Probiotic lactobacilli interfere with Streptococcus mutans biofilm formation in vitro

Preventive effects of probiotics on dental caries in vitro and in vivo

BACKGROUND

Dental caries is a common disease in the oral cavity, and the microorganisms in the cavity are colonized in the form of dental plaque biofilm. Streptococcus mutans is the main pathogen causing dental caries. Using probiotics to inhibit the growth and colonization of pathogenic bacteria, regulate mucosal immunity and improve oral microecological balance is an effective way to prevent or treat dental caries. The aim of this study was to evaluate the caries-prevention of probiotics in vitro and in rat caries models.

METHODS

The probiotics used in this study are a combination of 4 strains of bacteria. After the fermentation of 4 strains (L. plantarum, L. salivarius, L. rhamnosus, and L. paracasei) was completed, they were mixed in equal volume proportions and used as samples to be tested. The mixture was then assessed the ability to inhibit the growth of S. mutans in vitro and in vivo. SPSS Statistics 22.0 (SPSS, Inc., Chicago, IL, USA) was used for analysis.

RESULTS

In vitro the probiotics mixture could inhibit the growth of S. mutans and was able to remove biofilms formed by S. mutans. In a 42-day in vivo experiment, the probiotics group significantly reduced the level of S. mutans on the tooth surface of rats, reducing more than half the bacterial quantities compared with the caries model group (P < 0.05). The amount of S. mutans in the antagonist group was low and highly significant compared with the caries model group. Moreover, the mixture of 4 strains significantly reduced the caries scores (modified Keyes scoring method) in both the probiotic and antagonist groups (p < 0.05).

CONCLUSIONS

The study showed that the combination of the four strains can reduce the cavity scores, and the four strains can be used as products in oral care products. At the same time, the study also suggests that probiotic therapy can be an effective way to prevent dental caries.

Probiotics for oral health: a critical evaluation of bacterial strains

Oral health is critical for total body health and well-being; however, little improvement in oral health status has occurred in the U.S. over the past 20 years. Tooth decay and gum disease remain highly prevalent, with more than 90% and 50% of adults suffering from these conditions, respectively. To combat this lack of improvement, alternative approaches to dental care are now being suggested. One such alternative therapy is probiotics for oral care. In the oral cavity, probiotic strains have been shown to reduce levels of oral pathogens, inhibit the formation of dental caries, and reduce the levels of bacteria that cause halitosis. However, as the oral care probiotic market expands, many products contain bacterial species and strains with no documented health benefits leading to confusion and mistrust among consumers and clinicians. This confusion is enhanced by the regulatory status of probiotic products which puts the onus of safety and efficacy on the manufacturer rather than a central regulatory body. The overarching goal of this review is to provide consumers and clinicians with documented evidence supporting (or refuting) the health benefits of oral care probiotics marketed for sale in the United States. This includes defining what constitutes an oral care probiotic product and a strain level analysis of candidate probiotics from the genera Streptococcus, Lactobacillus, Bifidobacterium, and Bacillus. Additionally, prebiotics and postbiotics will be discussed. Finally, a set of considerations for consumers and clinicians is provided to empower probiotic product decision making. Together, this review will improve understanding of oral care probiotics marketed in the US for dental professionals and consumers.

Chemical Characterization and Effect of a Lactobacilli-Postbiotic on Streptococcus mutans Biofilm In Vitro

Postbiotic is the term used to define the soluble factors, metabolic products, or byproducts released by live probiotic bacteria or after its lysis. The objective of this study was to carry out the chemical characterization of the postbiotic of Lacticaseibacillus rhamnosus LR-32 and to evaluate its in vitro effect on the development of the Streptococcus mutans biofilm. After the cultivation of the probiotic strain, the postbiotic was extracted by centrifuging the culture and filtering the supernatant. This postbiotic was characterized by using gas chromatography coupled with mass spectrometry (GC-MS), and then it was used to determine the growth inhibition of S. mutans in its planktonic form; additionally, its effects on the following parameters in 48 h biofilm were evaluated: viable bacteria, dry weight, and gene expression of glucosyltransferases and VicR gene. The control group consisted of the biofilm without any treatment. A paired t-test was performed for statistical analysis, with the p-value set at 5%. Seventeen compounds of various chemical classes were identified in the postbiotic, including sugars, amino acids, vitamins, and acids. The treatment with the postbiotic led to an inhibition of the growth of S. mutans in its planktonic form, as well as a decrease in the number of viable bacteria, reduction in dry weight, and a negative regulation of the gene expression of gtfB, gtfC, gtfD, and vicR in its biofilm state, compared with the nontreated group (p < 0.05). The postbiotic of L. rhamnosus impaired the development of S. mutans biofilm.

Lactobacillus-derived components for inhibiting biofilm formation in the food industry

Biofilm, a microbial community formed by especially pathogenic and spoilage bacterial species, is a critical problem in the food industries. It is an important cause of continued contamination by foodborne pathogenic bacteria. Therefore, removing biofilm is the key to solving the high pollution caused by foodborne pathogenic bacteria in the food industry. Lactobacillus, a commonly recognized probiotic that is healthy for consumer, have been proven useful for isolating the potential biofilm inhibitors. However, the addition of surface components and metabolites of Lactobacillus is not a current widely adopted biofilm control strategy at present. This review focuses on the effects and preliminary mechanism of action on biofilm inhibition of Lactobacillus-derived components including lipoteichoic acid, exopolysaccharides, bacteriocins, secreted protein, organic acids and some new identified molecules. Further, the review discusses several modern biofilm identification techniques and particularly interesting new technology of biofilm inhibition molecules. These molecules exhibit stronger inhibition of biofilm formation, playing a pivotal role in food preservation and storage. Overall, this review article discusses the application of biofilm inhibitors produced by Lactobacillus, which would greatly aid efforts to eradicate undesirable bacteria from environment in the food industries.

Limosilactobacillus reuteri inhibits the acid tolerance response in oral bacteria

Probiotic bacteria show promising results in prevention of the biofilm-mediated disease caries, but the mechanisms are not fully understood. The acid tolerance response (ATR) allows biofilm bacteria to survive and metabolize at low pH resulting from microbial carbohydrate fermentation. We have studied the effect of probiotic strains: Limosilactobacillus reuteri and Lacticaseibacillus rhamnosus on ATR induction in common oral bacteria. Communities of L. reuteri ATCC PTA5289 and Streptoccus gordonii, Streptococcus oralis, Streptococcus mutans or Actinomyces naeslundii in the initial stages of biofilm formation were exposed to pH 5.5 to allow ATR induction, followed by a low pH challenge. Acid tolerance was evaluated as viable cells after staining with LIVE/DEAD®BacLight™. The presence of L. reuteri ATCC PTA5289 caused a significant reduction in acid tolerance in all strains except S. oralis. When S. mutans was used as a model organism to study the effects of additional probiotic strains (L. reuteri SD2112, L. reuteri DSM17938 or L. rhamnosus GG) as well as L. reuteri ATCC PTA5289 supernatant on ATR development, neither the other probiotic strains nor supernatants showed any effect. The presence of L. reuteri ATCC PTA5289 during ATR induction led to down-regulation of three key genes involved in tolerance of acid stress (luxS, brpA and ldh) in Streptococci. These data suggest that live cells of probiotic L. reuteri ATCC PTA5289 can interfere with ATR development in common oral bacteria and specific strains of L. reuteri may thus have a role in caries prevention by inhibiting development of an acid-tolerant biofilm microbiota.

Effect of Motiflor AS probiotic for oral health on cell viability in human gingival fibroblasts and human dental pulp stem cells

Objectives

In this study, it was aimed to investigate the possible effects of oral chewable probiotic tablets (PTs) produced to directly support the oral flora on the proliferation of human dental pulp stem cells (DPSCs) and human gingival fibroblast cells (HGFCs).

Materials and Methods

For analysis in this study, "Motiflor AS," a PT that dissolves in the mouth, containing 13.5mg Lactobacillus helveticus Rosell-52, L. rhamnosus Rosell-11, L. halivarus HA-118, and Bifidobacterium longum Rosell-175 was used. Cell survival and proliferation were analyzed by methyl-thiazole-diphenyl-tetrazolium (MTT) test and real-time cell analysis method (xCELLigence RTCA-DP) after 24-, 48-, and 72-h incubation periods.

Results

According to the data obtained with RTCA-DP software, there was a significant increase in the proliferation of human dental pulp stem cells (HDPSCs) and HGFCs in the 72-h incubation after PT application compared to the 24-h and 48-h incubations (P < 0.0001). After the MTT test, for HDPSCs, the cell proliferation rate was 62.8% and 85.6% in 24- and 48-h incubation, respectively, while HDPSCs cell proliferation rate in 72-h incubation was 135.2% (P < 0.0001). For HGFCs, the cell proliferation rate was 73% and 120.4% in 24- and 48-h incubation, respectively, while HDPSCs cell proliferation rate in 72-h incubation was 139.8% (P < 0.0001). When the results of the two tests applied were evaluated together, the results showed compatibility.

Conclusions

Based on the results, it has been concluded that PT will be useful for maintaining oral health and for dental and gingival patients who will/have undergone dental treatment. It should be keep in mind that protecting our oral and dental health is very important in terms of protecting our general health.

Can acid produced from probiotic bacteria alter the surface roughness, microhardness, and elemental composition of enamel? An in vitro study

Probiotics are live microorganisms that upon administration in adequate amounts provide various health benefits to the host. Probiotics are "lactic acid-producing bacteria" as they release large amounts of organic acids, particularly lactic acids, in their surrounding environment. Although the acids produced by probiotics are beneficial for gastrointestinal and vaginal health, the acidogenic nature of probiotics has raised concerns among dental professionals, especially concerning their effect on the enamel and dentin. Previous studies have found that probiotics can lower the pH of the saliva and cause essential elements like Calcium and Phosphorus to leach from the enamel. This can alter the surface topography of enamel and increase the risk of enamel defects. Studies have also noted that probiotic bacteria can replace cariogenic bacteria and lower the risk of tooth decay. However, the effect of acid produced by probiotics on the enamel surface remains unclear. Hence, the present study aims to evaluate the effect of probiotics on the surface roughness, microhardness, and elemental composition of enamel compared to 0.1 M Lactic acid (demineralizing agent). Twenty enamel sections were randomly divided into groups and subjected to a pH cycling model using a probiotic suspension and 0.1 M lactic acid. The changes in the surface roughness, microhardness, surface morphology, and elemental composition of the enamel with regard to Carbon, Oxygen, Sodium, Hydrogen, Magnesium, Phosphorus, Fluoride, Chlorine, and Calcium of the enamel were evaluated before and after the emersion in both the groups. The results showed a significant increase in the mean surface roughness in the probiotic group before and after the exposure. The microhardness of the enamel decreased along with altered arrangement of the enamel prisms, increased striations, scratch marks, and pitting after exposure to the probiotic group. A decrease in the atomic/weight% for Calcium, Phosphorous, Fluoride, Aluminium, and Oxygen and an increase in the weight/atomic% for Carbon, Nitrogen, and Sodium were noted compared to the baseline in the probiotic solution. The results in the probiotic group were comparable to the 0.1 M lactic acids. The pH changed from 5.78 to 3.06 at the end of 24 h in the probiotic group. Based on these findings, we conclude that exposure to probiotics can affect microhardness and surface roughness and cause leaching of essential elements like Calcium and Phosphorous from the enamel.

Postbiotic Metabolite of Lactiplantibacillus plantarum PD18 against Periodontal Pathogens and Their Virulence Markers in Biofilm Formation

Alternative methods to reduce infectious diseases caused by bacterial pathogens and their virulence factors, biofilm formations, have arisen to reduce the pressure on existing or currently developed disinfectants and antimicrobial agents. The current strategies for reducing the severity of periodontal pathogen-caused disease by using beneficial bacteria and their metabolites are highly desirable. Probiotic strains of lactobacilli related to foods from Thai-fermented foods were selected and their postbiotic metabolites (PM) were isolated with inhibitory activity on periodontal pathogens and their biofilm formation. The PM from Lactiplantibacillus plantarum PD18 (PD18 PM) with the highest antagonistic effect against Streptococcus mutans, Porphyromonas gingivalis, Tannerella forsythia and Prevotella loescheii was selected from 139 Lactobacillus isolates. The minimal inhibitory concentration (MIC) and minimum biofilm inhibitory concentration (MBIC) values of PD18 PM against the pathogens ranged from 1:2 to 1:4. The PD18 PM demonstrated the ability to prevent the biofilm formation of S. mutans and P. gingivalis by showing a significant reduction in viable cells, high percentages of biofilm inhibition at 92.95 and 89.68%, and the highest effective contact times at 5 and 0.5 min, respectively. L. plantarum PD18 PM showed potential as a promising natural adjunctive agent to inhibit periodontal pathogens and their biofilms.

In Vitro Preventive Effect and Mechanism of Action of Weissella cibaria CMU against Streptococcus mutans Biofilm Formation and Periodontal Pathogens

In this study, we evaluated the in vitro anti-biofilm, antibacterial, and anti-inflammatory activity of Weissella cibaria CMU (CMU), an oral probiotic, against periodontopathogens. Compared to other oral probiotics, CMU showed a superior inhibitory effect on the biofilm formation and growth of Streptococcus mutans on orthodontic wires and artificial teeth (p < 0.05). CMU exerted potent antibacterial effects against S. mutans and Porphyromonas gingivalis according to a line test. In human gingival fibroblasts (HGFs) stimulated by P. gingivalis, Fusobacterium nucleatum, or Prevotella intermedia, CMU suppressed the gene expression of pro-inflammatory cytokines [interleukin (IL)-6, IL-1β, IL-8, and tumor necrosis factor-α] in a dose-dependent manner (p < 0.05). CMU restored the production of the tissue inhibitor of metalloproteinase-1 following its inhibition by P. gingivalis, and it suppressed the expression of matrix metalloproteinase (MMP)-1 and -3 induced by periodontopathogens (p < 0.05). Moreover, CMU needed direct contact with HGFs to exert their anti-inflammatory function, indicating that they act directly on gingival cells to modulate local inflammation. Our preclinical study provides evidence for the potential benefits of topical CMU treatments in preventing the development of caries and periodontitis caused by the dysbiosis of the dental plaque microbiome.

Corrected and Republished from: "Understanding Lactobacillus paracasei and Streptococcus oralis Biofilm Interactions through Agent-Based Modeling"

As common commensals residing on mucosal tissues, Lactobacillus species are known to promote health, while some Streptococcus species act to enhance the pathogenicity of other organisms in those environments. In this study we used a combination of in vitro imaging of live biofilms and computational modeling to explore biofilm interactions between Streptococcus oralis, an accessory pathogen in oral candidiasis, and Lactobacillus paracasei, an organism with known probiotic properties. A computational agent-based model was created where the two species interact only by competing for space, oxygen, and glucose. Quantification of bacterial growth in live biofilms indicated that S. oralis biomass and cell numbers were much lower than predicted by the model. Two subsequent models were then created to examine more complex interactions between these species, one where L. paracasei secretes a surfactant and another where L. paracasei secretes an inhibitor of S. oralis growth. We observed that the growth of S. oralis could be affected by both mechanisms. Further biofilm experiments support the hypothesis that L. paracasei may secrete an inhibitor of S. oralis growth, although they do not exclude that a surfactant could also be involved. This contribution shows how agent-based modeling and experiments can be used in synergy to address multiple-species biofilm interactions, with important roles in mucosal health and disease. IMPORTANCE We previously discovered a role of the oral commensal Streptococcus oralis as an accessory pathogen. S. oralis increases the virulence of Candida albicans infections in murine oral candidiasis and epithelial cell models through mechanisms which promote the formation of tissue-damaging biofilms. Lactobacillus species have known inhibitory effects on biofilm formation of many microbes, including Streptococcus species. Agent-based modeling has great advantages as a means of exploring multifaceted relationships between organisms in complex environments such as biofilms. Here, we used an iterative collaborative process between experimentation and modeling to reveal aspects of the mostly unexplored relationship between S. oralis and L. paracasei in biofilm growth. The inhibitory nature of L. paracasei on S. oralis in biofilms may be exploited as a means of preventing or alleviating mucosal fungal infections.

Evaluation of Probiotic Effects of Lactobacilli on Mutans Streptococci: An In Vitro Study

AIM

The aim of the present study is to evaluate the probiotic effect of Lactobacillus acidophilus and Lactobacillus rhamnosus on clinical isolates of Mutans Streptococci (MS) and antibiotic susceptibility of these strains to commonly used antibiotics in dentistry.

MATERIALS AND METHODS

Plaque samples from permanent first molars were collected and transferred aseptically onto Mitis-Salivarius agar and incubated at 37°C for 24 hours in the presence of 5-10% CO₂. Mutans streptococci colonies were identified biochemically using Hi-Strep identification kit. The inhibitory activity of the clinical strains of MS on Lactobacilli was investigated using agar-overlay interference technique. Positive inhibition was appreciated as a clear zone around the Lactobacilli. Disk diffusion assay was done as described by CLSI M100-S25 for antibiotic susceptibility. The zone of growth inhibition caused by Lactobacilli and antibiotics on MS clinical strains was measured directly using a vernier caliper. Statistical analysis was done using independent t-test.

RESULTS

Mutans streptococci exhibited positive inhibition with both the probiotic strains and L. acidophilus showed more zones of inhibition than L. rhamnosus. Antibiotic susceptibility of clinical strains of MS showed sensitivity to penicillin and vancomycin, however, tetracycline and erythromycin showed very few resistant strains. The highest zone of inhibition was shown by cephalothin followed by penicillin, tetracycline, ciprofloxacin, erythromycin, and vancomycin.

CONCLUSION

L. rhamnosus and L. acidophilus have strong inhibitory effects on clinical strains of MS. Lactobacillus acidophilus showed a higher zone of inhibition. All the clinical strains of MS were sensitive to penicillin and vancomycin. The highest zone of inhibition was shown by cephalothin.

CLINICAL SIGNIFICANCE

Dental caries remains silent epidemic and increasing antibiotic resistance is another major challenge that threatens the world. Newer methods such as whole-bacteria replacement therapy using probiotics for decreasing harmful oral pathogens and reducing the intake of antibiotics must be explored. More researches to promote use of probiotics should be initiated due to its possible preventive and health maintenance benefits providing an end to new cavities and antibiotic resistance.

Postbiotics Derived from L. paracasei ET-22 Inhibit the Formation of S. mutans Biofilms and Bioactive Substances: An Analysis

Globally, dental caries is one of the most common non-communicable diseases for patients of all ages; Streptococcus mutans (S. mutans) is its principal pathogen. Lactobacillus paracasei (L. paracasei) shows excellent anti-pathogens and immune-regulation functions in the host. The aim of this study is to evaluate the effects of L. paracasei ET-22 on the formation of S. mutans biofilms. The living bacteria, heat-killed bacteria, and secretions of L. paracasei ET-22 were prepared using the same number of bacteria. In vitro, they were added into artificial-saliva medium, and used to coculture with the S. mutans. Results showed that the living bacteria and secretions of L. paracasei ET-22 inhibited biofilm-growth, the synthesis of water-soluble polysaccharide and water-insoluble polysaccharide, and virulence-gene-expression levels related to the formation of S. mutans biofilms. Surprisingly, the heat-killed L. paracasei ET-22, which is a postbiotic, also showed a similar regulation function. Non-targeted metabonomics technology was used to identify multiple potential active-substances in the postbiotics of L. paracasei ET-22 that inhibit the formation of S. mutans biofilms, including phenyllactic acid, zidovudine monophosphate, and citrulline. In conclusion, live bacteria and its postbiotics of L. paracasei ET-22 all have inhibitory effects on the formation of S. mutans biofilm. The postbiotics of L. paracasei ET-22 may be a promising biological anticariogenic-agent.

Antibiofilm activity and NMR-based metabolomic characterization of cell-free supernatant of Limosilactobacillus reuteri DSM 17938

The microbial biofilm has been defined as a "key virulence factor" for a multitude of microorganisms associated with chronic infections. Its multifactorial nature and variability, as well as an increase in antimicrobial resistance, suggest the need to identify new compounds as alternatives to the commonly used antimicrobials. The aim of this study was to assess the antibiofilm activity of cell-free supernatant (CFS) and its sub-fractions (SurE 10 K with a molecular weight <10 kDa and SurE with a molecular weight <30 kDa), produced by Limosilactobacillus reuteri DSM 17938, vs. biofilm-producing bacterial species. The minimum inhibitory biofilm concentration (MBIC) and the minimum biofilm eradication concentration (MBEC) were determined via three different methods and an NMR metabolomic analysis of CFS and SurE 10K was performed to identify and quantify several compounds. Finally, the storage stability of these postbiotics was evaluated by a colorimetric assay by analyzing changes in the CIEL*a*b parameters. The CFS showed a promising antibiofilm activity against the biofilm developed by clinically relevant microorganisms. The NMR of CFS and SurE 10K identifies and quantifies several compounds, mainly organic acids and amino acids, with lactate being the most abundant metabolite in all the analyzed samples. The CFS and SurE 10 K were characterized by a similar qualitative profile, with the exception of formate and glycine detected only in the CFS. Finally, the CIEL*a*b parameters assess the better conditions to analyze and use these matrices for the correct preservation of bioactive compounds.

Identification of a new probiotic strain, Lactiplantibacillus plantarum VHProbi® V38, and its use as an oral health agent

Introduction

Probiotics can be used to treat oral diseases such as dental caries, gingivitis, periodontitis, and halitosis.

Methods

This study screened for strains capable of inhibiting Streptococcus mutans,one of the primary pathogenic bacteria responsible for dental caries by agar diffusion in different samples. Strain identification was performed by 16S rDNA sequencing and the API 50CH system. The potential functions of the strains in terms of oral health properties were also tested by agglutination assays, growth inhibition assays, adhesion assays, biofilm removal assays and inhibition of adhesion in human primary gingival epithelial (HPGE) cells assays.

Results

This study identified a probiotic strain from fermented cabbages that has a strong inhibitory effect on Streptococcus mutans. The API 50CH system and 16S rDNA sequencing verified that this was a new strain and it was given the name, Lactiplantibacillus plantarum VHProbi^®V38. Agglutination, growth inhibition and adhesion, and biofilm removal tests indicated that L. plantarum VHProbi^® V38 inhibited and reduced S. mutans. This probiotic was shown to have a broad antibacterial spectrum, simultaneously inhibiting the growth of periodontal pathogenic bacteria such as Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Fusobacterium nucleatum. After 2 hours of co-cultivation with these pathogens, L. plantarum VHProbi^® V38 was able to significantly reduce pathogens adhesion on human primary gingival epithelial (HPGE) cells.

Discussion

These findings suggest that L. plantarum VHProbi^® V38 could potentially prevent and treat periodontal diseases caused by these pathogenic bacteria. L. plantarum VHProbi^® V38 also adheres strongly to HPGE cells and thus has potential as an oral probiotic. This study describes new methods that can be used to aid the screening and identification of oral probiotics.

Biofilms and Benign Colonic Diseases

The colon has a very large surface area that is covered by a dense mucus layer. The biomass in the colon includes 500-1000 bacterial species at concentrations of ~10¹² colony-forming units per gram of feces. The intestinal epithelial cells and the commensal bacteria in the colon have a symbiotic relationship that results in nutritional support for the epithelial cells by the bacteria and maintenance of the optimal commensal bacterial population by colonic host defenses. Bacteria can form biofilms in the colon, but the exact frequency is uncertain because routine methods to undertake colonoscopy (i.e., bowel preparation) may dislodge these biofilms. Bacteria in biofilms represent a complex community that includes living and dead bacteria and an extracellular matrix composed of polysaccharides, proteins, DNA, and exogenous debris in the colon. The formation of biofilms occurs in benign colonic diseases, such as inflammatory bowel disease and irritable bowel syndrome. The development of a biofilm might serve as a marker for ongoing colonic inflammation. Alternatively, the development of biofilms could contribute to the pathogenesis of these disorders by providing sanctuaries for pathogenic bacteria and reducing the commensal bacterial population. Therapeutic approaches to patients with benign colonic diseases could include the elimination of biofilms and restoration of normal commensal bacteria populations. However, these studies will be extremely difficult unless investigators can develop noninvasive methods for measuring and identifying biofilms. These methods that might include the measurement of quorum sensing molecules, measurement of bile acids, and identification of bacteria uniquely associated with biofilms in the colon.

Lactobacilli, a Weapon to Counteract Pathogens through the Inhibition of Their Virulence Factors

To date, several studies have reported an alarming increase in pathogen resistance to current antibiotic therapies and treatments. Therefore, the search for effective alternatives to counter their spread and the onset of infections is becoming increasingly important.

Discovery of Novel Iminosugar Compounds Produced by Lactobacillus paragasseri MJM60645 and Their Anti-Biofilm Activity against Streptococcus mutans

The oral cavity contains a number of microbes. They interact with each other and play an important role in human health. Among oral cariogenic microbes, Streptococcus mutans is recognized a major etiological bacteria of dental caries. Lactobacilli strains have been promoted as possible probiotic agents against S. mutans. However, their inhibitory mechanism has not been well elucidated yet. In the present study, two new compounds with strong antibiofilm activities were purified from the culture supernatant of Lactobacillus paragasseri MJM60645, which was isolated from the human oral cavity. These compounds showed strong inhibitory activities against S. mutans biofilm formation, with IC50 (concentration at which 50% biofilm was inhibited) of 30.4 μM for compound 1 and 18.9 μM for compound 2. However, these compounds did not show bactericidal activities against S. mutans. Structure elucidation by nuclear magnetic resonance (NMR) and mass spectrometry showed that compound 1 was composed of two arabinofuranose iminosugars jointed with one glycerol and oleic acid, and compound 2 was composed of two arabinofuranose iminosugars jointed with one glycerol and nervonic acid. To the best of our knowledge, these structures were discovered for the first time in this study. Treatment of S. mutans with compound 1 strongly downregulated expression levels of genes related to biofilm formation, including gtfB, gtfC, gtfD, gbpB, brpA, spaP, ftf, and smu0630 without affecting the expression of comDE or relA. This study provides new insights into novel molecules produced by Lactobacillus to regulate the pathogenesis of S. mutans, facilitating a better understanding of the mechanism for interactions between Lactobacillus and S. mutans. IMPORTANCE In this study, we isolated lactic acid bacteria that inhibit streptococcal biofilm from the oral cavity of infants and identified two novel compounds from the supernatant of their culture broth. The two compounds are structurally similar, and both consist of iminosugars, glycerol, and unsaturated fatty acid. A search of the SciFinder database revealed that these structures are novel and were discovered for the first time in this study. Mechanism studies have shown that these compounds can inhibit the expression of biofilm synthesis-related genes. This is the first report that lactic acid bacteria inhibit streptococcal biofilms by small molecules with new chemical structures. This study not only expands the understanding of natural products derived from lactic acid bacteria but also provides a new paradigm for the understanding of the interaction of bacteria in the oral microbiota.

Lactobacilli and human dental caries: more than mechanical retention

Lactobacilli have been considered as major contributors to human dental caries for over a century. Recent in vitro model studies have shown that when compared to Streptococcus mutans, a keystone pathogen of human dental caries, the ability of lactobacilli to form biofilms is poor, although differences exist between the different major species. Further studies using molecular and bioinformatics approaches provide evidence that multiple mechanisms, including adhesin-receptor mediated physical contact with S. mutans, facilitate the adherence and establishment of lactobacilli on the tooth surface. There is also evidence that under conditions like continuous sugar consumption, weak acids and other antimicrobials such as bacteriocins from lactobacilli can become detrimental to the microbial community, especially those in the proximity. Details on the underlying mechanisms of how different Lactobacillus sp. establish and persist in the highly complex microbiota on the tooth surface await further investigation.

Outside the limits of bacterial viability: postbiotics in the management of periodontitis

Periodontitis is a major cause of tooth loss in adults worldwide and is caused by an unbalanced oral microbiota in a susceptible host, ultimately leading to tissue breakdown and bone loss. Traditionally, the treatment for periodontitis is scaling and root planing; however, some cases require adjuvant therapy, such as antibiotics administration or surgery. Various factors are involved in the pathogenesis and interact in an unpredictable way, increasing the complexity of the disease and making it difficult to manage. In this context, the administration of probiotics aimed at resolving bacterial dysbiosis and the associated dysregulation of the immune system has been employed in clinical trials with encouraging results. However, the use of viable microorganisms is not risk-free, and immunocompromised patients may develop adverse effects. Therefore, the use of inactivated microbial cells, cell fractions, or soluble products and metabolites of probiotics, known as postbiotics, has gained increasing attention. In this commentary, we present the current literature assessing the impact of postbiotics on the growth and metabolism of periodontal pathogens, as well as on the progression of periodontitis in rodents and humans. We also discuss the limitations of the available data and what the scientific community should consider in order to transfer this innovative therapeutic modality from the bench to the bedside.

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.

Adjunctive probiotics after periodontal debridement versus placebo: a systematic review and meta-analysis

OBJECTIVE

To comprehensively investigate the efficacy of adjunctive probiotics compared to placebo, using conventional and novel treatment outcomes.

MATERIALS AND METHODS

Three databases (MEDLINE, EMBASE, and CENTRAL) were searched. Outcomes included percent change in the total number of deep sites before and after therapy, change in mean probing pocket depth (mm), percentage patients requiring additional therapy, risk for disease progression, and microbiological and immunological results. Meta-analysis was conducted to evaluate treatment effects wherever appropriate.

RESULTS

Ten studies were selected from 818 records. Meta-analysis showed that adjunctive probiotics had no additional benefit for percentage change of the total number of deeper sites (≥5 mm, ≥6 mm, ≥7 mm) before and after therapy. No significant difference was observed for mean probing pocket depth reduction at 3 and 6 months. Statistically significant beneficial odds ratios for need for additional therapy (OR = 0.19, 95% CI [0.07-0.56]) and risk of disease progression (OR = 0.32, 95% CI [0.14-0.73]) were observed with probiotic administration. Immunological rather than microbiological outcomes correlated more consistently with clinical findings. No adverse events were reported.

CONCLUSIONS

Adjunctive probiotics are safe in systemically healthy individuals and could offer additional patient-level benefits compared to placebo, hence its use can sometimes be justified.

Lactobacilli as Anti-biofilm Strategy in Oral Infectious Diseases: A Mini-Review

The spread of biofilm-related diseases in developed countries has led to increased mortality rates and high health care costs. A biofilm is a community of microorganisms that is irreversibly attached to a surface, behaving very differently from planktonic cells and providing resistance to antimicrobials and immune response. Oral diseases are an excellent example of infection associated with the formation of highly pathogenic biofilms. It is generally accepted that, when the oral homeostasis is broken, the overgrowth of pathogens is facilitated. Among them, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans are the main etiological agents of periodontitis, while Streptococcus mutans is strongly associated with the onset of dental caries. Other microorganisms, such as the fungus Candida albicans, may also be present and contribute to the severity of infections. Since the common antibiotic therapies usually fail to completely eradicate biofilm-related oral diseases, alternative approaches are highly required. In this regard, the topical administration of probiotics has recently gained interest in treating oral diseases. Thus, the present mini-review focuses on the possibility of using Lactobacillus spp. as probiotics to counteract biofilm-mediated oral infections. Many evidence highlight that Lactobacillus living cells can impede the biofilm formation and eradicate mature biofilms of different oral pathogens, by acting through different mechanisms. Even more interestingly, lactobacilli derivatives, namely postbiotics (soluble secreted products) and paraprobiotics (cell structural components) are able to trigger anti-biofilm effects too, suggesting that they can represent a novel and safer alternative to the use of viable cells in the management of biofilm-related oral diseases.

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.

Understanding Lactobacillus paracasei and Streptococcus oralis Biofilm Interactions through Agent-Based Modeling

As common commensals residing on mucosal tissues, Lactobacillus species are known to promote health, while some Streptococcus species act to enhance the pathogenicity of other organisms in those environments. In this study, we used a combination of in vitro imaging of live biofilms and computational modeling to explore biofilm interactions between Streptococcus oralis, an accessory pathogen in oral candidiasis, and Lactobacillus paracasei, an organism with known probiotic properties. A computational agent-based model was created where the two species interact only by competing for space, oxygen and glucose. Quantification of bacterial growth in live biofilms indicated that S. oralis biomass and cell numbers were much lower than predicted by the model. Two subsequent models were then created to examine more complex interactions between these species, one where L. paracasei secretes a surfactant, and another where L. paracasei secretes an inhibitor of S. oralis growth. We observed that the growth of S. oralis could be affected by both mechanisms. Further biofilm experiments support the hypothesis that L. paracasei may secrete an inhibitor of S. oralis growth, although they do not exclude that a surfactant could also be involved. This contribution shows how agent-based modeling and experiments can be used in synergy to address multiple species biofilm interactions, with important roles in mucosal health and disease. IMPORTANCE We previously discovered a role of the oral commensal Streptococcus oralis as an accessory pathogen. S. oralis increases the virulence of Candida albicans infections in murine oral candidiasis and epithelial cell models through mechanisms which promote the formation of tissue-damaging biofilms. Lactobacillus species have known inhibitory effects on biofilm formation of many microbes, including Streptococcus species. Agent-based modeling has great advantages as a means of exploring multifaceted relationships between organisms in complex environments such as biofilms. Here, we used an iterative collaborative process between experimentation and modeling to reveal aspects of the mostly unexplored relationship between S. oralis and L. paracasei in biofilm growth. The inhibitory nature of L. paracasei on S. oralis in biofilms may be exploited as a means of preventing or alleviating mucosal fungal infections.

Lactobacillus plantarum Lipoteichoic Acids Possess Strain-Specific Regulatory Effects on the Biofilm Formation of Dental Pathogenic Bacteria

Bacterial biofilm residing in the oral cavity is closely related to the initiation and persistence of various dental diseases. Previously, we reported the anti-biofilm activity of Lactobacillus plantarum lipoteichoic acid (Lp.LTA) on a representative dental cariogenic pathogen, Streptococcus mutans. Since LTA structure varies in a bacterial strain-specific manner, LTAs from various L. plantarum strains may have differential anti-biofilm activity due to their distinct molecular structures. In the present study, we isolated Lp.LTAs from four different strains of L. plantarum (LRCC 5193, 5194, 5195, and 5310) and compared their anti-biofilm effects on the dental pathogens, including S. mutans, Enterococcus faecalis, and Streptococcus gordonii. All Lp.LTAs similarly inhibited E. faecalis biofilm formation in a dose-dependent manner. However, their effects on S. gordonii and S. mutans biofilm formation were different: LRCC 5310 Lp.LTA most effectively suppressed the biofilm formation of all strains of dental pathogens, while Lp.LTAs from LRCC 5193 and 5194 hardly inhibited or even enhanced the biofilm formation. Furthermore, LRCC 5310 Lp.LTA dramatically reduced the biofilm formation of the dental pathogens on the human dentin slice infection model. Collectively, these results suggest that Lp.LTAs have strain-specific regulatory effects on biofilm formation of dental pathogens and LRCC 5310 Lp.LTA can be used as an effective anti-biofilm agent for the prevention of dental infectious diseases.

Effects of probiotic and fluoride mouthrinses on Streptococcus mutans in dental plaque around orthodontic brackets: A preliminary explorative randomized placebo-controlled clinical trial

Background:

Although it is shown that probiotic agents might reduce Streptococcus mutans, no study has evaluated this effect in the form of probiotic mouthrinse. The purpose of this study was to compare the effect of probiotic experimental mouthwash Lactobacillus plantarum versus sodium fluoride and placebo mouthwashes on the number of S. mutans present in dental plaque around orthodontic brackets in fixed orthodontic patients.

Materials and Methods:

This study was a randomized clinical trial. The total of 38 patients participate consisting of 12 patients in the fluoride group, 13 in the probiotic, and 12 in the placebo group. They were given mouthwashes to use twice a day for 2 weeks. Plaque sampling was performed using the 4-pass technique in all three groups in two stages: before the intervention and after 2 weeks of using the mouthwash. The number of bacteria present in the dental plaque was then reported based on the number of colonies grown on agar medium. Data were analyzed using Kruskal–Wallis and Wilcoxon tests (α = 0.05).

Results:

Gender distribution, mean age, and protocol adherence were not significantly different among all three groups. After the intervention, the number of S. mutans present in the dental plaque followed an increasing manner in the placebo (P = 0.005) and probiotic (P = 0.158) groups and decreased in fluoride group (P = 0.025).

Conclusion:

The L. plantarum probiotic mouthwash was ineffective in reduction of S. mutans in dental plaque. However, fluoride mouthwash is considerably effective against S. mutans and thus recommended.

Lactiplantibacillus plantarum 299v (LP299V®): three decades of research

This review aims to provide a comprehensive overview of the in vitro, animal, and clinical studies with the bacterial strain Lactiplantibacillus plantarum 299v (L. plantarum 299v; formerly named Lactobacillus plantarum 299v) published up until June 30, 2020. L. plantarum 299v is the most documented L. plantarum strain in the world, described in over 170 scientific publications out of which more than 60 are human clinical studies. The genome sequence of L. plantarum 299v has been determined and is available in the public domain (GenBank Accession number: NZ_LEAV01000004). The probiotic strain L. plantarum 299v was isolated from healthy human intestinal mucosa three decades ago by scientists at Lund University, Sweden. Thirty years later, a wealth of data coming from in vitro, animal, and clinical studies exist, showing benefits primarily for gastrointestinal health, such as reduced flatulence and abdominal pain in patients with irritable bowel syndrome (IBS). Moreover, several clinical studies have shown positive effects of L. plantarum 299v on iron absorption and more recently also on iron status. L. plantarum 299v is safe for human consumption and does not confer antibiotic resistance. It survives the harsh conditions of the human gastrointestinal tract, adheres to mannose residues on the intestinal epithelial cells and has in some cases been re-isolated more than ten days after administration ceased. Besides studying health benefits, research groups around the globe have investigated L. plantarum 299v in a range of applications and processes. L. plantarum 299v is used in many different food applications as well as in various dietary supplements. In a freeze-dried format, L. plantarum 299v is robust and stable at room temperature, enabling long shelf-lives of consumer healthcare products such as capsules, tablets, or powder sachets. The strain is patent protected for a wide range of indications and applications worldwide as well as trademarked as LP299V^®.

In Vitro Anti-Biofilm and Antibacterial Properties of Streptococcus downii sp. nov

The aim of this study was to evaluate the potential anti-biofilm and antibacterial activities of Streptococcus downii sp. nov. To test anti-biofilm properties, Streptococcus mutans, Actinomyces naeslundii, Veillonella parvula, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans were grown in a biofilm model in the presence or not of S. downii sp. nov. for up to 120 h. For the potential antibacterial activity, 24 h-biofilms were exposed to S. downii sp. nov for 24 and 48 h. Biofilms structures and bacterial viability were studied by microscopy, and the effect in bacterial load by quantitative polymerase chain reaction. A generalized linear model was constructed, and results were considered as statistically significant at p < 0.05. The presence of S. downii sp. nov. during biofilm development did not affect the structure of the community, but an anti-biofilm effect against S. mutans was observed (p < 0.001, after 96 and 120 h). For antibacterial activity, after 24 h of exposure to S. downii sp. nov., counts of S. mutans (p = 0.019) and A. actinomycetemcomitans (p = 0.020) were significantly reduced in well-structured biofilms. Although moderate, anti-biofilm and antibacterial activities of S. downii sp. nov. against oral bacteria, including some periodontal pathogens, were demonstrated in an in vitro biofilm model.

We Are One: Multispecies Metabolism of a Biofilm Consortium and Their Treatment Strategies

The ecological and medical significance of bacterial biofilms have been well recognized. Biofilms are harder to control than their planktonic free-living counterparts and quite recently, the focus of the study has shifted to the multispecies consortia, which represent the vast majority of real-case infection scenarios. Studies have begun to explore the complex interspecies interactions within these biofilms. However, only little attention is currently given to the role of cellular metabolites in the cell-to-cell communication. The concentration gradients of metabolic substrates and products affect the spatial growth of bacteria in multispecies biofilm. This, if looked into more deeply, can lead to identification of potential therapies targeting the specific metabolites and hence the coordinated protection in the bacterial community. Herein, we review the interspecies communications, including their metabolic cross-talking, in multispecies biofilm, to signify the importance of such interactions on the initial formation and subsequent growth of these biofilms. Multispecies biofilms with their species heterogeneity are more resilient to antimicrobial agents than their single species biofilm counterparts and this characteristic is of particular interest when dealing with pathogenic bacteria. In this Review, we also discuss the treatment options available, to include current and emerging avenues to combat pathogenic multispecies biofilms in the clinical, environmental, as well as industrial settings.

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.

Advances in Bacterial Biofilm Management for Maintaining Microbiome Homeostasis

Certain microbial biofilm in the human-microbiota community can negatively impact the host microbiome. This gives rise to various methods to prevent the formation of biofilms or to facilitate biofilm dispersal from surfaces and tissues in the host. Despite all these efforts, these persistent microbial biofilms on surfaces and in the host tissue can result in health problems to the host and its microbiome. It is the adaptive behavior of microbes within the biofilm that confers on these tenacious microbes the resistance to harsh environments, antibiotic treatments, and the ability to evade the host immune system. In this review, the approaches to combat microbial biofilm in the last decade are discussed. The biochemical pathway regulating biofilm formation is first discussed, followed by the discussion of the three approaches to combat biofilm formation: physical, chemical, and biological approaches. The advances in these approaches have given rise to methods of effectively dispersing the microbial biofilm and preventing the adherence of these microbial communities altogether. As there are numerous approaches to target biofilm, in this review the attempt is to provide insights on how these approaches have been used to modulate the host-microbiome by looking at the individual strengths and weaknesses.

Potential Properties of Lactobacillus plantarum F-10 as a Bio-control Strategy for Wound Infections

In this study, Lactobacillus plantarum F-10, a promising probiotic strain isolated from fecal microbiota of healthy breastfed infant, was assessed as a bio-control strategy for wound infections. Pseudomonas aeruginosa PAO1/ATCC 27853, methicillin-resistant Staphylococcus aureus ATCC 43300, and their hospital-derived strains isolated from skin chronic wound samples were used as important skin pathogens. The cell-free extract (CFE) of the strain F-10 was shown to inhibit the growth of all pathogens tested, while no inhibition was observed when CFE was neutralized. The strain displayed no hemolysis and exhibited a strong auto-aggregating phenotype (51.48 ± 1.45%, 5 h) as well as co-aggregation. Antibiotic resistance profile was found to be safe according to the European Food Safety Authority. Biofilm formation was measured by crystal violet assay and visualized with scanning electron microscopy and confocal laser scanning microscopy. One hundred percent reduction in biofilm formation of all pathogens tested was obtained by sub-MIC value (12.5 mg/ml) of CFE following 24-h co-incubation. Inhibition of quorum sensing-controlled virulence factors (motility, protease and elastase activity, production of pyocyanin and rhamnolipid) of P. aeruginosa strains was also observed. DPPH radical scavenging activity of the CFE was determined as 88.57 ± 0.49%. In conclusion, our results suggest that L. plantarum F-10 may represent an alternative bio-control strategy against skin infections with its antimicrobial, anti-biofilm, anti-quorum sensing, and antioxidant activity.

Effects of a derivative of reutericin 6 and gassericin A on the biofilm of Streptococcus mutans in vitro and caries prevention in vivo

It is known that Streptococcus mutans (S. mutans) is the leading cariogenic pathogen. Recently, an increasing number of antimicrobial peptides (AMPs) have been brought into consideration as anti-caries agents. Here, we designed and synthesized an AMP derived from reutericin 6 and/or gassericin A, named LN-7, and explored its effect on biofilm of S. mutans UA159 in vitro and development of dental caries in vivo. Antibacterial assays showed that LN-7 was more active against S. mutans (3.2 μM) than many peptide-based agents, capable of killing other types of Streptococci in oral cavity. In addition, LN-7 presented fast killing kinetics, with more than 97% S. mutans killed within 5 min. The mechanism of the antimicrobial activity mainly lies on the disruption of bacterial membrane. Effects of LN-7 on the biofilm formation and the viability of preformed biofilm were quantified by crystal violet staining, which showed that LN-7 could effectively inhibit the biofilm accumulation of S. mutans. Moreover, the biofilm of S. mutans treated with LN-7 displayed notable changes in bacterial viability and morphology, observed by confocal laser scanning microscopy and scanning electron microscopy. In addition, topical oral treatment with LN-7 could suppress the development of dental caries in vivo, reducing the occurrence of severe dental lesion in a rodent model. These results reveal a new peptide-based agent as a topical treatment for dental caries, opening the door to clinical studies to explore its potential for caries prevention.

Inhibition of Streptococcus mutans Biofilm Formation and Virulence by Lactobacillus plantarum K41 Isolated From Traditional Sichuan Pickles

Among cariogenic microbes, Streptococcus mutans is considered a major etiological pathogen of dental caries. Lactobacilli strains have been promoted as possible probiotic agents against S. mutans, although the inhibitory effect of Lactobacilli on caries has not yet been properly addressed. The objective of this study was to screen Lactobacillus strains found in traditional Sichuan pickles and to evaluate their antagonistic properties against S. mutans in vitro and in vivo. In the current study, we analyzed 54 Lactobacillus strains isolated from pickles and found that strain L. plantarum K41 showed the highest inhibitory effect on S. mutans growth as well as on the formation of exopolysaccharides (EPS) and biofilm in vitro. Scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM) revealed the reduction of both EPS and of the network-like structure in S. mutans biofilm when these bacteria were co-cultured with strain L. plantarum K41. Furthermore, when rats were treated with strain L. plantarum K41, there was a significant reduction in the incidence and severity of dental caries. Due to K41's origin in a high salinity environment, it showed a high tolerance to acids and salts. This may give this strain an advantage in harsh oral conditions. Results showed that L. plantarum K41 isolated from traditional Sichuan pickles effectively inhibited S. mutans biofilm formation and thus possesses a potential inhibitory effect on dental caries in vivo.

Inhibitory and preventive effects of Lactobacillus plantarum FB-T9 on dental caries in rats

Streptococcus mutans is recognized as the main cause of dental caries, and the formation of a plaque biofilm is required for caries development. This study aimed to determine the inhibitory effect of Lactobacillus plantarum FB-T9 on S. mutans biofilm formation in vitro and on the prevention and treatment of dental caries in rats. During in vitro experiments, FB-T9 exhibited good bacteriostatic ability in a plate competition assay. This strain also significantly reduced the biomass and viability of S. mutans biofilms and induced structural damage during the early (6 h), middle (12 h) and late (24 h) stages of biofilm formation. In a 70-day in vivo experiment, FB-T9 significantly reduced the levels of S. mutans on the dental surfaces of rats by more than 2 orders of magnitude of the levels in the dental caries model group (p < 0.05). Moreover, FB-T9 significantly reduced the caries scores (modified Keyes scoring method) in both the prevention and treatment groups (p < 0.05) and had great colonization potential in the oral cavity. These results indicate the potential usefulness of L. plantarum FB-T9 as a probiotic for the prevention and treatment of caries.

Heat-killed Lactobacillus reuteri and cell-free culture supernatant have similar effects to viable probiotics during interaction with Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

In the last decade, numerous studies have been published to clarify the role of probiotics, especially Lactobacillus reuteri, as an adjunct to conventional periodontal treatment. Although the health benefits of probiotics are numerous, they are live bacteria, and the administration of live organisms is not risk-free. We evaluated the antimicrobial effect of L reuteri and its cell-free culture supernatant on Porphyromonas gingivalis, a keystone periodontal pathogen, in vitro. We also evaluated the influence of this probiotic in its live, heat-killed (HKL, paraprobiotic) form and its supernatant on the Galleria mellonella invertebrate model after infection by P gingivalis.

METHODS

The interaction assay was conducted with P gingivalis and L reuteri preparations (live cells and supernatant preparation). For this, P gingivalis and L reuteri preparations were added to tubes containing Brain Heart Infusion broth and incubated for 3 days. The suspensions were then seeded onto appropriate culture media for the calculation of colony-forming units per mL (CFU/mL). An in vivo assay with the G mellonella model was also performed. Live L reuteri, HKL, or supernatant was inoculated 2 hours prior to infection with P gingivalis. Survival was evaluated over 7 days, and the number of hemocytes in the hemolymph was estimated 3 hours after P gingivalis infection. Data were then subjected to statistical testing (α = 5%).

RESULTS

Both live L reuteri and its supernatant had antimicrobial activity against P gingivalis (CFU reduction up to 86%, P < .05). Moreover, treatment with live and HKL had similar effects on G mellonella survival (increased survival up to 46%, P < .05). However, only live L reuteri was able to significantly increase the hemocyte density in this invertebrate model.

CONCLUSION

Lactobacillus reuteri antimicrobial activity against P gingivalis and its effects on G mellonella survival after infection with a periodontopathogen do not depend on cell viability. This allows the development of products without live bacterium while maintaining similar effects.

Antibacterial and Remineralization Efficacy of Casein Phosphopeptide, Glycomacropeptide Nanocomplex, and Probiotics in Experimental Toothpastes: An In Vitro Comparative Study

Objective  This article evaluates the antibacterial and remineralization potential of experimentally prepared toothpastes containing different mixtures of nano casein phosphopeptides (nCPP), nano amorphous calcium phosphate (nACP), probiotic ­ Lactobacillus rhamnosus B-445 ( L. rhamnosus ), and nano glycomacropeptide (nGMP).

Materials and Methods  Five experimental toothpaste samples were prepared and grouped, such that group (A0) was the experimental toothpaste base formula. Groups (A1), (A2), (A3), and (A4) were the experimental toothpastes containing: nCPP; nCPP and nACP; nCPP, nACP, and L. rhamnosus , and nCPP, nACP, and nGMP, ­respectively. Group (A5) was the commercial group (GC MI Paste Plus). The five groups were screened against Streptococcus mutans (ATCC 25175) growth, and investigated for their remineralizing potentials on demineralized bovine enamel using Vickers ­microhardness test (Vickers hardness number [VHN]). Scanning electron microscope (SEM) images were obtained for the demineralized and remineralized enamel of the two most effective toothpastes against in vitro bacterial induced enamel demineralization. Statistical analysis was performed using one-way analysis of variance (ANOVA) as well as repeated measures ANOVA followed by Tukey’s post hoc test.

Results  Both (A3) and (A4) were significantly higher in mean inhibition zone ­diameters than group (A1) and (A2). Group (A4) showed the highest statistical ­significance in the mean difference between VHN values of demineralization and 15 days remineralization period. SEM images showed the deposition of nano-sized particles fill the ­microrough surface pattern of the etched enamel.

Conclusion  All these findings suggest the use of probiotic, nCPP–nACP, and nGMP as a dental anticariogenic and remineralizing active agents.

Rational design of peptides with enhanced antimicrobial and anti-biofilm activities against cariogenic bacterium Streptococcus mutans

Streptococcus mutans (S. mutans) is known to be a leading cariogenic pathogen in the oral cavity. Antimicrobial peptides possess excellent properties to combat such pathogens. In this study, we compared the antimicrobial activity of novel linear reutericin 6- and/or gassericin A-inspired peptides and identified LR-10 as the leading peptide. Antibacterial assays demonstrate that LR-10 is more active against S. mutans (3.3 μM) than many peptide-based agents without resistance selection, capable of killing many oral pathogens, and tolerant of physiological conditions. LR-10 also presented a faster killing rate than chlorhexidine and erythromycin, and appeared to display selective activity against S. mutans within 10 s. S. mutans is usually encased in plaque biofilms. Biofilm inhibitory assays indicated that LR-10 had excellent inhibitory effect on the biofilm formation of S. mutans and biofilm-encased cells in vitro at low concentrations (6.5 μM). Consistent with most peptides, LR-10 kills S. mutans mainly by disrupting the cell membranes. Notably, both hemolytic activity assays and cytotoxicity tests indicated that LR-10 could keep biocompatible at the effective concentrations. Hence, LR-10 could be a good candidate for clinical treatment of dental caries.

The Gut and Parkinson's Disease-A Bidirectional Pathway

Humans evolved a symbiotic relationship with their gut microbiome, a complex microbial community composed of bacteria, archaea, protists, and viruses, including bacteriophages. The enteric nervous system (ENS) is a gateway for the bidirectional communication between the brain and the gut, mostly through the vagus nerve (VN). Environmental exposure plays a pivotal role in both the composition and functionality of the gut microbiome and may contribute to susceptibility to neurodegenerative disorders, such as Parkinson's disease (PD). The neuropathological hallmark of PD is the widespread appearance of alpha-synuclein aggregates in both the central and peripheral nervous systems, including the ENS. Many studies suggest that gut toxins can induce the formation of α-syn aggregates in the ENS, which may then be transmitted in a prion-like manner to the CNS through the VN. PD is strongly associated with aging and its negative effects on homeostatic mechanisms protecting from inflammation, oxidative stress, and protein malfunction. In this mini-review, we revisit some landmark discoveries in the field of Parkinson's research and focus on the gut-brain axis. In the process, we highlight evidence showing gut-associated dysbiosis and related microbial-derived components as important players and risk factors for PD. Therefore, the gut microbiome emerges as a potential target for protective measures aiming to prevent PD onset.

In vitro evaluation of probiotic strains for lactic acid production

Background

The growing interest on usage of probiotic lactobacilli in maintaining oral health has posed number of questions on its probable side effects. One such consideration could be an increased acid production in dental plaque, in turn leading to dental caries. Thus, the aim of this study was to comparatively evaluate the lactic acid producing ability of L. acidophilus and L. plantarum with and without dental plaque.

Material and Methods

The study consisted of five groups: 3 control groups (Supragingival plaque, L. acidophilus and L. plantarum) and 2 test groups (Supragingival plaque with L. acidophilus and Supragingival plaque with L. plantarum). 26 samples for each group were collected and their baseline spectrophotometric values were recorded. The acid production was initiated by adding 25?l fructose (10%) and stopped by centrifugation for 2 min. The concentration of the lactic acid produced was determined with the aid of COBAS INTEGRA 400 plus.

Results

On comparison of Lactic Acid estimation in mg/dl, the mean values of Plaque group was the highest followed by Plaque +L acidophilus, Plaque +L plantarum, L acidophilus and least in L plantarum. The posthoc analysis shows that the comparison of Group 1 (Plaque) and Group 2 (Plaque +L acidophilus) is statistically Significant results between all the groups except between the Plaque +L acidophilus and Plaque +L plantarum group.

Conclusions

The lactic acid producing ability of pure suspensions of L.acidophilus and L.plantarum and the lactic acid producing efficiency becomes more when they are added to the supragingival plaque. Key words:Probiotic, lactic Acid, plaque.

Endodontic biofilms: contemporary and future treatment options

Apical periodontitis is a biofilm-mediated infection. The biofilm protects bacteria from host defenses and increase their resistance to intracanal disinfecting protocols. Understanding the virulence of these endodontic microbiota within biofilm is essential for the development of novel therapeutic procedures for intracanal disinfection. Both the disruption of biofilms and the killing of their bacteria are necessary to effectively treat apical periodontitis. Accordingly, a review of endodontic biofilm types, antimicrobial resistance mechanisms, and current and future therapeutic procedures for endodontic biofilm is provided.

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.

Evaluating Streptococcus mutans Strain Dependent Characteristics in a Polymicrobial Biofilm Community

Aim: The purpose of this study was to investigate strain dependent differences of the cariogenic biofilm forming Streptococcus mutans within both simple and complex communities. Methods: A mono-species containing representative S. mutans clinical isolates (caries and non-caries), and a multispecies in vitro caries biofilm model containing Lactobacillus casei, Veillonella dispar, Fusobacterium nucleatum and Actinomyces naeslundii, and either of two representative S. mutans clinical isolates (caries and non-caries), was developed as a comparison model. Compositional analysis of total and live bacteria within biofilms, and transcriptional analysis of biofilm associated virulence factors were evaluated by live/dead PCR and quantitative PCR, respectively. Scanning electron microscopy (SEM) was used to analyze the architecture of biofilm. One-way analysis of variance and t-tests were used to investigate significant differences between independent groups of data. Results: Within a mono-species biofilm, different S. mutans strains responded similarly to one another during biofilm formation in different carbohydrate sources, with sucrose showing the highest levels of biofilm biomass and galactose showing the lowest. Within the polymicrobial biofilm system, compositional analysis of the bacteria within the biofilm showed that S. mutans derived from a caries-free patient was preferentially composed of both total and viable L. casei, whereas S. mutans derived from a caries patient was dominated by both total and viable S. mutans (p < 0.001). Normalized gene expression analysis of srtA, gtfB, ftf, spaP, gbpB, and luxS, showed a general upregulation within the S. mutans dominant biofilm. Conclusion: We were able to demonstrate that individual strains derived from different patients exhibited altered biofilm characteristics, which were not obvious within a simple mono-species biofilm model. Influencing the environmental conditions changed the composition and functionality S. mutans within the polymicrobial biofilm. The biofilm model described herein provides a novel and reproducible method of assessing the impact on the biofilm microbiome upon different environmental influences.

Lipoteichoic Acid Inhibits Staphylococcus aureus Biofilm Formation

A biofilm is an aggregate of microorganisms in which cells adhere to biological or non-biological surfaces and is responsible for various infectious diseases. Infections caused by Staphylococcus aureus, including pneumonia, endocarditis, and osteomyelitis, are often associated with colonization and biofilm formation. Although lipoteichoic acid (LTA) is involved in biofilm formation, the specific role of LTA is not clearly understood. In this study, we demonstrated that LTA released from Lactobacillus plantarum could inhibit S. aureus biofilm formation and aggregation without affecting the growth of S. aureus in various in vitro and in vivo models. L. plantarum LTA (Lp.LTA) also inhibited biofilm formation of S. aureus clinical isolates, including a methicillin-resistant strain. Remarkably, Lp.LTA not only interfered with S. aureus biofilm formation, but it also disrupted a pre-formed biofilm. Mechanism studies demonstrated that Lp.LTA inhibited expression of the ica-operon, which is responsible for the production of poly-N-acetylglucosamine, a key molecule required for S. aureus biofilm development. Lp.LTA increased the release of autoinducer-2 from S. aureus, which contributed to the inhibition of S. aureus biofilm formation. Moreover, Lp.LTA treatment enhanced susceptibility of the biofilm to various antibiotics and to macrophages. Interestingly, Lp.LTA without D-alanine moieties was not able to inhibit biofilm formation by S. aureus. In conclusion, the present study suggests that LTA can inhibit S. aureus biofilm formation, and therefore could be applied for preventing and/or treating infectious diseases caused by S. aureus biofilms.