategies to prevent bacterial-fungal mixed-species biofilms associated with dental caries.

Antimicrobial activity of Lactobacillus fermentum TcUESC01 against Streptococcus mutans UA159

Dental caries is a multifactorial chronic-infection disease, which starts with a bacterial biofilm formation caused mainly by Streptococcus mutans. The use of probiotics has shown numerous health benefits, including in the fight against oral diseases. Strains of Lactobacillus fermentum have already shown probiotic potential against S. mutans, but there are still few studies. Thus, the aim of our study was to evaluate the antimicrobial activity of the inoculum and metabolites produced by L. fermentum TcUESC01 against S. mutans UA159. For this, a growth curve of L. fermentum was performed and both the inoculum and the metabolites formed in the fermentation were tested against the growth of S. mutans UA159 in agar diffusion tests, and only its metabolites were tested to determine the minimum inhibitory concentration, minimal bactericidal concentration and inhibition of cell adhesion. Inhibition of biofilm formation, pH drop and proton permeability were also tested with the metabolites. The zone of inhibition began to be formed at 14 h and continued until 16 h. The inoculum containing L. fermentum also showed zone of inhibition. The MIC for the metabolites was 1280 mg/mL and the MBC was obtained with a concentration higher than the MIC equal to 5120 mg/mL. Half of the MIC concentration (640 mg/mL) was required to inhibit S. mutans adhesion to the surface of the microplates. In the biofilm analyzes, the treatment with the metabolites in the tested concentration was not able to reduce biomass, insoluble glucans and alkali soluble compared to the control biofilm (p > 0.05). The metabolites also did not affect acid production and acid tolerance of S. mutans cells in biofilms compared to saline group (p > 0.05). Lactic acid (50.38%) was the most abundant organic acid produced by L. fermentum. This is the first report showing that the metabolites produced by the Lactobacillus fermentum TcUESC01 have a potential to be used as an antimicrobial agent against S. mutans, showing anti-adherence and bactericidal activity against planktonic cells of S. mutans. Thus, further studies should be carried out in order to better understand the antimicrobial activity of metabolites of L. fermentum TCUESC01.

Effect of Short-Term Placebo-Controlled Consumption of Probiotic Yoghurt and Indian Curd on the Streptococcus mutans Level in Children Undergoing Fixed Interceptive Orthodontic Therapy

Objective

To examine the effect of short-term consumption of probiotic yoghurt, Indian curd, and ultra-heated yoghurt as placebo on the levels of salivary and plaque Streptococcus mutans (S. mutans) in children undergoing fixed interceptive orthodontic therapy.

Methods

A placebo-controlled double-blind study was carried out in a total of 30 children (8-15 years). The S. mutans level in the plaque and saliva were taken at the baseline and 2 weeks after the initiation of fixed orthodontic treatment by Dentocult SM kits. An equal number of participants randomized in three groups were asked to ingest 200 g of yoghurt containing Lactobacillus acidophilus La-1 and La-2 (>1×10⁹ cfu/mL) once daily, Indian curd, or ultra-heated control yoghurt without viable bacteria and were followed for the S. mutans level after 2 weeks.

Results

A significant reduction in salivary S. mutans levels was recorded after probiotic yoghurt ingestion (p=0.001) in addition to a reduction in the plaque S. mutans, which was observed after Indian curd consumption (p=0.026).

Conclusion

Our findings suggest that short-term daily consumption of probiotic yoghurt along with Indian curd may help to reduce the levels of S. mutans in the saliva and plaque in children undergoing interceptive fixed orthodontic therapy.

Inhibitory effect of probiotic Lactobacillus supernatants from the oral cavity on Streptococcus mutans biofilms

Probiotics can release bioactive substances that can inhibit the growth and biofilm formation of pathogenic microorganisms such as Streptococcus mutans. In this context, we evaluated whether the supernatants of Lactobacillus strains isolated from caries-free subjects can inhibit S. mutans, one of the most important bacteria for dental caries. First, the supernatants of 22 Lactobacillus strains were screened for antibacterial activity against S. mutans in planktonic cultures. All 22 Lactobacillus strains studied (100%) showed antibacterial activity. Thereafter, the Lactobacillus strains with the greatest reductions in the planktonic S. mutans cultures were tested on biofilms. The L. fermentum 20.4, L. paracasei 11.6, L. paracasei 20.3 and L. paracasei 25.4 strains could significantly reduce the number of S. mutans cells in biofilms formed in hydroxyapatite (p < 0.05). This reduction was also confirmed by scanning electron microscopy analysis and was not caused by the decreased pH value in the medium (p > 0.05). In addition, the supernatants of these probiotic strains could also reduce the total biomass of S. mutans biofilms (p < 0.05). In conclusion, most of the Lactobacillus strains tested have some antibacterial activity against S. mutans. L. fermentum 20.4, L. paracasei 11.6, L. paracasei 20.3 and L. paracasei 25.4 produce bioactive substances that caused a significant reduction in S. mutans biofilms.

Probiotic Lactobacillus sp. inhibit growth, biofilm formation and gene expression of caries-inducing Streptococcus mutans

Streptococcus mutans contributes significantly to dental caries, which arises from homoeostasic imbalance between host and microbiota. We hypothesized that Lactobacillus sp. inhibits growth, biofilm formation and gene expression of Streptococcus mutans. Antibacterial (agar diffusion method) and antibiofilm (crystal violet assay) characteristics of probiotic Lactobacillus sp. against Streptococcus mutans (ATCC 25175) were evaluated. We investigated whether Lactobacillus casei (ATCC 393), Lactobacillus reuteri (ATCC 23272), Lactobacillus plantarum (ATCC 14917) or Lactobacillus salivarius (ATCC 11741) inhibit expression of Streptococcus mutans genes involved in biofilm formation, quorum sensing or stress survival using quantitative real-time polymerase chain reaction (qPCR). Growth changes (OD600) in the presence of pH-neutralized, catalase-treated or trypsin-treated Lactobacillus sp. supernatants were assessed to identify roles of organic acids, peroxides and bacteriocin. Susceptibility testing indicated antibacterial (pH-dependent) and antibiofilm activities of Lactobacillus sp. against Streptococcus mutans. Scanning electron microscopy revealed reduction in microcolony formation and exopolysaccharide structural changes. Of the oral normal flora, L. salivarius exhibited the highest antibiofilm and peroxide-dependent antimicrobial activities. All biofilm-forming cells treated with Lactobacillus sp. supernatants showed reduced expression of genes involved in exopolysaccharide production, acid tolerance and quorum sensing. Thus, Lactobacillus sp. can inhibit tooth decay by limiting growth and virulence properties of Streptococcus mutans.

The Anti-inflammatory Effects of Glycerol-supplemented Probiotic Lactobacillus reuteri on Infected Epithelial cells In vitro

Background:

One of the most interesting effects of probiotics is their ability to modulate the immune system through the induction of cytokines and to enhance the host immune response.

Aims:

The purpose of this study was to evaluate the anti-inflammatory effect of glycerol-supplemented Lactobacillus reuteri on the transcription level of interleukin (IL)-8 and human-beta-defensin (hBD)-2 expressed by epithelial cells after exposure to bacteria.

Materials and Methods:

The confluent-cultured HaCat cell line (10⁵ cells/mL) was exposed to Streptococcus mutans ATCC-25175 and Porphyromonas gingivalis ATCC-33277 (10⁷ colony-forming units [CFU]/mL) for 24 h and challenged with probiotic L. reuteri ATCC-55730 (10⁷ CFU/mL) supplemented with glycerol. Subsequently, the transcription levels of IL-8 and hBD-2 in HaCat cells were analyzed using reverse-transcription polymerase chain reaction (RT-PCR). In addition, cell viability was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. All the obtained data were statistically analyzed using the one-way analysis of variance test, with P < 0.05 set as the level of significance.

Results:

The MTT assays confirmed no cytotoxic effects of glycerol-supplemented L. reuteri on HaCat cells (viability >90%). mRNA expression of IL-8 and hBD-2 increased after exposure to both bacteria. The presence of glycerol-supplemented L. reuteri significantly reduced the expression of IL-8 and hBD-2 on HaCat cells (P < 0.05).

Conclusion:

Glycerol-supplemented L. reuteri reduced the expression of IL-8 and hBD-2, and the results may be proof of principle for a probiotic approach to combating inflammation. However, further studies are needed to validate this probiotic effect.

Different frequencies of Porphyromonas gingivalis infection in cancers of the upper digestive tract

The high incidence rate of multiple carcinomas in the upper digestive tract is often explained in terms of involvement of the same underlying risk factors. It has been reported that the oral bacterium Streptococcus anginosus is associated with esophageal, gastric, and pharyngeal cancers. We previously reported occurrence of Porphyromonas gingivalis (P. gingivalis) DNA in esophagus cancer. In this study, the presence of P. gingivalis in specimens of various types of cancer from the upper digestive tract was investigated. Here we report that P. gingivalis was preferentially and frequently present in specimens of esophageal cancer as well as in those from dysplasia of the esophagus but rarely in matched noncancerous portions and are quite low or absent in cancers from the cardia or stomach. Therefore, it led us to propose that, the microorganism does not survive in conditions of high acidity. We then investigate the pH dependence of survival of P. gingivalis as well as the acid tolerance of it. We found that, exposure to acidic buffers of a wide range of pH values led to a decline in colony forming units of P. gingivalis, thus, providing a possible explanation for variations in frequencies of P. gingivalis infection in this study.

Probiotic Lactobacillus reuteri has antifungal effects on oral Candida species in vitro

Background: An alternative approach for managing Candida infections in the oral cavity by modulating the oral microbiota with probiotic bacteria has been proposed.

Objective: The aim was to investigate the antifungal potential of the probiotic bacterium Lactobacillus reuteri (DSM 17938 and ATCC PTA 5289) against six oral Candida species (C. albicans, C. glabrata, C. krusei, C. tropicalis, C. dubliniensis, and C. parapsilosis).

Design: The lactobacilli were tested for their ability to co-aggregate with and inhibit the growth of the yeasts assessed by spectrophotometry and the agar overlay inhibition assay. Additionally, the pH was evaluated with microsensors, and the production of hydrogen peroxide (H2O2) by the lactobacilli was verified.

Results: Both L. reuteri strains showed co-aggregation abilities with the yeasts. The lactobacilli almost completely inhibited the growth of C. albicans and C. parapsilosis, but did not affect C. krusei. Statistically significant differences in co-aggregation and growth inhibition capacities between the two L. reuteri strains were observed (p<0.001). The pH measurements suggested that C. krusei can resist the acids produced by the lactobacilli.

Conclusions:L. reuteri exhibited antifungal properties against five of the six most common oral Candida species. Further, the results reconfirms that the probiotic capacity of L. reuteri is strain specific.

Demineralization-remineralization dynamics in teeth and bone

Biomineralization is a dynamic, complex, lifelong process by which living organisms control precipitations of inorganic nanocrystals within organic matrices to form unique hybrid biological tissues, for example, enamel, dentin, cementum, and bone. Understanding the process of mineral deposition is important for the development of treatments for mineralization-related diseases and also for the innovation and development of scaffolds. This review provides a thorough overview of the up-to-date information on the theories describing the possible mechanisms and the factors implicated as agonists and antagonists of mineralization. Then, the role of calcium and phosphate ions in the maintenance of teeth and bone health is described. Throughout the life, teeth and bone are at risk of demineralization, with particular emphasis on teeth, due to their anatomical arrangement and location. Teeth are exposed to food, drink, and the microbiota of the mouth; therefore, they have developed a high resistance to localized demineralization that is unmatched by bone. The mechanisms by which demineralization-remineralization process occurs in both teeth and bone and the new therapies/technologies that reverse demineralization or boost remineralization are also scrupulously discussed. Technologies discussed include composites with nano- and micron-sized inorganic minerals that can mimic mechanical properties of the tooth and bone in addition to promoting more natural repair of surrounding tissues. Turning these new technologies to products and practices would improve health care worldwide.

The case in favour of probiotics before, during and after pregnancy: insights from the first 1,500 days

Successful human reproduction requires microbial homeostasis in the female reproductive tract, and colonisation of the newborn with beneficial microbes. In order to prevent several complications associated with dysbiosis, the administration of probiotics is more often being considered. The objective of the enclosed review was to examine the rationale for probiotic utility before and during pregnancy and in the early phase of infant life. The conclusions emerged from a panel of researchers who met during the International Scientific Association for Probiotics and Prebiotics (ISAPP) workshop held in Washington, DC, USA in 2015. The group concluded based upon the current literature, that a case can be made for the use of a specific sets of probiotic organisms during the first 1,500 days of life, with the goal of a healthy pregnancy to term, and a healthy start to life with lowered risk of infections and inflammatory events. The key to successfully translating these recommendations to practice is that products be made available and affordable to women in developed and developing countries.

Mechanisms and therapeutic effectiveness of lactobacilli

The gut microbiome is not a silent ecosystem but exerts several physiological and immunological functions. For many decades, lactobacilli have been used as an effective therapy for treatment of several pathological conditions displaying an overall positive safety profile. This review summarises the mechanisms and clinical evidence supporting therapeutic efficacy of lactobacilli. We searched Pubmed/Medline using the keyword ‘Lactobacillus’. Selected papers from 1950 to 2015 were chosen on the basis of their content. Relevant clinical and experimental articles using lactobacilli as therapeutic agents have been included. Applications of lactobacilli include kidney support for renal insufficiency, pancreas health, management of metabolic imbalance, and cancer treatment and prevention. In vitro and in vivo investigations have shown that prolonged lactobacilli administration induces qualitative and quantitative modifications in the human gastrointestinal microbial ecosystem with encouraging perspectives in counteracting pathology-associated physiological and immunological changes. Few studies have highlighted the risk of translocation with subsequent sepsis and bacteraemia following probiotic administration but there is still a lack of investigations on the dose effect of these compounds. Great care is thus required in the choice of the proper Lactobacillus species, their genetic stability and the translocation risk, mainly related to inflammatory disease-induced gut mucosa enhanced permeability. Finally, we need to determine the adequate amount of bacteria to be delivered in order to achieve the best clinical efficacy decreasing the risk of side effects.