Virulence and pathogenicity of Candida albicans is enhanced in biofilms containing oral bacteria

In vitro efficacy of synthetic lawsone derivative disinfectant solution on removing dual-species biofilms and effect on acrylic denture surface properties

Candida albicans (C. albicans) and Streptococcus mutans (S. mutans) biofilms involve in denture stomatitis. This study compared compound 1 to 2% chlorhexidine gluconate (CHX), Polident, and distilled water (DW) in biofilms reduction and effect on polymethylmethacrylate acrylic (PMMA) properties. The structure of lawsone (naphthoquinone derivative) was modified by the addition of an alkylnyloxy group to yield compound 1. Dual-species biofilms of C. albicans and S. mutans were developed on PMMA discs. The colony-forming unit count measured the number of residual biofilm cells after exposure to the test agents. PMMA discs were examined for color stability, surface roughness, hardness, and chemical structure after 28 days. At 3 min, compound 1 was less effective than CHX in reducing C. albicans (p = 0.004) and S. mutans (p = 0.034) but more effective than Polident in reducing C. albicans (p = 0.001). At 15 min, no viable cells were detectable for compound 1 and its effectiveness was comparable to CHX (p = 0.365). SEM showed fungal cell surface damages in CHX, compound 1 and Polident groups. Only color change was affected by time (p < 0.001) and type of test agent (p = 0.008), and only CHX reached a clinical perception level. Compound 1 is a promising agent for removing biofilm from the PMMA surface without substantially degrading surface properties.

Antimicrobial effects of XF drugs against Candida albicans and its biofilms

Compared with antibiotics for treating bacterial infections, there are a limited number of antifungal agents. This is due to several factors, including the difficulties of identifying suitable antifungals that target the fungal cell without damaging host cells, and the reduced rates of diagnosis of fungal infections compared with those caused by bacteria. The problem of treating fungal infections is exacerbated by an increasing incidence of antifungal resistance among human fungal pathogens. Three XF drugs (XF-73, XF-70, and DPD-207) have previously displayed innate bactericidal effects and a low propensity for microbial resistance, with XF-73 and XF-70 having a second, light-activated mechanism of action [known as photodynamic therapy (PDT)]. In an effort to expand the repertoire of antifungal agents, this research assessed the in vitro activity of XF drugs via both mechanisms of action against six strains of the fungal pathogen Candida albicans in both planktonic and biofilm cultures. In addition, this research examined the effects of XF drug treatment on biofilms of C. albicans in a reconstituted human oral epithelium model. All C. albicans strains tested were susceptible to XF-73 and XF-70, with minimum inhibitory concentrations (MICs) between 0.25 µg/mL and 2 µg/mL; DPD-207 was less potent, with MICs between 4 µg/mL and 16 µg/mL, and light activation did not enhance these MICs. Complete biofilm eradication was not reported at the tested XF drug concentrations. However, live and dead staining of C. albicans cells in biofilms after XF drug treatment demonstrated that XF-73 and XF-70 were active against most Candida biofilms tested from 64 µg/mL; again, light activation did not enhance anti-biofilm activity. Candida biofilms were more resistant to DPD-207, with fungicidal effects occurring from 256 µg/mL. XF-73 and XF-70 reduced penetration of C. albicans biofilm into reconstituted human oral epithelium (RHOE) and resulted in less damage (as determined by reduced lactate dehydrogenase release) than untreated biofilms. Overall, the results highlight the potential of XF drugs as new drugs for the management of topical infections caused by C. albicans. Further studies are warranted on the development of XF drugs as antifungals, particularly for XF-73 and XF-70.

Enterotypes of the human gut mycobiome

BACKGROUND

The fungal component of the human gut microbiome, also known as the mycobiome, plays a vital role in intestinal ecology and human health. However, the overall structure of the gut mycobiome as well as the inter-individual variations in fungal composition remains largely unknown. In this study, we collected a total of 3363 fungal sequencing samples from 16 cohorts across three continents, including 572 newly profiled samples from China.

RESULTS

We identify and characterize four mycobiome enterotypes using ITS profiling of 3363 samples from 16 cohorts. These enterotypes exhibit stability across populations and geographical locations and significant correlation with bacterial enterotypes. Particularly, we notice that fungal enterotypes have a strong age preference, where the enterotype dominated by Candida (i.e., Can_type enterotype) is enriched in the elderly population and confers an increased risk of multiple diseases associated with a compromised intestinal barrier. In addition, bidirectional mediation analysis reveals that the fungi-contributed aerobic respiration pathway associated with the Can_type enterotype might mediate the association between the compromised intestinal barrier and aging.

CONCLUSIONS

We show that the human gut mycobiome has stable compositional patterns across individuals and significantly correlates with multiple host factors, such as diseases and host age. Video Abstract.

Living together: The role of Candida albicans in the formation of polymicrobial biofilms in the oral cavity

The oral cavity of humans is colonized by diversity of microbial community, although dominated by bacteria, it is also constituted by a low number of fungi, often represented by Candida albicans. Although in the vast minority, this usually commensal fungus under certain conditions of the host (e.g., immunosuppression or antibiotic therapy), can transform into an invasive pathogen that adheres to mucous membranes and also to medical or dental devices, causing mucosal infections. This transformation is correlated with changes in cell morphology from yeast-like cells to hyphae and is supported by numerous virulence factors exposed by C. albicans cells at the site of infection, such as multifunctional adhesins, degradative enzymes, or toxin. All of them affect the surrounding host cells or proteins, leading to their destruction. However, at the site of infection, C. albicans can interact with different bacterial species and in its filamentous form may produce biofilms-the elaborated consortia of microorganisms, that present increased ability to host colonization and resistance to antimicrobial agents. In this review, we highlight the modification of the infectious potential of C. albicans in contact with different bacterial species, and also consider the mutual bacterial-fungal relationships, involving cooperation, competition, or antagonism, that lead to an increase in the propagation of oral infection. The mycofilm of C. albicans is an excellent hiding place for bacteria, especially those that prefer low oxygen availability, where microbial cells during mutual co-existence can avoid host recognition or elimination by antimicrobial action. However, these microbial relationships, identified mainly in in vitro studies, are modified depending on the complexity of host conditions and microbial dominance in vivo.

Candida albicans Adhesins Als1 and Hwp1 Modulate Interactions with Streptococcus mutans

Candida albicans and Streptococcus mutans are known to synergistically interact with each other in the oral cavity. For example, glucosyltransferase B (GtfB), secreted by S. mutans, can bind to the C. albicans cell surface, promoting dual-species biofilm formation. However, the fungal factors mediating interactions with S. mutans are unknown. The C. albicans adhesins Als1, Als3, and Hwp1 are key players in C. albicans single-species biofilm formation, but their roles, if any, in interacting with S. mutans have not been assessed. Here, we investigated the roles of the C. albicans cell wall adhesins Als1, Als3, and Hwp1 on forming dual-species biofilms with S. mutans. We assessed the abilities of the C. albicans wild-type als1Δ/Δ, als3Δ/Δ, als1Δ/Δ/als3Δ/Δ, and hwp1Δ/Δ strains to form dual-species biofilms with S. mutans by measuring optical density, metabolic activity, cell enumeration, biomass, thickness, and architecture of the biofilms. We observed that the C. albicans wild-type strain formed enhanced dual-species biofilms in the presence of S. mutans in these different biofilm assays, confirming that C. albicans and S. mutans synergistically interact in the context of biofilms. Our results reveal that C. albicans Als1 and Hwp1 are major players in interacting with S. mutans, since dual-species biofilm formation was not enhanced when the als1Δ/Δ or hwp1Δ/Δ strains were cultured with S. mutans in dual-species biofilms. Als3, however, does not seem to play a clear role in interacting with S. mutans in dual-species biofilm formation. Overall, our data suggest that the C. albicans adhesins Als1 and Hwp1 function to modulate interactions with S. mutans and could be potential targets for future therapeutics.

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.

Epithelial responses and Candida albicans pathogenicity are enhanced in the presence of oral streptococci

Experimental models that consider host-pathogen interactions are relevant for improving knowledge about oral candidiasis. The aim of this study was to assess the epithelial immune responses, Candida penetration of cell monolayers, and virulence during mixed species culture infections. Single species cultures of Candida albicans and mixed cultures (C. albicans, Streptococcus mutans, and Streptococcus sanguinis) were used to infect monolayers of HaCaT and FaDu ATCC HTB-43 cells for 12 h. After infection, IL-18 and IL-34 gene expression was measured to assess epithelial cell immune responses, and lactate dehydrogenase (LDH) activity was measured as an indicator of cell damage. Microscopy determined C. albicans morphology and penetration of fungal cells through the keratinocyte monolayer. Monolayers devoid of infection served as controls. Data were analyzed by an ANOVA one-way test followed by Tukey's post-hoc test (α = 0.05). The results found that IL-18 and IL-34 gene expression and LDH activity were significantly (p < 0.05) upregulated for both cell lines exposed to mixed species cultures compared with C. albicans alone. Candida albicans yeast and hyphae were evident in C. albicans only infections. In contrast, monolayers infected by C. albicans, S. mutans, and S. sanguinis exhibited higher microbial invasion with several hyphal aggregates detected. The presence of streptococci in C. albicans infection enhances the virulence and pathogenicity of the fungus with associated increased immune responses and tissue damage. Extrapolation of these findings to oral infection would indicate the added potential benefit of managing bacterial components of biofilms during treatment.

Flexural strength, surface roughness, micro-CT analysis, and microbiological adhesion of a 3D-printed temporary crown material

OBJECTIVE

To evaluate the thermocycling effect of 3D-printed resins on flexural strength, surface roughness, microbiological adhesion, and porosity.

MATERIALS AND METHODS

150 bars (8 × 2 × 2 mm) and 100 blocks (8 × 8 × 2 mm) were made and divided into 5 groups, according to two factors: "material" (AR: acrylic resin, CR: composite resin, BIS: bis-acryl resin, CAD: CAD/CAM resin, and PRINT: 3D-printed resin) and "aging" (non-aged and aged - TC). Half of them were subjected to thermocycling (10,000 cycles). The bars were subjected to mini-flexural strength (σ) test (1 mm/min). All the blocks were subjected to roughness analysis (Ra/Rq/Rz). The non-aged blocks were subjected to porosity analysis (micro-CT; n = 5) and fungal adherence (n = 10). Data were statistically analyzed (one-way ANOVA, two-way ANOVA; Tukey's test, α = 0.05).

RESULTS

For σ, "material" and "aging" factors were statistically significant (p < 0.0001). The BIS (118.23 ± 16.26A) presented a higher σ and the PRINT group (49.87 ± 7.55E) had the lowest mean σ. All groups showed a decrease in σ after TC, except for PRINT. The CRTC showed the lowest Weibull modulus. The AR showed higher roughness than BIS. Porosity revealed that the AR (1.369%) and BIS (6.339%) presented the highest porosity, and the CAD (0.002%) had the lowest porosity. Cell adhesion was significantly different between the CR (6.81) and CAD (6.37).

CONCLUSION

Thermocycling reduced the flexural strength of most provisional materials, except for 3D-printed resin. However, it did not influence the surface roughness. The CR showed higher microbiological adherence than CAD group. The BIS group reached the highest porosity while the CAD group had the lowest values.

CLINICAL RELEVANCE

3D-printed resins are promising materials for clinical applications because they have good mechanical properties and low fungal adhesion.

Alpha-Hemolysin from Staphylococcus aureus Obstructs Yeast-Hyphae Switching and Diminishes Pathogenicity in Candida albicans

The use of antibiotics can disrupt the body's natural balance and increase the susteptibility of patients towards fungal infections. Candida albicans is a dimorphic opportunistic fungal pathogen with niches similar to those of bacteria. Our aim was to study the interaction between this pathogen and bacteria to facilitate the control of C. albicans infection. Alpha-hemolysin (Hla), a protein secreted from Staphylococcus aureus, causes cell wall damage and impedes the yeast-hyphae transition in C. albicans. Mechanistically, Hla stimulation triggered the formation of reactive oxygen species that damaged the cell wall and mitochondria of C. albicans. The cell cycle was arrested in the G0/G1 phase, CDC42 was downregulated, and Ywp1 was upregulated, disrupting yeast hyphae switching. Subsequently, hyphae development was inhibited. In mouse models, C. albicans pretreated with Hla reduced the C. albicans burden in skin and vaginal mucosal infections, suggesting that S. aureus Hla can inhibit hyphal development and reduce the pathogenicity of candidiasis in vivo.

Human Oropharyngeal Candidiasis: From Etiology to Current Treatment

Oral candidiasis is a common but most harmful oral cavity infection caused by yeast-like fungus, this condition is called Oropharyngeal candidiasis. There are various species of candida that are responsible for oral cavity fungal infection including mostly Candida albicans. Different candida infections may be acute and chronic. Cell-mediated immunity, humoral immunity, and granulocytes are the immune factors for the cause of this infection. Different antifungal drugs like nystatin, fluconazole, and amphotericin are used to treat oral cavity fungal infections.

An organotypic oral mucosal infection model to study host-pathogen interactions

Early in vitro oral mucosal infection models (OMMs) failed to consider the suitability of the model environment to represent the host immune response. Denture stomatitis (DS) is mediated by Candida albicans, but the role of Staphylococcus aureus remains uncertain. A collagen hydrogel-based OMM containing HaCaT and HGF cell types was developed, characterised and employed to study of tissue invasion and pro-inflammatory cytokine production in response to pathogens. Models formed a robust epithelium. Despite their inflammatory baseline, 24-h infection with C. albicans, and/or S. aureus led to tissue invasion, and significantly upregulated IL-6 and IL-8 production by OMMs when compared to the unstimulated control. No significant difference in IL-6 or IL-8 production by OMMs was observed between single and dual infections. These attributes indicate that this newly developed OMM is suitable for the study of DS and could be implemented for the wider study of oral infection.

Cross-kingdom interaction between Candida albicans and oral bacteria

Candida albicans is a symbiotic fungus that commonly colonizes on oral mucosal surfaces and mainly affects immuno-compromised individuals. Polymicrobial interactions between C. albicans and oral microbes influence the cellular and biochemical composition of the biofilm, contributing to change clinically relevant outcomes of biofilm-related oral diseases, such as pathogenesis, virulence, and drug-resistance. Notably, the symbiotic relationships between C. albicans and oral bacteria have been well-documented in dental caries, oral mucositis, endodontic and periodontal diseases, implant-related infections, and oral cancer. C. albicans interacts with co-existing oral bacteria through physical attachment, extracellular signals, and metabolic cross-feeding. This review discusses the bacterial-fungal interactions between C. albicans and different oral bacteria, with a particular focus on the underlying mechanism and its relevance to the development and clinical management of oral diseases.

Inhibitory effect of ficin on Candida albicans biofilm formation and pre-formed biofilms

BACKGROUND

To investigate the effect of ficin, a type of proteases, on Candida albicans (C. albicans) biofilm, including forming and pre-formed biofilms.

METHODS

Crystal violet tests together with colony forming unit (CFU) counts were used to detect fungal biofilm biomass. Live/dead staining of biofilms observed by confocal laser scanning microscopy was used to monitor fungal activity. Finally, gene expression of C. albicans within biofilms was assessed by qRT-PCR.

RESULTS

According to our results, biofilm biomass was dramatically reduced by ficin in both biofilm formation and pre-formed biofilms, as revealed by the crystal violet assay and CFU count (p < 0.05). Fungal activity in biofilm formation and pre-formed biofilms was not significantly influenced by ficin according to live/dead staining. Fungal polymorphism and biofilm associated gene expression were influenced by ficin, especially in groups with prominent antibiofilm effects.

CONCLUSIONS

In summary, ficin effectively inhibited C. albicans biofilm formation and detached its preformed biofilm, and it might be used to treat C. albicans biofilm associated problems.

Host's Immunity and Candida Species Associated with Denture Stomatitis: A Narrative Review

Denture-related Candida stomatitis, which has been described clinically in the literature, is either localized or generalized inflammation of the oral mucosa in connection with a removable prosthesis. During this inflammatory process, the mycobacterial biofilm and the host’s immune response play an essential role. Among microorganisms of this mixed biofilm, the Candida species proliferates easily and changes from a commensal to an opportunistic pathogen. In this situation, the relationship between the Candida spp. and the host is influenced by the presence of the denture and conditioned both by the immune response and the oral microbiota. Specifically, this fungus is able to hijack the innate immune system of its host to cause infection. Additionally, older edentulous wearers of dentures may experience an imbalanced and decreased oral microbiome diversity. Under these conditions, the immune deficiency of these aging patients often promotes the spread of commensals and pathogens. The present narrative review aimed to analyze the innate and adaptive immune responses of patients with denture stomatitis and more particularly the involvement of Candida albicans sp. associated with this pathology.

Towards understanding mechanisms and functional consequences of bacterial interactions with members of various kingdoms in complex biofilms that abound in nature

The microbial world represents a phenomenal diversity of microorganisms from different kingdoms of life which occupy an impressive set of ecological niches. Most, if not all, microorganisms once colonise a surface develop architecturally complex surface-adhered communities which we refer to as biofilms. They are embedded in polymeric structural scaffolds serve as a dynamic milieu for intercellular communication through physical and chemical signalling. Deciphering microbial ecology of biofilms in various natural or engineered settings has revealed co-existence of microorganisms from all domains of life, including Bacteria, Archaea and Eukarya. The coexistence of these dynamic microbes is not arbitrary, as a highly coordinated architectural setup and physiological complexity show ecological interdependence and myriads of underlying interactions. In this review, we describe how species from different kingdoms interact in biofilms and discuss the functional consequences of such interactions. We highlight metabolic advances of collaboration among species from different kingdoms, and advocate that these interactions are of great importance and need to be addressed in future research. Since trans-kingdom biofilms impact diverse contexts, ranging from complicated infections to efficient growth of plants, future knowledge within this field will be beneficial for medical microbiology, biotechnology, and our general understanding of microbial life in nature.

Cross-kingdom microbial interactions in dental implant-related infections: is Candida albicans a new villain?

Candida albicans, an oral fungal opportunistic pathogen, has shown the ability to colonize implant surfaces and has been frequently isolated from biofilms associated with dental implant-related infections, possibly due to its synergistic interactions with certain oral bacteria. Moreover, evidence suggests that this cross-kingdom interaction on implant can encourage bacterial growth, leading to increased fungal virulence and mucosal damage. However, the role of Candida in implant-related infections has been overlooked and not widely explored or even considered by most microbiological analyses and therapeutic approaches. Thus, we summarized the scientific evidence regarding the ability of C. albicans to colonize implant surfaces, interact in implant-related polymicrobial biofilms, and its possible role in peri-implant infections as far as biologic plausibility. Next, a systematic review of preclinical and clinical studies was conducted to identify the relevance and the gap in the existing literature regarding the role of C. albicans in the pathogenesis of peri-implant infections.

Hydrogen peroxide potentiates antimicrobial photodynamic therapy in eliminating Candida albicans and Streptococcus mutans dual-species biofilm from denture base

BACKGROUND

Candida albicans (C.albicans) is the primary pathogen of denture biofilm. Moreover, it could establish a cross-kingdom relationship with bacteria to enhance its virulence and resistance to antifungal drugs. This study aimed to investigate the efficacy of antimicrobial photodynamic therapy (aPDT) in combination with hydrogen peroxide (H₂O₂) against C.albicans and Streptococcus mutans (S.mutans) dual-species biofilm formed on polymethyl methacrylate (PMMA) disk, and explore its involved mechanisms.

METHODS

C.albicans and S.mutans were grown on PMMA disk for 48 h to form biofilm and received different treatments. The treatments included:1) phosphate-buffered saline (PBS) group,2) 100 mM H₂O₂ group,3) aPDT group,4) aPDT+ H₂O₂ and 5) H₂O₂+aPDT group. Colony forming units (CFU), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and scanning electron microscope (SEM) were used to evaluate the antimicrobial effects. Extracellular polysaccharide substance (EPS) production and observation, cell permeability of biofilm, and uptake of toluidine blue O (TBO) by biofilm were assessed to investigate the involved mechanism.

RESULTS

There was no significant difference between PBS group and H₂O₂ group in viable microorganisms and metabolic activity of biofilm. The treatment protocols containing aPDT group reduced microorganism numbers and metabolic activity when compared to PBS group or H₂O₂ group (P<0.05). H₂O₂+aPDT treatment showed the highest antimicrobial efficacy in comparison with other treatments (P<0.05). Pretreatment with H₂O₂ could decrease EPS production and enhance cell permeability, leading to increased TBO uptake in biofilm.

CONCLUSION

Pretreatment with H₂O₂ improved aPDT efficiency in eliminating dual-species biofilm from PMMA disk by reducing EPS amount, enhancing cell permeability, and increasing TBO uptake.

Streptococcus salivarius K12 inhibits Candida albicans aggregation, biofilm formation and dimorphism

Candida albicans causes candidiasis, particularly in immunocompromised patients. Streptococcus salivarius K12 (K12) is a probiotic isolated from a healthy oral cavity. The study aimed to determine the effect of K12 on C. albicans aggregation, biofilm formation and dimorphism. C. albicans ATCC MYA-4901, acquired immunodeficiency syndrome (AIDS) isolate (ALC2), and oral cancer isolate (ALC3) and K12 were used in the study. All C. albicans strains and K12 were grown in yeast peptone dextrose agar and brain heart infusion agar, respectively, prior to aggregation, biofilm and dimorphism assays. Auto-aggregation of C. albicans MYA-4901 and ALC2 was categorised as high, while the co-aggregation of the strains was low in the presence of K12. C. albicans total cell count decreased significantly when co-cultured with K12 compared with monocultured C. albicans biofilm (p < 0.05). Inhibition of yeast-to-hyphae transition was also observed when co-cultured with K12. In conclusion, K12 inhibits C. albicans aggregation, biofilm formation and dimorphism.

Effect of different salivary glucose concentrations on dual-species biofilms of Candida albicans and Streptococcus mutans

Diabetes mellitus is one of the most prevalent diseases worldwide. The glucose levels found in the blood of diabetic patients can be reflected in the saliva, which can favor biofilm growth and predispose denture wearers to oral candidiasis. This study aimed to evaluate the effect of different salivary glucose concentrations on dual-species biofilms of Candida albicans and Streptococcus mutans. A 96-h biofilm was developed on acrylic resin specimens exposed to 'feast' (10% sucrose) and 'famine' periods. Biofilms were constantly exposed to salivary glucose concentrations equivalent to 0, 20, 60 and 100 mM. Higher salivary glucose concentrations resulted in increased counts of C. albicans and a higher quantity of insoluble extracellular polysaccharides. All biofilms presented high phospholipase activity. The biofilms were characterized by the predominance of yeast cells and microcolonies in all the groups analyzed with co-localization of both species. Higher salivary glucose concentrations formed more robust and potentially virulent biofilms.

The impact of the Fungus-Host-Microbiota interplay upon Candida albicans infections: current knowledge and new perspectives

Candida albicans is a major fungal pathogen of humans. It exists as a commensal in the oral cavity, gut or genital tract of most individuals, constrained by the local microbiota, epithelial barriers and immune defences. Their perturbation can lead to fungal outgrowth and the development of mucosal infections such as oropharyngeal or vulvovaginal candidiasis, and patients with compromised immunity are susceptible to life-threatening systemic infections. The importance of the interplay between fungus, host and microbiota in driving the transition from C. albicans commensalism to pathogenicity is widely appreciated. However, the complexity of these interactions, and the significant impact of fungal, host and microbiota variability upon disease severity and outcome, are less well understood. Therefore, we summarise the features of the fungus that promote infection, and how genetic variation between clinical isolates influences pathogenicity. We discuss antifungal immunity, how this differs between mucosae, and how individual variation influences a person's susceptibility to infection. Also, we describe factors that influence the composition of gut, oral and vaginal microbiotas, and how these affect fungal colonisation and antifungal immunity. We argue that a detailed understanding of these variables, which underlie fungal-host-microbiota interactions, will present opportunities for directed antifungal therapies that benefit vulnerable patients.

Mechanisms of Candida Resistance to Antimycotics and Promising Ways to Overcome It: The Role of Probiotics

Pathogenic Candida and infections caused by those species are now considered as a serious threat to public health. The treatment of candidiasis is significantly complicated by the increasing resistance of pathogenic strains to current treatments and the stagnant development of new antimycotic drugs. Many species, such as Candida auris, have a wide range of resistance mechanisms. Among the currently used synthetic and semi-synthetic antifungal drugs, the most effective are azoles, echinocandins, polyenes, nucleotide analogs, and their combinations. However, the use of probiotic microorganisms and/or the compounds they produce is quite promising, although underestimated by modern pharmacology, to control the spread of pathogenic Candida species.

Amphotericin B, fluconazole, and nystatin as development inhibitors of Candida albicans biofilms on a dental prosthesis reline material: Analytical models in vitro

STATEMENT OF PROBLEM

The use of antifungals has been suggested during the treatment of denture stomatitis associated with Candida albicans biofilms. However, how time, material surface, and substrates present during adhesion and biofilm development can influence clinical treatment is unclear.

PURPOSE

The purpose of this in vitro study was to investigate the growth kinetics of C. albicans biofilms on surfaces of specimens under the influence of adsorbed films and to evaluate the antibiofilm efficacy of antifungal agents: amphotericin B, fluconazole, and nystatin.

MATERIAL AND METHODS

Specimens of Silagum-Comfort Soft Relining were submerged in preconditioning systems: phosphate-buffered saline, artificial saliva, fetal bovine serum, and artificial saliva+fetal bovine serum. Planktonic cells were incubated (phosphate-buffered saline+specimens) for 1.5 hours (adhesion phase) and washed with phosphate-buffered saline solution. The specimens were then incubated (YNB+glucose) for 8, 24, and 48 hours (initial, intermediate, and maturation phases). The biofilm sessile minimum inhibitory concentration was determined by the broth microdilution method (7.81 to 500 μg/mL). The metabolic activity of the biofilms was tested by colorimetric assay (cell metabolic activity). Cell viability, relative biomass (μm³), and the thickness of the biofilm (μm) were evaluated by confocal laser scanning microscopy.

RESULTS

The highest bioactivity was recorded in the presence of fetal bovine serum. Biofilms treated with fluconazole and amphotericin B were partially inhibited in a dose-dependent manner. Nystatin inhibited metabolic activity mainly from ≥15.63 or 62.5 μg/mL. Variations in magnitude parameters (relative biomass and thickness) were observed depending on the development phases of biofilms, whereas biological parameters (percentage of nonviable cells) were constant throughout the formation of C. albicans biofilms.

CONCLUSIONS

The data suggest that partial (fluconazole and amphotericin B) or more effective (nystatin) reduction of metabolic activity of C. albicans biofilms occurred depending on the time and the antifungal and its concentrations.

Glucose effect on Candida albicans biofilm during tissue invasion

OBJECTIVE

To evaluate, in vitro, the effect of two glucose concentrations (0.1 mM and 1.0 mM, simulating glucose concentration in saliva of healthy and diabetic individuals) on Candida albicans biofilm grown on epithelial monolayer.

MATERIAL AND METHODS

C. albicans was inoculated on epithelial monolayers supplemented with 0.1 mM, 1.0 mM or no glucose. Control groups without C. albicans were also evaluated. Tissue response was assessed through the production of Interleukin-1α, Interleukin-8, Interleukin-6, Interleukin-10 and tumor necrosis factor-α. The complex of monolayer and biofilms were evaluated by quantitative reverse transcription polymerase chain reaction for expression of E-cadherin (CDH1), Caspase-3 (CASP3), β-defensin-1 (DEFB-1) and β-defensin-3 (DEFB-3). The biofilm architecture was visualized by confocal laser scanning microscopy.

RESULTS

The production of Interleukin-1α and Interleukin-8 were increased in the presence of C. albicans (p < 0.05). Glucose did not interfere in the release of any cytokine evaluated. C. albicans downregulated transcripts for CDH1 (p < 0.05). Glucose did not induce a significant change in CDH1, CASP3, DEFB-1 and DEFB-3 messenger RNA expression. The biofilms were more structured in the presence of glucose, but no difference in the diffusion of hyphae through the epithelial cells were observed.

CONCLUSIONS

The data suggest that glucose concentration does not affect the behavior of C. albicans during tissue invasion and other mechanisms must be related to the greater susceptibility of diabetic individuals to candidiasis.

Measuring Streptococcus mutans, Streptococcus sanguinis and Candida albicans biofilm formation using a real-time impedance-based system

Candida albicans and streptococci are amongst the most common fungal and bacterial organisms present in the oral cavity, with a growing body of evidence implicating C. albicans in increased caries severity and in the formation of the cariogenic biofilm. However, the interactive mechanisms between cariogenic streptococci and Candida are yet to be elucidated. In this study, the real-time biofilm formation of C. albicans, S. mutans and S. sanguinis was assessed individually and in combination using the xCELLigence system, an impedance-based microbial biofilm monitoring system. The impedance signal was the highest for C. albicans, followed by S. mutans and S. sanguinis. Although the streptococcal mixed adhesion was found to follow a similar trend to that of S. sanguinis, the introduction of C. albicans resulted in higher adhesion patterns, with the combined growth of S. sanguinis and C. albicans and the combination of all three species resulting in higher biofilm formation than any of the individual organisms over time. This study, the first to use impedance for real-time monitoring of interkingdom biofilms, adds to the body of evidence that C. albicans and oral streptococcal adhesion are interlinked and suggests that interkingdom interactions induce changes in the oral biofilm dynamics over time.

Potential of Novel Bacterial Cellulose Dressings Chemisorbed with Antiseptics for the Treatment of Oral Biofilm Infections

Infections of the oral cavity are caused by multicellular communities of microbes, referred to as biofilms. Due to the high tolerance of biofilms to antibiotics and specific conditions within the oral cavity, there is an ongoing search for carriers that are able to deliver high local concentrations of potent antimicrobials that can eradicate pathogenic biofilms. Bacterial cellulose, owing to its high flexibility, absorbance, and release potential, meets these demands. In this work we chemisorbed bacterial cellulose with antiseptics containing povidone-iodine or polihexanide and analyzed their ability to eradicate in vitro biofilms formed by oral pathogens, such as Aggregatibacter actinomycetemcomitans, Enterococcus faecalis, Candida albicans, Streptococcus mutans, Staphylococcus aureus, and Pseudomonas aeruginosa. In tests performed by means of standard laboratory methods and with a long contact time (24 h), all antiseptics released from the cellulose dressings displayed a very high antibiofilm efficacy. On the other hand, when conditions imitating the oral cavity were used and cellulose dressings were applied for a 0.5–1 h contact time, the antiseptics released from the dressings displayed lower, though still acceptable, activity. Our findings indicate that besides species-specific resistance to particular antiseptic agents, environmental and experimental settings play an essential role in outcomes. Finally, in a proof-of-concept experiment performed in an oral cavity typodont model, we demonstrated the high flexibility and adhesiveness of antiseptic-containing cellulose dressings. Our novel findings, if developed in further studies, may lead to the introduction of new types of dressings that are able to efficiently deal with biofilm infections of the oral cavity.

Molecular community profiling of the bacterial microbiota associated with denture-related stomatitis

Denture-associated stomatitis (DS) affects over two-thirds of denture-wearers. DS presents as erythema of the palatal mucosa in areas where denture-surface associated polymicrobial biofilms containing the fungus Candida albicans exist. The contribution of the oral bacterial microbiota toward the infection is unknown. Therefore, this study characterised the bacterial microbiota of sites within the oral cavity to identify potential associations with occurrence of DS. Denture-wearing patients were recruited (denture stomatitis (DS) n = 8; non-denture stomatitis (NoDS) n = 11) and the oral bacterial microbiota of the tongue, palate and denture-fitting surface was characterised using next-generation sequencing. Operational taxonomic units (OTUs) were identified to bacterial genera and species, and presence/absence and relative abundances were examined. A significant (P = 0.007) decrease in the number of OTUs and thus, diversity of the microbiota was observed in tongue samples of DS patients (vs non-DS). The microbiota of denture-fitting surfaces and palatal mucosae were similar. Large differences in the abundance of bacterial genera and species were observed at each sample site, and unique presence/absence of bacteria was noted. Presence/absence and relative abundance of specific bacteria associated with DS warrants further in vitro and in vivo evaluation, particularly as our previous work has shown C. albicans virulence factor modulation by oral bacteria.

A Multispecies Biofilm In Vitro Screening Model of Dental Caries for High-Throughput Susceptibility Testing

There is a current need to develop and optimize new therapeutics for the treatment of dental caries, but these efforts are limited by the relatively low throughput of relevant in vitro models. The aim of this work was to bridge the 96-well microtiter plate system with a relevant multispecies dental caries model that could be reproducibly grown to allow for the high-throughput screening of anti-biofilm therapies. Various media and inoculum concentrations were assessed using metabolic activity, biomass, viability, and acidity assays to determine the optimal laboratory-controlled conditions for a multispecies biofilm composed of Streptococcus gordonii, Streptococcus mutans, and Candida albicans. The selected model encompasses several of the known fundamental characteristics of dental caries-associated biofilms. The 1:1 RPMI:TSBYE 0.6% media supported the viability and biomass production of mono- and multispecies biofilms best. Kinetic studies over 48 h in 1:1 RPMI:TSBYE 0.6% demonstrated a stable biofilm phase between 10 and 48 h for all mono- and multispecies biofilms. The 1:1:0.1 S. gordonii: S. mutans: C. albicans multispecies biofilm in 1:1 RPMI:TSBYE 0.6% is an excellent choice for a high-throughput multispecies model of dental caries. This high-throughput multispecies model can be used for screening novel therapies and for better understanding the treatment effects on biofilm interactions and stability.

Modulation of Candida albicans virulence in in vitro biofilms by oral bacteria

Candida-associated denture stomatitis presents as erythema of the palatal mucosa and is caused by biofilms containing the fungus Candida albicans that co-reside with oral bacteria on the denture-fitting surface. This study aimed to assess the effect of several frequently encountered oral bacteria on the expression of C. albicans virulence factors in in vitro polymicrobial biofilms. Biofilms containing C. albicans and selected bacterial species were grown on denture acrylic, and analysed by microscopy and by qPCR for expression of putative virulence genes. Candida albicans-only biofilms showed limited hyphal production. Hyphal development was significantly (P < 0·001) increased when biofilms also contained four species of oral bacteria (Streptococcus sanguinis, Streptococcus gordonii, Actinomyces odontolyticus and Actinomyces viscosus), as was the expression of virulence genes (P < 0·05). Importantly, inclusion of Porphyromonas gingivalis in the biofilm consortium resulted in significant (P < 0·05) inhibition of virulence gene expression and production of hyphae. The in vitro expression of C. albicans virulence factors was modulated in polymicrobial biofilms. The complexity of this modulation was highlighted by the reversal of effects following introduction of a single bacterial species into a biofilm community. SIGNIFICANCE AND IMPACT OF THE STUDY: The impact of individual bacterial species on Candida albicans virulence highlights both the complexity of predicting infection mediated by polymicrobial communities and the potential for management through pro- or prebiotic therapy. The possibility to selectively modulate microbial virulence by addition of, or treatment with pro- or prebiotics avoids the use of conventional antimicrobial compounds, thus reducing the contribution to potential drug resistance. Understanding which bacterial species modulate virulence, and the mechanisms by which this occurs, particularly in biofilms, provides excellent foundations for further research questions, and the potential for novel clinical interventions.

Cross-Domain and Viral Interactions in the Microbiome

The importance of the microbiome to human health is increasingly recognized and has become a major focus of recent research. However, much of the work has focused on a few aspects, particularly the bacterial component of the microbiome, most frequently in the gastrointestinal tract. Yet humans and other animals can be colonized by a wide array of organisms spanning all domains of life, including bacteria and archaea, unicellular eukaryotes such as fungi, multicellular eukaryotes such as helminths, and viruses. As they share the same host niches, they can compete with, synergize with, and antagonize each other, with potential impacts on their host. Here, we discuss these major groups making up the human microbiome, with a focus on how they interact with each other and their multicellular host.

Sutures modified by incorporation of chlorhexidine and cinnamaldehyde: anti-Candida effect, bioavailability and mechanical properties

Abstract Introduction Antimicrobial sutures are a therapeutic alternative for the control of oral infections. Objective Incorporate Chlorhexidine (CHX) and Cinnamaldehyde (CN) in sutures and evaluate the anti-Candida effect, release of antimicrobials and mechanical properties. Material and method Silk (S) and Polyglactin 910 (P) sutures were aseptically sectioned (20 mm) and immersed for incorporation in 0.12% CHX, 0.4% CN and 0.9% saline solutions under stirring for 60 minutes (n = 10 / group). Suspensions of 500 μL of Candida albicans (ATCC 90028/ 1 × 106 CFU/mL) were used to evaluate fungal adhesion after the 48 h period at 37°C. The release of CLX and CN were evaluated at 0, 24 and 48 hours (n=3/group) by UV-VIS spectrophotometer (275 nm). The tensile strength and displacement (n=5/group) were evaluated after incorporation (30 mm/min, 50N). Data were analyzed by Anova and Tukey (α = 5%). Result No anti-Candida effect was observed on S and P sutures incorporated with CLX and CN (p>0.05). However, progressive release was verified up to 48 after treatment with CLX (S = 0.075 / P = 0.073 μg/mL) and CN (S = 35.33 /P= 5.72 μg/mL). There was a decrease in tensile strength in S (CLX = 9.9 / CN = 9.9 N) and P (CLX = 14.4 / CN = 15.5 N) (p<0.05). No differences were observed for the displacement for S (CLX = 19.3 / CN=20.7 mm) and P (CLX = 16.2 / CN=15.8 mm) (p>0.05). Conclusion The incorporation of CLX and CN did not have a positive effect on the biological and mechanical properties of the sutures evaluated.

Candida albicans Increases Dentine Demineralization Provoked by Streptococcus mutans Biofilm

Streptococcus mutans are considered the most cariogenic bacteria, but it has been suggested that Candida albicans could increase their cariogenicity. However, the effect of this dual-species microorganisms' combination on dentine caries has not been experimentally evaluated. Biofilms of C. albicans, S. mutans and C. albicans + S. mutans (n = 12/biofilm) were grown in ultra-filtered tryptone yeast extract broth culture medium for 96 h on root dentine slabs of known surface hardness and exposed 8 times per day for 3 min to 10% sucrose. The medium was changed 2 times per day (after the 8 cariogenic challenges and after the overnight period of famine), and aliquots were analyzed to determinate the pH (indicator of biofilm acidogenicity). After 96 h, the biofilms were collected to determine the wet weight, colony-forming units, and the amounts of extracellular polysaccharides (soluble and insoluble). Dentine demineralization was assessed by surface hardness loss (% SHL). The architecture of the biofilms was analyzed by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). Data were analyzed by ANOVA followed by Tukey's test (α = 0.05). The dual-species C. albicans + S. mutans biofilm provoked higher % SHL on dentine (p < 0.05) than the S. mutans and C. albicans biofilm. This was supported by the results of biofilm acidogenicity and the amounts of soluble (6.4 ± 2.14 vs. 4.0 ± 0.94 and 1.9 ± 0.97, respectively) and insoluble extracellular polysaccharides (24.9 ± 9.22 vs. 18.9 ± 5.92 and 0.7 ± 0.48, respectively) (p < 0.05). The C. albicans biofilm alone presented low cariogenicity. The images by CLSM and TEM, respectively, suggest that the C. albicans + S. mutans biofilm is more voluminous than the S. mutans biofilm, and S. mutans cells interact with C. albicans throughout polysaccharides from the biofilm matrix. These findings show that C. albicans enhances the cariogenic potential of the S. mutans biofilm, increasing dentine demineralization.

Candida Interactions with the Oral Bacterial Microbiota

The human oral cavity is normally colonized by a wide range of microorganisms, including bacteria, fungi, Archaea, viruses, and protozoa. Within the different oral microenvironments these organisms are often found as part of highly organized microbial communities termed biofilms, which display consortial behavior. Formation and maintenance of these biofilms are highly dependent on the direct interactions between the different members of the microbiota, as well as on the released factors that influence the surrounding microbial populations. These complex biofilm dynamics influence oral health and disease. In the latest years there has been an increased recognition of the important role that interkingdom interactions, in particular those between fungi and bacteria, play within the oral cavity. Candida spp., and in particular C. albicans, are among the most important fungi colonizing the oral cavity of humans and have been found to participate in these complex microbial oral biofilms. C. albicans has been reported to interact with individual members of the oral bacterial microbiota, leading to either synergistic or antagonistic relationships. In this review we describe some of the better characterized interactions between Candida spp. and oral bacteria.

Influence of Streptococcus mitis and Streptococcus sanguinis on virulence of Candida albicans: in vitro and in vivo studies

The aim was to evaluate in vitro possible interactions, gene expression, and biofilm formation in species of Candida albicans, Streptococcus mitis, and Streptococcus sanguinis and their in vivo pathogenicity. The in vitro analysis evaluated the effects of S. mitis and S. sanguinis on C. albicans's biofilm formation by CFU count, filamentation capacity, and adhesion (ALS1, ALS3, HWP1) and transcriptional regulatory gene (BCR1, CPH1, EFG1) expression. In vivo studies evaluated the pathogenicity of the interaction of the microorganisms on Galleria mellonella, with analyses of the CFU per milliliter count and filamentation. In vitro results indicated that there was an observed decrease in CFU (79.4-71.5%) in multi-species biofilms. The interaction with S. mitis inhibited filamentation, which seems to increase its virulence factor with over-expression of genes ALS1, ALS3, and HWP1 as well the interaction with S. sanguinis as ALS3 and HWP1. S. mitis upregulated BRC1, CPH1, and EFG1. The histological images of in vivo study indicate an increase in the filamentation of C. albicans when in interaction with the other species. It was concluded that S. mitis interaction suggests increased virulence factors of C. albicans, with periods of lower virulence and proto-cooperation in the interaction with S. sanguinis.

Tipping the Balance: C. albicans Adaptation in Polymicrobial Environments

Candida albicans is a pleiomorphic fungus which co-exists with commensal bacteria in mucosal and skin sites of mammalian hosts. It is also a major co-isolated organism from polymicrobial systemic infections, with high potential for morbidity or mortality in immunocompromised patients. Traditionally, resident mucosal bacteria have been thought to antagonize C. albicans in its ability to colonize or cause infection. However, recent investigations have revealed synergistic relationships with certain bacterial species that colonize the same mucosal sites with C. albicans. Such relationships broaden the research landscape in pathogenesis but also contribute to clinical challenges in the prevention or treatment of mucosal candidiasis. This review sheds light on interactions of C. albicans and mucosal bacteria, with special emphasis on the effects of the resident bacterial microbiota on C. albicans physiology as they relate to its adaptation in mucosal sites as a commensal colonizer or as a pathogenic organism.

Optimizing resin-dentin bond stability using a bioactive adhesive with concomitant antibacterial properties and anti-proteolytic activities

Secondary caries and hybrid layer degradation are two major challenges encountered in long-term resin-dentin bond stability. As a link between resin and dentin, adhesives that possess both antimicrobial and anti-proteolytic activities are in demand for eliminating bacteria-induced secondary caries and preventing hybrid layers from degradation. In the present study, a new quaternary ammonium methacryloxy silane (QAMS) prepared from sol-gel chemistry was incorporated into experimental adhesives to examine their antimicrobial effect and anti-proteolytic potential. This functional methacrylate resin monomer contains polymerizable methacryloxy functionalities as well as a positively-charged quaternary ammonium functionality with a long, lipophilic -C₁₈H₃₇ alkyl chain for puncturing the cell wall/membrane of surface-colonizing organisms. Antibacterial testing performed using agar diffusion test, live/dead bacterial staining and colony-forming unit counts all indicated that the QAMS-containing adhesives killed Streptococcus mutans and Actinomyces naeslundii in a dose-dependent manner via a predominant contact-killing mechanism. Gelatinolytic activity within the hybrid layers created by these adhesives was examined using in-situ zymography. Hybrid layers created with 0% QAMS-containing adhesive exhibited intense green fluorescence emitted by the hydrolyzed fluorescein-conjugated gelatin, with 4-fold increase in enzymatic activity compared with an experimental adhesive containing 5% QAMS. Taken together, incorporation of 5% QAMS in the experimental adhesive provides simultaneous antimicrobial and anti-proteolytic activities that are crucial for the maintenance of long-term resin-dentin bond integrity.

STATEMENT OF SIGNIFICANCE

Durability of resin-dentin interfacial bond remains a clinically-significant challenge. Secondary caries caused by bacteria and the degradation of hybrid layers via endogenous dentin proteases are two important contributors to the poor resin-dentin bond durability. The present study developed a new 5% QAMS-containing adhesive that provides simultaneous antimicrobial and dentin protease inhibition functions to extend the longevity of resin-dentin bonds.

A Proposal of Remedies for Oral Diseases Caused by Candida: A Mini Review

An opportunistic pathogen, Candida is not only related to oral problems such as oral candidiasis and denture stomatitis, but also to systemic diseases such as aspiration pneumonia and fungemia. The carriage rate of Candida species in the oral cavity of individuals wearing dentures and with removable orthodontic appliances, has increased. Moreover, it is one of the causal pathogens in refractory infected root canals because of its resistance to antifungal drugs in root canal therapy and poses a great challenge during the treatment of patients. This problem has led to the search for alternative strategies for the treatment and management of C. albicans infections. In this mini review, recent preventive strategies against Candida infection in the oral mucosa with natural product-derived antifungal molecules were discussed. Inhibitory strategies by introducing competitive naturally-derived antifungal peptide molecules with Candida adhesion molecules were specifically introduced. In addition, novel sterilization methods for Candida-infected root canals and tooth structures in the oral cavity were considered, with focused attention on the activities of reactive oxygen species. The possibility of application of these novel strategies in clinical treatments and daily life was also proposed.

Candida Biofilms: Threats, Challenges, and Promising Strategies

Candida species are fungal pathogens known for their ability to cause superficial and systemic infections in the human host. These pathogens are able to persist inside the host due to the development of pathogenicity and multidrug resistance traits, often leading to the failure of therapeutic strategies. One specific feature of Candida species pathogenicity is their ability to form biofilms, which protects them from external factors such as host immune system defenses and antifungal drugs. This review focuses on the current threats and challenges when dealing with biofilms formed by Candida albicans, Candida glabrata, Candida tropicalis, and Candida parapsilosis, highlighting the differences between the four species. Biofilm characteristics depend on the ability of each species to produce extracellular polymeric substances (EPS) and display dimorphic growth, but also on the biofilm substratum, carbon source availability and other factors. Additionally, the transcriptional control over processes like adhesion, biofilm formation, filamentation, and EPS production displays great complexity and diversity within pathogenic yeasts of the Candida genus. These differences not only have implications in the persistence of colonization and infections but also on antifungal resistance typically found in Candida biofilm cells, potentiated by EPS, that functions as a barrier to drug diffusion, and by the overexpression of drug resistance transporters. The ability to interact with different species in in vivo Candida biofilms is also a key factor to consider when dealing with this problem. Despite many challenges, the most promising strategies that are currently available or under development to limit biofilm formation or to eradicate mature biofilms are discussed.

Denture-associated biofilm infection in three-dimensional oral mucosal tissue models

Purpose

In vitro analyses of virulence, pathogenicity and associated host cell responses are important components in the study of biofilm infections. The Candida-related infection, denture-associated oral candidosis, affects up to 60 % of denture wearers and manifests as inflammation of palatal tissues contacting the denture-fitting surface. Commercially available three-dimensional tissue models can be used to study infection, but their use is limited for many academic research institutions, primarily because of the substantial purchase costs. The aim of this study was to develop and evaluate the use of in vitro tissue models to assess infections by biofilms on acrylic surfaces through tissue damage and Candida albicans virulence gene expression.

Methodology

In vitro models were compared against commercially available tissue equivalents (keratinocyte-only, SkinEthic; full-thickness, MatTek Corporation). An in vitro keratinocyte-only tissue was produced using a cancer-derived cell line, TR146, and a full-thickness model incorporating primary fibroblasts and immortalised normal oral keratinocytes was also generated. The in vitro full-thickness tissues incorporated keratinocytes and fibroblasts, and have potential for future further development and analysis.

Results

Following polymicrobial infection with biofilms on acrylic surfaces, both in-house developed models were shown to provide equivalent results to the SkinEthic and MatTek models in terms of tissue damage: a significant (P<0.05) increase in LDH activity for mixed species biofilms compared to uninfected control, and no significant difference (P>0.05) in the expression of most C. albicans virulence genes when comparing tissue models of the same type.

Conclusion

Our results confirm the feasibility and suitability of using these alternative in vitro tissue models for such analyses.

[Study of the infectivity of Candida on peripheral vascular catheters collected from the University Hospital of Tlemcen]

Yeasts can adhere to medical implants and cause infections responsible for high morbidity and mortality among hospitalized patients. The objective of this study is to investigate the infectivity on peripheral vascular catheters collected from general surgery and cardiology in University Hospital of Tlemcen. The results showed that from 29 samples altered by yeast, 35 Candida sp. strains were isolated. However, Candida albicans is the most isolated species in an infectious context. Risk factors that accompanied the infections are the duration of implantation, male gender, and bacterial presence.

The mycobiome: Role in health and disease, and as a potential probiotic target in gastrointestinal disease

The human gastrointestinal (GI) tract is home to trillions of microorganisms, some beneficial and others potentially harmful. Recent advances in science have allowed us to identify the multitude of organisms inhabiting the GI tract and parse out those that play a role in inflammatory bowel disease (IBD). Unfortunately, most research has focused on studying only the bacteria while ,overlooking a key player, fungus. In order to address this issue, we have focused our efforts on studying the fungal community in the GI tract known as the mycobiome. We found that patients with Crohn's disease (CD) tend to have much higher levels of the fungus Candida tropicalis compared to their healthy family members, as well as two bacteria, Escherichia coli and Serratia marcescens. Furthermore, we showed that these three organisms worked together to form robust biofilms capable of exacerbating intestinal inflammation. Herein, we discuss the role of the mycobiome in health and disease, and highlight the importance of maintaining balance of the GI microbiota. Additionally, taking into consideration recent next generation sequencing data, we provide insight into potentially new therapeutic approaches in the treatment of IBD through the use of antifungals and/or probiotics aimed at establishing and maintaining a healthy balance of the GI total microbial community including fungi and bacteria.

Candida albicans and Pseudomonas aeruginosa Interact To Enhance Virulence of Mucosal Infection in Transparent Zebrafish

Polymicrobial infections often include both fungi and bacteria and can complicate patient treatment and resolution of infection. Cross-kingdom interactions among bacteria, fungi, and/or the immune system during infection can enhance or block virulence mechanisms and influence disease progression. The fungus Candida albicans and the bacterium Pseudomonas aeruginosa are coisolated in the context of polymicrobial infection at a variety of sites throughout the body, including mucosal tissues such as the lung. In vitro, C. albicans and P. aeruginosa have a bidirectional and largely antagonistic relationship. Their interactions in vivo remain poorly understood, specifically regarding host responses in mediating infection. In this study, we examine trikingdom interactions using a transparent juvenile zebrafish to model mucosal lung infection and show that C. albicans and P. aeruginosa are synergistically virulent. We find that high C. albicans burden, fungal epithelial invasion, swimbladder edema, and epithelial extrusion events serve as predictive factors for mortality in our infection model. Longitudinal analyses of fungal, bacterial, and immune dynamics during coinfection suggest that enhanced morbidity is associated with exacerbated C. albicans pathogenesis and elevated inflammation. The P. aeruginosa quorum-sensing-deficient ΔlasR mutant also enhances C. albicans pathogenicity in coinfection and induces extrusion of the swimbladder. Together, these observations suggest that C. albicans-P. aeruginosa cross talk in vivo can benefit both organisms to the detriment of the host.