Comparison of periodontitis-associated oral biofilm formation under dynamic and static conditions

Understanding the Influence of Rheology on Biofilm Adhesion and Implication for Food Safety

Understanding biofilm rheology is crucial for industrial and domestic food safety practices. This comprehensive review addresses the knowledge gap on the rheology of biofilm. Specifically, the review explores the influence of fluid flow, shear stress, and substrate properties on the initiation, structure, and functionality of biofilms, as essential implications for food safety. The viscosity and shear-thinning characteristics of non-Newtonian fluids may impact the attachment and detachment dynamics of biofilms, influencing their stability and resilience under different flow conditions. The discussion spans multiple facets, including the role of extracellular polymeric substances (EPSs) in biofilm formation, the impact of rheological attributes of biofilm on their adhesion to surfaces, and the influence of shear forces between biofilms and substrate's surface characteristics on biofilm stability. Analytical techniques, encompassing rheometry, microscopy, and molecular biology approaches, are scrutinized for their contributions to understanding these interactions. The paper delves into the implications for the food industry, highlighting potential risks associated with biofilm formation and proposing strategies for effective control and prevention. Future research directions and the integration of rheological considerations into food safety regulations are underscored as pivotal steps in mitigating biofilm-related risks. The synthesis of microbiology, materials science, and engineering perspectives offers a multidimensional exploration of rheology-biofilm interactions, laying the groundwork for informed interventions in diverse industrial settings.

Classical and Modern Models for Biofilm Studies: A Comprehensive Review

Biofilms are structured microbial communities that adhere to various abiotic and biotic surfaces, where organisms are encased in an exo-polysaccharide matrix. Organisms within biofilms use various mechanisms that help them resist external challenges, such as antibiotics, rendering them more resistant to drugs. Therefore, researchers have attempted to develop suitable laboratory models to study the physical features of biofilms, their resistance mechanisms against antimicrobial agents, and their gene and protein expression profiles. However, current laboratory models suffer from various limitations. In this comprehensive review, we have summarized the various designs that have been used for laboratory biofilm models, presenting their strengths and limitations. Additionally, we have provided insight into improving these models to more closely simulate real-life scenarios, using newly developed techniques in additive manufacturing, synthetic biology, and bioengineering.

The effect of dental material type and masticatory forces on periodontitis-derived subgingival microbiomes

Restorative dental materials can frequently extend below the gingival margin, serving as a potential haven for microbial colonization, and altering the local oral microbiome to ignite infection. However, the contribution of dental materials on driving changes of the composition of the subgingival microbiome is under-investigated. This study evaluated the microbiome-modulating properties of three biomaterials, namely resin dental composites (COM), antimicrobial piezoelectric composites (BTO), and hydroxyapatite (HA), using an optimized in vitro subgingival microbiome model derived from patients with periodontal disease. Dental materials were subjected to static or cyclic loading (mastication forces) during biofilm growth. Microbiome composition was assessed by 16S rRNA gene sequencing. Dysbiosis was measured in terms of subgingival microbial dysbiosis index (SMDI). Biomaterials subjected to cyclic masticatory loads were associated with enhanced biofilm viability except on the antibacterial composite. Biomaterials held static were associated with increased biofilm biomass, especially on HA surfaces. Overall, the microbiome richness (Chao index) was similar for all the biomaterials and loading conditions. However, the microbiome diversity (Shannon index) for the HA beams was significantly different than both composites. In addition, beta diversity analysis revealed significant differences between composites and HA biomaterials, and between both loading conditions (static and cyclic). Under static conditions, microbiomes formed over HA surfaces resulted in increased dysbiosis compared to composites through the enrichment of periopathogens, including Porphyromonas gingivalis, Porphyromonas endodontalis, and Fretibacterium spp., and depletion of commensals such as Granulicatella and Streptococcus spp. Interestingly, cyclic loading reversed the dysbiosis of microbiomes formed over HA (depletion of periopathogenes) but increased the dysbiosis of microbiomes formed over composites (enrichment of Porphyromonas gingivalis and Fusobacterim nucleatum). Comparison of species formed on both composites (control and antibacterial) showed some differences. Commercial composites enriched Selenomonas spp. and depleted Campylobacter concisus. Piezoelectric composites effectively controlled the microbiome viability without significantly impacting the species abundance. Findings of this work open new understandings of the effects of different biomaterials on the modulation of oral biofilms and the relationship with oral subgingival infections.

An in vitro dynamic bioreactor model for evaluating antimicrobial effectiveness on periodontal polymicrobial biofilms: a proof-of-concept study

BACKGROUND

The aim of this study was to investigate an in vitro dynamic bioreactor model by evaluating the antimicrobial effect of clinically relevant amoxicillin doses on polymicrobial microcosm biofilms derived from subgingival plaque.

METHODS

Biofilms from pooled subgingival plaque were grown for 108  hours in control and experimental dynamic biofilm reactors. Amoxicillin was subsequently infused into the experimental reactor to simulate the pharmacokinetic profile of a standard 500 mg thrice-daily dosing regimen over 5 days and biofilms were assessed by live/dead staining, scanning electron microscopy, and quantitative polymerase chain reaction.

RESULTS

Following establishment of the oral microcosm biofilms, confocal imaging analysis showed a significant increase in dead bacteria at 8 hours (p = 0.0095), 48 hours (p = 0.0070), 96 hours (p = 0.0140), and 120 hours (p < 0.0001) in the amoxicillin-treated biofilms compared to the control biofilms. Nevertheless, viable bacteria remained in the center of the biofilm at all timepoints. Significant reductions/elimination in Campylobacter rectus, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, and Peptostreptococcus anaerobius was observed among the amoxicillin-treated biofilms at the 96 and 120 hour timepoints.

CONCLUSION

A novel in vitro dynamic model of oral microcosm biofilms was effective in modeling the antimicrobial effect of a pharmacokinetically simulated clinically relevant dose of amoxicillin.

Selenium Nanoparticle Activity against S. mutans Biofilms as a Potential Treatment Alternative for Periodontitis

The disruption of periodontal biofilms and prevailing antimicrobial resistance issues continue to pose a great challenge to the treatment of periodontitis. Here, we report on selenium nanoparticles (SeNPs) as a treatment alternative for periodontitis by determining their antibiofilm activity against S. mutans biofilms and the potential role of particle size in disrupting biofilms. SeNPs were synthesised via a reduction reaction. Various physicochemical characterisations were conducted on the NPs, including size and shape. The microbroth dilution method was used to conduct the biofilm and antibiofilm assay against S. mutans, which was analysed by absorbance. SeNPs displayed hydrodynamic sizes as low as 46 ± 4 nm at a volume ratio of 1:5 (sodium selenite/ascorbic acid) with good monodispersity and stability. Hydrodynamic sizes of SeNPs after resuspension in tryptic soy broth supplemented with 2.5% sucrose (TSB + 2.5% suc.) and incubated at 37 °C for 24 h, ranged from 112 to 263 nm, while the zeta potential values increased to greater than -11 mV. The biofilm assay indicated that S. mutans are weakly adherent, bordering on moderately adherent biofilm producers. The minimum biofilm inhibitory concentration (MBIC) was identified at 500 µg/mL. At a 1000 µg/mL concentration, SeNPs were able to inhibit S. mutan biofilms up to 99.87 ± 2.41% at a volume ratio of 1:1. No correlation was found between antibiofilm activity and particle size; however, antibiofilm activity was proven to be concentration-dependant. SeNPs demonstrate antibiofilm activity and may be useful for further development in treating periodontitis.

Characterization of Antibiofilm and Antimicrobial Effects of Trigona Stingless Bee Honey Compared to Stinging Bee Centaurea hyalolepis and Citrus Honeys

The antibiofilm and antimicrobial properties of tropical honey types including Malaysian stingless bee honey remain explicitly unexplored when compared with Apies honey. The antibiofilm and antimicrobial activities of the Malaysian Trigona honey were characterized with two stinging bee honey types (Centaurea hyalolepis and Citrus honeys) from Jordan. The antibiofilm and antimicrobial investigations were conducted on a set of seven microbial strains; five bacterial species of Pseudomonas aeruginosa ATCC 10145, Streptococcus pyogenes ATCC 19615, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 13883, and two fungal strains Candida albicans ATCC 10231 and Candida krusei ATCC 14243. The antimicrobial investigations revealed a broad spectrum activity for Trigona honey against Gram-positive, Gram-negative, and fungal strains over the two honey types. One-way ANOVA showed a significant difference (p < 0.001) in the zone of inhibition ranging from 9 to 25 mm and minimum inhibition activity (MIC) ranged from 9.4-29.6% (w/v) against the microbial strains. Moreover, the addition of honey to established biofilms has induced a degradation activity in the biofilm mass. Two-way ANOVA showed a significant biofilm degradation proportion (p < 0.001) ranging from 1.3% to 91.3% following treatment with Trigona honey and the other honey types in relevance to the concentration ranging from 10% to 50% (w/v). Moreover, the antibiofilm activity was highly consistent with MIC affecting bacterial growth inhibition. In conclusion, a robust antimicrobial and antibiofilm activity for Trigona stingless bee honey over the stinging bee Centaurea hyalolepis and Citrus honeys is noticed which endows the usage of Trigona honey in the antimicrobial industry.

Evaluating models and assessment techniques for understanding oral biofilm complexity

Oral biofilms are three-dimensional (3D) complex entities initiating dental diseases and have been evaluated extensively in the scientific literature using several biofilm models and assessment techniques. The list of biofilm models and assessment techniques may overwhelm a novice biofilm researcher. This narrative review aims to summarize the existing literature on biofilm models and assessment techniques, providing additional information on selecting an appropriate model and corresponding assessment techniques, which may be useful as a guide to the beginner biofilm investigator and as a refresher to experienced researchers. The review addresses previously established 2D models, outlining their advantages and limitations based on the growth environment, availability of nutrients, and the number of bacterial species, while also exploring novel 3D biofilm models. The growth of biofilms on clinically relevant 3D models, particularly melt electrowritten fibrous scaffolds, is discussed with a specific focus that has not been previously reported. Relevant studies on validated oral microcosm models that have recently gaining prominence are summarized. The review analyses the advantages and limitations of biofilm assessment methods, including colony forming unit culture, crystal violet, 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt assays, confocal microscopy, fluorescence in situ hybridization, scanning electron microscopy, quantitative polymerase chain reaction, and next-generation sequencing. The use of more complex models with advanced assessment methodologies, subject to the availability of equipment/facilities, may help in developing clinically relevant biofilms and answering appropriate research questions.

A Cross-Sectional Study on the Knowledge, Attitudes, and Oral Hygiene Practices of Secondary School Students in Al-Qunfudah District, Saudi Arabia

Background Oral health is closely related to general health awareness and good oral hygiene practices, which makes it an important aspect of general health and well-being. The current study assessed the knowledge, attitudes, and practices of oral hygiene among secondary school students in Al-Qunfudah district, Saudi Arabia. Methods A convenient sample of 383 male and female secondary school students in the Al-Qunfudah district, Saudi Arabia, was included in this descriptive cross-sectional study. The research data were collected from the study sample through a self-administered online survey via WhatsApp and Telegram electronic applications. Finally, the collected data were coded and analyzed through the Statistical Package for the Social Sciences (SPSS) version 25.0 (SPSS Inc., Chicago, IL) and expressed in frequencies, percentages, mean, and standard deviation. The chi-squared and Fisher's exact tests were applied to assess the relationship between the participants' knowledge and practice scores of oral hygiene and their demographic characteristics. A P-value of less than 0.05 was regarded as significant. Results In this study, female students represented 70% of the sample, and most of them were Saudi (97.0%). Many of them identified the great impact of oral hygiene on overall health (89.2%), and more than two-thirds indicated that brushing their teeth regularly would prevent oral problems (89.2%). Nearly two-thirds of them perceived that dental problems would affect their school attendance; however, 59.1% ignored the important role of schools in maintaining students' oral hygiene. The poor practice of dental care was observed among students, as 47.5% brush their teeth twice daily and a third replace their brushes every three months. Despite the fact that the majority of the study population had adequate knowledge (44.4%) and a positive attitude (78.6%) toward oral hygiene, only 39.9% could effectively apply it. The knowledge of oral hygiene was significantly better among females (P = 0.005), older students (P = 0.001), those at a higher academic level (P = 0.016), and students from Al-Qunfudah city (P = 0.007). Furthermore, older pupils, those with a higher academic level, and those from Al-Qunfudah city performed better in terms of dental hygiene than their peers (P-value was 0.001 for each). Conclusion  Secondary school students generally have adequate awareness levels and positive attitudes toward oral hygiene, but they practice it with remarkably little consistency. Schools should emphasize their crucial roles in enhancing oral health among their students of different education levels through their curriculum and frequent monitoring of students. Persuasive and realistic oral health education initiatives are recommended for schoolchildren and their family members or caregivers, with a particular emphasis on males, younger children, and those living in rural areas.

Effect of Processing Methods of Human Saliva on the Proteomic Profile and Protein-Mediated Biological Processes

The use of saliva as a protein source prior to microbiological and biological assays requires previous processing. However, the effect of these processing methods on the proteomic profile of saliva has not been tested. Stimulated human saliva was collected from eight healthy volunteers. Non-processed saliva was compared with 0.22 μm filtered, 0.45 μm filtered, and pasteurized saliva, by liquid chromatography-mass spectrometry. Data are available via ProteomeXchange with identifier PXD039248. The effect of processed saliva on microbial adhesion was tested using bacterial and fungus species and in biological cell behavior using HaCaT immortalized human keratinocytes. Two hundred and seventy-eight proteins were identified in non-processed saliva, of which 54 proteins (≈19%) were exclusive. Saliva processing reduced identified proteins to 222 (≈80%) for the 0.22 μm group, 219 (≈79%) for the 0.45 μm group, and 201 (≈72%) for the pasteurized saliva, compared to non-processed saliva. The proteomic profile showed similar molecular functions and biological processes. The different saliva processing methods did not alter microbial adhesion (ANOVA, p > 0.05). Interestingly, pasteurized saliva reduced keratinocyte cell viability. Saliva processing methods tested reduced the proteomic profile diversity of saliva but maintained similar molecular functions and biological processes, not interfering with microbial adhesion and cell viability, except for pasteurization, which reduced cell viability.

The Current Antimicrobial and Antibiofilm Activities of Synthetic/Herbal/Biomaterials in Dental Application

Herbal and chemical products are used for oral care and biofilm treatment and also have been reported to be controversial in the massive trials conducted in this regard. The present review is aimed at evaluating the potential of relevant herbal and chemical products and comparing their outcomes to conventional oral care products and summarizing the current state of evidence of the antibiofilm properties of different products by evaluating studies from the past eleven years. Chlorhexidine gluconate (CHX), essential oils (EOs), and acetylpyridinium chloride were, respectively, the most commonly studied agents in the included studies. As confirmed by all systematic reviews, CHX and EO significantly control the plaque formation and gingival indices. Fluoride is another interesting reagent in oral care products that has shown promising results of oral health improvement, but the evidence quality needs to be refined. The synergy between natural plants and chemical products should be targeted in the future to accede to the formation of new, efficient, and healthy anticaries strategies. Moreover, to discover their biofilm-interfering or biofilm-inhibiting activities, effective clinical trials are needed. In this review article, therapeutic applications of herbal/chemical materials in oral biofilm infections are discussed in recent years (2010-2022).

Operational culture conditions determinate benzalkonium chloride resistance in L. monocytogenes-E. coli dual species biofilms

Biofilms pose a serious challenge to the food industry. Higher resistance of biofilms to any external stimuli is a major hindrance for their eradication. In this study, we compared the growth dynamics and benzalkonium chloride (BAC) resistance of dual species Listeria monocytogenes-Escherichia coli 48 h biofilms formed on stainless steel (SS) coupons surfaces under batch and fed-batch cultures. Differences between both operational culture conditions were evaluated in terms of total viable adhered cells (TVAC) in the coupons during 48 h of the mixed-culture and of reduction of viable adhered cells (RVAC) obtained after BAC-treatment of a 48 h biofilm of L. monocytogenes-E. coli formed under both culture conditions. Additionally, epifluorescence microscopy (EFM) and confocal scanning microscopy (CLSM) permitted to visualize the 2D and 3D biofilms structure, respectively. Observed results showed an increase in the TVAC of both strains during biofilm development, being the number of E. coli adhered cells higher than L. monocytogenes in both experimental systems (p < 0.05). Additionally, the number of both strains were higher approximately 2.0 log CFU/coupon in batch conditions compared to fed-batch system (p < 0.05). On the contrary, significantly higher resistance to BAC was observed in biofilms formed under fed-batch conditions. Furthermore, in batch system both strains had a similar reduction level of approximately 2.0 log CFU/coupon, while significantly higher resistance of E. coli compared to L. monocytogenes (reduction level of 0.69 and 1.72 log CFU/coupon, respectively) (p < 0.05) was observed in fed-batch system. Microscopic image visualization corroborated these results and showed higher complexity of 2D and 3D structures in dual species biofilms formed in batch cultures. Overall, we can conclude that the complexity of the biofilm structure does not always imply higher resistance to external stimuli, and highlights the need to mimic industrial operational conditions in the experimental systems in order to better assess the risk associated to the presence of pathogenic bacterial biofilms.

Relevance of Biofilm Models in Periodontal Research: From Static to Dynamic Systems

Microbial biofilm modeling has improved in sophistication and scope, although only a limited number of standardized protocols are available. This review presents an example of a biofilm model, along with its evolution and application in studying periodontal and peri-implant diseases. In 2011, the ETEP (Etiology and Therapy of Periodontal and Peri-Implant Diseases) research group at the University Complutense of Madrid developed an in vitro biofilm static model using representative bacteria from the subgingival microbiota, demonstrating a pattern of bacterial colonization and maturation similar to in vivo subgingival biofilms. When the model and its methodology were standardized, the ETEP research group employed the validated in vitro biofilm model for testing in different applications. The evolution of this model is described in this manuscript, from the mere observation of biofilm growth and maturation on static models on hydroxyapatite or titanium discs, to the evaluation of the impact of dental implant surface composition and micro-structure using the dynamic biofilm model. This evolution was based on reproducing the ideal microenvironmental conditions for bacterial growth within a bioreactor and reaching the target surfaces using the fluid dynamics mimicking the salivary flow. The development of this relevant biofilm model has become a powerful tool to study the essential processes that regulate the formation and maturation of these important microbial communities, as well as their behavior when exposed to different antimicrobial compounds.

Implication of Surface Properties, Bacterial Motility, and Hydrodynamic Conditions on Bacterial Surface Sensing and Their Initial Adhesion

Biofilms are structured microbial communities attached to surfaces, which play a significant role in the persistence of biofoulings in both medical and industrial settings. Bacteria in biofilms are mostly embedded in a complex matrix comprised of extracellular polymeric substances that provide mechanical stability and protection against environmental adversities. Once the biofilm is matured, it becomes extremely difficult to kill bacteria or mechanically remove biofilms from solid surfaces. Therefore, interrupting the bacterial surface sensing mechanism and subsequent initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Noting that the process of bacterial adhesion is influenced by many factors, including material surface properties, this review summarizes recent works dedicated to understanding the influences of surface charge, surface wettability, roughness, topography, stiffness, and combination of properties on bacterial adhesion. This review also highlights other factors that are often neglected in bacterial adhesion studies such as bacterial motility and the effect of hydrodynamic flow. Lastly, the present review features recent innovations in nanotechnology-based antifouling systems to engineer new concepts of antibiofilm surfaces.

Interaction between Lactobacillus reuteri and periodontopathogenic bacteria using in vitro and in vivo (G. mellonella) approaches

Periodontitis is a multifactorial inflammatory disease, and the major cause of tooth loss in adults. New therapies have been proposed for its treatment, including the use of probiotics such as Lactobacillus reuteri. The objective of this study was to evaluate the antimicrobial effects of L. reuteri: live, heat-killed and culture filtrate (cell-free supernatant), on periodontopathogenic bacteria (Fusobacterium nucleatum and Aggregatibacter actinomycetemcomitans) in vitro, as well as the in vivo survival curve, hemocyte density and microbial recovery using Galleria mellonella. For in vitro assays, all preparations reduced colony forming units of F. nucleatum, while only live L. reuteri reduced the growth of A. actinomycetemcomitans. All treatments reduced periodontopathogenic bacteria growth in vivo. The treatment with the supernatant increased the survival of larvae infected with F. nucleatum more than the treatment with live L. reuteri, and none of the treatments altered the survival of A. actinomycetemcomitans-infected larvae. In addition, the treatment with L. reuteri preparations did not alter the hemocyte count of F. nucleatum- and A. actinomycetemcomitans-infected larvae. This study demonstrated that L. reuteri preparations exerted antimicrobial effects and increased the survival of G. mellonella infected by F. nucleatum, although only live L. reuteri was able to reduce the growth of A. actinomycetemcomitans in vitro.

Nanoparticles having amphiphilic silane containing Chlorin e6 with strong anti-biofilm activity against periodontitis-related pathogens

OBJECTIVES

The objectives of this study were to: (1) develop the multifunctional nanoparticles containing Chlorin e6 (Ce6), Coumarin 6 (C6) and Fe₃O₄ nanoparticles (NPs); and (2) investigate the inhibitory effects of the nanoparticles via antibacterial photodynamic therapy (aPDT) against three species of periodontitis-related pathogens for the first time.

MATERIALS AND METHODS

Ce6 and C6 were co-loaded into the Fe₃O₄-silane core-shell structure to form multifunctional nanoparticles (denoted "Fe₃O₄-silane@Ce6/C6 MNPs"). The physical and chemical properties of nanoparticles were characterized. Biofilm properties of Streptococcus sanguinis, Porphyromonas gingivalis and Fusobacterium nucleatum were tested. Colony-forming units (CFU), live/dead assay, and metabolic activity of biofilms were determined to evaluate the aPDT function mediated by the Fe₃O₄-silane@Ce6/C6 MNPs. Fluorescence imaging and the targeted antibacterial effects were also investigated.

RESULTS

Fe₃O₄-silane@Ce6/C6 MNPs showed superparamagnetic properties, chemical stability and water-solubility, with no cytotoxicity. Fe₃O₄ NPs did not compromise the emission peaks of C6 and Ce6. The Fe₃O₄-silane@Ce6/C6-mediated aPDT had much greater reduction in biofilms than the control groups (p < 0.05). Biofilm CFU was reduced by about 4-5 orders of magnitude via Fe₃O₄-silane@Ce6/C6-mediated aPDT. The co-loading of Ce6 and C6 enabled the real-time aPDT monitoring by ratio emissions with the same wavelength. Fe₃O₄ with magnetic field enabled the targeting of infection sites by killing bacteria via magnetic field.

CONCLUSION

The multifunctional nanoparticles exerted strong anti-biofilm activity against periodontitis-related pathogens, with excellent biocompatibility, real-time monitoring, and magnetically-targeting capacities. The multifunctional nanoparticles have great potential in antibacterial applications to inhibit the occurrence and progression of periodontitis.

Antibacterial, Hydrophilic Effect and Mechanical Properties of Orthodontic Resin Coated with UV-Responsive Photocatalyst

Photocatalysts have multiple applications in air purifiers, paints, and self-cleaning coatings for medical devices such as catheters, as well as in the elimination of xenobiotics. In this study, a coating of a UV-responsive photocatalyst, titanium dioxide (TiO₂), was applied to an orthodontic resin. The antibacterial activity on oral bacteria as well as hydrophilic properties and mechanical properties of the TiO₂-coated resin were investigated. ultraviolet A (UVA) (352 nm) light was used as the light source. Antibacterial activity was examined with or without irradiation. Measurements of early colonizers and cariogenic bacterial count, i.e., colony forming units (CFU), were performed after irradiation for different time durations. Hydrophilic properties were evaluated by water contact angle measurements. While, for the assessment of mechanical properties, flexural strength was measured by the three-point bending test. In the coat(+)light(+) samples the CFU were markedly decreased compared to the control samples. Water contact angle of the coat(+)light(+) samples was decreased after irradiation. The flexural strength of the specimen irradiated for long time showed a higher value than the required standard value, indicating that the effect of irradiation was weak. We suggest that coating with the ultraviolet responsive photocatalyst TiO₂ is useful for the development of orthodontic resin with antimicrobial properties.