Dental composite materials containing carolacton inhibit biofilm growth of Streptococcus mutans

Myxobacteria: biology and bioactive secondary metabolites

Myxobacteria are Gram-negative eubacteria and they thrive in a variety of habitats including soil rich in organic matter, rotting wood, animal dung and marine environment. Myxobacteria are a promising source of new compounds associated with diverse bioactive spectrum and unique mode of action. The genome information of myxobacteria has revealed many orphan biosynthetic pathways indicating that these bacteria can be the source of several novel natural products. In this review, we highlight the biology of myxobacteria with emphasis on their habitat, life cycle, isolation methods and enlist all the bioactive secondary metabolites purified till date and their mode of action.

Evaluating antibacterial and surface mechanical properties of chitosan modified dental resin composites

BACKGROUND

The antibacterial properties are beneficial and desired for dental restorative composite materials. The incorporation of various antimicrobial agents into resin composites may compromise their physical and mechanical properties hence limiting their applications.

OBJECTIVE

The aim of the current study is to evaluate the antibacterial activity and the hardness of microhybrid and flowable resin based composites (RBCs) modified using novel antimicrobial agent chitosan (CS).

METHODS

The antibacterial activity of microhybrid and flowable RBCs modified with 0, 0.25, 0.5 and 1% w/w chitosan (CS) against Actinomyces viscous bacteria was explored using agar diffusion test and direct contact methods. The hardness of control and experimental RBCs was determined by Vickers hardness (VH) tester.

RESULTS

The results revealed that control and experimental flowable and microhybrid RBCs did not demonstrate growth inhibition zone in the lawn growth of Actinomyces viscous. The direct contact test revealed that colony forming unit (CFU) count of Actinomyces viscous was comparable among the experimental and control materials. The flowable RBCs containing 1% CS had significantly higher VH compared to control and other experimental flowable RBC groups. The microhybrid RBCs consisting of 0.50% CS exhibited significantly higher VH compared to experimental microhybrid RBC group containing 1% CS.

Combating the Coronavirus Pandemic: Early Detection, Medical Treatment, and a Concerted Effort by the Global Community

The World Health Organization (WHO) has declared the outbreak of 2019 novel coronavirus, known as 2019-nCoV, a pandemic, as the coronavirus has now infected over 2.6 million people globally and caused more than 185,000 fatalities as of April 23, 2020. Coronavirus disease 2019 (COVID-19) causes a respiratory illness with symptoms such as dry cough, fever, sudden loss of smell, and, in more severe cases, difficulty breathing. To date, there is no specific vaccine or treatment proven effective against this viral disease. Early and accurate diagnosis of COVID-19 is thus critical to curbing its spread and improving health outcomes. Reverse transcription-polymerase chain reaction (RT-PCR) is commonly used to detect the presence of COVID-19. Other techniques, such as recombinase polymerase amplification (RPA), loop-mediated isothermal amplification (LAMP), clustered regularly interspaced short palindromic repeats (CRISPR), and microfluidics, have allowed better disease diagnosis. Here, as part of the effort to expand screening capacity, we review advances and challenges in the rapid detection of COVID-19 by targeting nucleic acids, antigens, or antibodies. We also summarize potential treatments and vaccines against COVID-19 and discuss ongoing clinical trials of interventions to reduce viral progression.

Deep sequencing of biofilm microbiomes on dental composite materials

Background: The microbiome on dental composites has not been studied in detail before. It has not been conclusively clarified whether restorative materials influence the oral microbiome. Methods: We used Illumina Miseq next-generation sequencing of the 16S V1-V2 region to compare the colonisation patterns of bovine enamel (BE) and the composite materials Grandio Flow (GF) and Grandio Blocs (GB) after 48 h in vivo in 14 volunteers. Applying a new method to maintain the oral microbiome ex vivo for 48 h also, we compared the microbiome on GF alone and with the new antimicrobial substance carolacton (GF+C). Results: All in vitro biofilm communities showed a higher diversity and richness than those grown in vivo but the very different atmospheric conditions must be considered. Contrary to expectations, there were only a few significant differences between BE and the composite materials GB and GF either in vivo or in vitro: Oribacterium, Peptostreptococcaceae [XI][G-1] and Streptococcus mutans were more prevalent and Megasphaera, Prevotella oulorum, Veillonella atypica, V. parvula, Gemella morbillorum, and Fusobacterium periodonticum were less prevalent on BE than on composites. In vivo, such preferences were only significant for Granulicatella adiacens (more prevalent on BE) and Fusobacterium nucleatum subsp. animalis (more prevalent on composites). On DNA sequence level, there were no significant differences between the biofilm communities on GF and GF+C. Conclusion: We found that the oral microbiome showed an increased richness when grown on various composites compared to BE in vitro, but otherwise changed only slightly independent of the in vivo or in vitro condition. Our new ex vivo biofilm model might be useful for pre-clinical testing of preventive strategies.

Evaluation of Restorative Materials Containing Preventive Additives in a Secondary Caries Model in vitro

The incorporation of antibacterial agents into dental restorative materials is a promising strategy for secondary caries prevention. Previously, Carolacton affected Streptococcus mutans biofilm formation on composite materials in vitro. The present study evaluated secondary caries formation adjacent to Carolacton-containing composites and conventional restorative materials using an artificial biofilm model. Standardized cavities were prepared in bovine dentin-enamel samples (n = 175) and restored with various dental materials (Tetric EvoCeram [T], GrandioSo composite without [G] and with Carolacton [GC], Grandio Flow without [F] and with Carolacton [FC], GrandioSo containing sodium fluoride [GNaF], and Ketac Fil [K]). After artificial aging, S. mutans was grown on the samples for 7 days. The investigation of gap sizes and secondary caries formation was performed using confocal laser scanning microscopy and transversal microradiography. Median gap size in enamel was 9.4 µm (interquartile range 7.9–12.7). Compared to all other groups significant differences in gap sizes could be observed for Ketac Fil (p < 0.001; Mann-Whitney test). Only GrandioSo composite containing 30% sodium fluoride and Ketac Fil showed significantly smaller lesion areas in enamel (p < 0.001; Mann-Whitney test) than all other groups which was confirmed by the mineral loss data (p < 0.001; Mann-Whitney test). Based on the present in vitro results, it seems that Carolacton-containing composite in the current formulation within the shown simplified monoculture biofilm model is not able to prevent caries formation compared to fluoride-releasing restorative materials.

Inhibition of Streptococcus mutans and S. sobrinus biofilms by liamocins from Aureobasidium pullulans

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Liamocins are polyol lipids that specifically inhibit Streptococcus spp..

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Liamocins inhibited biofilms of S. mutans and S. sobrinus in MTP assays.

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MTP results were verified in biofilm flow cell assays.

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Liamocins are potential new inhibitors of oral streptococcal biofilms.

The aim of this study was to determine if the novel anti-streptococcal inhibitors, liamocins, also inhibit biofilm formation by S. mutans and S. sobrinus. S. mutans strain ATCC 25175 and S. sobrinus strain ATCC 33478 were tested for biofilm formation in a rapid microtiter plate (MTP) assay and the effects of added liamocins were determined. This assay measures relative biofilm growth on pin lids. Results were verified in a biofilm flow cell assay, using hydroxyapatite-coated coupons to simulate dental material. Planktonic cultures of S. mutans and S. sobrinus were inhibited by 0.1 mg liamocins/ml. When liamocins were added after the adhesion phase in a rapid microtiter plate assay, S. mutans was inhibited 53% by 5 mg liamocins/ml, while S. sobrinus was more sensitive, showing 100% inhibition at 0.5 mg liamocins/ml. When liamocins were added during the adhesion phase, biofilms of S. mutans showed 78% inhibition at 3.0 mg liamocins/ml. In a biofilm flow cell assay, liamocins added after the adhesion phase at 0.5 mg liamocins/ml inhibited biofilms of S. sobrinus, and appeared to remove biofilms over time. Liamocins were shown for the first time to inhibit biofilm formation by S. mutans and S. sobrinus. Since liamocins are specific for Streptococcus spp., they are potential new inhibitors of oral streptococcal biofilms that should not affect normal oral microflora.

Natural saliva as an adjuvant in a secondary caries model based on Streptococcus mutans

OBJECTIVE

Two factors for secondary caries formation were evaluated using an artificial biofilm model, saliva as additive in culture medium and bonding procedures of composite materials for artificial gap creation.

DESIGN

Standardized cavities were prepared in bovine tooth samples (n = 44), treated with two different bonding pretreatments, restored and after artificial ageing incubated with Streptococcus mutans in a Mueller-Hinton-Broth-Sugar medium with or without human saliva for seven days. Secondary caries formation was analyzed using confocal laser scanning microscopy and transversal microradiography.

RESULTS

Lesions were significantly pronounced in groups using saliva, but were not influenced by the bonding pretreatments.

CONCLUSIONS

The results indicate that the addition of saliva, but not the type of bonding procedure influences the outcome in the present biofilm-based secondary caries model.

A highly efficient bactericidal surface based on the co-capture function and photodynamic sterilization

Bacterial infection is posing a great threat to human life, and constructing a platform to capture or kill the bacteria attached on a material surface is of particular significance.

Diverted Total Synthesis of Carolacton-Inspired Analogs Yields Three Distinct Phenotypes in Streptococcus mutans Biofilms

The oral microbiome is a dynamic environment inhabited by both commensals and pathogens. Among these is Streptococcus mutans, the causative agent of dental caries, the most prevalent childhood disease. Carolacton has remarkably specific activity against S. mutans, causing acid-mediated cell death during biofilm formation; however, its complex structure limits its utility. Herein, we report the diverted total synthesis and biological evaluation of a rationally designed library of simplified analogs that unveiled three unique biofilm phenotypes further validating the role of natural product synthesis in the discovery of new biological phenomena.

Twelve-membered macrolactones: privileged scaffolds for the development of new therapeutics

Natural products commonly produced as secondary metabolites of various plants and micro-organisms represent a diverse chemical space of compounds. The diversity of natural products makes them an attractive target for interrogation by both chemists and biologists alike. Indeed, the study of 12-membered macrolactones has already led to the discovery of lead drug compounds and new biological targets, which has motivated the development of diverted total synthetic routes to libraries of analogs. This review explores the discovery, biological characterization, and synthesis of several 12-membered macrolactones, exploiting examples that underscore their importance in the drug discovery field. It is our hope that this review will motivate further interest in this class of natural products, a group of molecules that we think merit the classification of 'privileged scaffolds' within the medicinal chemistry community, to further investigate and develop novel compounds with promising bioactivity.

Stereoselective Total Synthesis of Carolacton

A short and convergent strategy for the stereoselective total synthesis of biologically active natural product carolacton has been accomplished. Our synthesis highlights the Urpi acetal aldol, Crimmins aldol, Ireland-Claisen rearrangement, TiCl₄-assisted aldol followed by β-hydroxy elimination to construct C₇-C₈ olefin, and ring-closing metathesis as the key steps for achieving the target molecule with an overall yield of 18.8%.

The carolactam strategy is ineffective: synthesis and biological evaluation of carolactam

The lactam analogue of carolacton was prepared which has lost biofilm inhibitory activity towards Streptococcus mutans.

Natural products from myxobacteria: novel metabolites and bioactivities

Covering: 2011-July 2016Myxobacteria are a rich source for structurally diverse secondary metabolites with intriguing biological activities. Here we report on new natural products that were isolated from myxobacteria in the period of 2011 to July 2016. Some examples of recent advances on modes-of-action are also summarised along with a more detailed overview on five compound classes currently assessed in preclinical studies.

Antibacterial effect of copper-bearing titanium alloy (Ti-Cu) against Streptococcus mutans and Porphyromonas gingivalis

Formation of bacterial biofilms on dental implant material surfaces (titanium) may lead to the development of peri-implant diseases influencing the long term success of dental implants. In this study, a novel Cu-bearing titanium alloy (Ti-Cu) was designed and fabricated in order to efficiently kill bacteria and discourage formation of biofilms, and then inhibit bacterial infection and prevent implant failure, in comparison with pure Ti. Results from biofilm based gene expression studies, biofilm growth observation, bacterial viability measurements and morphological examination of bacteria, revealed antimicrobial/antibiofilm activities of Ti-Cu alloy against the oral specific bacterial species, Streptococcus mutans and Porphyromonas gingivalis. Proliferation and adhesion assays with mesenchymal stem cells, and measurement of the mean daily amount of Cu ion release demonstrated Ti-Cu alloy to be biocompatible. In conclusion, Ti-Cu alloy is a promising dental implant material with antimicrobial/antibiofilm activities and acceptable biocompatibility.

The biofilm inhibitor Carolacton inhibits planktonic growth of virulent pneumococci via a conserved target

New antibacterial compounds, preferentially exploiting novel cellular targets, are urgently needed to fight the increasing resistance of pathogens against conventional antibiotics. Here we demonstrate that Carolacton, a myxobacterial secondary metabolite previously shown to damage Streptococcus mutans biofilms, inhibits planktonic growth of Streptococcus pneumoniae TIGR4 and multidrug-resistant clinical isolates of serotype 19A at nanomolar concentrations. A Carolacton diastereomer is inactive in both streptococci, indicating a highly specific interaction with a conserved cellular target. S. mutans requires the eukaryotic-like serine/threonine protein kinase PknB and the cysteine metabolism regulator CysR for susceptibility to Carolacton, whereas their homologues are not needed in S. pneumoniae, suggesting a specific function for S. mutans biofilms only. A bactericidal effect of Carolacton was observed for S. pneumoniae TIGR4, with a reduction of cell numbers by 3 log units. The clinical pneumonia isolate Sp49 showed immediate growth arrest and cell lysis, suggesting a bacteriolytic effect of Carolacton. Carolacton treatment caused a reduction in membrane potential, but not membrane integrity, and transcriptome analysis revealed compensatory reactions of the cell. Our data show that Carolacton might have potential for treating pneumococcal infections.

Template assisted surface microstructuring of flowable dental composites and its effect on microbial adhesion properties

OBJECTIVES

Despite their various advantages, such as good esthetic properties, absence of mercury and adhesive bonding to teeth, modern dental composites still have some drawbacks, e.g., a relatively high rate of secondary caries on teeth filled with composite materials. Recent research suggests that microstructured biomaterials surfaces may reduce microbial adhesion to materials due to unfavorable physical material-microbe interactions. The objectives of this study were, therefore, to test the hypotheses that (i) different surface microstructures can be created on composites by a novel straightforward approach potentially suitable for clinical application and (ii) that these surface structures have a statistically significant effect on microbial adhesion properties.

METHODS

Six different dental composites were initially tested for their suitability for microstructuring by polydimethylsiloxane (PDMS) templates. Each composite was light-cured between a glass slide and a microstructured PDMS template. The nano-hybrid composite Grandio Flow was the only tested composite with satisfying structurability, and was therefore used for the bacterial adhesion tests. Composites samples were structured with four different microstructures (flat, cubes, linear trapezoid structures, flat pyramids) and incubated for 4h in centrifuged saliva. The bacterial adherence was then characterized by colony forming units (CFUs) and scanning electron microscopy (SEM).

RESULTS

All four microstructures were successfully transferred from the PDMS templates to the composite Grandio Flow. The CFU-test as well as the quantitative analysis of the SEM images showed the lowest bacterial adhesion on the flat composite samples. The highest bacterial adhesion was observed on the composite samples with linear trapezoid structures, followed by flat pyramids and cubes. The microstructure of dental composite surfaces statistically significantly influenced the adhesion of oral bacteria.

SIGNIFICANCE

Modifying the composite surface structure may be a clinically suitable approach to control the microbial adhesion and thus, to reduce the risk of secondary caries at dental composite restorations. Smaller composite surface structures may be useful for accomplishing this.

Highly efficient antibacterial surface grafted with a triclosan-decorated poly(N-hydroxyethylacrylamide) brush

This work presented a highly efficient antibacterial Ti-surface which was grafted with poly(N-hydroxyethylacrylamide) (PHEAA) brush and further decorated with triclosan (TCS). The modified surfaces were characterized using contact angle measurements, X-ray photoelectron spectroscopy, and attenuated total reflectance Fourier transform infrared. The antibacterial performance of the modified surfaces was evaluated using the Streptococcus mutans and Actinomyces naeslundii attachment test. The Ti surface with PHEAA brush (Ti-PHEAA) was able to resist the adhesion of the bacteria, while the TCS-decorated Ti surface (Ti-TCS) showed the capability of killing the bacteria adhered on the surface. As we coupled the TCS to the PHEAA brush, the surface showed highly efficient antibacterial performance due to the combination of the resistance to the bacteria adhesion and its activity of killing bacteria.

Synthesis of new carolacton derivatives and their activity against biofilms of oral bacteria

Carolacton, a secondary metabolite isolated from the extracts ofSorangium cellulosum, causes membrane damage and cell death in biofilms of different oral bacteria.

Antibiotics from myxobacteria

Covering: up to the end of 2013. Myxobacteria produce a vast range of structurally diverse natural products with prominent biological activities. Here, we provide a detailed description and judge the potential of all antibiotically active myxobacterial compounds as lead structures, pointing out their particularities and, if known, their mode of action. Thus, the review provides an overview of the potential of specific compounds, suitable for future investigations and possible clinical applications.

A concise synthesis of carolacton

A synthesis of carolacton, a myxobacterial natural product that has profound effects on Streptococcus mutans biofilms, is reported. The synthesis proceeds via a longest linear sequence of 14 steps from an Evans β-ketoimide and enabled preliminary evaluations of the effects of late-stage intermediates on S. mutans biofilms. These studies suggest that further investigations into carolacton’s structure–function relationships are warranted.

A QM/MM MD study of the pH-dependent ring-opening catalysis and lid motif flexibility in glucosamine 6-phosphate deaminase

QM/MM MD and MM MD simulations reveal pH-dependent proton-shuttle ring-opening mechanisms of GlcN6P and dynamical behavior of the lid motif inSmuNagB.