Mature Biofilm Degradation by Potential Probiotics: Aggregatibacter actinomycetemcomitans versus Lactobacillus spp

Postbiotics as candidates in biofilm inhibition in food industries

Food-borne pathogen-related biofilms in food processing environments pose significant risks to human health. To ensure human and environmental safety, natural substances with anti-microbial properties and generally recognized as safe (GRAS) status are the future disinfectants of the food industry. The use of postbiotics in food products is gaining attention due to their many benefits. Postbiotics are soluble substances produced by probiotics or released after their lysis, such as bacteriocins, biosurfactants (BSs), and exopolysaccharides (EPS). Postbiotics have drawn attention because of their clear chemical structure, safety dose parameters, long shelf life, and the content of various signaling molecules, which may have anti-biofilm and antibacterial activities. The main mechanisms of postbiotics to combat biofilm contain suppression of twitching motility, disturbing quorum sensing (QS), and reduction of virulence factors. However, there are obstacles to using these compounds in the food matrix because some factors (temperature and pH) can limit the anti-biofilm impact of postbiotics. Therefore, by using encapsulation or application of these compounds in packaging films, the effect of interfering factors can be eliminated. This review summarizes the concept and safety of postbiotics, focusing on their antibiofilm effect, as well as discussing the encapsulation of postbiotics and their application in packaging films.

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.

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.

An in vitro study on the efficacy of hydrogen peroxide mediated high-power photodynamic therapy affecting Enterococcus faecalis biofilm formation and dispersal

OBJECTIVE

Biofilms are involved in failure of root canal treatment due to their high resistance to antimicrobial agents, which make their removal as a big challenge. The present study aims at utilizing hydrogen peroxide (HP) plus high frequency laser reinforced antimicrobial photodynamic therapy (a-PDT) as a complementary therapy against Enterococcus faecalis (E. faecalis) at planktonic and biofilm stages.

MATERIALS AND METHODS

E. faecalis at planktonic and biofilm stages was treated with the photosensitizer HP, followed by no irradiation or irradiation with a power of 2.5 W (ʎ = 980 nm). The cell viability, anti-biofilm, anti-metabolic potential, and temperature changes were evaluated.

RESULTS

The combination of HP and 980 nm diode laser intensely boosted antibacterial and anti-biofilm efficacy compared with either component alone, affirming HP reinforcement as a bacteriostatic agent. The maximum effect on biofilm occurs in 5.25% sodium hypochlorite (NaOCl) group. During laser irradiations, the mean of temperature changes remains below 5.6 °C.

CONCLUSIONS

It could be concluded that the HP could improve anti-biofilm efficacy as a photosensitizer in a-PDT.

Evaluation of Antioxidant and Antibacterial Effects of Lyophilized Cell-Free Probiotic Supernatants of Three Lactobacillus spp. and Their Cytocompatibility Against Periodontal Ligament Stem Cells

Background

Periodontitis is a chronic disease characterized by the inflammation of the periodontium and leads to progressive damage, such as gingival atrophy, alveolar bone loss, and tooth loss. Streptococcus mutans and Aggregatibacter actinomycetemcomitans are bacteria that support the occurrence of periodontitis via the ability to form biofilms or damage the alveolar bone and periodontal ligaments. On the other hand, periodontal ligament stem cells (PDLSCs) are cells with differentiation capability into osteoblasts or osteoblasts. Due to their role in periodontal homeostasis and regeneration, PDLSCs are considered to control periodontitis progression. However, probiotics are helpful microorganisms known to have antimicrobial and immune-regulating effects.

Objectives

This study aimed to evaluate the antioxidant activity and antimicrobial effects of lyophilized cell-free supernatants (LCFSs) derived from three probiotic strains of Lactobacillus on S. mutans and A. actinomycetemcomitans. Moreover, the effect of these lyophilized supernatants was investigated on the viability and migration capability of PDLSCs.

Methods

The antibacterial effects of LCFSs of three probiotic bacteria were investigated by determining the minimum inhibitory concentration and minimum bactericidal concentration. Then, the effect of LCFSs on the survival and migration of PDLSCs was investigated by the MTT method (at 24 and 72 hours) and scratch test (at 0, 24, and 48 hours), respectively. Finally, the antioxidant effect of LCFSs was assessed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and ferric reducing/antioxidant power methods.

Results

The antibacterial properties of different concentrations of acidic and neutral LCFSs derived from three studied probiotic bacteria on S. mutans and A. actinomycetemcomitans were observed within the range of 12.5 - 50% (v/v) (1/8 - 1/2 dilutions with culture medium). Although there were no significant toxic (~ 100% viability) and wound healing effects on PDLSCs when the cells were exposed to either acidic or neutral studied LCFSs in a concentration of 5% (v/v), they showed significant antioxidant activity (~ 90% DPPH inhibition and 0.5 mM Fe2+/L).

Conclusions

The results revealed that 5% (v/v) 48-hour acidic and neutral supernatants of three studied probiotics might play a beneficial role in controlling periodontitis.

In Vitro Selection of Lactobacillus and Bifidobacterium Probiotic Strains for the Management of Oral Pathobiont Infections Associated to Systemic Diseases

The human oral pathobionts Aggregatibacter actinomycetemcomitans, Streptococcus mitis and Streptococcus mutans, in dysbiosis-promoting conditions, lead to oral infections, which also represent a threat to human systemic health. This scenario may be worsened by antibiotic misuse, which favours multi-drug resistance, making the research on pathogen containment strategies more than crucial. Therefore, we aimed to in vitro select the most promising probiotic strains against oral pathogen growth, viability, biofilm formation, and co-aggregation capacity, employing both the viable probiotics and their cell-free supernatants (CFSs). Interestingly, we also assessed probiotic efficacy against the three-pathogen co-culture, mimicking an environment similar to that in vivo. Overall, the results showed that Lactobacillus CFSs performed better than the Bifidobacterium, highlighting Limosilactobacillus reuteri LRE11, Lacticaseibacillus rhamnosus LR04, Lacticaseibacillus casei LC04, and Limosilactobacillus fermentum LF26 as the most effective strains, opening the chance to deeper investigation of their action and CFS composition. Altogether, the methodologies presented in this study can be used for probiotic efficacy screenings, in order to better focus the research on a viable probiotic, or on its postbiotics, suitable in case of infections.

3-Phenyllactic acid generated in medicinal plant extracts fermented with plant-derived lactic acid bacteria inhibits the biofilm synthesis of Aggregatibacter actinomycetemcomitans

In the present study, the effect of PLA on a periodontic pathogen, Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), the biofilm, and virulence-related genes was investigated. We confirmed that two lactic acid bacteria (LAB) strains isolated from plant sources, Lactiplantibacillus plantarum MSC-C2 and Pediococcus pentosaceus K40, secrete PLA into the de Man, Rogosa & Sharpe (MRS) broth when supplemented with phenyl pyruvic acid (PPA) as a precursor to PLA. Moreover, PLA was generated in the fermentation broths of two medicinal plant extracts, Paeonia lactiflora Pall (PR) and Carthamus tinctorius (CT), when used by each LAB strain and each extract supplemented with PPA. We determined that the minimum inhibitory concentration (MIC) of PLA against A. actinomycetemcomitans was 20 mM. PLA significantly decreased biofilm formation and suppressed the transcription of pgA, ltxA, and cdtB genes, which encode the poly-N-acetylglucosamine (PGA) polysaccharide of biofilm matrix and exotoxins leukotoxin and cytolethal distending toxin (CDT), respectively. The PLA produced by the MSC-C2 and K40 strains was increased several times by the addition of PPA to the MRS broth. The anti-biofilm effect of the extracts from the fermentation broth was proportional to the increasing PLA concentration, while a cumulatively higher effect than that of PLA alone suggested a combinational effect of PLA and the other metabolites, such as lactic acid (LA). Among the two medicinal plants, PLA, produced after the addition of PPA, was higher in PR extract in case of both the LAB strains. PLA production by the MSC-C2 strain in the PR extract reached 4.8 ± 0.23 mM, which was obviously higher than that in the MRS broth (3.88 ± 0.12 mM) supplemented with 1 mg/ml PPA. The activity to inhibit biofilm formation in the fermented PR extract was clearly high. PLA formed in the fermented PR extract downregulated the dispersin B encoding the dspB gene together with pgA, ltxA, and cdtB. In conclusion, this study shows a promising activity of PLA against the A. actinomycetemcomitans biofilm and virulence genes. In addition, the combinational effect of PLA and the medicinal plant extract can be achieved by fermentation with a specific plant-derived LAB strain.

Nisin probiotic prevents inflammatory bone loss while promoting reparative proliferation and a healthy microbiome

Dysbiosis of the oral microbiome mediates chronic periodontal disease. Realignment of microbial dysbiosis towards health may prevent disease. Treatment with antibiotics and probiotics can modulate the microbial, immunological, and clinical landscape of periodontal disease with some success. Antibacterial peptides or bacteriocins, such as nisin, and a nisin-producing probiotic, Lactococcus lactis, have not been examined in this context, yet warrant examination because of their biomedical benefits in eradicating biofilms and pathogenic bacteria, modulating immune mechanisms, and their safety profile in humans. This study's goal was to examine the potential for nisin and a nisin-producing probiotic to abrogate periodontal bone loss, the host inflammatory response, and changes in oral microbiome composition in a polymicrobial mouse model of periodontal disease. Nisin and a nisin-producing Lactococcus lactis probiotic significantly decreased the levels of several periodontal pathogens, alveolar bone loss, and the oral and systemic inflammatory host response. Surprisingly, nisin and/or the nisin-producing L. lactis probiotic enhanced the population of fibroblasts and osteoblasts despite the polymicrobial infection. Nisin mediated human periodontal ligament cell proliferation dose-dependently by increasing the proliferation marker, Ki-67. Nisin and probiotic treatment significantly shifted the oral microbiome towards the healthy control state; health was associated with Proteobacteria, whereas 3 retroviruses were associated with disease. Disease-associated microbial species were correlated with IL-6 levels. Nisin or nisin-producing probiotic's ability to shift the oral microbiome towards health, mitigate periodontal destruction and the host immune response, and promote a novel proliferative phenotype in reparative connective tissue cells, addresses key aspects of the pathogenesis of periodontal disease and reveals a new biomedical application for nisin in treatment of periodontitis and reparative medicine.

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

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

Probiotic Species in the Management of Periodontal Diseases: An Overview

Periodontal diseases are one of the most common chronic inflammatory diseases of the oral cavity, which are initiated and sustained by pathogenic plaque biofilms. Central to modern periodontology is the idea that dysbiosis of periodontal microecology and disorder of host inflammatory response gives rise to degradation of periodontal tissues together, which eventually leads to tooth loss, seriously affecting the life quality of patients. Probiotics were originally used to treat intestinal diseases, while in recent years, extensive studies have been exploring the utilization of probiotics in oral disease treatment and oral healthcare. Probiotic bacteria derived from the genera Lactobacillus, Bifidobacterium, Streptococcus, and Weissella are found to play an effective role in the prevention and treatment of periodontal diseases via regulating periodontal microbiota or host immune responses. Here, we review the research status of periodontal health-promoting probiotic species and their regulatory effects. The current issues on the effectiveness and safety of probiotics in the management of periodontal diseases are also discussed at last. Taken together, the use of probiotics is a promising approach to prevent and treat periodontal diseases. Nevertheless, their practical use for periodontal health needs further research and exploration.

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.

Evaluation of the Role of Probiotics As a New Strategy to Eliminate Microbial Toxins: a Review

Probiotics are living microorganisms that have favorable effects on human and animal health. The most usual types of microorganisms recruited as probiotics are lactic acid bacteria (LAB) and bifidobacteria. To date, numerous utilizations of probiotics have been reported. In this paper, it is suggested that probiotic bacteria can be recruited to remove and degrade different types of toxins such as mycotoxins and algal toxins that damage host tissues and the immune system causing local and systemic infections. These microorganisms can remove toxins by disrupting, changing the permeability of the plasma membrane, producing metabolites, inhibiting the protein translation, hindering the binding to GTP binding proteins to GM1 receptors, or by preventing the interaction between toxins and adhesions. Here, we intend to review the mechanisms that probiotic bacteria use to eliminate and degrade microbial toxins.

Using Lactobacilli to Fight Escherichia coli and Staphylococcus aureus Biofilms on Urinary Tract Devices

The low efficacy of conventional treatments and the interest in finding natural-based approaches to counteract biofilm development on urinary tract devices have promoted the research on probiotics. This work evaluated the ability of two probiotic strains, Lactobacillus plantarum and Lactobacillus rhamnosus, in displacing pre-formed biofilms of Escherichia coli and Staphylococcus aureus from medical-grade silicone. Single-species biofilms of 24 h were placed in contact with each probiotic suspension for 6 h and 24 h, and the reductions in biofilm cell culturability and total biomass were monitored by counting colony-forming units and crystal violet assay, respectively. Both probiotics significantly reduced the culturability of E. coli and S. aureus biofilms, mainly after 24 h of exposure, with reduction percentages of 70% and 77% for L. plantarum and 76% and 63% for L. rhamnosus, respectively. Additionally, the amount of E. coli biofilm determined by CV staining was maintained approximately constant after 6 h of probiotic contact and significantly reduced up to 67% after 24 h. For S. aureus, only L. rhamnosus caused a significant effect on biofilm amount after 6 h of treatment. Hence, this study demonstrated the potential of lactobacilli to control the development of pre-established uropathogenic biofilms.

Pre and Probiotics Involved in the Modulation of Oral Bacterial Species: New Therapeutic Leads in Mental Disorders?

This systematic review aims to identify probiotics and prebiotics for modulating oral bacterial species associated with mental disorders. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guideline, we search the electronic MEDLINE database published till January 2021 to identify the studies on probiotics and/or prebiotics for preventing and treating major oral dysbiosis that provokes mental disorders. The outcome of the search produces 374 records. After excluding non-relevant studies, 38 papers were included in the present review. While many studies suggest the potential effects of the oral microbiota on the biochemical signalling events between the oral microbiota and central nervous system, our review highlights the limited development concerning the use of prebiotics and/or probiotics in modulating oral dysbiosis potentially involved in the development of mental disorders. However, the collected studies confirm prebiotics and/or probiotics interest for a global or targeted modulation of the oral microbiome in preventing or treating mental disorders. These outcomes also offer exciting prospects for improving the oral health of people with mental disorders in the future.

Lactobacilli postbiotics reduce biofilm formation and alter transcription of virulence genes of Aggregatibacter actinomycetemcomitans

Periodontitis is characterized by a dysbiotic microbial community and treatment strategies include the reestablishment of symbiosis by reducing pathogens abundance. Aggregatibacter actinomycetemcomitans (Aa) is frequently associated with rapidly progressing periodontitis. Since the oral ecosystem may be affected by metabolic end-products of bacteria, we evaluated the effect of soluble compounds released by probiotic lactobacilli, known as postbiotics, on Aa biofilm and expression of virulence-associated genes. Cell-free pH-neutralized supernatants (CFS) of Lactobacillus rhamnosus Lr32, L. rhamnosus HN001, Lactobacillus acidophilus LA5, and L. acidophilus NCFM were tested against a fimbriated clinical isolate of Aa JP2 genotype (1 × 10⁷  CFU/well) on biofilm formation for 24 hr, and early and mature preformed biofilms (2 and 24 hr). Lactobacilli CFS partially reduced Aa viable counts and biofilms biomass, but did not affect the number of viable non-adherent bacteria, except for LA5 CFS. Furthermore, LA5 CFS and, in a lesser extent HN001 CFS, influenced Aa preformed biofilms. Lactobacilli postbiotics altered expression profile of Aa in a strain-specific fashion. Transcription of cytolethal distending toxin (cdtB) and leukotoxin (ltxA) was downregulated by CFS of LA5 and LR32 CFS. Although all probiotics produced detectable peroxide, transcription of katA was downregulated by lactobacilli CFS. Transcription of dspB was abrogated by LR32 and NCFM CFS, but increased by HN001, whereas expression of pgA was not affected by any postbiotic. Our data indicated the potential of postbiotics from lactobacilli, especially LA5, to reduce colonization levels of Aa and to modulate the expression of virulence factors implicated in evasion of host defenses.

A strategy to control colonization of pathogens: embedding of lactic acid bacteria on the surface of urinary catheter

Indwelling urinary catheterization is one of the major causes of urinary tract infection (UTI) in hospitalized patients worldwide. A catheter serves as a surface for the colonization and formation of biofilm by UTI-related pathogenic bacteria. To combat the biofilm formation on its surface, several strategies have already been employed such as coating it with antibiofilm and antimicrobial compounds. For instance, the application of lactic acid bacteria (LAB) offers a potential strategy for the treatment of biofilm formation on the surface of the urinary catheter due to its ability to kill the pathogenic bacteria. The killing of pathogenic bacteria by LAB occurs via the production of antimicrobial compounds such as lactic acid, bacteriocin, and hydrogen peroxide. LAB also displays a competitive exclusion mechanism to prevent the adhesion of pathogens on the surfaces. Hence, LAB has been extensively applied as a bacteriotherapy to combat infectious diseases. Several strategies have been employed to attach LAB to a surface, but its easy detachment during long time exposure becomes one of the drawbacks in its application. Here, we have proposed a novel strategy for its adhesion on the surface of the urinary catheter with the utilization of mannose-specific adhesin (Msa) protein in a way similar as uropathogenic bacteria interacts between Msa present on the tip of the type I fimbriae/pilus and the mannose moieties on the host epithelial cell surfaces. KEY POINTS: • Urinary tract infection (UTI) is one of the common hospital-acquired infections, which is associated with the application of an indwelling urinary catheter. • Based on the competitive exclusions properties of LAB, attachment of the LAB on the catheter surface would be a promising approach to control the formation of pathogenic biofilm. • The strategy employed for the adhesion of LAB is via a covalent interaction of its mannose-specific adhesin (Msa) protein to the mannose residues grafted on the catheter surface.

Anti-Biofilm Properties of Saccharomyces cerevisiae CNCM I-3856 and Lacticaseibacillus rhamnosus ATCC 53103 Probiotics against G. vaginalis

Bacterial vaginosis (BV) is characterized by the presence of a polymicrobial biofilm where Gardnerella vaginalis plays a key role. Previously, we demonstrated that Saccharomyces cerevisiae CNCM (French National Collection of Cultures of Microorganisms) I-3856 is helpful in resolving experimental simulated BV in mice. In this study, we analyzed its capacity to affect G. vaginalis biofilms and to potentiate the activity of standard antimicrobial agents. We also investigated the anti-biofilm activity of Lacticaseibacillus rhamnosus GG (ATCC 53103), a well-known strain for its intestinal healthy benefits. Biofilm biomass was assessed by crystal violet staining, and G. vaginalis viability was assessed by a colony forming unit (CFU) assay. Here, for the first time, we demonstrated that S. cerevisiae CNCM I-3856 as well as L. rhamnosus GG were able (i) to significantly inhibit G. vaginalis biofilm formation, (ii) to markedly reduce G. vaginalis viability among the biomass constituting the biofilm, (iii) to induce disaggregation of preformed biofilm, and (iv) to kill a consistent amount of bacterial cells in a G. vaginalis preformed biofilm. Furthermore, S. cerevisiae CNCM I-3856 strongly potentiates the metronidazole effect on G. vaginalis biofilm viability. These results suggest that S. cerevisiae CNCM I-3856 as well as L. rhamnosus GG could be potential novel therapeutic agents against bacterial vaginosis.

Mitigation of the Toxic Effects of Periodontal Pathogens by Candidate Probiotics in Oral Keratinocytes, and in an Invertebrate Model

The larvae of the wax moth Galleria mellonella and human oral keratinocytes were used to investigate the protective activity of the candidate oral probiotics Lactobacillus rhamnosus GG (LHR), Lactobacillus reuteri (LR), and Streptococcus salivarius K-12 (SS) against the periodontal pathogens Fusobacterium nucleatum (FN), Porphyromonas gingivalis (PG), and Aggregatibacter actinomycetemcomitans (AA). Probiotics were delivered to the larvae (i) concomitantly with the pathogen in the same larval pro-leg; (ii) concomitantly with the pathogen in different pro-legs, and (iii) before inoculation with the pathogen in different pro-legs. Probiotics were delivered as viable cells, cell lysates or cell supernatants to the oral keratinocytes concomitantly with the pathogen. The periodontal pathogens killed at least 50% of larvae within 24 h although PG and FN were significantly more virulent than AA in the order FN > PG > AA and were also significantly lethal to mammalian cells. The candidate probiotics, however, were not lethal to the larvae or human oral keratinocytes at doses up to 10⁷ cells/larvae. Wax worm survival rates increased up to 60% for some probiotic/pathogen combinations compared with control larvae inoculated with pathogens only. SS was the most effective probiotic against FN challenge and LHR the least, in simultaneous administration and pre-treatment, SS and LR were generally the most protective against all pathogens (up to 60% survival). For P. gingivalis, LR > LHR > SS, and for A. actinomycetemcomitans SS > LHR and LR. Administering the candidate probiotics to human oral keratinocytes significantly decreased the toxic effects of the periodontal pathogens. In summary, the periodontal pathogens were variably lethal to G. mellonella and human oral keratinocytes and the candidate probiotics had measurable protective effects, which were greatest when administrated simultaneously with the periodontal pathogens, suggesting protective effects based on bacterial interaction, and providing a basis for mechanistic studies.

Effect of Probiotic Clostridium butyricum NCTC 7423 Supernatant on Biofilm Formation and Gene Expression of Bacteroides fragilis

Enterotoxigenic Bacteroides fragilis (ETBF) is the main pathogen causing severe inflammatory diseases and colorectal cancer. Its biofilm plays a key role in the development of colorectal cancer. The objective of this study was to determine the antagonistic effects of cell-free supernatants (CFS) derived from Clostridium butyricum against the growth and biofilm of ETBF. Our data showed that C. butyricum CFS inhibited the growth of B. fragilis in planktonic culture. In addition, C. butyricum CFS exhibited an antibiofilm effect by inhibiting biofilm development, disassembling preformed biofilms and reducing the metabolic activity of cells in biofilms. Using confocal laser scanning microscopy, we found that C. butyricum CFS significantly suppressed the proteins and extracellular nucleic acids among the basic biofilm components. Furthermore, C. butyricum CFS significantly downregulated the expression of virulence- and efflux pump-related genes including ompA and bmeB3 in B. fragilis. Our findings suggest that C. butyricum can be used as biotherapeutic agent by inhibiting the growth and biofilm of ETBF.

The Battle of Probiotics and Their Derivatives Against Biofilms

Biofilm-related infections have been a major clinical problem and include chronic infections, device-related infections and malfunction of medical devices. Since biofilms are not fully available for the human immune system and antibiotics, they are difficult to eradicate and control; therefore, imposing a global threat to human health. There have been avenues to tackle biofilms largely based on the disruption of their adhesion and maturation. Nowadays, the use of probiotics and their derivatives has gained a growing interest in battling against pathogenic biofilms. In the present review, we have a close look at probiotics with the ultimate objective of inhibiting biofilm formation and maturation. Overall, insights into the mechanisms by which probiotics and their derivatives can be used in the management of biofilm infections would be warranted.

Monospecific Biofilms of Pseudoalteromonas Promote Larval Settlement and Metamorphosis of Mytilus coruscus

As a stage of life cycle, larval settlement and metamorphosis are critical processes for persistence of many marine invertebrate populations. Bacterial biofilms (BFs) could induce larval settlement and metamorphosis. Pseudoalteromonas, a widely distributed genus of marine bacteria, showed inductive effects on several invertebrates. However, how Pseudoalteromonas BFs induce settlement and metamorphosis of Mytilus coruscus remains unclear. Pseudoalteromonas marina BFs with the highest inducing activity were further investigated to define inductive cues. Surface-bound products of P. marina BFs could induce larval settlement and metamorphosis. P. marina BFs treated with formalin, antibiotics, ultraviolet irradiation, heat and ethanol significantly reduced inductive effects and cell survival rates. The confocal laser scanning microscopy and the biovolume analysis showed the dominance of α-polysaccharides on P. marina BFs. Treatment of BFs with amylases, proteases and lipase led to the decrease of inducing activity, suggesting that inductive cues of P. marina BFs may comprise of molecular domains of polysaccharides, proteins, and lipids. Finding inductive cues of BFs could put forward further studies about the mechanism of larval settlement and metamorphosis of marine invertebrates.

The Flagellar Gene Regulates Biofilm Formation and Mussel Larval Settlement and Metamorphosis

Biofilms are critical components of most marine systems and provide biochemical cues that can significantly impact overall community composition. Although progress has been made in the bacteria–animal interaction, the molecular basis of modulation of settlement and metamorphosis in most marine animals by bacteria is poorly understood. Here, Pseudoalteromonas marina showing inducing activity on mussel settlement and metamorphosis was chosen as a model to clarify the mechanism that regulates the bacteria–mussel interaction. We constructed a flagellin synthetic protein gene fliP deletion mutant of P. marina and checked whether deficiency of fliP gene will impact inducing activity, motility, and extracellular polymeric substances of biofilms. Furthermore, we examined the effect of flagellar proteins extracted from bacteria on larval settlement and metamorphosis. The deletion of the fliP gene caused the loss of the flagella structure and motility of the ΔfliP strain. Deficiency of the fliP gene promoted the biofilm formation and changed biofilm matrix by reducing β-polysaccharides and increasing extracellular proteins and finally reduced biofilm-inducing activities. Flagellar protein extract promoted mussel metamorphosis, and ΔfliP biofilms combined with additional flagellar proteins induced similar settlement and metamorphosis rate compared to that of the wild-type strain. These findings provide novel insight on the molecular interactions between bacteria and mussels.

Blocking Activin Receptor Ligands Is Not Sufficient to Rescue Cancer-Associated Gut Microbiota-A Role for Gut Microbial Flagellin in Colorectal Cancer and Cachexia?

Colorectal cancer (CRC) and cachexia are associated with the gut microbiota and microbial surface molecules. We characterized the CRC-associated microbiota and investigated whether cachexia affects the microbiota composition. Further, we examined the possible relationship between the microbial surface molecule flagellin and CRC. CRC cells (C26) were inoculated into mice. Activin receptor (ACVR) ligands were blocked, either before tumor formation or before and after, to increase muscle mass and prevent muscle loss. The effects of flagellin on C26-cells were studied in vitro. The occurrence of similar phenomena were studied in murine and human tumors. Cancer modulated the gut microbiota without consistent effects of blocking the ACVR ligands. However, continued treatment for muscle loss modified the association between microbiota and weight loss. Several abundant microbial taxa in cancer were flagellated. Exposure of C26-cells to flagellin increased IL6 and CCL2/MCP-1 mRNA and IL6 excretion. Murine C26 tumors expressed more IL6 and CCL2/MCP-1 mRNA than C26-cells, and human CRC tumors expressed more CCL2/MCP-1 than healthy colon sites. Additionally, flagellin decreased caspase-1 activity and the production of reactive oxygen species, and increased cytotoxicity in C26-cells. Conditioned media from flagellin-treated C26-cells deteriorated C2C12-myotubes and decreased their number. In conclusion, cancer increased flagellated microbes that may promote CRC survival and cachexia by inducing inflammatory proteins such as MCP-1. Cancer-associated gut microbiota could not be rescued by blocking ACVR ligands.

Removal of Staphylococcus aureus from skin using a combination antibiofilm approach

Staphylococcus aureus (S. aureus) including methicillin resistant S. aureus (MRSA) is one of the primary microorganisms responsible for surgical site infection (SSI). Since S. aureus contamination is known to originate from the skin, eradicating it on the skin surface at surgical sites is an important intervention to reduce the chance of SSIs. Here we developed and evaluated the efficacy of a combination probiotic/brush sonication strategy for skin preparation at surgical, injection and insertion sites in medicine. A 24 h biofilm on porcine skin explants was used as a worst-case scenario for the evaluation of preparation strategies. Conventional ethanol wipes achieved 0.8~2 log reduction in viable bacteria depending on how many times wiped (x4 or x6). Brush sonication or probiotic supernatant pre-treatment alone achieved a similar reduction as ethanol wipes (1.4 and 0.7~1.4 log reduction, respectively). Notably, combining sonication and probiotic pre-treatment achieved a 4 log reduction in viable bacteria. In addition, probiotic supernatant incubation times as short as 2 h achieved the full effect of this reduction in the combined strategy. These findings suggest the promising potential of combination-format skin preparation strategies that can be developed to more effectively penetrate cracks and folds in the skin to remove biofilms.

Combining brush sonication with secretions from probiotic bacteria cleans skin before surgery more effectively than ethanol wipes. Researchers in the USA, led by K. Scott Phillips at the United States Food and Drug Administration, investigated removal of Staphylococcus aureus biofilm from pig skin as a “worst case” pre-surgical scenario. This bacterium is a major cause of serious and drug-resistant surgical site infections. Brush sonication or treatment with probiotic-derived solutions were individually approximately as effective as ethanol wipes, but in combination they proved substantially more effective. The treatment with the secretions surrounding probiotic bacterial cells requires exposure for several hours, but this could be readily achieved using a pre-surgery ointment. The sonication and probiotic combination could be developed into a highly effective pre-surgical procedure, penetrating cracks and folds in the skin to remove dangerous biofilms.

The effects of a probiotic milk drink on bacterial composition in the supra- and subgingival biofilm: a pilot study

Probiotics can convert a dysbiotic bacterial environment into a healthy one. The aim of the present study was to assess the effect of daily intake of a probiotic milk drink on the composition of bacterial species in dental supra- and subgingival biofilms. Sixteen dental students were enrolled into this study with a crossover, within subject, design. The participants were asked to allow plaque accumulation by refraining from cleaning their molars during two separate periods, each lasting three weeks. Each period consisted of an initial professional dental cleaning procedure done at the university clinic, then a 3 week plaque accumulation period, followed by a return to the clinic for supra- and subgingival plaque sampling. The first period served as a control, and during the second plaque accumulation period the participants drank 200 ml probiotic milk beverage each day. The accumulated plaque removed at the end of the accumulation period was later tested against a panel of 20 oral bacterial species using the checkerboard method. Three weeks consumption of a probiotic beverage led to a significant reduction in 15 of 20 bacterial species present in supragingival plaque and a reduction in 4 of 20 bacterial species in subgingival plaque (all P<0.05). This study showed a favorable effect of probiotics on periodontopathic bacteria in dental biofilms. The potential influence of this kind of probiotic in prevention or treatment of periodontal inflammation deserves further study.

Spatial Organization Plasticity as an Adaptive Driver of Surface Microbial Communities

Biofilms are dynamic habitats which constantly evolve in response to environmental fluctuations and thereby constitute remarkable survival strategies for microorganisms. The modulation of biofilm functional properties is largely governed by the active remodeling of their three-dimensional structure and involves an arsenal of microbial self-produced components and interconnected mechanisms. The production of matrix components, the spatial reorganization of ecological interactions, the generation of physiological heterogeneity, the regulation of motility, the production of actives enzymes are for instance some of the processes enabling such spatial organization plasticity. In this contribution, we discussed the foundations of architectural plasticity as an adaptive driver of biofilms through the review of the different microbial strategies involved. Moreover, the possibility to harness such characteristics to sculpt biofilm structure as an attractive approach to control their functional properties, whether beneficial or deleterious, is also discussed.

Traditionally used herbal medicines with antibacterial effect on Aggegatibacter actinomycetemcomitans: Boswellia serrata and Nigella sativa

Background:

Since bacterial strains developed resistance against commonly used antibiotics and side effects became more serious, other alternatives have been postulated. There is an answer for this issue in ancient medicine. Many plants have been proved to provide antibacterial effect. In this study, Boswellia serrata (BS) and Nigella sativa (NS) were assessed to evaluate the antibacterial effect on Aggregatibacter actinomycetemcomitans (A.a) known as main pathogen of aggressive periodontitis.

Materials and Methods:

Broth microdilution method was used to obtain minimum inhibitory concentration (MIC) of crude extract of BS and NS. Furthermore, the logarithm of colony forming units grown in fresh brain heart infusion bacterial culture was assessed. Three groups including BS+ (containing only BS), NS+ (containing only NS), and BS-NS− (control group) were defined. For each group, the experiment was repeated 12 times.

Results:

MIC of BS and NS were 512 μg/mL and 128 μg/mL, respectively. No growth was observed in our negative control group. The mean ± standard deviation of logarithm of CFU/mL for BS, NS, and control group was 4.32 ± 0.36, 3.61 ± 0.3, and 5.57 ± 0.19, respectively. ANOVA test revealed significant difference (P values < 0.0001) of these groups which was later confirmed using the post hoc test of Tukey's honest significant difference (all P < 0.0001).

Conclusions:

Both BS and NS are effective against A.a which should be taken into account as appropriate ingredient for oral hygiene products.