Live and heat-killed Lactobacillus spp. interfere with Streptococcus mutans and Streptococcus oralis during biofilm development on titanium surface

Computational and experimental strategies for combating MBL P. aeruginosa (MBLPA) biofilms using phytochemicals: Targeting the quorum sensing network

Pseudomonas aeruginosa is a Gram-negative opportunistic bacterium, ubiquitously found in nature and causative agent in many infections. Due to increased antibiotic resistance, there is a need to develop more robust antibacterial agents from natural sources. In this study, we worked on two metallo-β-lactamase (MBL) producing Pseudomonas aeruginosa strains and targeted the Quorum Sensing mechanism (QS) of these bacteria to combat antibiotic resistance. Our study aimed at using phytochemicals which have been used since centuries in herbal medicine. We used fifteen commercially available phytochemicals and check their effects on biofilm formation, quorum sensing and inter-related mechanisms. Sub-inhibitory concentration of isoliquiritin inhibited biofilm formation 55 % in P8 at day 6 and 48 % in P6 at day 6; quorum sensing 83 % in P6 and 61 % in P8 whereas sub-inhibitory concentration of 6-gingerol suppressed biofilm formation by 48 % in P8 at day 6 and 44 % in P6 at day 6; quorum sensing 69 % in P6 and 48 % in P8, respectively. The results indicated isoliquiritin, epigallocatechin gallate, eugenol, luteolin and chrysin to be the potential candidates in inhibiting QS and related mechanisms. Isoliquiritin which was never been used before against biofilm and QS related studies, showed remarkable results and found to be more efficient in inhibiting QS than 6-gingerol -a known QS inhibitor. For examining the molecular interaction between phytochemicals and QS, In-silico molecular docking was performed between phytoligands and four QS proteins (Las I, Las R, RhlI and Rhl R). In-silico docking analysis revealed that isoliquiritin showed strong bond with amino acids (Trp34, Asp35, Asp35, Tyr105, Arg104, Val138, Thr140) present at the active site of RhlI with binding energy value of -8.4 kcal/mol as compared to that of 6-gingerol with Rhl1 (-7.3 kcal/mol). In conclusion, our study may help in controlling nosocomial infections caused by carbapenem-resistant metallo beta-lactamase P. aeruginosa (MBL-PA) by utilizing these phytochemicals in biofilms disruption and quorum sensing inhibition. Moreover their synergism with antibiotics may help in lowering the MIC of carbapenem antibiotics against such Multi-drug resistant strains.

Elimination of Pathogen Biofilms via Postbiotics from Lactic Acid Bacteria: A Promising Method in Food and Biomedicine

Pathogenic biofilms provide a naturally favorable barrier for microbial growth and are closely related to the virulence of pathogens. Postbiotics from lactic acid bacteria (LAB) are secondary metabolites and cellular components obtained by inactivation of fermentation broth; they have a certain inhibitory effect on all stages of pathogen biofilms. Postbiotics from LAB have drawn attention because of their high stability, safety dose parameters, and long storage period, which give them a broad application prospect in the fields of food and medicine. The mechanisms of eliminating pathogen biofilms via postbiotics from LAB mainly affect the surface adhesion, self-aggregation, virulence, and QS of pathogens influencing interspecific and intraspecific communication. However, there are some factors (preparation process and lack of target) which can limit the antibiofilm impact of postbiotics. Therefore, by using a delivery carrier and optimizing process parameters, the effect of interfering factors can be eliminated. This review summarizes the concept and characteristics of postbiotics from LAB, focusing on their preparation technology and antibiofilm effect, and the applications and limitations of postbiotics in food processing and clinical treatment are also discussed.

Probiotic Lactobacillus plantarum Ln4 Showing Antimicrobial and Antibiofilm Effect against Streptococcus mutans KCTC 5124 Causing Dental Caries

Dental caries has known as an infectious disease that is considered a serious global public health problem. Recently, report indicate that probiotics play a vital role in maintaining oral health. Therefore, this study aimed to evaluate the prevention effects of Lactobacillus plantarum Ln4 against dental infection by the pathogenic bacterium Streptococcus mutans KCTC 5124 through biofilm formation inhibition. To evaluate such prevention effects against S. mutans KCTC 5124, antimicrobial activity, auto-aggregation, co-aggregation, cell surface hydrophobicity, total exopolysaccharide (EPS) production rate, and biofilm formation were analyzed. Results showed that L. plantarum Ln4 showed higher antimicrobial activity than L. rhamnosus GG (LGG). In the group treated with L. plantarum Ln4, the co-aggregation (58.85%), cell surface hydrophobicity (16.75%), and EPS production rate (73.29%) values were lower than those of LGG and the negative control. Additionally, crystal violet staining and confocal laser scanning microscopy (CLSM) revealed that L. plantarum Ln4 effectively inhibited biofilm formation in S. mutans KCTC 5124. Therefore, L. plantarum Ln4 could be used in the industry as a probiotics to prevent and improve oral health.

Postbiotic production: harnessing the power of microbial metabolites for health applications

Postbiotics, which are bioactive substances derived from the metabolic processes of beneficial microbes, have received considerable attention in the field of microbiome science in recent years, presenting a promising path for exploration and innovation. This comprehensive analysis looks into the multidimensional terrain of postbiotic production, including an extensive examination of diverse postbiotic classes, revealing their sophisticated mechanisms of action and highlighting future applications that might significantly affect human health. The authors thoroughly investigate the various mechanisms that support postbiotic production, ranging from conventional fermentation procedures to cutting-edge enzyme conversion and synthetic biology approaches. The review, as an acknowledgment of the field's developing nature, not only highlights current achievements but also navigates through the problems inherent in postbiotic production. In order to successfully include postbiotics in therapeutic interventions and the production of functional food ingredients, emphasis is given to critical elements, including improving yields, bolstering stability, and assuring safety. The knowledge presented herein sheds light on the expanding field of postbiotics and their potential to revolutionize the development of novel therapeutics and functional food ingredients.

Mechanism Insights of Antibacterial Surfaces Coated with Dead Probiotics

To understand the antimicrobial effect of surfaces fabricated with dead probiotics, we prepared surfaces decorated with dead probiotics Lactobacillus rhamnosus GG (LGG) with varied inactivation methods and explored their inhibitory interactions with Pseudomonas aeruginosa (PAO1). By combining several techniques, i.e., digital holographic microscopy (DHM), atomic force microscopy (AFM), RNA sequencing, and metabolomic analysis, we studied the three-dimensional (3D) swimming behaviors, surface adhesion, biofilm formation, and adaptive responses of PAO1 near such surfaces. The results show that planktonic PAO1 decreases their flick and reverse motions by downregulating the chemotaxis pathway and accelerates with less accumulation near dead LGG surfaces by upregulating the flagellar assembly pathway and decreasing cyclic adenosine monophosphate. Distinct from live siblings, the surfaces decorated with dead LGG show a significant reduction in adhesion strength with PAO1 and inhibit biofilm formation with more downregulated genes in the Pseudomonas quinolone signal and biofilm formation pathway. We demonstrate that the antibacterial ability of such surfaces stems from the gradually released lysate from the dead LGG that is unfavorable to PAO1 in close proximity. The releasing rate and order depend on the cell membrane integrity, which closely relates to the inactivation methods.

Paraprobiotics: definition, manufacturing methods, and functionality

Probiotics are living microorganisms that are beneficial to the host, enhancing the immune response by promoting antibody production, regulating cytokine secretion, and stimulating T cells. However, probiotics have limitations in that they require viability control and have a short shelf life. Recently, the use of paraprobiotics has gained attention. These include dead bacterial cells, bacterial fractions, and cell lysate that have health benefits and are stable and safe for use. Paraprobiotics comprise molecules of bacterial cell wall compounds, such as peptidoglycans, teichoic acids, polysaccharides, and cell surface proteins. Paraprobiotics are manufactured by a diverse range of techniques, including thermal treatments, high pressure, ultraviolet rays, sonication, ionizing radiation, and pH modification. Their beneficial health effects include immunomodulatory, intestinal balancing, anticancer, and antimicrobial activities. Therefore, this review summarizes and discusses the manufacturing methods and bioavailability of paraprobiotics and suggests their potential health advantages.

Alleviation of dental caries by use of isolated potential probiotic and its characterization

Streptococcus mutans plays a major role in biofilm formation and pathogenic bacterial adhesion. Here we investigated the abilities of our isolates from diverse conventional sources to characterize the beneficial bacteria for inhibition of S. mutans. Enterobacter cloacae PS-74, a beneficial bacteria isolated from yoghurt, is gram negative, rod shaped, and resistant to acid, bile salt, and amylase. PS-74 cell-free supernatants (CFS) demonstrated highest zone of inhibition of 29 ± 1.7 mm. Further, the minimum inhibitory concentration (MIC) value of CFS PS-74 was recorded to be 10 μL and its minimum bactericidal concentration (MBC) value was found to be 15μL which led to 99.9% log reduction of S. mutans. Moreover, the biofilm formation was reduced by 84.91% at MIC15 of CFS PS-74 which alleviate the dental caries formation by S. mutans. This is the first report on E. cloacae PS-74, which was studied for its probiotic properties to inhibit S. mutans MTCC-890 due to the production of organic acids and employed in oral treatment.

Antagonistic Interactions of Lactic Acid Bacteria from Human Oral Microbiome against Streptococcus mutans and Candida albicans

Oral probiotic lactic acid bacteria can exhibit antagonistic activities against pathogens associated with diseases in the oral cavity. Therefore, twelve previously isolated oral strains were assessed for antagonistic evaluation against selected oral test microorganisms Streptococcus mutans and Candida albicans. Two separate co-culturing analyses were performed, where all tested strains showed the presence of antagonistic activity and four strains, Limosilactobacillus fermentum N 2, TC 3-11, and NA 2-2, and Weissella confusa NN 1, significantly inhibited Streptococcus mutans by 3-5 logs. The strains showed antagonistic activity against Candida albicans, and all exhibited pathogen inhibition by up to 2 logs. Co-aggregation capability was assessed, showing co-aggregative properties with the selected pathogens. Biofilm formation and antibiofilm activity of the tested strains against the oral pathogens were assayed, where the strains showed specificity in self-biofilm formation and well-expressed antibiofilm properties by most of them above 79% and 50% against Streptococcus mutans and Candida albicans, respectively. The tested LAB strains were assayed by a KMnO₄ antioxidant bioassay, where most of the native cell-free supernatants exhibited total antioxidant capacity. These results show that five tested strains are promising candidates to be included in new functional probiotic products for oral healthcare.

Carbon dots labeled Lactiplantibacillus plantarum: a fluorescent multifunctional biocarrier for anticancer drug delivery

A carbon dots (CDs)-biolabeled heat-inactivated Lactiplantibacillus plantarum (HILP) hybrid was investigated as a multifunctional probiotic drug carrier with bioimaging properties using prodigiosin (PG) as anticancer agent. HILP, CDs and PG were prepared and characterized using standard methods. CDs-labeled HILP (CDs/HILP) and PG loaded CDs/HILP were characterized by transmission electron microscopy (TEM), laser scanning confocal microscopy (LSCM) and for entrapment efficiency (EE%) of CDs and PG, respectively. PG-CDs/HILP was examined for stability and PG release. the anticancer activity of PG-CDs/HILP was assessed using different methods. CDs imparted green fluorescence to HILP cells and induced their aggregation. HILP internalized CDs via membrane proteins, forming a biostructure with retained fluorescence in PBS for 3 months at 4°C. Loading PG into CDs/HILP generated a stable green/red bicolor fluorescent combination permitting tracking of both drug carrier and cargo. Cytotoxicity assay using Caco-2 and A549 cells revealed enhanced PG activity by CDs/HILP. LCSM imaging of PG-CDs/HILP-treated Caco-2 cells demonstrated improved cytoplasmic and nuclear distribution of PG and nuclear delivery of CDs. CDs/HILP promoted PG-induced late apoptosis of Caco-2 cells and reduced their migratory ability as affirmed by flow cytometry and scratch assay, respectively. Molecular docking indicated PG interaction with mitogenic molecules involved in cell proliferation and growth regulation. Thus, CDs/HILP offers great promise as an innovative multifunctional nanobiotechnological biocarrier for anticancer drug delivery. This hybrid delivery vehicle merges the physiological activity, cytocompatibility, biotargetability and sustainability of probiotics and the bioimaging and therapeutic potential of CDs.

Inhibition of Staphylococcus aureus biofilms by poly-L-aspartic acid nanoparticles loaded with Litsea cubeba essential oil

Staphylococcus aureus (S. aureus) biofilms contamination on various food-contacting surfaces is considered a significant threat in the field of food. Poly-L-aspartic acid (PASP) was proven to damage biofilm by affecting bacterial adhesion, metabolic activity, and extracellular polymeric substances in this study. Especially for eDNA, its generation was reduced by 49.4 %. After treatment with 5 mg/mL of PASP, the number of S. aureus in the biofilm at different growth stages decreased by 1.20-1.68 log CFU/mL. The nanoparticles prepared by PASP and hydroxypropyl trimethyl ammonium chloride chitosan were used to embed LC-EO (EO@PASP/HACCNPs). The results indicated that the particle size of the optimized nanoparticles was 209.84 nm with an encapsulation rate of 70.28 %. Compared to LC-EO alone, EO@PASP/HACCNPs had more significant permeation and dispersion effects on biofilms and possessed long-lasting anti-biofilm activity. For the biofilm grown for 72 h, the population of S. aureus in the EO@PASP/HACCNPs-treated biofilm was additionally reduced by 0.63 log CFU/mL compared with the LC-EO-treated group. EO@PASP/HACCNPs were also applied to different food-contacting materials. The lowest inhibition rate of EO@PASP/HACCNPs on S. aureus biofilm still reached 97.35 %. The sensory properties of the chicken breast were not affected by EO@PASP/HACCNPs.

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.

Lactobacillus paracasei CNCM I-5220-derived postbiotic protects from the leaky-gut

The maintenance of intestinal barrier function is essential for preventing different pathologies, such as the leaky gut syndrome (LGS), which is characterized by the passage of harmful agents, like bacteria, toxins, and viruses, into the bloodstream. Intestinal barrier integrity is controlled by several players, including the gut microbiota. Various molecules, called postbiotics, are released during the natural metabolic activity of the microbiota. Postbiotics can regulate host–microbe interactions, epithelial homeostasis, and have overall benefits for our health. In this work, we used in vitro and in vivo systems to demonstrate the role of Lactobacillus paracasei CNCM I-5220-derived postbiotic (LP-PBF) in preserving intestinal barrier integrity. We demonstrated in vitro that LP-PBF restored the morphology of tight junctions (TJs) that were altered upon Salmonella typhimurium exposure. In vivo, LP-PBF protected the gut vascular barrier and blocked S. typhimurium dissemination into the bloodstream. Interestingly, we found that LP-PBF interacts not only with the host cells, but also directly with S. typhimurium blocking its biofilm formation, partially due to the presence of biosurfactants. This study highlights that LP-PBF is beneficial in maintaining gut homeostasis due to the synergistic effect of its different components. These results suggest that LP-PBF could be utilized in managing several pathologies displaying an impaired intestinal barrier function.

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.

Potential oral probiotic Lactobacillus pentosus MJM60383 inhibits Streptococcus mutans biofilm formation by inhibiting sucrose decomposition

Streptococcus mutans is known as a contributor to dental caries. In this work, Lactobacillus pentosus MJM60383 was selected for its strong antagonistic activity against S. mutans and was characterized by good oral probiotic properties including lysozyme tolerance, adhesive ability to oral cells, good aggregation (auto-aggregation, co-aggregation) ability, hydrogen peroxide production and inhibition of biofilm formation of S. mutans. L. pentosus MJM60383 also exhibited safety as a probiotic characterized by no hemolytic activity, no D-lactate production, no biogenic amine production, and susceptibility to antibiotics. Furthermore, the biofilm formation of S. mutans was also significantly inhibited by the supernatant of L. pentosus MJM60383. An anti-biofilm mechanism study revealed that sucrose decomposition and the production of water-insoluble exopolysaccharides by S. mutans were inhibited by the treatment with L. pentosus MJM60383 supernatant. Real-time PCR analysis indicated that the supernatant of L. pentosus MJM60383 significantly inhibited the mRNA expression of S. mutans glycosyltransferases, which synthesize glucan to construct biofilm architecture and mediate bacterial adherence. Our study demonstrated L. pentosus MJM60383 as a potential oral probiotic and revealed its anti-biofilm mechanism.

The Influence of the Degree of Thermal Inactivation of Probiotic Lactic Acid Bacteria and Their Postbiotics on Aggregation and Adhesion Inhibition of Selected Pathogens

The study aimed to evaluate the effect of thermal inactivation of potentially probiotic lactic acid bacteria (LAB) strains isolated from food on their ability to compete with pathogenic microorganisms. Five strains of LAB, previously isolated from food and characterized, one commercial reference strain of Lactiplantibacillus plantarum 299v, and two indicator strains of Staphylococcus aureus 25923 and Listeriamonocytogenes 15313 were used in the study. The experiment consisted in applying a stress factor (high temperature: 80 °C, at a different time: 5, 15, and 30 min) to the tested LAB cells to investigate the in vitro properties such as hydrophobicity abilities (against p-xylene and n-hexadecane), auto-aggregation, co-aggregation with pathogens, and inhibition of pathogens adhesion to the porcine gastric mucin. The bacterial strains showed various hydrophobicity to p-xylene (36-73%) and n-hexadecane (11-25%). The affinity for solvents expanded with increasing thermal inactivation time. All LAB isolates were able to auto-aggregate (ranging from 17 to 49%). Bacterial strains subjected to 5 and 15 min of thermal inactivation had the highest auto-aggregation ability in comparison to viable and heat-killed cells for 30 min. The LAB strains co-aggregated with pathogens to different degrees; among them, the highest scores of co-aggregation were observed for L. monocytogenes, reaching 27% (with 15 min of heat-killed LAB cells). All LAB strains reduced the adherence of pathogenic bacteria in the competition test, moreover, heat-killed cells (especially 15 min inactivated) were more efficient than viable cells. The properties of selected LAB strains as moderately heat-stressed forms analyzed in the study increased the prevention of colonization and elimination of pathogenic bacteria in the in vitro model of gastrointestinal tract. The thermal inactivation process may therefore preserve and modifies some characteristics of bacterial cells.

Lactobacillus cell envelope-coated nanoparticles for antibiotic delivery against cariogenic biofilm and dental caries

Background

Due to their prevalence, dental caries ranks first among all diseases endangering human health. Therefore, the prevention of caries is of great significance, as caries have become a serious public health problem worldwide. Currently, using nanoscale drug delivery systems to prevent caries has received increased attention. However, the preventive efficacy of these systems is substantially limited due to the unique physiological structure of cariogenic biofilms. Thus, novel strategies aimed at combating cariogenic biofilms to improve preventive efficiency against caries are meaningful and very necessary. Herein, inspired by cell membrane coating technology and Lactobacillus strains, we coated triclosan (TCS)-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (TCS@PLGA-NPs) with an envelope of Lactobacillus (LA/TCS@PLGA-NPs) and investigated their potential as a nanoparticle delivery system against cariogenic biofilms and dental caries.

Results

LA/TCS@PLGA-NPs were successfully prepared with favorable properties, including a coated envelope, controllable size, negative charge, sustained drug-release kinetics and so on. The LA/TCS@PLGA-NPs inherited native properties from the source cell surface, thus the LA/TCS@PLGA-NPs adhered to S. mutans, integrated into the S. mutans biofilm, and interfered with the biofilm formation of S. mutans. The nanoparticles significantly inhibited the activity, biomass and virulence gene expression of S. mutans biofilms in vitro. Additionally, LA/TCS@PLGA-NPs exhibited a long-lasting inhibitory effect on the progression of caries in vivo. The safety performance of the nanoparticles is also favorable.

Conclusions

Our findings reveal that the antibiofilm effect of LA/TCS@PLGA-NPs relies not only on the inheritance of native properties from the Lactobacillus cell surface but also on the inhibitory effect on the activity, biomass and virulence of S. mutans biofilms. Thus, these nanoparticles could be considered feasible candidates for a new class of effective drug delivery systems for the prevention of caries. Furthermore, this work provides new insights into cell membrane coating technology and presents a novel strategy to combat bacterial biofilms and associated infections.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01563-x.

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.

In Vitro Evaluation of the Effect of Oral Probiotic Weissella cibaria on the Formation of Multi-Species Oral Biofilms on Dental Implant Surfaces

Oral probiotics are beneficial bacteria that can help prevent periodontal disease. However, little is known about the effects of oral probiotics on the formation of implant biofilms. This study aimed to evaluate the effects of oral probiotics Weissella cibaria CMU and CMS1 in an in vitro complex biofilm model on titanium implant surfaces. First, it was identified through colony biofilm assay that W. cibaria CMU and CMS1 inhibit the formation of multi-species biofilms formed by eight types of bacteria. Two types of saliva-coated titanium discs inoculated with early (Streptococcus gordonii, Streptococcus oralis, Streptococcus sanguinis, Actinomyces naeslundii, and Veillonella parvula), secondary (Fusobacterium nucleatum and Prevotella intermedia), and late (Porphyromonas gingivalis) colonizers were treated with the oral probiotics and then incubated anaerobically for three days. The effects of oral probiotics on titanium disc biofilm formation were analyzed using culture methods, quantitative polymerase chain reaction (qPCR), and microscopic analysis. Both probiotics significantly inhibited the formation of biofilm, and all eight bacterial species were significantly reduced. The effectiveness of both probiotic strains was confirmed by all the methods used. Oral probiotics may have dramatically reduced the biofilm formation of secondary colonizers that act as bridges, thus inhibiting biofilm formation on the titanium surface. Our results suggest that the probiotic W. cibaria offers new possibilities for the prevention of peri-implant mucositis.

Microbial Biofilm Decontamination on Dental Implant Surfaces: A Mini Review

Introduction

After insertion into the bone, implants osseointegrate, which is required for their long-term success. However, inflammation and infection around the implants may lead to implant failure leading to peri-implantitis and loss of supporting bone, which may eventually lead to failure of implant. Surface chemistry of the implant and lack of cleanliness on the part of the patient are related to peri-implantitis. The only way to get rid of this infection is decontamination of dental implants.

Objective

This systematic review intended to study decontamination of microbial biofilm methods on titanium implant surfaces used in dentistry.

Methods

The electronic databases Springer Link, Science Direct, and PubMed were explored from their inception until December 2020 to identify relevant studies. Studies included had to evaluate the efficiency of new strategies either to prevent formation of biofilm or to treat matured biofilm on dental implant surfaces.

Results and Discussion

In this systematic review, 17 different groups of decontamination methods were summarized from 116 studies. The decontamination methods included coating materials, mechanical cleaning, laser treatment, photodynamic therapy, air polishing, anodizing treatment, radiation, sonication, thermal treatment, ultrasound treatment, chemical treatment, electrochemical treatment, antimicrobial drugs, argon treatment, and probiotics.

Conclusion

The findings suggest that most of the decontamination methods were effective in preventing the formation of biofilm and in decontaminating established biofilm on dental implants. This narrative review provides a summary of methods for future research in the development of new dental implants and decontamination techniques.

Contributions of Escherichia coli and Its Motility to the Formation of Dual-Species Biofilms with Vibrio cholerae

Biofilm formation is important in both the environmental and intestinal phases of the Vibrio cholerae life cycle. Nevertheless, most studies of V. cholerae biofilm formation focus on monospecies cultures, whereas nearly all biofilm communities found in nature consist of a variety of microorganisms. Multispecies biofilms formed between V. cholerae and other bacteria in the environment and the interactions that exist between these species are still poorly understood. In this study, the influence of Escherichia coli on the biofilm formation of V. cholerae was studied in the context of both in vitro coculture and in vivo coinfection. To understand the underlying synergistic mechanisms between these two species and to investigate the role of E. coli in V. cholerae biofilm formation, different pathotypes of E. coli and corresponding deletion mutants lacking genes that influence flagellar motility, curli fibers, or type I pili were cocultured with V. cholerae. Our findings demonstrate that the presence of commensal E. coli increases biofilm formation at the air-liquid interface in vitro and the generation of biofilm-like multicellular clumps in mouse feces. Examination of laboratory E. coli flagellar-motility ΔfliC and ΔmotA mutants in dual-species biofilm formation suggests that flagellar motility plays an important role in the synergistic interaction and coaggregation formation between V. cholerae and E. coli. This study facilitates a better understanding of how V. cholerae resides in harsh environments and colonizes the intestine. IMPORTANCE Biofilms play an important role in the V. cholerae life cycle. Until now, only monospecies biofilm formation of V. cholerae has been well studied. However, in nature, bacteria live in complex microbial communities, where biofilm is mostly composed of multiple microbial species that interact to cooperate with or compete against each other. Uncovering how V. cholerae forms multispecies biofilms is critical for furthering our understanding of how V. cholerae survives in the environment and transitions to infecting the human host. In this work, the dual-species biofilm containing V. cholerae and Escherichia coli was investigated. We demonstrate that the presence of commensal E. coli increased overall biofilm formation. Furthermore, we demonstrate that the motility of E. coli flagella is important for V. cholerae and E. coli to form coaggregation clumps in a dual-species biofilm. These results shed light on a new mechanism for understanding the survival and pathogenesis of V. cholerae.

The biosurfactants iturin, lichenysin and surfactin, from vaginally isolated lactobacilli, prevent biofilm formation by pathogenic Candida

Lactic acid bacteria (LAB), particularly lactobacilli, are major components of the vaginal microbiota. Lactobacilli are facultative anaerobes forming a critical line of defense against pathogenic microorganisms, including those forming biofilms, such as Candida spp. This study aimed to investigate the anti-adhesion capabilities of vaginal Lactobacillus isolates against biofilms formed by pathogenic Candida species. When the extracellular biosurfactant activities of culture supernatants from 120 Lactobacillus isolates were evaluated by the oil-spreading method, clear spreading zones were recognized. Biofilm formation was quantified by the crystal violet plate assay, and different isolates exhibited anti-adhesion activity that ranged from 65.6to 74.4% inhibition against Candida spp. biofilms. Liquid chromatography high-resolution electrospray ionization mass spectrometry (LC-HRESIMS) identified biosurfactants, extracted from three representative Lactobacillus isolates, as surfactin, iturin and lichenysin. Finally, the distribution of representative genes from six different biosynthetic clusters, related to the production of different biosurfactants, was investigated by the polymerase chain reaction. In conclusion, surfactin, iturin and lichenysin were identified for the first time in vaginal Lactobacillus spp. These biosurfactants, which showed strong anti-adherence activity may be used as promising antibiofilm agents in equipment care to prevent vaginal infections by pathogenic Candida spp. with the prospect of reducing nosocomial infections.

Inhibitory effects of Lactobacillus brevis KU15153 against Streptococcus mutans KCTC 5316 causing dental caries

This study determined the inhibitory effect of Lactobacillus brevis KU15153 against cariogenic Streptococcus mutans KCTC 5316. Antimicrobial activity, auto-aggregation, cell surface hydrophobicity, exopolysaccharides (EPS) production, biofilm formation, and morphological changes were assessed in the presence of L. brevis KU15153. L. brevis KU15153 exhibited the highest antimicrobial activity against S. mutans KCTC 5316 (28.67 ± 4.16 mm). Auto-aggregation (38.32%), cell surface hydrophobicity (27.08%), and EPS production rate (58.52%) of S. mutans KCTC 5316 slightly decreased upon treatment with L. brevis KU15153. Additionally, crystal violet stanning and scanning electron microscopy confirmed the L. brevis KU15153-mediated inhibition of biofilm formation by S. mutans KCTC 5316 in comparison to that observed in the negative control (untreated S. mutans KCTC 5316). These results indicate that the L. brevis KU15153 could be used as a potential probiotic for maintaining oral health.

Method-induced variation in the bacterial cell surface hydrophobicity MATH test

Bacterial cell surface hydrophobicity is a relevant property in determining the ability of bacteria to adhere to inert surfaces. This property has been measured using the microbial adhesion to hydrocarbon (MATH) test. Several reports in the literature establish the percentage of adhesion to hydrocarbons (PoAtH) value produced by the MATH test for a broad variety of bacteria. Discrepancies in PoAtH values reported for the same strain of a specific microorganism suggest that some method-induced variation may exist, as different research teams employ different versions of the assay. The objective of the present study was to compare the performance of different versions of the MATH test as reported in the literature, to quantify the magnitude of the method-induced variation on PoAtH values. The study demonstrated that PoAtH values are influenced twice as much by variations in the employed assay than by actual differences in cell surface composition or architecture. The two L. reuteri strains studied responded differently to changes in assay conditions showing 40 and 70% method-dependent variation for strain ATCC 53609 and 55730, respectively. These results highlight the need to properly standardize the MATH test to enable comparison of PoAtH values produced by independent research teams.

Baicalein Inhibits Streptococcus mutans Biofilms and Dental Caries-Related Virulence Phenotypes

Dental caries, the most common oral disease, is a major public healthcare burden and affects more than three billion people worldwide. The contemporary understanding of the need for a healthy microbiome and the emergence of antimicrobial resistance has resulted in an urgent need to identify compounds that curb the virulence of pathobionts without microbial killing. Through this study, we have demonstrated for the first time that 5,6,7-trihydroxyflavone (Baicalein) significantly downregulates crucial caries-related virulence phenotypes in Streptococcus mutans. Baicalein significantly inhibited biofilm formation by Streptococcus mutans UA159 (MBIC50 = 200 μM), without significant growth inhibition. Notably, these concentrations of baicalein did not affect the commensal S. gordonii. Strikingly, baicalein significantly reduced cell surface hydrophobicity, autoaggregation and acid production by S. mutans. Mechanistic studies (qRT-PCR) showed downregulation of various genes regulating biofilm formation, surface attachment, quorum sensing, acid production and competence. Finally, we demonstrate the potential translational value of baicalein by reporting synergistic interaction with fluoride against S. mutans biofilms.

Quantification and gene expression of Lactobacillus casei group species associated with dentinal lesions in early childhood caries

Background

Considering that the Lactobacillus casei group is strongly associated with caries progression, the use of lactobacilli as probiotics must be balanced due to their possible involvement in dental caries.

Objective

This study aimed to detect and quantify L. paracasei, L. rhamnosus, and L. casei group species in the active and arrested dentinal lesions of preschoolers. It also aimed to determine the expression profiles of lactobacilli genes related to adhesion, extracellular polymeric substance regulation, and pyruvate oxidation.

Methods

Total ribonucleic acid (RNA) was extracted from dentinal lesion samples (25 active, 13 arrested) of children between 2 and 5 years of age. The samples were converted to complementary deoxyribonucleic acid (cDNA), and quantitative polymerase chain reaction (qPCR) analyses were performed to quantify and determine the relative abundance (measured by percentage of total bacteria) of L. paracasei, L. rhamnosus, and L. casei group species. The expression profiles of L. paracasei/casei genes (spaC and spxB) and L. rhamnosus genes (spaE and wzb) were assessed. The Student t-test and the Mann-Whitney U test were used for comparisons.

Results

The L. casei group species were found to be part of the viable microbial community in dentinal caries. L. paracasei (p = 0.001), L. rhamnosus (p = 0.022), and L. casei (p = 0.004) group species were abundant in the active dentinal lesions compared to the arrested dentinal lesions. Only the wzb gene (p = 0.006) exhibited a statistically significant difference between the active and arrested lesions in terms of its expression profile; it was expressed to a higher extent in the active dentinal lesions.

Conclusions

The L. casei group species presented in large numbers in the active dentinal caries lesions, indicating that these microorganisms are related to caries activity, and the wzb gene may play an important role in caries progression.

The Use of Probiotics to Fight Biofilms in Medical Devices: A Systematic Review and Meta-Analysis

Medical device-associated infections (MDAI) are a critical problem due to the increasing usage of medical devices in the aging population. The inhibition of biofilm formation through the use of probiotics has received attention from the medical field in the last years. However, this sparse knowledge has not been properly reviewed, so that successful strategies for biofilm management can be developed. This study aims to summarize the relevant literature about the effect of probiotics and their metabolites on biofilm formation in medical devices using a PRISMA-oriented (Preferred Reporting Items for Systematic reviews and Meta-Analyses) systematic search and meta-analysis. This approach revealed that the use of probiotics and their products is a promising strategy to hinder biofilm growth by a broad spectrum of pathogenic microorganisms. The meta-analysis showed a pooled effect estimate for the proportion of biofilm reduction of 70% for biosurfactants, 76% for cell-free supernatants (CFS), 77% for probiotic cells and 88% for exopolysaccharides (EPS). This review also highlights the need to properly analyze and report data, as well as the importance of standardizing the in vitro culture conditions to facilitate the comparison between studies. This is essential to increase the predictive value of the studies and translate their findings into clinical applications.

Short Communication: Oral Administration of Heat-killed Lactobacillus brevis KB290 in Combination with Retinoic Acid Provides Protection against Influenza Virus Infection in Mice

Influenza virus type A (IAV) is a seasonal acute respiratory disease virus with severe symptoms, and an effective preventive measure is required. Despite many reports describing the potentially protective effects of lactic acid bacteria, few studies have investigated the effects of nutritional supplement combinations. This study reports the effect of the combined intake of heat-killed Lactobacillus brevis KB290 (KB290) and vitamin A (VA) on mice challenged with a sublethal dose of IAV. For 2 weeks, five groups of mice were fed either placebo, KB290, VA, or a combination of KB290 and VA (KB290+VA). After subsequent IAV challenge, bodyweight and general health were monitored for up to 2 weeks. Viral titres were determined in the lungs of animal subgroups euthanised at days 3, 7, and 14 after IAV challenge. A significant loss was observed in the bodyweights of IAV-infected animals from day 1 post-IAV challenge, whereas the mice fed KB290+VA did not lose any weight after IAV infection, indicating successful protection from the infection. Additionally, mice in the KB290+VA group showed the highest reduction in lung viral titres. In conclusion, the combination of KB290 and VA could be a useful food supplement relevant for protection against seasonal influenza virus infection in humans.

Postbiotics-parabiotics: the new horizons in microbial biotherapy and functional foods

Probiotics have several health benefits by modulating gut microbiome; however, techno-functional limitations such as viability controls have hampered their full potential applications in the food and pharmaceutical sectors. Therefore, the focus is gradually shifting from viable probiotic bacteria towards non-viable paraprobiotics and/or probiotics derived biomolecules, so-called postbiotics. Paraprobiotics and postbiotics are the emerging concepts in the functional foods field because they impart an array of health-promoting properties. Although, these terms are not well defined, however, for time being these terms have been defined as here. The postbiotics are the complex mixture of metabolic products secreted by probiotics in cell-free supernatants such as enzymes, secreted proteins, short chain fatty acids, vitamins, secreted biosurfactants, amino acids, peptides, organic acids, etc. While, the paraprobiotics are the inactivated microbial cells of probiotics (intact or ruptured containing cell components such as peptidoglycans, teichoic acids, surface proteins, etc.) or crude cell extracts (i.e. with complex chemical composition)". However, in many instances postbiotics have been used for whole category of postbiotics and parabiotics. These elicit several advantages over probiotics like; (i) availability in their pure form, (ii) ease in production and storage, (iii) availability of production process for industrial-scale-up, (iv) specific mechanism of action, (v) better accessibility of Microbes Associated Molecular Pattern (MAMP) during recognition and interaction with Pattern Recognition Receptors (PRR) and (vi) more likely to trigger only the targeted responses by specific ligand-receptor interactions. The current review comprehensively summarizes and discussed various methodologies implied to extract, purify, and identification of paraprobiotic and postbiotic compounds and their potential health benefits.

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.

Carbohydrate Metabolism Regulated by Antisense vicR RNA in Cariogenicity

Streptococcus mutans is a major cariogenic pathogen that resides in multispecies oral microbial biofilms. The VicRK 2-component system is crucial for bacterial adaptation, virulence, and biofilm organization and contains a global and vital response regulator, VicR. Notably, we identified an antisense vicR RNA (AS vicR) associated with an adjacent RNase III–encoding ( rnc) gene that was relevant to microRNA-size small RNAs (msRNAs). Here, we report that ASvicR overexpression significantly impeded bacterial growth, biofilm exopolysaccharide synthesis, and cariogenicity in vivo. Transcriptome analysis revealed that the AS vicR RNA mainly regulated carbohydrate metabolism. In particular, overproducing AS vicR demonstrated a reduction in galactose and glucose metabolism by monosaccharide composition analysis. The results of high-performance gel permeation chromatography revealed that the water-insoluble glucans isolated from AS vicR presented much lower molecular weights. Furthermore, direct evidence showed that total RNAs were disrupted by rnc-encoded RNase III. With the coexpression of T4 RNA ligase, putative msRNA1657, which is an rnc-related messenger RNA, was verified to bind to the 5′-UTR regions of the vicR gene. Furthermore, AS vicR regulation revealed a sponge regulatory-mediated network for msRNA associated with adjacent RNase III–encoding genes. There was an increase in AS vicR transcript levels in clinical S. mutans strains from caries-free children, while the expression of AS vicR was decreased in early childhood caries patients; this outcome may be explored as a potential strategy contributing to the management of dental caries. Taken together, our findings suggest an important role of AS vicR-mediated sponge regulation in S. mutans, indicating the characterization of lactose metabolism by a vital response regulator in cariogenicity. These findings have a number of implications and have reshaped our understanding of bacterial gene regulation from its transcriptional conception to the key roles of regulatory RNAs.

Establishment of the molecular beacon-loop-mediated isothermal amplification method for the rapid detection of Porphyromonas gingivalis

Porphyromonas gingivalis, a clinically important oral pathogen causing periodontal disease, is difficult to culture in routine conditions. Hence, it is necessary to establish a reliable technique to detect this pathogen. Previously, our laboratory developed a new isothermal detection method, called MB-LAMP (molecular beacon-Loop-mediated isothermal amplification), which combines the advantages of LAMP and qPCR through the accurate and quantitative detection of LAMP products. This approach offers significant potential for the point-of-care detection of P. gingivalis. Here, MB-LAMP was used to detect P. gingivalis targeting a specific fragment, and the sensitivity was as high as 1.4 × 10^-1 pg μL^-1. The method showed no cross-reaction with 14 other bacterial pathogens. For clinical samples, this assay showed a high diagnostic sensitivity (100%) and specificity (100%), equivalent to that of real-time quantitative polymerase chain reaction (real-time qPCR). Moreover, detection with MB-LAMP was significantly faster than that with real-time qPCR, reducing the time required for clinical diagnosis. Finally, we established an absolute quantification method with MB-LAMP for P. gingivalis using pilot samples. Thus, the highly specific, sensitive, and rapid assay developed in this study makes it feasible to diagnose P. gingivalis.

Inhibitory effect of probiotic lactobacilli supernatants on single and mixed non-albicans Candida species biofilm

OBJECTIVES

Oral candidiasis is one of the most common human fungal infections. While most cases of the Candida species isolated from the oral cavity are Candida albicans, a large number of candidiasis is attributed to non-albicans Candida species. In this study, we aim to evaluate the in vitro inhibition of supernatants of Lactobacillus gasseri and Lactobacillus rhamnosus on the single and mixed species biofilm of non-albicans Candida species, including Candida tropicalis, Candida krusei and Candida parapsilosis.

DESIGN

Cell-free supernatants of Lactobacillus gasseri and Lactobacillus rhamnosus were prepared. Single and mixed non-albicans Candida species biofilm were formed in the 96-well microplate and on the surfaces of medical grade silicone. Biomass and cell viability were tested with crystal violet and cell counting kit-8. In order to examine the ability of the supernatant to disrupt pre-formed biofilm, supernatant was added to 24h-old biofilms. Biofilm architecture on silicone was investigated by scanning electron microscopy and confocal laser scanning microscopy was used to examine live/dead organisms within biofilm.

RESULTS

Single and mixed species biofilms and cell viability of non-albicans Candida biofilms were inhibited by probiotic lactobacilli supernatants. Matrue biofilm formation was disrupted by lactobacilli supernatants added at 24h after biofilm initiation. Examination with confocal laser scanning microscopy and scanning electron microscopy confirmed that lactobacilli supernatants inhibited the mixed biofilms and damaged the cells.

CONCLUSIONS

Our data elucidate the inhibitory activity of probiotic lactobacilli on non-albicans Candida biofilm, so as to support their utility as an adjunctive therapeutic mode against oral candida infections.