Effects of Lactobacillus reuteri-derived biosurfactant on the gene expression profile of essential adhesion genes (gtfB, gtfC and ftf) of Streptococcus mutans

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

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

Propolis nanoparticle enhances the potency of antimicrobial photodynamic therapy against Streptococcus mutans in a synergistic manner

Less invasive removal approaches have been recommended for deep caries lesions. Antimicrobial photodynamic therapy (aPDT) and propolis nanoparticle (PNP) are highlighted for the caries management plan. Evidence is lacking for an additive effect of combination PNP with photosensitizer (PS) in aPDT. This study aimed to investigate the individual and synergistic effects of chlorophyllin-phycocyanin mixture (PhotoActive⁺) and toluidine blue O (TBO) as PSs in combination with PNP in the aPDT process (aPDT^plus) against major important virulence factors of Streptococcus mutans. Following characterization, biocompatibility of the PSs alone, or in combination with PNP were investigated on human gingival fibroblast cell. The in vitro synergy of PhotoActive⁺ or TBO and PNP was evaluated by the checkerboard method. The bacteria's virulence properties were surveyed in the presence of the PSs, individually as well as in combination. When the PSs were examined in combination (synergistic effect, FIC Index < 0.5), a stronger growth inhibitory activity was exhibited than the individual PSs. The biofilm formation, as well as genes involved in biofilm formation, showed greater suppression when the PSs were employed in combination. Overall, the results of this study suggest that the combination of PhotoActive⁺ or TBO with PNP with the least cytotoxicity effects and the highest antimicrobial activites would improve aPDT outcomes, leading to synergistic effects and impairing the virulence of S. mutans.

Diversity of Bacteria and Bacterial Products as Antibiofilm and Antiquorum Sensing Drugs Against Pathogenic Bacteria

The increase in antibiotic resistance of pathogenic bacteria has led to the development of new therapeutic approaches to inhibit biofilm formation as well as interfere quorum sensing (QS) signaling systems. The QS system is a phenomenon in which pathogenic bacteria produce signaling molecules that are involved in cell to cell communication, production of virulence factors, biofilm maturation, and several other functions. In the natural environment, several non-pathogenic bacteria are present as mixed population along with pathogenic bacteria and they control the behavior of microbial community by producing secondary metabolites. Similarly, non-pathogenic bacteria also take advantages of the QS signaling molecule as a sole carbon source for their growth through catabolism with enzymes. Several enzymes are produced by bacteria which disrupt the biofilm architecture by degrading the composition of extracellular polymeric substances (EPS) such as exopolysaccharide, extracellular- DNA and protein. Thus, the interference of QS system by bacterial metabolic products and enzymatic catalysis, modification of the QS signaling molecules as well as enzymatic disruption of biofilm architecture have been considered as the alternative therapeutic approaches. This review article elaborates on the diversity of different bacterial species with respect to their metabolic products as well as enzymes and their molecular modes of action. The bacterial enzymes and metabolic products will open new and promising perspectives for the development of strategies against the pathogenic bacterial infections.

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

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

Lactobacillus rhamnosus biosurfactant inhibits biofilm formation and gene expression of caries-inducing Streptococcus mutans

BACKGROUND

It is cleared that some probiotic strains inhibit biofilm formation of oral bacteria, but its mechanisms are not clearly understood yet. It is proposed that one of the mechanisms can be biosurfactant production, a structurally diverse group of surface-active compounds synthesized by microorganisms. Hence, this study focused on the evaluation of the anti-biofilm and antiadhesive activities of the L. rhamnosus derived-biosurfactant against Streptococcus mutans and its effect on gtfB/C and ftf genes expression level.

MATERIALS AND METHODS

In this in vitro study Lactobacillus rhamnosus ATCC7469 overnight culture was used for biosurfactant production. The biosurfactant effect on the surface tension reduction was confirmed by drop collapse method. Chemical bonds in the biosurfactant were identified by Fourier transform infrared (FTIR). Anti-biofilm and antiadhesive activities of the biosurfactant were determined on glass slides and in 96-well culture plates, respectively. The effect of the biosurfactant on gtfB/C and ftf genes expression level was also investigated after biofilm formation, total RNA extraction, and reverse transcription by quantitative real-time reverse transcriptase polymerase chain reaction (PCR) assay (quantitative PCR). The data were assessed by one-way analysis of variance in the Tukey-Kramer postdeviation test for all pairs. P < 0.05 was considered statistically significant.

RESULTS

The FTIR results of biosurfactant showed that it was protein rich. It also showed anti-biofilm formation activity on the glass slide and antiadhesive activity till 40% on microtiter plate wells. It also showed a significant reduction (P < 0.05) in gtfB/C and ftf genes expression level.

CONCLUSION

L. rhamnosus-derived biosurfactant exhibits a significant inhibitory effect on biofilm formation ability of S. mutans due to downregulation of biofilm formation associated genes, gtfB/C and ftf. L. rhamnosus-derived biosurfactant with substantial antiadhesive activity is suitable candidates for use in new generations of microbial antiadhesive agents.

In Vitro Antimicrobial Activity and Downregulation of Virulence Gene Expression on Helicobacter pylori by Reuterin

Helicobacter pylori is an infectious agent commonly associated with gastrointestinal diseases. The use of probiotics to treat this infection has been documented, however, their potential antimicrobial metabolites have not yet been investigated. In the present study, the effect of reuterin produced by Lactobacillus reuteri on H. pylori growth and virulence gene expression was evaluated. It was observed that reuterin caused significant (P < 0.05) H. pylori growth inhibition at concentrations from 0.08 to 20.48 mM, with minimal inhibitory concentrations (MICs) of 20.48 mM for H. pylori ATCC700824 and 10.24 mM for H. pylori ATCC43504. In a reuterin bacterial killing assay, it was observed that half of the MIC value for H. pylori (ATCC700824) significantly (P < 0.01) reduced colony numbers from 5.65 ± 0.35 to 3.78 ± 0.35 Log₁₀ CFU/mL after 12 h of treatment and then increased them to 5.25 ± 0.23 Log₁₀ CFU/mL at 24 h; at its MIC value (20.48 mM), reuterin abrogated (P < 0.01) H. pylori (ATCC700824) growth after 20 h of culture. In addition, reuterin significantly (P < 0.01) reduced H. pylori (ATCC 43504) colony numbers from 5.65 ± 0.35 to 4.1 ± 0.12 Log10 CFU/mL from 12 to 24 h of treatment and abrogated its growth at its MIC value (10.24 mM), after 20 h of treatment. Reuterin did not alter normal human gastric Hs738.St/Int cell viability at the concentrations tested for H. pylori strains. Furthermore, 10 μM reuterin was shown to significantly (P < 0.01) reduce mRNA relative expression levels of H. pylori virulence genes vacA and flaA at 3 h post-treatment, whose effect was higher at 6 h post-treatment, as measured by RT-qPCR. The observed direct antimicrobial effect and the downregulation of expression of virulence genes on H. pylori by reuterin may contribute to the understanding of the mechanisms of action of probiotics against H. pylori.

Prevention of Cross-contamination Risk by Disinfection of Irreversible Hydrocolloid Impression Materials with Ozonated Water

Background:

Disinfection of dental impression is mandatory for preventing the cross infection between dental staff and dental laboratory. Ozone as a disinfectant can be used in various ways in dentistry. The aim of this study was to evaluate the efficacy of ozonated water for disinfection of irreversible hydrocolloid impression materials and preventing cross-contamination.

Methods:

Thirty-two circular specimens (1 cm diameter and 2 mm thickness) of irreversible hydrocolloid impression material were made. Thirty specimens were contaminated with Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 51299), and Candida albicans (PTCC 5027). Except control samples (n = 2), the other specimens were immersed in ozonated water for 5 and 10 min (5 sample each group). Trypsin was used for separating microorganisms. Diluted microbial solution was analyzed microbiologically for colony-forming units (CFUs). Two-way repeated measure ANOVA and Scheffe post hoc test were used for data analysis (α = 0.05).

Results:

The number of CFUs after disinfection with ozonated water was decreased significantly (11.84%, 61.55%, and 20.27% after 5 min and 11.03%, 14.50%, and 16.99% after 10 min for P. aeruginosa, S. aureus, and C. albicans, respectively) (P < 0.001). Increasing the time of disinfection resulted in significant reduction in a number of S. aureus only (P < 0.001) although they did not vanish microorganisms completely.

Conclusions:

Immersion of irreversible hydrocolloid impression material in ozonated water for 10 min will not lead to complete disinfection but decreases the microorganisms to a level that can prevent infection transmission.

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

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

Biosurfactants: promising bioactive molecules for oral-related health applications

Biosurfactants are naturally produced molecules that demonstrate potentially useful properties such as the ability to reduce surface tensions between different phases. Besides having similar properties to their artificial chemical counterparts, they are regarded as environmental friendly, biodegradable and less toxic, which make them desirable candidates for downstream applications. The structure-activity-related properties of the biosurfactants which are directly correlated with potency of the biosurfactants as antimicrobial agents, the ability of the biosurfactants to alter surface energies and their ability to increase bioavailability are particularly what attract researchers to exploit their potential use in the oral-related health applications. Current research into biosurfactant indicates significant future potential for use in cosmetic and therapeutic oral hygiene product formulations and related medical device treatments.

Biosurfactant/s from Lactobacilli species: Properties, challenges and potential biomedical applications

Lactic acid bacteria are generally believed to have positive roles in maintaining good health and immune system in humans. A number of Lactobacilli spp. are known to produce important metabolites, among which biosurfactants in particular have shown antimicrobial activity against several pathogens in the intestinal tract and female urogenital tract partly through interfering with biofilm formation and adhesion to the epithelial cells surfaces. Around 46 reports are documented on biosurfactant production from Lactobacillus spp. of which six can be broadly classified as cell free biosurfactant and 40 as cell associated biosurfactants and only approximately 50% of those have reported on the structural composition which, in order of occurrence were mainly proteinaceous, glycolipidic, glycoproteins, or glycolipopeptides in nature. Due to the proteinaceous nature, most biosurfactant produced by strains of Lactobacillus are generally believed to be surlactin type with high potential toward impeding pathogens adherence. Researchers have recently focused on the anti-adhesive and antibiofilm properties of Lactobacilli-derived biosurfactants. This review briefly discusses the significance of Lactobacilli-derived biosurfactants and their potential applications in various fields. In addition, we highlight the exceptional prospects and challenges in fermentation economics of Lactobacillus spp.-derived biosurfactants' production processes.

Production and Biomedical Applications of Probiotic Biosurfactants

Biosurfactants have been widely used for environmental and industrial applications. However, their use in medical field is still limited. Probiotic biosurfactants possess an immense antimicrobial, anti-adhesive, antitumor, and antibiofilm potential. Moreover, they have an additional advantage over conventional microbial surfactants because probiotics are an integral part of normal human microflora and their biosurfactants are innocuous to human. So, they can be effectively exploited for medicinal use. Present review is aimed to discourse the production and biomedical applications of probiotic biosurfactants.