Isolation and Bacteriocin-Related Typing of Streptococcus dentisani

Anti-caries Streptococcus spp.: A potential preventive tool for special needs patients

INTRODUCTION

Probiotics are living microorganisms that act on the host-microbiome interface to restore the microbiota's physiological homeostasis. Numerous probiotics have been marketed with inhibitory activity against Streptococcus mutans and consequently with a potential anti-caries effect, mainly of the genera Lactobacillus and Bifidobacterium, whose main disadvantage is their limited ability to settle in the oral cavity.

METHODS

This narrative review describes the main Streptococcus spp. with probiotic anti-Streptococcus mutans activity, whose substantivity is greater than that of Lactobacillus spp. and consequently with anti-caries potentiality. We performed a literature review in the PubMed, Science Direct and Google Scholar databases of articles published in English (without time restriction) related to caries and probiotics.

RESULTS

The potential identified anti-caries probiotics included Streptococcus spp. A12, Streptococcus oralis (AJ3), Streptococcus oligofermentans, Streptococcus salivarius (K12, M18, JH, LAB813, 24SMB), Streptococcus spp. with arginolytic activity (S. sanguinis, S. gordonii, S. ratti, S. parasanguinis, S. intermedius, S. australis, and S. cristatus), Streptococcus rattus (JH145), Streptococcus dentisani and Streptococcus downii.

CONCLUSIONS

The possibility of using these Streptococcus spp. as probiotics that inhibit the growth of dental plaque and the development of carious lesions represents a potential tool of particular interest for individuals with physical or intellectual disabilities that impede the routine and effective application of mechanical dental plaque removal techniques.

Probiotic Effect of Streptococcus dentisani on Oral Pathogens: An In Vitro Study

Probiotics, including Streptococcus dentisani, have been proposed as an alternative to re-establish the ecology of the oral cavity and inhibit the formation of pathogenic biofilms. The main objective of this work was to assess the probiotic ability of S. dentisani against Streptococcus mutans, Streptococcus mitis, and Candida albicans biofilms. The ability of the strains to form a monospecies biofilm and the probiotic potential of S. dentisani using the competition, exclusion, and displacement strategies were determined. All strains were moderate biofilm producers. The ability of S. dentisani to compete with and exclude S. mutans and S. mitis during biofilm formation was not significant. However, S. dentisani significantly reduced pathologic streptococcal biofilms using the displacement strategy. Also S. dentisani reduced the formation of the C. albicans biofilm mainly through competition and displacement. In vitro, S. dentisani exhibited probiotic potential to reduce the formation of potentially pathogenic biofilms. Further investigation is required to understand the biofilm-inhibiting mechanisms exhibited by this probiotic strain.

How probiotics, prebiotics, synbiotics, and postbiotics prevent dental caries: an oral microbiota perspective

Dental caries, a highly prevalent oral disease, impacts a significant portion of the global population. Conventional approaches that indiscriminately eradicate microbes disrupt the natural equilibrium of the oral microbiota. In contrast, biointervention strategies aim to restore this balance by introducing beneficial microorganisms or inhibiting cariogenic ones. Over the past three decades, microbial preparations have garnered considerable attention in dental research for the prevention and treatment of dental caries. However, unlike related pathologies in the gastrointestinal, vaginal, and respiratory tracts, dental caries occurs on hard tissues such as tooth enamel and is closely associated with localized acid overproduction facilitated by cariogenic biofilms. Therefore, it is insufficient to rely solely on previous mechanisms to delineate the role of microbial preparations in the oral cavity. A more comprehensive perspective should involve considering the concepts of cariogenic biofilms. This review elucidates the latest research progress, mechanisms of action, challenges, and future research directions regarding probiotics, prebiotics, synbiotics, and postbiotics for the prevention and treatment of dental caries, taking into account the unique pathogenic mechanisms of dental caries. With an enhanced understanding of oral microbiota, personalized microbial therapy will emerge as a critical future research trend.

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.

Biofilm ecology associated with dental caries: Understanding of microbial interactions in oral communities leads to development of therapeutic strategies targeting cariogenic biofilms

A biofilm is a sessile community characterized by cells attached to the surface and organized into a complex structural arrangement. Dental caries is a biofilm-dependent oral disease caused by infection with cariogenic pathogens, such as Streptococcus mutans, and associated with frequent exposure to a sugar-rich diet and poor oral hygiene. The virulence of cariogenic biofilms is often associated with the spatial organization of S. mutans enmeshed with exopolysaccharides on tooth surfaces. However, in the oral cavity, S. mutans does not act alone, and several other microbes contribute to cariogenic biofilm formation. Microbial communities in cariogenic biofilms are spatially organized into complex structural arrangements of various microbes and extracellular matrices. The balance of microbiota diversity with reduced diversity and a high proportion of acidogenic-aciduric microbiota within the biofilm is closely related to the disease state. Understanding the characteristics of polymicrobial biofilms and the association of microbial interactions within the biofilm (e.g., symbiosis, cooperation, and competition) in terms of their potential role in the pathogenesis of oral disease would help develop new strategies for interventions in virulent biofilm formation.

Oral Commensal Streptococci: Gatekeepers of the Oral Cavity

Oral commensal streptococci are primary colonizers of the oral cavity. These streptococci produce many adhesins, metabolites, and antimicrobials that modulate microbial succession and diversity within the oral cavity. Often, oral commensal streptococci antagonize cariogenic and periodontal pathogens such as Streptococcus mutans and Porphyromonas gingivalis, respectively. Mechanisms of antagonism are varied and range from the generation of hydrogen peroxide, competitive metabolite scavenging, the generation of reactive nitrogen intermediates, and bacteriocin production. Furthermore, several oral commensal streptococci have been shown to alter the host immune response at steady state and in response to oral pathogens. Collectively, these features highlight the remarkable ability of oral commensal streptococci to regulate the structure and function of the oral microbiome. In this review, we discuss mechanisms used by oral commensal streptococci to interact with diverse oral pathogens, both physically and through the production of antimicrobials. Finally, we conclude by exploring the critical roles of oral commensal streptococci in modulating the host immune response and maintaining health and homeostasis.

The salivary microbiome shows a high prevalence of core bacterial members yet variability across human populations

Human saliva contains diverse bacterial communities, reflecting health status, dietary patterns and contributing to variability in the sensory perception of food. Many descriptions of the diversity of the salivary microbiome have focused on the changes induced by certain diseased states, but the commonalities and differences within healthy saliva have not been fully described. Here, we define and explore the core membership of the human salivary microbial community by collecting and re-analysing raw 16S rRNA amplicon sequencing data from 47 studies with 2206 saliva samples. We found 68 core bacterial taxa that were consistently detected. Differences induced by various host intrinsic and behaviour factors, including gender, age, geographic location, tobacco usage and alcohol consumption were evident. The core of the salivary microbiome was verified by collecting and analysing saliva in an independent study. These results suggest that the methods used can effectively define a core microbial community in human saliva. The core salivary microbiome demonstrated both stability and variability among populations. Geographic location was identified as the host factor that is most associated with the structure of salivary microbiota. The independent analysis confirmed the prevalence of the 68 core OTUs we defined from the global data and provides information about how bacterial taxa in saliva varies across human populations.

Functional Fermented Probiotics, Prebiotics, and Synbiotics from Non-Dairy Products: A Perspective from Nutraceutical

The current trend of health-conscious consumers and healthy food habits prompts researchers to explore developing food products with synbiotic benefits. Synbiotic foods have gained popularity in recent years due to their functional, nutritional, physiological, and therapeutic characteristics. Lactose intolerance, dyslipidemia, and allergic milk proteins become the barriers in the development of dairy probiotics. The present scenario of an increase in the demand for vegetarian products leads to a rise in the consumption of non-dairy probiotics. Prebiotics like, resistant starch, inulin, and polyphenols are selectively used by gut microbiota to enhance the selection and colonization of probiotics bacteria. Probiotic's action mechanisms include the production of bacteriocins, peptides, short-chain fatty acids, amino acids, vitamins, and other metabolites. Therefore, this review article explores the alternative sources of probiotics so it will help to an understanding of non-dairy based functional fermented foods for both pro and prebiotics. Dietary fibers in vegetables, fruits, and cereals are one of prospective prebiotics and highlighted the various methods for making non-dairy synbiotics based on dietary fibers, such as microencapsulation, freeze-drying, and spray drying is also addressed.

Molecular Detection of Streptococcus downii sp. nov. from Dental Plaque Samples from Patients with Down Syndrome and Non-Syndromic Individuals

A new bacterial species has recently been identified in the dental plaque of an adolescent with Down syndrome. The species is known as Streptococcus downii sp. nov. (abbreviated to S. downii), and it inhibits the growth of S. mutans and certain periodontal pathogens. The aim of this study was to determine the distribution of S. downii in the oral cavity of individuals with Down syndrome. Methods: A specific polymerase chain reaction for the operon of bacteriocin (class IIb lactobin A/cerein 7B family) was designed to detect S. downii in individuals with Down syndrome (n = 200) and in the general population (n = 100). We also compared the whole genome of S. downii and the regions related to its bacteriocins against 127 metagenomes of supragingival plaque of the “Human Microbiome Project”. Results: We detected the specific gene of the S. downii bacteriocin in an individual with Down syndrome (Cq, 34.52; GE/μL, 13.0) and in an individual of the non-syndromic control group (Cq, 34.78 Cq; GE/μL, 4.93). The prevalence of S. downii was ≤1% both in Down syndrome and in the general population, which did not allow for clinical-microbiological correlations to be established. This result was confirmed by detecting only one metagenome with an ANIm with approximately 95% homology and with 100% homology with ORFs that code class IIb lactobiocin A/cerein 7B bacteriocins among the 127 metagenomes of the “Human Microbiome Project” tested. Conclusions: The detection rate of S. downii in the supragingival dental plaque was very low, both in the Down syndrome individuals and in the non-syndromic controls. A clinical-microbiological correlation could therefore not be established.

Streptococcus dentisani is a common inhabitant of the oral microbiota worldwide and is found at higher levels in caries-free individuals

Streptococcus dentisani has been proposed as a promising probiotic against tooth decay, due to its ability to buffer acidic pH and to inhibit the growth of oral pathogens. However, it is unknown if this bacterial species has a global distribution. The current study aimed to establish the presence of S. dentisani in oral samples from different geographic locations by identifying the sequence of its 16S rRNA gene in available datasets from across the globe. In addition, an analytical and cross-sectional study was carried out to determine if the levels of this probiotic strain are higher in caries-free individuals compared to those with dental caries. Samples from various geographical sources demonstrated that S. dentisani is present in saliva and dental plaque from individuals of different continents. Typical S. dentisani levels in saliva ranged from 10⁴ to 10⁵ cells/ml and a total of 10⁶-10⁷ cells in dental plaque. Using real-time qPCR, S. dentisani was quantified from supragingival dental plaque of 25 caries-free and 29 caries-active individuals from a Mexican children population, where significantly higher proportions of S. dentisani were found in the caries-free group (p = 0.002). Finally, a negative correlation was found between caries levels (as measured by the dmft caries index) and the percentage of S. dentisani (p < 0.001). Thus, the current manuscript indicates that this species has a global distribution, can be found in saliva and dental plaque, and appears to be present in higher numbers in plaque samples from caries-free children.

Interactions between probiotic and oral pathogenic strains

More than 6 billion bacteria and other microorganisms live in the adult oral cavity. As a result of any deleterious effect on this community, some microorganisms will survive better than others, which may trigger pathogenic processes like caries, halitosis, gingivitis or periodontitis. Oral dysbiosis is among the most frequent human health hazards globally. Quality of life of patients deteriorates notably, while treatments are often unpleasant, expensive and irreversible, e.g. tooth loss. In the experiments reported here, we investigated the individual interactions between 8 pathogenic and 8 probiotic strains and a commercially available probiotic product. Almost all pathogens, namely Fusobacterium nucleatum, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Streptococcus mutans, Streptococcus oralis, Streptococcus gordonii, Enterococcus faecalis and Prevotella buccae are pathogens frequently occurring in the oral cavity. The used probiotic strains were Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus delbrueckii, Bifidobacterium thermophilum and two Streptococcus dentisani isolates. Using a modified agar diffusion method, we investigated capability of the probiotic bacteria to prevent the growth of the pathogenic ones in order to identify candidates for future therapeutic treatments. The results indicated successful bacteriocin production, i.e. growth inhibition, against every pathogenic bacterium by at least 5 probiotic strains.

Suppressive effects of Streptococcus thermophilus KLDS 3.1003 on some foodborne pathogens revealed through in vitro, in vivo and genomic insights

Foodborne diseases (FBDs) remain a persistent global challenge and recent research efforts suggest that lactic acid bacteria (LAB) strains can contribute towards their prevention and treatment. This study investigates the genetic properties of Streptococcus thermophilus KLDS 3.1003 as a potential probiotic and health-promoting LAB strain as well as its in vitro and in vivo activities against two foodborne pathogens. In vitro, its antimicrobial activities and tolerance levels in simulated bile salts and acids were determined. The cytotoxic effects of the LAB strain in RAW264.7 cells were also evaluated. For in vivo evaluation, 24 BALB/c mice were orally administered control and trial diets for 14 days. Genomic analyses of this strain's bacteriocin configuration, stress response system and multidrug resistance genes were annotated to validate in vitro and in vivo results. In vitro antimicrobial results show that the cells and CFS of S. thermophilus KLDS 3.1003 could inhibit both pathogens with the former being more effective (P < 0.05). In addition, its cell-free supernatant (CFS) could inhibit the growth of both pathogens, with catalase treatment having the highest effect against it. More so, after 3 h of incubation, survivability levels of S. thermophilus KLDS 3.1003 were significantly high (P < 0.05). LPS-induced RAW264.7 cell activities were also significantly reduced by 108-109 CFU mL-1 of S. thermophilus KLDS. In vivo, significant weight losses were inhibited in the TSTEC group compared to the TSTSA group (P < 0.05). Moreover, pathogen-disrupted blood biochemical parameters like HDL, LDL, TP, TG, AST, ALT and some minerals were restored in the respective prevention groups (TSTEC and TSTSA). Genomic analyses showed that S. thermophilus KLDS 3.1003 has bacteriocin-coding peptides, which accounts for its antimicrobial abilities in vitro and in vivo. S. thermophilus KLDS 3.1003 is also endowed with intact genes for acid tolerance, salt-resistance, cold and heat shock responses and antioxidant activities, which are required to promote activities against the selected foodborne pathogens. This study showed that S. thermophilus KLDS 3.1003 has the genomic capacity to inhibit foodborne pathogens' growth in vitro and in vivo, thus qualifying it as a potential probiotic, antimicrobial and bio-therapeutic candidate.

A concerted probiotic activity to inhibit periodontitis-associated bacteria

Periodontitis can result in tooth loss and the associated chronic inflammation can provoke several severe systemic health risks. Adjunctive to mechanical treatment of periodontitis and as alternatives to antibiotics, the use of probiotic bacteria was suggested. In this study, the inhibitory effect of the probiotic Streptococcus salivarius subsp. salivarius strains M18 and K12, Streptococcus oralis subsp. dentisani 7746, and Lactobacillus reuteri ATCC PTA 5289 on anaerobic periodontal bacteria and Aggregatibacter actinomycetemcomitans was tested. Rarely included in other studies, we also quantified the inverse effect of pathogens on probiotic growth. Probiotics and periodontal pathogens were co-incubated anaerobically in a mixture of autoclaved saliva and brain heart infusion broth. The resulting genome numbers of the pathogens and of the probiotics were measured by quantitative real-time PCR. Mixtures of the streptococcal probiotics were also used to determine their synergistic, additive, or antagonistic effects. The overall best inhibitor of the periodontal pathogens was L. reuteri ATCC PTA 5289, but the effect is coenzyme B12-, anaerobiosis-, as well as glycerol-dependent, and further modulated by L. reuteri strain DSM 17938. Notably, in absence of glycerol, the pathogen-inhibitory effect could even turn into a growth spurt. Among the streptococci tested, S. salivarius M18 had the most constant inhibitory potential against all pathogens, followed by K12 and S. dentisani 7746, with the latter still having significant inhibitory effects on P. intermedia and A. actinomycetemcomitans. Overall, mixtures of the streptococcal probiotics did inhibit the growth of the pathogens equally or–in the case of A. actinomycetemcomitans- better than the individual strains. P. gingivalis and F. nucleatum were best inhibited by pure cultures of S. salivarius K12 or S. salivarius M18, respectively. Testing inverse effects, the growth of S. salivarius M18 was enhanced when incubated with the periodontal pathogens minus/plus other probiotics. In contrast, S. oralis subsp. dentisani 7746 was not much influenced by the pathogens. Instead, it was significantly inhibited by the presence of other streptococcal probiotics. In conclusion, despite some natural limits such as persistence, the full potential for probiotic treatment is by far not utilized yet. Especially, further exploring concerted activity by combining synergistic strains, together with the application of oral prebiotics and essential supplements and conditions, is mandatory.

A single system detects and protects the beneficial oral bacterium Streptococcus sp. A12 from a spectrum of antimicrobial peptides

The commensal bacterium Streptococcus sp. A12 has multiple properties that may promote the stability of health-associated oral biofilms, including overt antagonism of the dental caries pathogen Streptococcus mutans. A LanFEG-type ABC transporter, PcfFEG, confers tolerance to the lantibiotic nisin and enhances the ability of A12 to compete against S. mutans. Here, we investigated the regulation of pcfFEG and adjacent genes for a two-component system, pcfRK, to better understand antimicrobial peptide resistance by A12. Induction of pcfFEG-pcfRK was the primary mechanism to respond rapidly to nisin. In addition to nisin, PcfFEG conferred tolerance by A12 to a spectrum of lantibiotic and non-lantibiotic antimicrobial peptides produced by a diverse collection of S. mutans isolates. Loss of PcfFEG resulted in the altered spatio-temporal arrangement of A12 and S. mutans in a dual-species biofilm model. Deletion of PcfFEG or PcfK resulted in constitutive activation of pcfFEG and expression of pcfFEG was inhibited by small peptides in the pcfK mutant. Transcriptional profiling of pcfR or pcfK mutants combined with functional genomics revealed peculiarities in PcfK function and a novel panel of genes responsive to nisin. Collectively, the results provide fundamental insights that strengthen the foundation for the design of microbial-based therapeutics to control oral infectious diseases.

Topic Application of the Probiotic Streptococcus dentisani Improves Clinical and Microbiological Parameters Associated With Oral Health

Streptococcus dentisani 7746, isolated from dental plaque of caries-free individuals, has been shown to have several beneficial effects in vitro which could contribute to promote oral health, including an antimicrobial activity against oral pathogens by the production of bacteriocins and a pH buffering capacity through ammonia production. Previous work has shown that S. dentisani was able to colonize the oral cavity for 2–4 weeks after application. The aim of the present work was to evaluate its clinical efficacy by a randomized, double-blind, placebo-controlled parallel group study. Fifty nine volunteers were enrolled in the study and randomly assigned to a treatment or placebo group. The treatment consisted of a bucco-adhesive gel application (2.5 10⁹ cfu/dose) with a dental splint for 5 min every 48 h, for a period of 1 month (i.e., 14 doses). Dental plaque and saliva samples were collected at baseline, 15 and 30 days after first application, and 15 days after the end of treatment. At baseline, there was a significant correlation between S. dentisani levels and frequency of toothbrushing. Salivary flow, a major factor influencing oral health, was significantly higher in the probiotic group at day 15 compared with the placebo (4.4 and 3.4 ml/5 min, respectively). In the probiotic group, there was a decrease in the amount of dental plaque and in gingival inflammation, but no differences were observed in the placebo group. The probiotic group showed a significant increase in the levels of salivary ammonia and calcium. Finally, Illumina sequencing of plaque samples showed a beneficial shift in bacterial composition at day 30 relative to baseline, with a reduction of several cariogenic organisms and the key players in plaque formation, probably as a result of bacteriocins production. Only 58% of the participants in the probiotic group showed increased plaque levels of S. dentisani at day 30 and 71% by day 45, indicating that the benefits of S. dentisani application could be augmented by improving colonization efficiency. In conclusion, the application of S. dentisani 7746 improved several clinical and microbiological parameters associated with oral health, supporting its use as a probiotic to prevent tooth decay.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

This comprehensive review of the 2019 restorative dental literature is offered to inform busy dentists regarding remarkable publications and noteworthy progress made in the profession. Developed by the Scientific Investigation Committee of the American Academy of Restorative Dentistry, each author brings discipline-specific expertise to 1 of 8 sections of the report: (1) prosthodontics; (2) periodontics, alveolar bone, and peri-implant tissues; (3) implant dentistry; (4) dental materials and therapeutics; (5) occlusion and temporomandibular disorders; (6) sleep-related breathing disorders; (7) oral medicine and oral and maxillofacial surgery; and (8) dental caries and cariology. The report targets important information likely to influence day-to-day dental treatment decisions. Each review is not intended to stand alone but to update interested readers so that they may visit source material when greater detail is desired. As the profession moves toward evidence-based clinical decision-making, an incredible volume of potentially valuable dental literature continues to increase. It is the intention of this review and its authors to provide assistance in negotiating the extensive dental literature published in 2019. It is our hope that readers find this work useful in the clinical management of dental patients.

A pilot study to assess oral colonization and pH buffering by the probiotic Streptococcus dentisani under different dosing regimes

Bacterial colonization in the oral cavity is critical for efficient action of probiotics. However, limited colonization rates have been reported in many clinical trials. The aim of this pilot clinical study was to evaluate the colonization efficiency of Streptococcus dentisani under different dosing schedules and pre-treatment conditions. Eleven adult volunteers enrolled in the study. A professional ultrasound cleaning was performed in quadrants 1 and 4. The probiotic was applied in all four quadrants at a total dose of 10¹⁰ CFUs, administered in a buccoadhesive gel for 5 min, either in a single dose (n = 5) or daily for a week (n = 6). Dental plaque and saliva samples were collected at baseline and after 14 and 28 days of first application. Amounts of S. dentisani and the cariogenic organism Streptococcus mutans were measured by qPCR and salivary pH was measured by reflectometry. There was a significant increase in S. dentisani cells at day 14 but not at day 28 under both dosing schedules. A non-significant higher colonization was found in the half-mouth with previous professional cleaning as compared to the intact half. There was a significant increase in salivary pH at day 14 (p = 0.024) and day 28 (p = 0.014), which was stronger in multi-dose patients, and a significant decrease in S. mutans at day 28 (p < 0.01). The results indicate that S. dentisani is transiently able to colonize the oral cavity and that it buffers oral pH, especially after multiple dosing. Future randomized, placebo-controlled clinical trials should evaluate its use to prevent tooth decay.