Activity of tyrosol against single and mixed-species oral biofilms

Integrating uterine microbiome and metabolome to advance the understanding of the uterine environment in dairy cows with metritis

BACKGROUND

Metritis is a prevalent uterine disease that affects the welfare, fertility, and survival of dairy cows. The uterine microbiome from cows that develop metritis and those that remain healthy do not differ from calving until 2 days postpartum, after which there is a dysbiosis of the uterine microbiome characterized by a shift towards opportunistic pathogens such as Fusobacteriota and Bacteroidota. Whether these opportunistic pathogens proliferate and overtake the uterine commensals could be determined by the type of substrates present in the uterus. The objective of this study was to integrate uterine microbiome and metabolome data to advance the understanding of the uterine environment in dairy cows that develop metritis. Holstein cows (n = 104) had uterine fluid collected at calving and at the day of metritis diagnosis. Cows with metritis (n = 52) were paired with cows without metritis (n = 52) based on days after calving. First, the uterine microbiome and metabolome were evaluated individually, and then integrated using network analyses.

RESULTS

The uterine microbiome did not differ at calving but differed on the day of metritis diagnosis between cows with and without metritis. The uterine metabolome differed both at calving and on the day of metritis diagnosis between cows that did and did not develop metritis. Omics integration was performed between 6 significant bacteria genera and 153 significant metabolites on the day of metritis diagnosis. Integration was not performed at calving because there were no significant differences in the uterine microbiome. A total of 3 bacteria genera (i.e. Fusobacterium, Porphyromonas, and Bacteroides) were strongly correlated with 49 metabolites on the day of metritis diagnosis. Seven of the significant metabolites at calving were among the 49 metabolites strongly correlated with opportunistic pathogenic bacteria on the day of metritis diagnosis. The main metabolites have been associated with attenuation of biofilm formation by commensal bacteria, opportunistic pathogenic bacteria overgrowth, tissue damage and inflammation, immune evasion, and immune dysregulation.

CONCLUSIONS

The data integration presented herein helps advance the understanding of the uterine environment in dairy cows with metritis. The identified metabolites may provide a competitive advantage to the main uterine pathogens Fusobacterium, Porphyromonas and Bacteroides, and may be promising targets for future interventions aiming to reduce opportunistic pathogenic bacteria growth in the uterus.

'Green' silver nanoparticles combined with tyrosol as potential oral antimicrobial therapy

OBJECTIVES

This study aimed to evaluate silver nanoparticles (AgNPs) obtained by a 'green' route associated or not to tyrosol (TYR) against Streptococcus mutans and Candida albicans in planktonic and biofilms states.

METHODS

AgNPs were obtained by a 'green' route using pomegranate extract. The minimum inhibitory concentration (MIC) against S. mutans and C. albicans was determined for AgNPs and TYR combined and alone, and fractional inhibitory concentration index (FICI) was calculated. Single biofilms of C. albicans and S. mutans were cultivated for 24 h and then treated with drugs alone or in combination for 24 h.

RESULTS

AgNPs and TYR were effective against C. albicans and S. mutans considering planktonic cells alone and combined. The MIC values obtained for C. albicans was 312.5 µg/mL (AgNPs) and 50 mM (TYR) and for S. mutans was 78.1 µg/mL (AgNPs) and 90 mM (TYR). The combination of these antimicrobial agents was also effective against both microorganisms: 2.44 µg/mL/0.08 mM (AgNPs/TYR) for C. albicans and 39.05 µg/mL /1.25 mM (AgNPs/TYR) for S. mutans. However, synergism was observed only for C. albicans (FICI 0.008). When biofilm was evaluated, a reduction of 4.62 log10 was observed for S. mutans biofilm cells treated with AgNPs (p < 0.05, Tukey test). However, the addition of TYR to AgNPs did not improve their action against biofilm cells (p > 0.05). AgNPs combined with TYR demonstrated a synergistic effect against C. albicans biofilms.

CONCLUSIONS

These findings suggest the potential use of AgNPs with or without TYR against C. albicans and S. mutans, important oral pathogens.

CLINICAL SIGNIFICANCE

AgNPs obtained by a 'green' route combined or not with TYR can be an alternative to develop several types of oral antimicrobial therapies and biomaterials.

Total transcriptome response for tyrosol exposure in Aspergillus nidulans

Although tyrosol is a quorum-sensing molecule of Candida species, it has antifungal activity at supraphysiological concentrations. Here, we studied the effect of tyrosol on the physiology and genome-wide transcription of Aspergillus nidulans to gain insight into the background of the antifungal activity of this compound. Tyrosol efficiently reduced germination of conidia and the growth on various carbon sources at a concentration of 35 mM. The growth inhibition was fungistatic rather than fungicide on glucose and was accompanied with downregulation of 2199 genes related to e.g. mitotic cell cycle, glycolysis, nitrate and sulphate assimilation, chitin biosynthesis, and upregulation of 2250 genes involved in e.g. lipid catabolism, amino acid degradation and lactose utilization. Tyrosol treatment also upregulated genes encoding glutathione-S-transferases (GSTs), increased specific GST activities and the glutathione (GSH) content of the cells, suggesting that A. nidulans can detoxify tyrosol in a GSH-dependent manner even though this process was weak. Tyrosol did not induce oxidative stress in this species, but upregulated "response to nutrient levels", "regulation of nitrogen utilization", "carbon catabolite activation of transcription" and "autophagy" genes. Tyrosol may have disturbed the regulation and orchestration of cellular metabolism, leading to impaired use of nutrients, which resulted in growth reduction.

Metabolomics and Microbiomics Insights into Differential Surface Fouling of Three Macroalgal Species of Fucus (Fucales, Phaeophyceae) That Co-Exist in the German Baltic Sea

The brown algal genus Fucus provides essential ecosystem services crucial for marine environments. Macroalgae (seaweeds) release dissolved organic matter, hence, are under strong settlement pressure from micro- and macrofoulers. Seaweeds are able to control surface epibionts directly by releasing antimicrobial compounds onto their surfaces, and indirectly by recruiting beneficial microorganisms that produce antimicrobial/antifouling metabolites. In the Kiel Fjord, in the German Baltic Sea, three distinct Fucus species coexist: F. vesiculosus, F. serratus, and F. distichus subsp. evanescens. Despite sharing the same habitat, they show varying fouling levels; F. distichus subsp. evanescens is the least fouled, while F. vesiculosus is the most fouled. The present study explored the surface metabolomes and epiphytic microbiota of these three Fucus spp., aiming to uncover the factors that contribute to the differences in the fouling intensity on their surfaces. Towards this aim, algal surface metabolomes were analyzed using comparative untargeted LC-MS/MS-based metabolomics, to identify the marker metabolites influencing surface fouling. Their epiphytic microbial communities were also comparatively characterized using high-throughput amplicon sequencing, to pinpoint the differences in the surface microbiomes of the algae. Our results show that the surface of the least fouling species, F. distichus subsp. evanescens, is enriched with bioactive compounds, such as betaine lipids MGTA, 4-pyridoxic acid, and ulvaline, which are absent from the other species. Additionally, it exhibits a high abundance of the fungal genera Mucor and Alternaria, along with the bacterial genus Yoonia-Loktanella. These taxa are known for producing antimicrobial/antifouling compounds, suggesting their potential role in the observed fouling resistance on the surface of the F. distichus subsp. evanescens compared to F. serratus and F. vesiculosus. These findings provide valuable clues on the differential surface fouling intensity of Fucus spp., and their importance in marine chemical defense and fouling dynamics.

Fungal quorum-sensing molecules and antiseptics: a promising strategy for biofilm modulation?

New strategies to control fungal biofilms are essential, especially those that interfere in the biofilm organization process and cellular communication, known as quorum sensing. The effect of antiseptics and quorum-sensing molecules (QSMs) have been considered with regard to this; however, little has been elucidated, particularly because studies are often restricted to the action of antiseptics and QSMs against a few fungal genera. In this review, we discuss progress reported in the literature thus far and analyze, through in silico methods, 13 fungal QSMs with regard to their physicochemical, pharmacological, and toxicity properties, including their mutagenicity, tumorigenicity, hepatotoxicity, and nephrotoxicity. From these in silico analyses, we highlight 4-hydroxyphenylacetic acid and tryptophol as having satisfactory properties and, thus, propose that these should be investigated further as antifungal agents. We also recommend future in vitro approaches to determine the association of QSMs with commonly used antiseptics as potential antibiofilm agents.

Current and prospective therapeutic strategies: tackling Candida albicans and Streptococcus mutans cross-kingdom biofilm

Candida albicans (C. albicans) is the most frequent strain associated with cross-kingdom infections in the oral cavity. Clinical evidence shows the co-existence of Streptococcus mutans (S. mutans) and C. albicans in the carious lesions especially in children with early childhood caries (ECC) and demonstrates the close interaction between them. During the interaction, both S. mutans and C. albicans have evolved a complex network of regulatory mechanisms to boost cariogenic virulence and modulate tolerance upon stress changes in the external environment. The intricate relationship and unpredictable consequences pose great therapeutic challenges in clinics, which indicate the demand for de novo emergence of potential antimicrobial therapy with multi-targets or combinatorial therapies. In this article, we present an overview of the clinical significance, and cooperative network of the cross-kingdom interaction between S. mutans and C. albicans. Furthermore, we also summarize the current strategies for targeting cross-kingdom biofilm.

Biofilm ecology associated with dental caries: Understanding of microbial interactions in oral communities leads to development of therapeutic strategies targeting cariogenic biofilms

A biofilm is a sessile community characterized by cells attached to the surface and organized into a complex structural arrangement. Dental caries is a biofilm-dependent oral disease caused by infection with cariogenic pathogens, such as Streptococcus mutans, and associated with frequent exposure to a sugar-rich diet and poor oral hygiene. The virulence of cariogenic biofilms is often associated with the spatial organization of S. mutans enmeshed with exopolysaccharides on tooth surfaces. However, in the oral cavity, S. mutans does not act alone, and several other microbes contribute to cariogenic biofilm formation. Microbial communities in cariogenic biofilms are spatially organized into complex structural arrangements of various microbes and extracellular matrices. The balance of microbiota diversity with reduced diversity and a high proportion of acidogenic-aciduric microbiota within the biofilm is closely related to the disease state. Understanding the characteristics of polymicrobial biofilms and the association of microbial interactions within the biofilm (e.g., symbiosis, cooperation, and competition) in terms of their potential role in the pathogenesis of oral disease would help develop new strategies for interventions in virulent biofilm formation.

Pomegranate Extract Potentiates the Anti-Demineralizing, Anti-Biofilm, and Anti-Inflammatory Actions of Non-Alcoholic Mouthwash When Associated with Sodium-Fluoride Trimetaphosphate

This study investigated the anti-caries and anti-inflammatory effects of mouthwash formulations containing Punica granatum (pomegranate) peel extract (PPE), sodium-trimetaphosphate, and low concentrations of fluoride. PPE was characterized using high-performance liquid chromatography (ellagic acid and punicalagin). Total phenolics were quantified among formulations, and their stability was analyzed for 28 days. The formulation effects were evaluated as follows: (1) inorganic component concentration and reduced demineralization on bovine enamel blocks subjected to pH cycling; (2) anti-biofilm effect on dual-biofilms of Streptococcus mutans ATCC 25175 and Candida albicans ATCC 10231 treated for 1 and 10 min, respectively; and (3) cytotoxicity and production of inflammatory mediators (interleukin-6 and tumor necrosis factor-alpha). The formulation containing 3% PPE, 0.3% sodium-trimetaphosphate, and 225 ppm of fluoride resulted in a 34.5% surface hardness loss; a 13% (treated for 1 min) and 36% (treated for 10 min) biofilm reduction in S. mutans; a 26% (1 min) and 36% (10 min) biofilm reduction in C. albicans; absence of cytotoxicity; and anti-inflammatory activity confirmed by decreased interleukin-6 production in mouse macrophages. Thus, our results provide a promising prospect for the development of an alcohol-free commercial dental product with the health benefits of P. granatum that have been recognized for a millennium.

In vitro antimicrobial effects of chitosan on microcosm biofilms of oral candidiasis

OBJECTIVE

This study assessed the effects of chitosan (CS) on microcosm biofilms derived from saliva of patients with Candida-associated denture stomatitis.

METHODS

Five removable denture wearers with denture stomatitis were included in the study. The minimum inhibitory concentration (MIC) of CS against clinical isolates of Candida albicans was determined according to the broth microdilution method. Pooled saliva from the donors was used as an inoculum for the formation of biofilms, which were developed during 72 h on acrylic surfaces in the Amsterdam Active Attachment model. The biofilms were then treated with different concentrations of CS, and the antibiofilm effects were evaluated through the quantification of colony-forming units (CFUs), total biomass (TB), metabolic activity (MA), lactic acid production (LAP), and cell viability (by confocal laser scanning microscopy). Chlorhexidine, miconazole, and nystatin were tested as positive controls, while the negative control (NC) was the untreated biofilm. Data were analyzed by 1-way ANOVA and Fischer LSD's post hoc test (α=0.05).

RESULTS

MIC values of CS ranged from 500 to 800 µg/mL. For CFUs, 2500 µg/mL CS was the most effective treatment in reducing total anaerobes, mutans streptococci, and Lactobacillus spp., significantly differing from the controls. For C. albicans CFUs, CS and positive controls did not differ from each other but led to significant reductions compared to NC. Regarding TB, MA, LAP, and cell viability, 2500 µg/mL CS promoted the greatest reductions compared to NC.

CONCLUSION

CS has similar or superior effects to conventional active principles on important parameters of oral candidiasis microcosm biofilms.

CLINICAL RELEVANCE

The antibiofilm effects of CS show that this compound has great potential to improve the clinical condition of denture stomatitis patients, and formulations containing this natural polymer could be useful for controlling oral candidiasis.

Bacterial-fungal metabolic interactions within the microbiota and their potential relevance in human health and disease: a short review

The composition of the microbiota is the focus of many recent publications describing the effects of the microbiota on host health. In recent years, research has progressed further, investigating not only the diversity of genes and functions but also metabolites produced by microorganisms composing the microbiota of various niches and how these metabolites affect and shape the microbial community. While an abundance of data has been published on bacterial interactions, much less data are available on the interactions of bacteria with another component of the microbiota: the fungal community. Although present in smaller numbers, fungi are essential to the balance of this complex microbial ecosystem. Both bacterial and fungal communities produce metabolites that influence their own population but also that of the other. However, to date, interkingdom interactions occurring through metabolites produced by bacteria and fungi have rarely been described. In this review, we describe the major metabolites produced by both kingdoms and discuss how they influence each other, by what mechanisms and with what consequences for the host.

Silver nanoparticles associated with a polyphosphate and fluoride enhance the prevention of enamel demineralization and impact on dual-biofilm adhesion

OBJECTIVES

The aim of this study were to produce a multifunctional nanocomposite combining silver nanoaparticles (Ag), sodium trimetaphosphate (TMP) and fluoride (F), to investigate its effect on dental enamel demineralization and on biofilms of Streptococcus mutans and Candida albicans.

METHODS

Bovine enamel blocks were submitted to five pH cycles and treated 2x/day with 100ppm F, 225ppm F, 100ppm F+0.2%TMP or 100ppm F+0.2%TMP+10% Ag (100F/TMP/Ag). Next, surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), enamel fluoride (F) and calcium (Ca) concentration were determined. Biofilms from single and dual species of S. mutans and C. albicans were treated with 100F/TMP/Ag, Ag or chlorhexidine gluconate for 24h. The antibiofilm effect was evaluated by colony-forming unit counting and Scanning Electron Microscopy.

RESULTS

The nanocomposite reduced 43.0% of %SH and was similar with samples treated with 225F, 100F/TMP and 100/TMP/Ag. The attribute of F and/or TMP in reducing ΔKHN in 5-20 μm was not affected by the addiction of Ag (110F = 225F = 100F/TMP = 100F/TMP/Ag > Negative Control). Further, 100F/TMP/Ag strongly reduced viable cells of S. mutans in dual biofilms (∼5 log₁₀cm²) and structurally affected the biofilms.

CONCLUSION

The 100F/TMP/F promoted a protective effect against enamel demineralization and was able to significantly inhibit the growth of biofilms of S. mutans and C. albicans.

CLINICAL SIGNIFICANCE

The focus on prevention and non-invasive dental treatment is the most effective and least costly way to improve the population's oral health conditions. We present a nanocomposite for a multiple approach in prevention of caries.

In it together: Candida-bacterial oral biofilms and therapeutic strategies

Under natural environmental settings or in the human body, the majority of microorganisms exist in complex polymicrobial biofilms adhered to abiotic and biotic surfaces. These microorganisms exhibit symbiotic, mutualistic, synergistic, or antagonistic relationships with other species during biofilm colonization and development. These polymicrobial interactions are heterogeneous, complex and hard to control, thereby often yielding worse outcomes than monospecies infections. Concerning fungi, Candida spp., in particular, Candida albicans is often detected with various bacterial species in oral biofilms. These Candida-bacterial interactions may induce the transition of C. albicans from commensal to pathobiont or dysbiotic organism. Consequently, Candida-bacterial interactions are largely associated with various oral diseases, including dental caries, denture stomatitis, periodontitis, peri-implantitis, and oral cancer. Given the severity of oral diseases caused by cross-kingdom consortia that develop hard-to-remove and highly drug-resistant biofilms, fundamental research is warranted to strategically develop cost-effective and safe therapies to prevent and treat cross-kingdom interactions and subsequent biofilm development. While studies have shed some light, targeting fungal-involved polymicrobial biofilms has been limited. This mini-review outlines the key features of Candida-bacterial interactions and their impact on various oral diseases. In addition, current knowledge on therapeutic strategies to target Candida-bacterial polymicrobial biofilms is discussed.

Plausible Mechanistic Insights in Biofilm Eradication Potential against Candida spp. Using In Situ-Synthesized Tyrosol-Functionalized Chitosan Gold Nanoparticles as a Versatile Antifouling Coating on Implant Surfaces

In the present study, tyrosol-functionalized chitosan gold nanoparticles (Chi-TY-AuNPs) were prepared as an alternative treatment strategy to combat fungal infections. Various biophysical techniques were used to characterize the synthesized Chi-TY-AuNPs. The antifungal and antibiofilm activities of Chi-TY-AuNPs were evaluated against Candida albicans and C. glabrata, and efforts have been made to elucidate the possible mechanism of action. Chi-TY-AuNPs showed a high fungicidal effect against both sessile and planktonic cells of Candida spp. Additionally, Chi-TY-AuNPs completely eradicated (100%) the mature biofilms of both the Candida spp. FESEM analysis highlighted the morphological alterations in Chi-TY-AuNP-treated Candida biofilm cells. The effect of Chi-TY-AuNPs on the ECM components showed significant reduction in protein content in the C. glabrata biofilm and substantial decrease in extracellular DNA content of both the Candida spp. ROS generation analysis using DCFDA-PI staining showed high ROS levels in both the Candida spp., whereas pronounced ROS production was observed in the Chi-TY-AuNP-treated C. glabrata biofilm. Biochemical analysis revealed decreased ergosterol content in Chi-TY-AuNP-treated C. glabrata cells, while inconsequential changes were observed in C. albican s. Furthermore, the transcriptional expression of selected genes (ergosterol biosynthesis, efflux, sterol importer, and glucan biogenesis) was reduced in C. glabrata in response to Chi-TY-AuNPs except ERG11 and CDR1. Conclusively, the result showed the biofilm inhibition and biofilm eradication efficacy of Chi-TY-AuNPs in both the Candida spp. Findings of the present study manifest Chi-TY-AuNPs as a potential therapeutic solution to Candida biofilm-related chronic infections and overcome biofilm antifungal resistance.

Assembly and antifungal effect of a new fluconazole-carrier nanosystem

Aim: To assemble, characterize and assess the antifungal effects of a new fluconazole (FLZ)-carrier nanosystem. Materials & methods: The nanosystem was prepared by loading FLZ on chitosan (CS)-coated iron oxide nanoparticles (IONPs). Antifungal effects were evaluated on planktonic cells (by minimum inhibitory concentration determination) and on biofilms (by quantification of cultivable cells, total biomass, metabolism and extracellular matrix) of Candida albicans and Candida glabrata. Results: Characterization results ratified the formation of a nanosystem (<320 nm) with FLZ successfully embedded. IONPs-CS-FLZ nanosystem reduced minimum inhibitory concentration values and, in general, showed similar antibiofilm effects compared with FLZ alone. Conclusion: IONPs-CS-FLZ nanosystem was more effective than FLZ mainly in inhibiting Candida planktonic cells. This nanocarrier has potential to fight fungal infections.

Nanocarriers of Miconazole or Fluconazole: Effects on Three-Species Candida Biofilms and Cytotoxic Effects In Vitro

The contribution of different Candida species in oral fungal infections has stimulated the search for more effective therapies. This study assessed the antibiofilm effects of nanocarriers of miconazole (MCZ) or fluconazole (FLZ) on Candida biofilms, and their cytotoxic effects on murine fibroblasts. Three-species biofilms (Candida albicans/Candida glabrata/Candida tropicalis) were formed on 96-well plates, and they were treated with nanocarriers (iron oxide nanoparticles coated with chitosan—“IONPs-CS”) of MCZ or FLZ at 39/78/156 µg/mL; antifungals alone at 156 µg/mL and artificial saliva were tested as positive and negative controls, respectively. Biofilms were analyzed by colony forming units (CFU), biomass, metabolic activity, and structure/viability. The cytotoxicity (L929 cells) of all treatments was determined via 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) reduction assay. Data were submitted to one- or two-way ANOVA, followed by Tukey’s or Fisher LSD’s tests (p < 0.05). IONPs-CS-MCZ at 78 µg/mL promoted similar antibiofilm and cytotoxic effects compared with MCZ at 156 µg/mL. In turn, IONPs-CS-FLZ at 156 µg/mL was overall the most effective FLZ antibiofilm treatment, surpassing the effects of FLZ alone; this nanocarrier was also less cytotoxic compared with FLZ alone. It can be concluded that both nanocarriers are more effective alternatives to fight Candida biofilms compared with their respective positive controls in vitro, being a promising alternative for the treatment of oral fungal infections.

Mixed biofilms of pathogenic Candida-bacteria: regulation mechanisms and treatment strategies

Mixed-species biofilm is one of the most frequently recorded clinical problems. Mixed biofilms develop as a result of interactions between microorganisms of a single or multiple species (e.g. bacteria and fungi). Candida spp., particularly Candida albicans, are known to associate with various bacterial species to form a multi-species biofilm. Mixed biofilms of Candida spp. have been previously detected in vivo and on the surfaces of many biomedical instruments. Treating infectious diseases caused by mixed biofilms of Candida and bacterial species has been challenging due to their increased resistance to antimicrobial drugs. Here, we review and discuss the clinical significance of mixed Candida-bacteria biofilms as well as the signalling mechanisms involved in Candida-bacteria interactions. We also describe possible approaches for combating infections associated with mixed biofilms, such as the use of natural or synthetic drugs and combination therapy. The review presented here is expected to contribute to the advances in the biomedical field on the understanding of underlying interaction mechanisms of pathogens in mixed biofilm, and alternative approaches to treating the related infections.

Microbial Interkingdom Biofilms and the Quest for Novel Therapeutic Strategies

Fungal and bacterial species interact with each other within polymicrobial biofilm communities in various niches of the human body. Interactions between these species can greatly affect human health and disease. Diseases caused by polymicrobial biofilms pose a major challenge in clinical settings because of their enhanced virulence and increased drug tolerance. Therefore, different approaches are being explored to treat fungal-bacterial biofilm infections. This review focuses on the main mechanisms involved in polymicrobial drug tolerance and the implications of the polymicrobial nature for the therapeutic treatment by highlighting clinically relevant fungal-bacterial interactions. Furthermore, innovative treatment strategies which specifically target polymicrobial biofilms are discussed.

Antimicrobial action of NeoMTA Plus on mono- and dual-species biofilms of Enterococcus faecalis and Candida albicans: An in vitro study

OBJECTIVE

To evaluate the antimicrobial action of NeoMTA Plus on mono- and dual-species biofilms of Enterococcus faecalis and Candida albicans.

MATERIAL AND METHODS

A total of 171 sterile dentin blocks, measuring 4 mm × 4 mm × 1 mm, were incubated in media containing E. faecalis (3.1 × 10⁸ cells/mL) and/or C. albicans (1 × 10⁷ cells/mL) for 2 d. These blocks were randomly divided into three groups: the control (no treatment with biomaterials), MTA (treated with an MTA sample with width and thickness same as those of the dentin block after the material was set), and NeoMTA Plus (treated with NeoMTA Plus in a fashion similar to the treatment of the MTA group) groups. The biomaterials remained in contact with the biofilms for 24 h. Quantitative analyses of the number of colony-forming units (CFUs) and metabolic activity (XTT), were performed. Furthermore, qualitative analysis of biofilm structure was performed by scanning electron microscopy. Data were statistically analyzed considering a significance level of 5%.

RESULTS

XTT and the number of CFUs were similar among the groups (p > 0.05). The type of biofilm (mono- or dual-species) or the biomaterial used (MTA or NeoMTA Plus) did not affect the results. Biofilm structure exhibited a robust architecture composed of yeast and bacterial cell multilayers and was homogeneous among the groups.

CONCLUSION

NeoMTA Plus was not effective against mono- and dual-species biofilms of E. faecalis and C. albicans. Further research investigating biofilm removal methods including those involving the use of biomaterials with antiseptics and other supporting therapies is warranted.

Novel Colloidal Nanocarrier of Cetylpyridinium Chloride: Antifungal Activities on Candida Species and Cytotoxic Potential on Murine Fibroblasts

Nanocarriers have been used as alternative tools to overcome the resistance of Candida species to conventional treatments. This study prepared a nanocarrier of cetylpyridinium chloride (CPC) using iron oxide nanoparticles (IONPs) conjugated with chitosan (CS), and assessed its antifungal and cytotoxic effects. CPC was immobilized on CS-coated IONPs, and the nanocarrier was physico-chemically characterized. Antifungal effects were determined on planktonic cells of Candida albicans and Candida glabrata (by minimum inhibitory concentration (MIC) assays) and on single- and dual-species biofilms of these strains (by quantification of cultivable cells, total biomass and metabolic activity). Murine fibroblasts were exposed to different concentrations of the nanocarrier, and the cytotoxic effect was evaluated by MTT reduction assay. Characterization methods confirmed the presence of a nanocarrier smaller than 313 nm. IONPs-CS-CPC and free CPC showed the same MIC values (0.78 µg mL⁻¹). CPC-containing nanocarrier at 78 µg mL⁻¹ significantly reduced the number of cultivable cells for all biofilms, surpassing the effect promoted by free CPC. For total biomass, metabolic activity, and cytotoxic effects, the nanocarrier and free CPC produced statistically similar outcomes. In conclusion, the IONPs-CS-CPC nanocarrier was more effective than CPC in reducing the cultivable cells of Candida biofilms without increasing the cytotoxic effects of CPC, and may be a useful tool for the treatment of oral fungal infections.

Tyrosol 1,2,3-triazole analogues as new acetylcholinesterase (AChE) inhibitors

The present work proposed the preparation of triazolic analogues of tyrosol, a biophenol found in olive oil and whose wide range of bioactivities has been the target of many studies. We obtained fifteen novel tyrosol derivatives and the compounds of the series were later evaluated as acetylcholinesterase (AChE) inhibitors. The study of AChE inhibition is important for the development of new drugs and pesticides, and especially the research for managing Alzheimer's disease. The most active compound, namely 7-({1-[2-(4-hydroxyphenyl)ethyl]-1H-1,2,3-triazol-4-yl}methoxy)-4-methyl-2H-chromen-2-one (30), showed IC₅₀ value of 14.66 ± 2.29 μmol L^-1. Docking experiments corroborated by kinetic assay are suggestive of a competitive inhibition mechanism. Derivatives interacted with amino acids from the AChE active site associated to the development of Alzheimer's disease. The results indicate that the compounds synthesized have a high potential as prototypes for the development of new acetylcholinesterase inhibitors.

Antimicrobial, antibiofilm and cytotoxic effects of a colloidal nanocarrier composed by chitosan-coated iron oxide nanoparticles loaded with chlorhexidine

OBJECTIVES

This study evaluated the antimicrobial and antibiofilm effects of a colloidal nanocarrier for chlorhexidine (CHX) on Candida glabrata and Enterococcus faecalis, as well as tested its cytotoxic effect on murine fibroblasts.

METHODS

Iron oxide nanoparticles (IONPs) were coated with chitosan (CS) and loaded with CHX at 31.2, 78 and 156 μg/mL. Antimicrobial effects were assessed by determining the minimum inhibitory concentration (MIC), using the broth microdilution method, and fractional inhibitory concentration index (FICI). Preformed biofilms (48 h) were treated with different concentrations of the nanocarrier (24 h) and quantified by colony-forming units (CFUs), total biomass and metabolic activity. For cytotoxicity, the viability of L929 cells was evaluated by MTT assay after 24 and 48 h of exposure to the nanocarrier. Data were submitted to ANOVA and Fisher LSD or Tukey post-hoc tests (α = 0.05).

RESULTS

MIC and FICI results showed an indifferent interaction among the components of the nanocarrier for all strains evaluated. CHX alone and nanocarrier containing 156 μg/mL CHX did not differ from each other in reducing the number of CFUs. However, the nanocarrier containing 156 μg/mL CHX promoted the highest reductions in total biofilm biomass and metabolism, surpassing the effect of CHX alone. After 24 and 48 h of exposure, the nanocarrier reduced CHX toxicity to the L929 cell at low concentrations.

CONCLUSION

These findings suggest that the CHX nanocarrier has potential to be used in the control of oral diseases associated with C. glabrata and E. faecalis.

CLINICAL RELEVANCE

CHX has improved the antibiofilm effect and reduced the cytotoxicity (at low concentrations) when conjugated to CS-coated IONPs. This new colloidal formulation has potential as an alternative antimicrobial agent to pure CHX for the control of biofilm-related oral diseases, such as oral candidiasis and endodontic infections.

Fungal Quorum-Sensing Molecules: A Review of Their Antifungal Effect against Candida Biofilms

The number of effective therapeutic strategies against biofilms is limited; development of novel therapies is urgently needed to treat a variety of biofilm-associated infections. Quorum sensing is a special form of microbial cell-to-cell communication that is responsible for the release of numerous extracellular molecules, whose concentration is proportional with cell density. Candida-secreted quorum-sensing molecules (i.e., farnesol and tyrosol) have a pivotal role in morphogenesis, biofilm formation, and virulence. Farnesol can mediate the hyphae-to-yeast transition, while tyrosol has the opposite effect of inducing transition from the yeast to hyphal form. A number of questions regarding Candida quorum sensing remain to be addressed; nevertheless, the literature shows that farnesol and tyrosol possess remarkable antifungal and anti-biofilm effect at supraphysiological concentration. Furthermore, previous in vitro and in vivo data suggest that they may have a potent adjuvant effect in combination with certain traditional antifungal agents. This review discusses the most promising farnesol- and tyrosol-based in vitro and in vivo results, which may be a foundation for future development of novel therapeutic strategies to combat Candida biofilms.

Novel nanocarrier of miconazole based on chitosan-coated iron oxide nanoparticles as a nanotherapy to fight Candida biofilms

Overexposure of microorganisms to conventional drugs has led to resistant species that require new treatment strategies. This study prepared and characterized a nanocarrier of miconazole (MCZ) based on iron oxide nanoparticles (IONPs) functionalized with chitosan (CS), and tested its antifungal activity against biofilms of Candida albicans and Candida glabrata. IONPs-CS-MCZ nanocarrier was prepared by loading MCZ on CS-covered IONPs and characterized by physicochemical methods. Minimum inhibitory concentration (MIC) of the nanocarrier was determined by the microdilution method. Biofilms were developed (48 h) in microtiter plates and treated with MCZ-carrying nanocarrier at 31.2 and 78 μg/mL, in both the presence and absence of an external magnetic field (EMF). Biofilms were evaluated by total biomass, metabolic activity, cultivable cells (CFU), extracellular matrix components, scanning electron microscopy and confocal microscopy. Data were analyzed by two-way ANOVA and Holm-Sidak test (p < 0.05). A nanocarrier with diameter lower than 50 nm was obtained, presenting MIC values lower than those found for MCZ, and showing synergism for C. albicans and indifference for C. glabrata (fractional inhibitory concentration indexes of <0.12 and <0.53, respectively). IONPs-CS-MCZ did not affect total biomass and extracellular matrix. IONPs-CS-MCZ containing 78 μg/mL MCZ showed a superior antibiofilm effect to MCZ in reducing CFU and metabolism for single biofilms of C. albicans and dual-species biofilms. The EMF did not improve the nanocarrier effects. Microscopy confirmed the antibiofilm effect of the nanocarrier. In conclusion, IONPs-CS-MCZ was more effective than MCZ mainly against C. albicans planktonic cells and number of CFU and metabolism of the biofilms.

Management of Streptococcus mutans-Candida spp. Oral Biofilms' Infections: Paving the Way for Effective Clinical Interventions

Oral diseases are considered the most common noncommunicable diseases and are related to serious local and systemic disorders. Oral pathogens can grow and spread in the oral mucosae and frequently in biomaterials (e.g., dentures or prostheses) under polymicrobial biofilms, leading to several disorders such as dental caries and periodontal disease. Biofilms harbor a complex array of interacting microbes, increasingly unapproachable to antimicrobials and with dynamic processes key to disease pathogenicity, which partially explain the gradual loss of response towards conventional therapeutic regimens. New drugs (synthesized and natural) and other therapies that have revealed promising results for the treatment or control of these mixed biofilms are presented and discussed here. A structured search of bibliographic databases was applied to include recent research. There are several promising new approaches in the treatment of Candida spp.-Streptococcus mutans oral mixed biofilms that could be clinically applied in the near future. These findings confirm the importance of developing effective therapies for oral Candida-bacterial infections.

Streptococcus mutans and Actinomyces naeslundii Interaction in Dual-Species Biofilm

The study of bacterial interaction between Streptococcus mutans and Actinomyces naeslundii may disclose important features of biofilm interspecies relationships. The aim of this study was to characterize-with an emphasis on biofilm formation and composition and metabolic activity-single- and dual-species biofilms of S. mutans or A. naeslundii, and to use a drip flow reactor (DFR) to evaluate biofilm stress responses to 0.2% chlorhexidine diacetate (CHX). Single- and dual-species biofilms were grown for 24 h. The following factors were evaluated: cell viability, biomass and total proteins in the extracellular matrix, 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide-"XTT"-reduction and lactic acid production. To evaluate stress response, biofilms were grown in DFR. Biofilms were treated with CHX or 0.9% sodium chloride (NaCl; control). Biofilms were plated for viability assessment. Confocal laser-scanning microscopy (CLSM) was also performed. Data analysis was carried out at 5% significance level. S. mutans viability and lactic acid production in dual-species biofilms were significantly reduced. S. mutans showed a higher resistance to CHX in dual-species biofilms. Total protein content, biomass and XTT reduction showed no significant differences between single- and dual-species biofilms. CLSM images showed the formation of large clusters in dual-species biofilms. In conclusion, dual-species biofilms reduced S. mutans viability and lactic acid production and increased S. mutans' resistance to chlorhexidine.

Candida spp./Bacteria Mixed Biofilms

The ability to form biofilms is a common feature of microorganisms, such as bacteria or fungi. These consortiums can colonize a variety of surfaces, such as host tissues, dentures, and catheters, resulting in infections highly resistant to drugs, when compared with their planktonic counterparts. This refractory effect is particularly critical in polymicrobial biofilms involving both fungi and bacteria. This review emphasizes Candida spp.-bacteria biofilms, the epidemiology of this community, the challenges in the eradication of such biofilms, and the most relevant treatments.

Is Implant Coating With Tyrosol- and Antibiotic-loaded Hydrogel Effective in Reducing Cutibacterium (Propionibacterium) acnes Biofilm Formation? A Preliminary In Vitro Study

BACKGROUND

Studies have suggested that Cutibacterium acnes (formerly known as Propionibacterium) is the most frequently isolated pathogen after shoulder arthroplasty. To address the burden of periprosthetic joint infections associated with this pathogen, new prevention methods are needed. Tyrosol has a promising record of effectiveness in the field of biofilm-associated infections; however, to our knowledge, it has not been tested against C. acnes thus far.

QUESTIONS/PURPOSES

In this in vitro study, we asked: (1) Is tyrosol effective in inhibiting and eradicating C. acnes planktonic growth? (2) Is there synergy between tyrosol and rifampicin? (3) Is supplementation of hydrogel with tyrosol at the minimum inhibitory and subinhibitory concentrations efficacious in reducing free-floating C. acnes growth? (4) Is implant hydrogel coating (either alone or combined with tyrosol, rifampicin, or vancomycin) beneficial in reducing C. acnes biofilm formation? (5) Is the administration of soluble tyrosol an effective measure against C. acnes biofilm formation?

METHODS

We assessed C. acnes planktonic growth and eradication by inspecting visually the results of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. We also evaluated macroscopically the presence of synergy among tyrosol and rifampicin by means of the MIC checkerboard testing. Thereafter, we addressed colorimetrically the efficacy of tyrosol-loaded Defensive Antibacterial Coating (DAC®) hydrogel against the C. acnes free-floating form by means of the XTT cell proliferation reduction assay. Then, we explored photometrically the effect of hydrogel and soluble tyrosol at reducing C. acnes biofilm formation on titanium alloy disks that simulated orthopaedic implants by using the minimum biofilm inhibition concentration assay. In particular, 16 disks were sequentially allocated to each of the following testing conditions: (1) hydrogel alone; (2) tyrosol-loaded hydrogel; (3) rifampicin-supplemented hydrogel; (4) vancomycin-loaded hydrogel; and (5) soluble tyrosol. Subsequently, implants were sonicated and cell viability was evaluated in terms of the XTT assay.

RESULTS

Tyrosol was effective in inhibiting C. acnes planktonic (free-floating) growth demonstrating MIC values of 63 mM (9 mg/mL) and MBC values of 250 mM (35 mg/mL). Concerning synergy assessment, the checkerboard testing revealed additivity among tyrosol and rifampicin with a fractional inhibitory concentration index of 0.56. In addition, a hydrogel coating with tyrosol at the MIC showed no difference in the inhibition of free-floating C. Acnes form over control (median absorbance [MA] for tyrosol-supplemented hydrogel versus control groups were 0.21 [interquartile range {IQR}, 0.19-0.24] versus 0.26 [IQR, 0.23-0.31], p = 0.066). Furthermore, loaded hydrogel with tyrosol at 597 mg/mL (1 M) was no more effective than control in reducing C. acnes biofilm formation (MAs for tyrosol versus control were 0.12 [IQR, 0.11-0.13] versus 0.14 [IQR, 0.12-0.16], respectively; p = 0.076). This was also the case when we considered hydrogel in conjunction with vancomycin and rifampicin (MAs for vancomycin at 2% and 5% and rifampicin at 1% versus biofilm control were 0.139 [IQR, 0.133-0.143] and 0.141 [IQR, 0.133-0.143] and 0.135 [IQR, 0.128-0.146] versus 0.142 [IQR, 0.136-0.144], correspondingly). In contrast, soluble tyrosol at 597 mg/mL (1 M) inhibited biofilm formation compared to control (MAs for tyrosol and control groups were 0.11 [IQR, 0.09-0.13] versus 0.13 [IQR, 0.12-0.14], p = 0.007).

CONCLUSIONS

Although the implant coating with hydrogel (either pure or supplemented with antimicrobial agents) did not diminish C. acnes biofilm development in vitro, soluble tyrosol at 597 mg/mL (1 M) exceeded the meaningful biofilm inhibition threshold of 80%.

CLINICAL RELEVANCE

The results of the current preclinical investigation did not support the use of a fast, bioresorbable hydrogel as a coating method against C. acnes biofilms. Instead, direct local administration of soluble tyrosol at high concentrations should be further tested in future animal studies.

Fungal Quorum-Sensing Molecules and Inhibitors with Potential Antifungal Activity: A Review

The theory of persisting independent and isolated regarding microorganisms is no longer accepted. To survive and reproduce they have developed several communication platforms within the cells which facilitates them to adapt the surrounding environmental changes. This cell-to-cell communication is termed as quorum sensing; it relies upon the cell density and can stimulate several traits of microbes including biofilm formation, competence, and virulence factors secretion. Initially, this sophisticated mode of communication was discovered in bacteria; later, it was also confirmed in eukaryotes (fungi). As a consequence, many quorum-sensing molecules and inhibitors have been identified and characterized in various fungal species. In this review article, we will primarily focus on fungal quorum-sensing molecules and the production of inhibitors from fungal species with potential applications for combating fungal infections.

Antimicrobial Activity of Compounds Containing Silver Nanoparticles and Calcium Glycerophosphate in Combination with Tyrosol

Nanocomposites containing antimicrobial agents and calcium phosphates have been developed. Thus, this study assessed the effects of two compounds containing silver nanoparticles (AgNPs) and β-calcium glycerophosphate (CaGP), associated or not with tyrosol (TYR), against planktonic cells and biofilms of Candida albicans and Streptococcus mutans. The nanocompounds were synthesized through chemical and 'green' processes and characterized by scanning electron microscopy. The minimum and fractional inhibitory concentrations of each compound were determined for planktonic cells. Next, 24-h single biofilms of C. albicans and S. mutans were treated for 24 h with the nanocompounds alone or in combination with TYR, and the antibiofilm effect was assessed through enumeration of colony forming units. Biofilm data were statistically examined using one-way ANOVA and the Kruskal-Wallis test (α = 0.05). The chemically synthesized nanocompound in combination with TYR demonstrated a synergistic effect against planktonic cells of C. albicans and S. mutans. For the nanocompound obtained through the 'green' route associated with TYR, a synergistic effect was observed only against C. albicans. For biofilms, only the combination obtained through the 'green' route + TYR demonstrated a synergistic effect against C. albicans. Our results may contribute to the development of oral care products containing AgNPs-CaGP and TYR to combat oral infections.

Voriconazole inhibits cross-kingdom interactions between Candida albicans and Actinomyces viscosus through the ergosterol pathway

Candida albicans and Actinomyces viscosus are prominent microbes associated with dental root caries. The aim of this study was to investigate the effect of C. albicans on A. viscosus biofilms and to identify the mechanisms associated with this interaction. A. viscosus and C. albicans strains (wide-type and mutants) were used to form biofilms in vitro and in vivo, which were subsequently analysed by crystal violet assay and scanning electron microscopy (SEM) to investigate the effect of C. albicans on A. viscosus growth. A viable plate count and survival curve for C. albicans mutants and A. viscosus combinations were used to identify which C. albicans pathway was crucial for cross-kingdom interactions. Voriconazole was used to block their interactions both in vitro and in vivo. SEM, fluorescence in situ hybridisation (FISH), quantitative PCR and survival curve analyses were performed to evaluate the activity of voriconazole on C. albicans and A. viscosus interactions. The biomass and virulence of mixed-species biofilms were significantly enhanced compared with the A. viscosus biofilm alone. However, this was not observed in the mixed-species biofilms with the C. albicans mutant erg11Δ/Δ in vitro and in vivo, indicating that azoles may work on the mixed-species biofilms. As expected, voriconazole can effectively reduce the biomass of mixed-species biofilms. A high concentration of voriconazole (1 µg/mL) reduced the abundance of C. albicans, whilst a low voriconazole concentration (0.25 µg/mL) blocked their interactions similar to the effect of the erg11Δ/Δ mutant. Voriconazole may be a candidate strategy to combat root caries pathogens.

Effects of tyrosol and farnesol on Candida albicans biofilm

The present in vitro study examined the effects of the quorum‑sensing molecules farnesol and tyrosol on the development of Candida albicans biofilm in order to elucidate their role as novel adjuvants in oral hygiene. The investigation was conducted in C. albicans ATCC 10231 and C. albicans isolates from dentures and was performed in flat‑bottomed 96‑well polystyrene plates. Yeast growth and their capacity to form biofilms were evaluated following 24 and 48 h incubations at 37˚C in Sabouraud broth supplemented with 0.001‑3 mM farnesol and/or 1‑20 mM tyrosol. Yeast growth was assessed by turbidimetry and biofilms were quantitated by crystal violet staining, under aerobic and anaerobic conditions. The viability of the fungal cells was controlled by the culture of planktonic cells and by examination of the biofilms using fluorescence microscopy following staining with fluorescein diacetate and ethidium bromide. Farnesol at 3 mM exerted a stronger action when added at the beginning of biofilm formation (>50% inhibition) than when added to preformed biofilms (<10% inhibition). Similarly, tyrosol at 20 mM had a greater effect on biofilm formation (>80% inhibition) than on preformed biofilms (<40% inhibition). Despite significant reductions in attached biomass, yeast growth varied little in the presence of the investigated molecules, as corroborated by the turbidimetry, culture of supernatants on solid culture medium followed by counting of colony‑forming units and viability tests using fluorescence microscopy. At the highest tested concentration, the molecules had a greater effect during the initial phases of biofilm formation. The effect of farnesol during anaerobiosis was not significantly different from that observed during aerobiosis, unlike that of tyrosol during anaerobiosis, which exhibited slightly reduced yeast biofilm inhibition. In conclusion, the present study demonstrated the specific anti‑biofilm effect, independent of fungicidal or fungistatic action, of farnesol and tyrosol, as tested in C. albicans ATCC 10231 and 6 strains isolated from dentures. Prior to suggesting the use of these molecules for preventive purposes in oral hygiene, further studies are required in order to clarify the metabolic pathways and cellular mechanisms involved in their antibiofilm effect, as well as the repercussions on the oral microbiome.

Antibiofilm effect of chlorhexidine-carrier nanosystem based on iron oxide magnetic nanoparticles and chitosan

This study synthesized and characterized a chlorhexidine (CHX)-carrier nanosystem based on iron oxide magnetic nanoparticles (IONPs) and chitosan (CS), and evaluated its antimicrobial effect on mono- and dual-species biofilms of Candida albicans and Streptococcus mutans. CHX was directly solubilized in CS-coated IONPs and maintained under magnetic stirring for obtaining the IONPs-CS-CHX nanosystem. Antimicrobial susceptibility testing for planktonic cells was performed by determining the minimum inhibitory concentration (MIC) of the nanosystem and controls. The effects of the IONPs-CS-CHX nanosystem on the formation of mono- and dual-species biofilms, as well as on pre-formed biofilms were assessed by quantification of total biomass, metabolic activity and colony-forming units. Data were analyzed by the Kruskal-Wallis' test or one-way analysis of variance, followed by the Student-Newman-Keuls' or Holm-Sidak's tests (α = 0.05), respectively. Physico-chemical results confirmed the formation of a nanosystem with a size smaller than 40 nm. The IONPs-CS-CHX nanosystem and free CHX showed similar MIC values for both species analyzed. In general, biofilm quantification assays revealed that the CHX nanosystem at 78 μg/mL promoted similar or superior antibiofilm effects compared to its counterpart at 39 μg/mL and free CHX at 78 μg/mL. These findings highlight the potential of CS-coated IONPs as preventive or therapeutic agents carrying CHX to fight biofilm-associated oral diseases.

Virulence Factors in Candida albicans and Streptococcus mutans Biofilms Mediated by Farnesol

The aim of this study was to evaluate the effect of farnesol on the production of acids and hydrolytic enzymes by biofilms of Streptococcus mutans and Candida albicans. The present study also evaluated the time-kill curve and the effect of farnesol on matrix composition and structure of single-species and dual-species biofilms. Farnesol, at subinhibitory concentrations, showed a significant reduction in S. mutans biofilm acid production, but did not alter C. albicans hydrolytic enzyme production. The number of cultivable cells of both microorganisms was significantly reduced after 8 h of contact with farnesol. Extracellular matrix protein content was reduced for biofilms formed in the presence of farnesol. In addition, confocal laser scanning and scanning electron microscopy displayed structural alterations in all biofilms treated with farnesol, which included reduction in viable cells and extracellular matrix. In conclusion, farnesol showed favorable properties controlling some virulence factors of S. mutans and C. albicans biofilms. These findings should stimulate further studies using this quorum-sensing molecule, combined with other drugs, to prevent or treat biofilm-associated oral diseases.

Green synthesis of silver nanoparticles combined to calcium glycerophosphate: antimicrobial and antibiofilm activities

AIM

To synthesize, characterize and evaluate the antimicrobial and antibiofilm activities of novel nanocomposites containing silver nanoparticles (AgNPs) associated or not to β-calcium glycerophosphate.

MATERIALS & METHODS

These nanocomposites were produced through a 'green' route using extracts of different parts of pomegranate. Antimicrobial and antibiofilm properties against Candida albicans and Streptococcus mutans were determined by the minimum bactericidal/fungicidal concentration and biofilm density after treatments.

RESULTS

All extracts used were successful in producing AgNPs. Composites made with peel extracts showed the highest antimicrobial and antibiofilm activity against both microorganisms tested and performed similarly or even better than chlorhexidine.

CONCLUSION

AgNPs associated or not to calcium glycerophosphate produced by a 'green' process may be a promising novel antimicrobial agent against oral microorganisms.

Antifungal Compounds against Candida Infections from Traditional Chinese Medicine

Infections caused by Candida albicans, often refractory and with high morbidity and mortality, cause a heavy burden on the public health while the current antifungal drugs are limited and are associated with toxicity and resistance. Many plant-derived molecules including compounds isolated from traditional Chinese medicine (TCM) are reported to have antifungal activity through different targets such as cell membrane, cell wall, mitochondria, and virulence factors. Here, we review the recent progress in the anti-Candida compounds from TCM, as well as their antifungal mechanisms. Considering the diverse targets and structures, compounds from TCM might be a potential library for antifungal drug development.

Understanding the link between antimicrobial properties of dietary olive phenolics and bacterial ATP synthase

The naturally occurring olive phenolics tyrosol, hydroxytyrosol, dihydroxyphenylglycol (DHPG), and oleuropein are known to have antioxidant, antitumor, and antibacterial properties. In the current study, we examined whether the antimicrobial properties of tyrosol, hydroxytyrosol, DHPG, and oleuropein were linked to the inhibition of bacterial ATP synthase. Tyrosol, hydroxytyrosol, DHPG, and oleuropein inhibited Escherichia coli wild-type and mutant membrane-bound F1Fo ATP synthase to variable degrees. The growth properties of wild-type, null, and mutant strains in presence of above olive phenolics were also abrogated to variable degrees on limiting glucose and succinate. Tyrosol and oleuropein synergistically inhibited the wild-type enzyme. Comparative wild-type and mutant F1Fo ATP synthase inhibitory profiles suggested that αArg-283 is an important residue and olive phenolics bind at the polyphenol binding pocket of ATP synthase. Growth patterns of wild-type, null, and mutant strains in the presence of tyrosol, hydroxytyrosol, DHPG, and oleuropein also hint at the possibility of additional molecular targets. Our results demonstrated that ATP synthase can be used as a molecular target and the antimicrobial properties of olive phenolics in general and tyrosol in particular can be linked to the binding and inhibition of bacterial ATP synthase.

Differential effects of the combination of tyrosol with chlorhexidine gluconate on oral biofilms

OBJECTIVE

This study assessed the effect of tyrosol and chlorhexidine gluconate in combination against Candida albicans, Candida glabrata, and Streptococcus mutans in the planktonic state or forming biofilms in vitro.

MATERIALS AND METHODS

Checkerboard assays were performed for determination of minimum inhibitory concentration. Biofilms were cultivated during 24 h on specimens of acrylic resin and hydroxyapatite and treated with the drugs alone or in combination twice a day for 1 min, during 3 days. The antibiofilm effect was determined by quantification of the metabolic activity and cultivable cells. The drug combination was also applied on C. albicans to investigate its action on the number of hyphae. Data were statistically examined by two-way ANOVA and Holm-Sidak test (P < 0.05).

RESULTS

The effect of drug combination on planktonic cells was classified as antagonistic for C. albicans and indifferent for the other strains. Also, the drugs were ineffective against the tested biofilms. However, the drug combination showed a synergistic effect in reducing the number of hyphae by C. albicans.

CONCLUSION

The combination of tyrosol with chlorhexidine gluconate was only effective in reducing the number of hyphae by C. albicans, a relevant virulence factor of this species.