Biofilm formation by oral clinical isolates of Candida species

The antimicrobial activity of an antiseptic soap against Candida Albicans and Streptococcus Mutans single and dual-species biofilms on denture base and reline acrylic resins

To evaluate the effect of antiseptic soap on single and dual-species biofilms of Candida albicans and Streptococcus mutans on denture base and reline resins. Samples of the resins were distributed into groups (n = 9) according to the prevention or disinfection protocols. In the prevention protocol, samples were immersed in the solutions (Lifebuoy, 0.5% sodium hypochlorite solution and PBS) for 7, 14 and 28 days before the single and dual-species biofilms formation. Overnight denture disinfection was simulated. In the disinfection protocol, samples were immersed in the same solutions during 8 hours after the single and dual-species biofilms formation. Antimicrobial activity was analyzed by counting colony-forming units (CFU/mL) and evaluating cell metabolism. Cell viability and protein components of the biofilm matrix were evaluated using confocal laser scanning microscopy (CLSM). Data were submitted to ANOVA, followed by Tukey's post-test (α = 0.05) or Dunnett's T3 multiple comparisons test. In the prevention protocol, Lifebuoy solution effectively reduced the number of CFU/mL of both species. In addition, the solution decreased the cell metabolism of the microorganisms. Regarding disinfection protocol, the Lifebuoy solution was able of reduce approximately of 2-3 logs for all the biofilms on the denture base and reline resin. Cellular metabolism was also reduced. The images obtained with CLSM corroborate these results. Lifebuoy solution was effective in reducing single and dual-species biofilms on denture base and reline resins.

Evaluation of mixed biofilm production by Candida spp. and Staphylococcus aureus strains co-isolated from cystic fibrosis patients in northwest Algeria

Cystic fibrosis patients' lungs are chronically colonized by multiple microbial species capable of forming biofilms. This study aimed to characterize the polymicrobial biofilm formed by Candida spp. and S. aureus, co-isolated from sputum samples of cystic fibrosis patients regarding microbial density, metabolic activity, and structure. 67 samples from 28 patients were collected with a 96% alteration rate. 34% showed alterations by both Candida spp. and Gram-positive bacteria, predominantly Candida spp. and S. aureus in 77% of cases, accounting for 6 associations. Biofilm biomass was quantified using the crystal violet assay, and metabolic activity was assessed using the MTT reduction assay. Scanning electron microscopy analyzed the C. tropicalis/S. aureus24 biofilm architecture. Candida spp. isolates demonstrated the ability to form mixed biofilms with S. aureus. The C. tropicalis/S. aureus24 association exhibited the highest production of biofilm and metabolic activity, along with the C. albicans17/C. rugosa/S. aureus7 in both single and mixed biofilms.

Lactoferrin as a potential therapeutic for the treatment of Candida-associated denture stomatitis

BACKGROUND

The use of prostheses in the oral cavity creates favorable conditions for Candida colonization, which may subsequently lead to Candida-associated denture stomatitis (CADS). Due to its many contributing factors and frequent relapses, CADS is difficult to manage. Given the rise in drug resistance among fungal species, it is critical to develop new therapeutic approaches, reduce the required dosage of medications, and minimize the toxicity and side effects of therapy.

HIGHLIGHT

Salivary lactoferrin, a multifunctional glycoprotein, is thought to be the first line of defense against microbial invasion of mucosal surfaces.

CONCLUSION

Current research emphasizes the capability of lactoferrin and its derivatives to eliminate a broad spectrum of Candida species. It may be an appealing option for use in monotherapy or in combination with common medications for oral stomatitis treatment. This review provides an overview of the current understanding of lactoferrin's anti-fungal effects in oral candidiasis.

Anti-Microbial Effect of AgBr-NP@CTMAB on Streptococcus Mutans and Assessment of Surface Roughness Hardness and Flexural Strength of PMMA

Purpose

To investigate the inhibition of Streptococcus mutans (S.mutans) and its biofilm by AgBr-nanoparticles (NP) @CTMAB (cetyltrimethyl-ammonium bromide) and evaluate the changes in Polymethyl methacrylate (PMMA)'s surface roughness (Ra), microhardness, and flexural strength during prolonged immersion in AgBr-NP@CTMAB for application in the denture cleaning industry.

Patients and Methods

The antibacterial activity of AgBr-NP@CTMAB against S.mutans was measured colony formation assay, OD600 and laser confocal microscopy. Changes in the specimens' values for surface roughness, microhardness, and flexural strength (MPa) were measured after immersion solutions for 180 or 360 days.

Results

The AgBr-NP@CTMAB solution exhibited a robust antibacterial effect on planktonic S. mutans, with a minimum bactericidal concentration of 5 µg/mL. The 10 µg/mL AgBr-NP@CTMAB solution efficiently inhibited S. mutans biofilm formation. (2) No significant difference in surface roughness after immersion in AgBr-NP@CTMAB (10 µg/mL and 20 µg/mL) comparing with distilled water (P > 0.05) and Polident had significantly higher than distilled water (P < 0.05). There was a significant decrease in the surface hardness of the PMMA specimens that were immersed in the Polident compared with those in distilled water (P < 0.05). While, no significant differences in surface hardness after immersion in the AgBr-NP@CTMAB (P > 0.05). The result of flexural strength suggested that there was no statistically significant difference (P < 0.05) between AgBr-NP@CTMAB as well as Polident and water.

Conclusion

AgBrNP@CTMAB can efficiently inhibit the growth of plankton S.mutans and biofilm formation, without affecting the flexural strength, microhardness, or surface roughness of PMMA. Therefore, AgBrNP@CTMAB holds promise as a new denture cleaning agent.

Thymoquinone Antifungal Activity against Candida glabrata Oral Isolates from Patients in Intensive Care Units-An In Vitro Study

The number of Candida spp. infections and drug resistance are dramatically increasing worldwide, particularly among immunosuppressed patients, and it is urgent to find novel compounds with antifungal activity. In this work, the antifungal and antibiofilm activity of thymoquinone (TQ), a key bioactive constituent of black cumin seed Nigella sativa L., was evaluated against Candida glabrata, a WHO 'high-priority' pathogen. Then, its effect on the expression of C. glabrata EPA6 and EPA7 genes (related to biofilm adhesion and development, respectively) were analyzed. Swab samples were taken from the oral cavity of 90 hospitalized patients in ICU wards, transferred to sterile falcon tubes, and cultured on Sabouraud Dextrose Agar (SDA) and Chromagar Candida for presumptive identification. Next, a 21-plex PCR was carried out for the confirmation of species level. C. glabrata isolates underwent antifungal drug susceptibility testing against fluconazole (FLZ), itraconazole (ITZ), amphotericin B (AMB), and TQ according to the CLSI microdilution method (M27, A3/S4). Biofilm formation was measured by an MTT assay. EPA6 and EPA7 gene expression was assessed by real-time PCR. From the 90 swab samples, 40 isolates were identified as C. glabrata with the 21-plex PCR. Most isolates were resistant to FLZ (n = 29, 72.5%), whereas 12.5% and 5% were ITZ and AMB resistant, respectively. The minimum inhibitory concentration (MIC₅₀) of TQ against C. glabrata was 50 µg/mL. Importantly, TQ significantly inhibited the biofilm formation of C. glabrata isolates, and EPA6 gene expression was reduced significantly at MIC₅₀ concentration of TQ. TQ seems to have some antifungal, antibiofilm (adhesion) effect on C. glabrata isolates, showing that this plant secondary metabolite is a promising agent to overcome Candida infections, especially oral candidiasis.

Influence of Fabrication Technique on Adhesion and Biofilm Formation of Candida albicans to Conventional, Milled, and 3D-Printed Denture Base Resin Materials: A Comparative In Vitro Study

The aim of this study was to evaluate the adhesion and biofilm formation of Candida albicans (C. albicans) on conventionally fabricated, milled, and 3D-printed denture base resin materials in order to determine the susceptibility of denture contamination during clinical use. Specimens were incubated with C. albicans (ATCC 10231) for 1 and 24 h. Adhesion and biofilm formation of C. albicans were assessed using the field emission scanning electron microscopy (FESEM). The XTT (2,3-(2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide) assay was used for the quantification of fungal adhesion and biofilm formation. The data were analyzed using GraphPad Prism 8.02 for windows. One-way ANOVA with Tukey's post hoc testing were performed with a statistical significance level set at α = 0.05. The quantitative XTT biofilm assay revealed significant differences in the biofilm formation of C. albicans between the three groups in the 24 h incubation period. The highest proportion of biofilm formation was observed in the 3D-printed group, followed by the conventional group, while the lowest candida biofilm formation was observed in the milled group. The difference in biofilm formation among the three tested dentures was statistically significant (p < 0.001). The manufacturing technique has an influence on the surface topography and microbiological properties of the fabricated denture base resin material. Additive 3D-printing technology results in increased candida adhesion and the roughest surface topography of maxillary resin denture base as compared to conventional flask compression and CAD/CAM milling techniques. In a clinical setting, patients wearing additively manufactured maxillary complete dentures are thus more susceptible to the development of candida-associated denture stomatitis and accordingly, strict oral hygiene measures and maintenance programs should be emphasized to patients.

Similarities and Differences among Species Closely Related to Candida albicans: C. tropicalis, C. dubliniensis, and C. auris

Although Candida species are widespread commensals of the microflora of healthy individuals, they are also among the most important human fungal pathogens that under certain conditions can cause diseases (candidiases) of varying severity ranging from mild superficial infections of the mucous membranes to life-threatening systemic infections. So far, the vast majority of research aimed at understanding the molecular basis of pathogenesis has been focused on the most common species—Candida albicans. Meanwhile, other closely related species belonging to the CTG clade, namely, Candida tropicalis and Candida dubliniensis, are becoming more important in clinical practice, as well as a relatively newly identified species, Candida auris. Despite the close relationship of these microorganisms, it seems that in the course of evolution, they have developed distinct biochemical, metabolic, and physiological adaptations, which they use to fit to commensal niches and achieve full virulence. Therefore, in this review, we describe the current knowledge on C. tropicalis, C. dubliniensis, and C. auris virulence factors, the formation of a mixed species biofilm and mutual communication, the environmental stress response and related changes in fungal cell metabolism, and the effect of pathogens on host defense response and susceptibility to antifungal agents used, highlighting differences with respect to C. albicans. Special attention is paid to common diagnostic problems resulting from similarities between these species and the emergence of drug resistance mechanisms. Understanding the different strategies to achieve virulence, used by important opportunistic pathogens of the genus Candida, is essential for proper diagnosis and treatment.

Niacin Limitation Promotes Candida glabrata Adhesion to Abiotic Surfaces

Candida glabrata is a prevalent fungal pathogen in humans, which is able to adhere to host cells and abiotic surfaces. Nicotinic acid (NA) limitation has been shown to promote the adherence of C. glabrata to human epithelial cells. Clinically, the elderly and hospitalized patients who are prone to C. glabrata–related denture stomatitis often suffer from vitamin deficiency. This study aimed to investigate C. glabrata adhesion to abiotic surfaces, including acrylic resin (a denture material) surfaces, cell surface hydrophobicity and adhesion gene expression. C. glabrata CBS138 was grown in media containing decreasing NA concentrations (40, 0.4, 0.04 and 0.004 µM). Adherence of C. glabrata to glass coverslips and acrylic resin was analyzed. C. glabrata adhesion to both surfaces generally increased with decreasing NA concentrations. The highest adhesion was found for the cells grown with 0.004 µM NA. The cell surface hydrophobicity test indicated that NA limitation enhanced hydrophobicity of C. glabrata cells. Quantitative PCR showed that of all adhesion genes tested, EPA1, EPA3 and EPA7 were significantly up-regulated in both 0.004 µM NA and 0.04 µM NA groups compared to those in the 40 µM NA group. No significant up- or down-regulation under NA limitation was observed for the other tested adhesion genes, namely AWP3, AWP4, AWP6 and EPA6. NA limitation resulted in increased expression of some adhesion genes, higher surface hydrophobicity of C. glabrata and enhanced adhesion to abiotic surfaces. NA deficiency is likely a risk factor for C. glabrata–related denture stomatitis in the elderly.

Inhibitory effect of 405-nm blue LED light on the growth of Candida albicans and Streptococcus mutans dual-species biofilms on denture base resin

We investigated whether irradiation with 405-nm blue LED light could inhibit the growth of not only single- but dual-species biofilms formed by Candida albicans and Streptococcus mutans on denture base resin and cause the alteration in gene expression related to adhesion and biofilm formation. C. albicans and S. mutans single-/dual-species biofilms were formed on the denture base specimens. The biofilms were irradiated with 405-nm blue LED light (power density output: 280 mW/cm²) for 0 (control) and 40 min. Dual-species biofilms were analyzed using CFU assay and fluorescence microscopy, and single-/dual-species biofilms were analyzed using alamarBlue assays and gene expression analysis. To assess the inhibitory effect of irradiation on dual-species biofilms, specimens after irradiation were aerobically incubated for 12 h. After incubation, the inhibition of growth was assessed using CFU assays and fluorescence microscopy. Data were analyzed using the Mann-Whitney U or Student's t test (p < 0.05). Irradiation produced a significant inhibitory effect on biofilms. Fluorescence microscopy revealed that almost all C. albicans and S. mutans cells were killed by irradiation, and there was no notable difference in biofilm thickness immediately after irradiation and after irradiation and incubation for 12 h. alamarBlue assays indicated the growth of the biofilms was inhibited for 12-13 h. The expression of genes associated with adhesion and biofilm formation-als1 in C. albicans and ftf, gtfC, and gtfB in S. mutans-significantly reduced by irradiation. Irradiation with 405-nm blue LED light effectively inhibited the growth of C. albicans and S. mutans dual-species biofilms for 12 h.

Action of disinfectant solutions on adaptive capacity and virulence factors of the Candida spp. biofilms formed on acrylic resin

BACKGROUND

Understanding the behavior of Candida spp. when exposed to denture disinfectants is essential to optimize their effectiveness. Changes in the virulence factors may cause increased resistance of Candida spp. to disinfectant agents.

OBJECTIVE

To evaluate the microbial load, cellular metabolism, hydrolytic enzyme production, hyphae formation, live cell and biofilm quantification of Candida albicans, Candida tropicalis and Candida glabrata after exposure to disinfectant solutions.

METHODOLOGY

Simple biofilms were grown on heat-polymerized acrylic resin specimens, and divided into groups according to solutions/strains: distilled water (control); 0.25% sodium hypochlorite (NaOCl 0.25% ); 10% Ricinus communis (RC 10%); and 0.5% Chloramine T (CT 0.5%). The virulence factors were evaluated using the CFU count (microbial load), XTT method (cell metabolism), epifluorescence microscopy (biofilm removal and live or dead cells adhered), protease and phospholipase production and hyphae formation. Data were analyzed (α=0.05) by one-way ANOVA/ Tukey post hoc test, Kruskal-Wallis test and Wilcoxon test.

RESULTS

NaOCl 0.25% was the most effective solution. CT 0.5% reduced the number of CFUs more than RC 10% and the control. RC 10% was effective only against C. glabrata. RC 10% and CT 0.5% decreased the cellular metabolism of C. albicans and C. glabrata. Enzyme production was not affected. Hyphal growth in the RC 10% and CT 0.5% groups was similar to that of the control. CT 0.5% was better than RC 10% against C. albicans and C. tropicalis when measuring the total amount of biofilm and number of living cells. For C. glabrata, CT 0.5% was equal to RC 10% in the maintenance of living cells; RC 10% was superior for biofilm removal.

CONCLUSIONS

The CT 0.5% achieved better results than those of Ricinus communis at 10%, favoring the creation of specific products for dentures. Adjustments in the formulations of RC 10% are necessary due to efficacy against C. glabrata. The NaOCl 0.25% is the most effective and could be suitable for use as a positive control.

Abundance interaction in Candida albicans and Candida glabrata mixed biofilms under diverse conditions

Candida albicans and Candida glabrata are frequently coisolated from the oral cavity in immunosuppressive or immunocompromised individuals. Their relationship is usually defined as competition as C. glabrata can inhibit growth of C. albicans in cohabitation. In this study, eight C. albicans isolates as well as two C. glabrata strains were used to investigate the effects of culture medium (Roswell Park Memorial Institute [RPMI]-1640, YPD, YND), incubation time (24 h, 48 h, 72 h, 96 h), initial inoculum (C. glabrata: C. albicans = 2:1, 1:1, 1:2), and medium state (static and dynamic states) on viable cell enumeration and relative abundance in both Candida SB and MB. The results showed that in most cases, C. glabrata and C. albicans SB and MB flourished in RPMI-1640 at 24 h under dynamic state compared with other conditions. Except YPD medium, there were high proportions of preponderance of C. albicans over C. glabrata in MB compared with SB. High initial inoculum promoted corresponding Candida number in both SB and MB and its abundance in MB relative to SB. This study revealed an impact of several environmental conditions on the formation of C. albicans and C. glabrata SB and MB and their abundance in MB in comparison with SB, deepening our understanding of both Candida interaction and their resistance mechanism in MB.

LAY SUMMARY

This study described the effects of diverse experimental conditions on the numbers of Candida albicans and Candida glabrata single biofilms and mixed biofilms and their abundance.

Microbicidal effect of 405-nm blue LED light on Candida albicans and Streptococcus mutans dual-species biofilms on denture base resin

This study investigated: (1) the microbicidal effect of 405-nm blue LED light irradiation on biofilm formed by Candida albicans hyphae and Streptococcus mutans under dual-species condition on denture base resin, (2) the generation of intracellular reactive oxygen species (ROS) induced by irradiation, and (3) the existence of intracellular porphyrins, which act as a photosensitizer. Denture base resin specimens were prepared and C. albicans and S. mutans dual-species biofilms were allowed to form on the specimens. The biofilms were irradiated with 405-nm blue LED light and analyzed using the colony-forming unit assay, fluorescence microscopy, and scanning electron microscopy (SEM). Single-species biofilms of C. albicans and S. mutans formed on the specimens were irradiated with 405-nm blue LED light. After the irradiation, the intracellular ROS levels in C. albicans and S. mutans cells were measured. In addition, the level of intracellular porphyrins in C. albicans and S. mutans were measured. Irradiation for more than 30 min significantly inhibited the colony formation ability of C. albicans and S. mutans. Fluorescence microscopy revealed that almost all C. albicans and S. mutans cells were killed by irradiation. SEM images showed various cell damage patterns. Irradiation led to the generation of intracellular ROS and porphyrins were present in both C. albicans and S. mutans cells. In conclusion, irradiation with 405-nm blue light-emitting diode light for 40 min effectively disinfect C. albicans hyphae and S. mutans dual-species biofilms and possibly react with intracellular porphyrins resulting in generation of ROS in each microorganism.

Heat Shock Protein 60, Insights to Its Importance in Histoplasma capsulatum: From Biofilm Formation to Host-Interaction

Heat shock proteins (Hsps) are among the most widely distributed and evolutionary conserved proteins, acting as essential regulators of diverse constitutive metabolic processes. The Hsp60 of the dimorphic fungal Histoplasma capsulatum is the major surface adhesin to mammalian macrophages and studies of antibody-mediated protection against H. capsulatum have provided insight into the complexity involving Hsp60. However, nothing is known about the role of Hsp60 regarding biofilms, a mechanism of virulence exhibited by H. capsulatum. Considering this, the present study aimed to investigate the influence of the Hsp60 on biofilm features of H. capsulatum. Also, the non-conventional model Galleria mellonella was used to verify the effect of this protein during in vivo interaction. The use of invertebrate models such as G. mellonella is highly proposed for the evaluation of pathogenesis, immune response, virulence mechanisms, and antimicrobial compounds. For that purpose, we used a monoclonal antibody (7B6) against Hsp60 and characterized the biofilm of two H. capsulatum strains by metabolic activity, biomass content, and images from scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). We also evaluated the survival rate of G. mellonella infected with both strains under blockage of Hsp60. The results showed that mAb 7B6 was effective to reduce the metabolic activity and biomass of both H. capsulatum strains. Furthermore, the biofilms of cells treated with the antibody were thinner as well as presented a lower amount of cells and extracellular polymeric matrix compared to its non-treated controls. The blockage of Hsp60 before fungal infection of G. mellonella larvae also resulted in a significant increase of the larvae survival compared to controls. Our results highlight for the first time the importance of the Hsp60 protein to the establishment of the H. capsulatum biofilms and the G. mellonella larvae infection. Interestingly, the results with Hsp60 mAb 7B6 in this invertebrate model suggest a pattern of fungus-host interaction different from those previously found in a murine model, which can be due to the different features between insect and mammalian immune cells such as the absence of Fc receptors in hemocytes. However further studies are needed to support this hypothesis

Microbial interactions and immunity response in oral Candida species

Oral candidiasis are among the most common noncommunicable diseases, related with serious local and systemic illnesses. Although these infections can occur in all kinds of patients, they are more recurrent in immunosuppressed ones such as patients with HIV, hepatitis, cancer or under long antimicrobial treatments. Candida albicans continues to be the most frequently identified Candida spp. in these disorders, but other non-C. albicans Candida are rising. Understanding the immune responses involved in oral Candida spp. infections is a key feature to a successful treatment and to the design of novel therapies. In this review, we performed a literature search in PubMed and WoS, in order to examine and analyze common oral Candida spp.-bacteria/Candida-Candida interactions and the host immunity response in oral candidiasis.

Current Aspects in the Biology, Pathogeny, and Treatment of Candida krusei, a Neglected Fungal Pathogen

Fungal infections represent a constant and growing menace to human health, because of the emergence of new species as causative agents of diseases and the increment of antifungal drug resistance. Candidiasis is one of the most common fungal infections in humans and is associated with a high mortality rate when the fungi infect deep-seated organs. Candida krusei belongs to the group of candidiasis etiological agents, and although it is not isolated as frequently as other Candida species, the infections caused by this organism are of special relevance in the clinical setting because of its intrinsic resistance to fluconazole. Here, we offer a thorough revision of the current literature dealing with this organism and the caused disease, focusing on its biological aspects, the host-fungus interaction, the diagnosis, and the infection treatment. Of particular relevance, we provide the most recent genomic information, including the gene prediction of some putative virulence factors, like proteases, adhesins, regulators of biofilm formation and dimorphism. Moreover, C. krusei veterinary aspects and the exploration of natural products with anti-C. krusei activity are also included.

Candida Biofilms: An Update on Developmental Mechanisms and Therapeutic Challenges

Fungi of the genus Candida are important etiological agents of superficial and life-threatening infections in individuals with a compromised immune system. One of the main characteristics of Candida is its ability to form highly drug tolerance biofilms in the human host. Biofilms are a dynamic community of multiple cell types whose formation over time is orchestrated by a network of transcription regulators. In this brief review, we provide an update of the processes involved in biofilm formation by Candida spp. (formation, treatment, and control), as well as the transcriptional circuitry that regulates its development and interactions with other microorganisms. Candida albicans is known to build mixed species biofilms with other Candida species and with various other bacterial species in different host niches. Taken together, these properties play a key role in Candida pathogenesis. In addition, this review gathers recent studies with new insights and perspectives for the treatment and control of Candida biofilms.

Susceptibility to Oral Antiseptics and Virulence Factors Ex Vivo Associated with Candida spp. Isolated from Dental Prostheses

PURPOSE

To isolate Candida spp. from dental prosthesis users' saliva and to evaluate the isolates for the presence of several virulence factors. This research also aimed to investigate the antifungal activity of 3 commercial mouthwashes/oral antiseptic formulations containing 0.12% chlorhexidine, 0.07% cetylpyridinium, or 0.075% cetylpyridinium against planktonic and sessile (biofilm mode) yeast cells.

MATERIALS AND METHODS

Forty-three Candida yeasts were isolated from 32 of 70 selected patients, and the virulence factors of C. albicans, C. krusei, C. glabrata, C. tropicalis, and C. parapsilosis species were investigated by polymerase chain reaction (PCR) and proteinase in plates. Minimum inhibitory concentration (MIC), and in vitro biofilm assay evaluated the antifungal activity of antiseptics.

RESULTS

C. albicans, C. krusei, C. glabrata, C. tropicalis, and C. parapsilosis were detected in mono and mixed cultures. Only C. albicans displayed genes related to adhesion and proteinases (ALS2, ALS3, SAP1, and SAP3). The aspartate proteinase activity was found in 60.46% of isolates. The tested antiseptic formulations exhibited a MIC less than 1.25% toward yeasts in the planktonic mode. According to XTT ((2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) assay results, most Candida isolates and all mixed cultures formed biofilms within 24 hours. The evaluated antiseptic formulations were also active against biofilms.

CONCLUSION

Most virulence factors investigated here (ALS2, ALS3, SAP1, and SAP3) occurred in the majority of the Candida spp. isolates, especially in C. albicans. The tested mouthwash formulations were effective against all the yeast isolates in both the planktonic and sessile growth modes. Developing alternative therapies that can avoid or control biofilm formation is necessary to prevent oral candidiasis and other Candida spp. infections.

Candida sp. Infections in Patients with Diabetes Mellitus

Candidiasis has increased substantially worldwide over recent decades and is a significant cause of morbidity and mortality, especially among critically ill patients. Diabetes mellitus (DM) is a metabolic disorder that predisposes individuals to fungal infections, including those related to Candida sp., due to a immunosuppressive effect on the patient. This review aims to discuss the latest studies regarding the occurrence of candidiasis on DM patients and the pathophysiology and etiology associated with these co-morbidities. A comprehensive review of the literature was undertaken. PubMed, Scopus, Elsevier’s ScienceDirect, and Springer’s SpringerLink databases were searched using well-defined search terms. Predefined inclusion and exclusion criteria were applied to classify relevant manuscripts. Results of the review show that DM patients have an increased susceptibility to Candida sp. infections which aggravates in the cases of uncontrolled hyperglycemia. The conclusion is that, for these patients, the hospitalization periods have increased and are commonly associated with the prolonged use of indwelling medical devices, which also increase the costs associated with disease management.

Twice-daily red and blue light treatment for Candida albicans biofilm matrix development control

Phototherapy has been proposed as a direct means of affecting local bacterial infections. However, the use of phototherapy to prevent fungal biofilm development has received comparatively less attention. This study aimed to determine the effects of red light treatment and blue light treatment, without a photosensitizer, on the development of Candida albicans biofilm. During the development of 48-h biofilms of C. albicans SN 425 (n = 10), the biofilms were exposed twice-daily to noncoherent blue and red light (LumaCare; 420 nm and 635 nm). The energy density applied was 72 J cm^-2 for blue light and 43.8 J cm², 87.6 J cm², and 175.5 J cm² for red light. Positive control (PC) and negative control (NC) groups were treated twice-daily for 1 min with 0.12% chlorhexidine (CHX) and 0.89% NaCl respectively. Biofilms were analyzed for colony forming units (CFU), dry-weight, and exopolysaccharides (EPS-soluble and EPS-insoluble). Data was analyzed by one-way ANOVA and Tukey post hoc test (α = 0.05). Dry-weight was lower than NC (p < 0.001) and approached PC levels with both red and blue light treatments. CFU were also lower in groups exposed to blue light and higher durations of red light (p < 0.05). EPS-soluble and EPS-insoluble measures were variably reduced by these light exposures. In conclusion, twice-daily exposure to both blue and red lights affect the biofilm development and physiology of polysaccharide production and are potential mechanisms for the control of C. albicans biofilm matrix development.

Role of biofilm morphology, matrix content and surface hydrophobicity in the biofilm-forming capacity of various Candida species

The present study aimed to evaluate the role of biofilm morphology, matrix content and surface hydrophobicity in the biofilm-forming capacity of Candida albicans and non-albicans Candida (NAC) spp. Biofilm formation was determined by microtitre plate assay and bright-field and scanning electron microscopy. The matrix carbohydrates, proteins and e-DNA were quantified by phenol-sulfuric acid, bicinchoninic acid and UV spectroscopy, respectively. Specific glycosyl residues were detected by dot blot. The cell-surface hydrophobicity was determined by hydrocarbon adhesion assay. Candida tropicalis was found to exhibit the highest adherence to polystyrene. It formed dense biofilms with extensive pseudohyphae and hyphal elements, high hydrophobicity and the greatest amount of matrix carbohydrates, proteins and e-DNA. C. albicans displayed higher adherence and a complex biofilm morphology with larger aggregates than Candida parapsilosis and Candida krusei, but had lower matrix content and hydrophobicity. Thus, the combinatorial effect of increased filamentation, maximum matrix content and high hydrophobicity contributes to the enhanced biofilm-forming capacity of C. tropicalis.

Comparative Study of the Effects of Fluconazole and Voriconazole on Candida glabrata, Candida parapsilosis and Candida rugosa Biofilms

Infections by non-albicans Candida species are a life-threatening condition, and formation of biofilms can lead to treatment failure in a clinical setting. This study was aimed to demonstrate the in vitro antibiofilm activity of fluconazole (FLU) and voriconazole (VOR) against C. glabrata, C. parapsilosis and C. rugosa with diverse antifungal susceptibilities to FLU and VOR. The antibiofilm activities of FLU and VOR in the form of suspension as well as pre-coatings were assessed by XTT [2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction assay. Morphological and intracellular changes exerted by the antifungal drugs on Candida cells were examined by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results of the antibiofilm activities showed that FLU drug suspension was capable of killing C. parapsilosis and C. rugosa at minimum inhibitory concentrations (MICs) of 4× MIC FLU and 256× MIC FLU, respectively. While VOR MICs ranging from 2× to 32× were capable of killing the biofilms of all Candida spp tested. The antibiofilm activities of pre-coated FLU were able to kill the biofilms at ¼× MIC FLU and ½× MIC FLU for C. parapsilosis and C. rugosa strains, respectively. While pre-coated VOR was able to kill the biofilms, all three Candida sp at ½× MIC VOR. SEM and TEM examinations showed that FLU and VOR treatments exerted significant impact on Candida cell with various degrees of morphological changes. In conclusion, a fourfold reduction in MIC₅₀ of FLU and VOR towards ATCC strains of C. glabrata, C. rugosa and C. rugosa clinical strain was observed in this study.

The essential oil of Allium sativum as an alternative agent against Candida isolated from dental prostheses

BACKGROUND

The colonization of the surfaces of dental prostheses by Candida albicans is associated with the development of denture stomatitis. In this context, the use of fluconazole has been proposed, but its disadvantage is microbial resistance. Meanwhile, the oil of Allium sativum has shown an effect in controlling biofilm formation by C. albicans.

AIMS

The objective of this study was to determine the antifungal activities of the essential oil of A. sativum and fluconazole against clinical isolates of Candida species obtained from rigid, acrylic-based partial or total dentures and to compare these agents' effects on both biofilm and planktonic cells.

METHODS

A total of 48 clinical isolates obtained from the acrylic surface of partial or complete dentures were examined, and the following species were identified: C. albicans, Candida glabrata, Candida tropicalis, and Candida krusei. For each isolate, the antifungal activities of the essential oil of A. sativum and fluconazole against both biofilm and planktonic cells were evaluated using the Clinical & Laboratory Standards Institute (CLSI) M27-A3 method. The isolates were also evaluated by semiquantitative XTT reduction.

RESULTS

All planktonic Candida isolates were susceptible to the essential oil of A. sativum, whereas 4.2% were resistant to fluconazole. Regarding susceptibilities in biofilms, 43.8% of biofilms were resistant to A. sativum oil, and 91.7% were resistant to fluconazole.

CONCLUSIONS

All planktonic cells of the different Candida species tested are susceptible to <1mg/ml A. sativum oil, and the majority are susceptible to fluconazole. Susceptibility decreases in biofilm cells, with increased resistance to fluconazole compared with A. sativum oil. The essential oil of A. sativum is thus active against clinical isolates of Candida species obtained from dentures, with effects on both biofilm and planktonic cells in vitro.

Candida glabrata's recurrent infections: biofilm formation during Amphotericin B treatment

Candida species are responsible for recurrent human infections, mostly in immunocompromised patients, due to their high vulnerability. Candida glabrata has a major role in systemic candidiasis and Amphotericin B (AmB), a polyene only used in hospitals, is frequently used to treat this disease. Lately, however, clinical evidences of Candida recurrent infections during these treatments are being described, probably due to biofilm (re)formation during this therapy. Thus, this work aims at inferring if C. glabrata biofilms are still being formed during AmB treatment. For that, C. glabrata biofilms were formed in the presence of AmB and analysed by dry weight. Matrix composition was analysed quantifying carbohydrates and, specifically, β-1,3 glucans. Results demonstrated that, although in a lesser extent, C. glabrata is able to develop biofilms in the presence of AmB, with a thick extracellular matrix, with an increase on carbohydrates, especially β-1,3 glucans. Therefore, it is confirmed that complex biofilms of C. glabrata can be formed during an AmB treatment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study shows new insights regarding recurrent candidiasis. The authors demonstrated that Amphotericin B did not totally prevent the development of biofilms during Candida glabrata's infection treatment and that the change in the biofilm matrices may have a high responsibility for the fail in the treatment of systemic candidiasis.

Characterization of a novel antibiofilm effect of nitric oxide-releasing aspirin (NCX-4040) on Candida albicans isolates from denture stomatitis patients

Candida albicans biofilms play a key role in denture stomatitis, one of the most common oral pathologies in elderly people. Because biofilms are highly resistant to antifungals, new pharmacological strategies are needed. Aspirin and nitric oxide-donor molecules have both shown antibiofilm effects on C. albicans, making them promising candidates for treatment. In this study, we evaluated the antifungal/antibiofilm effect of a nitric-oxide releasing aspirin (NO-ASA) on C. albicans isolates from denture stomatitis patients in vitro. Disk diffusion assays showed that while NO-ASA had no antifungal effect, the drug potentiated fluconazole inhibition zone diameters, increasing the effect of fluconazole by 20–30% (p<0.05). The effect of NO-ASA on the morphogenesis of C. albicans was evaluated using light microscopy after inducing hyphae formation. For all clinical strains assayed, 125 μM NO-ASA significantly decreased the number of filamentous cells present (p<0.01). Adhesion to abiotic surfaces, a critical event for biofilm formation, was evaluated in 96-well polystyrene plates using crystal violet assay; 125 μM NO-ASA significantly inhibited adhesion. Biofilms were observed with scanning electron microscopy (SEM) and quantified using XTT reduction assay. NO-ASA decreased biofilm formation (IC₅₀ ranging from 300 μM to 700 μM), consistent with SEM findings of altered biofilm microarchitecture. PGE₂ and carboxy-PTIO (an NO scavenger) both blocked the antibiofilm effects of NO-ASA, suggesting that the efficacy of NO-ASA may be associated with both inhibition of PGE₂ synthesis and release of NO. NO-ASA is a promising novel antibiofilm agent for treating fluconazole-resistant strains of C. albicans.

Oral mucositis caused by Candida glabrata biofilms: failure of the concomitant use of fluconazole and ascorbic acid

OBJECTIVES

Candida glabrata is becoming one of the most prevalent pathogenic yeasts in cases of oral diseases. Mucositis is an recurrent oral infection in immunocompromised patients, and the actual guidelines recommend the use of fluconazole (Flu) for many cases. However, the azole resistance by C. glabrata is renowned, causing a reduced therapeutic response, especially when it occurs in biofilms. In this study, we performed an in vitro evaluation of an alternative pharmacotherapy for C. glabrata biofilm infections, combining ascorbic acid (AA) with Flu. AA is recognized for degrading β-glucans, an important compound of the biofilm matrices, which prevent drug diffusion.

MATERIALS AND METHODS

Routine clinical 30 or 40 mg/l doses of Flu were applied to C. glabrata biofilms simultaneously with 200 or 300 mg/l of AA.

RESULTS

The results showed that this combination effectively promoted the degradation of the biofilm network, but unfortunately, also stimulated the growth of the yeasts population due to release of several glucose monomers during β-glucans hydrolysis.

DISCUSSION

AA lead to the hydrolysis of the β-glucans of the matrix, liberating glucose molecules which are used as carbon souce by the yeasts, thus suppressing the desired antifungal effect of the drug combination with Flu.

CONCLUSIONS

Unlike to what happens in treatment of bacterial infection, AA should not be used together with Flu in the treating oral mucositis caused by Candida.

Candida species from oral cavity of HIV-infected children exhibit reduced virulence factors in the HAART era

This study aimed to assess, in vitro, the biofilm viability and the phospholipase and protease production of Candida spp. from the saliva of HIV infected children and healthy controls, and to correlate the results with the use of medical data. A total of 79 isolates were analyzed: 48 Candida albicans isolates (33/15) and 20 Candida parapsilosis sensu lato complex isolates (12/8) (from HIV/control patients, respectively), and 8 Candida krusei, 1 Candida tropicalis, 1 Candida dubliniensis and 1 Candida guilliermondii from HIV patients. The XTT (2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-Carboxanilide) reduction assay analyzed the biofilm viability. Phospholipase and protease assays were performed using the egg yolk and Bovine Serum Albumin agar plate methods, respectively. All isolates were able to form biofilm with cell viability. Quantitatively, Candida isolates from both groups presented a similar ability to form biofilm (p > 0.05). The biofilm viability activity was higher in C. albicans isolates than in non-albicans Candida isolates (p < 0.05) for both groups. Phospholipase activity was detected in 32 isolates (40.5%) and it was significantly higher in the HIV group (p = 0.006). Protease activity was detected in 66 isolates (84.8%) and most of them were relatively/very strong producers. No statistical association with medical data was found in the HIV group. Although Candida spp. isolates from HIV-positive children presented higher phospholipase production, in vitro they exhibited reduced virulence factors compared to isolates from healthy individuals. This finding may enlighten the role played by immunosuppression in the modulation of Candida virulence attributes.

Inhibitory effect of alpha-mangostin on Candida biofilms

The objective of this study was to determine the inhibitory effect of alpha-mangostin on Candida biofilms. Candida species including Candida albicans, Candida krusei, Candida tropicalis, and Candida glabrata were tested. Candida biofilms were formed in flat-bottomed 96-well microtiter plates. The metabolic activity of cells within biofilms was quantified using the XTT assay. The results demonstrated that alpha-mangostin showed a significant anti-biofilm effect on both developing biofilms and preformed biofilms of Candida species. It may be concluded that alpha-mangostin could be an anti-biofilm agent against Candida species. Further in vivo investigations are needed to uncover the therapeutic values of this medicinal plant.

In vitro Paracoccidioides brasiliensis biofilm and gene expression of adhesins and hydrolytic enzymes

Paracoccidioides species are dimorphic fungi that initially infect the lungs but can also spread throughout the body. The spreading infection is most likely due to the formation of a biofilm that makes it difficult for the host to eliminate the infection. Biofilm formation is crucial for the development of infections and confines the pathogen to an extracellular matrix. Its presence is associated with antimicrobial resistance and avoidance of host defenses. This current study provides the first description of biofilm formation by Paracoccidioides brasiliensis (Pb18) and an analysis of gene expression, using real-time PCR, associated with 3 adhesins and 2 hydrolytic enzymes that could be associated with the virulence profile. Biofilm formation was analyzed using fluorescence microscopy, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Metabolic activity was determined using the XTT reduction assay. P. brasiliensis was able to form mature biofilm in 144 h with a thickness of 100 μm. The presence of a biofilm was found to be associated with an increase in the expression of adhesins and enzymes. GP43, enolase, GAPDH and aspartyl proteinase genes were over-expressed, whereas phospholipase was down-regulated in biofilm. The characterization of biofilm formed by P. brasiliensis may contribute to a better understanding of the pathogenesis of paracoccidioidomycosis as well as the search for new therapeutic alternatives; while improving the effectiveness of treatment.

Mixed biofilms formed by C. albicans and non-albicans species: a study of microbial interactions

Most Candida infections are related to microbial biofilms often formed by the association of different species. The objective of this study was to evaluate the interactions between Candida albicans and non-albicans species in biofilms formed in vitro. The non-albicans species studied were:Candida tropicalis, Candida glabrata and Candida krusei. Single and mixed biofilms (formed by clinical isolates of C. albicans and non-albicans species) were developed from standardized suspensions of each strain (10(7) cells/mL), on flat-bottom 96-well microtiter plates for 48 hour. These biofilms were analyzed by counting colony-forming units (CFU/mL) in Candida HiChrome agar and by determining cell viability, using the XTT 2,3-bis (2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide colorimetric assay. The results for both the CFU/mL count and the XTT colorimetric assay showed that all the species studied were capable of forming high levels of in vitro biofilm. The number of CFU/mL and the metabolic activity of C. albicans were reduced in mixed biofilms with non-albicans species, as compared with a single C. albicans biofilm. Among the species tested, C. krusei exerted the highest inhibitory action against C. albicans. In conclusion, C. albicans established antagonistic interactions with non-albicans Candida species in mixed biofilms.

Candida/Candida biofilms. First description of dual-species Candida albicans/C. rugosa biofilm

Denture liners have physical properties that favour plaque accumulation and colonization by Candida species, irritating oral tissues and causing denture stomatitis. To isolate and determine the incidence of oral Candida species in dental prostheses, oral swabs were collected from the dental prostheses of 66 patients. All the strains were screened for their ability to form biofilms; both monospecies and dual-species combinations were tested. Candida albicans (63 %) was the most frequently isolated microorganism; Candida tropicalis (14 %), Candida glabrata (13 %), Candida rugosa (5 %), Candida parapsilosis (3 %), and Candida krusei (2 %) were also detected. The XTT assay showed that C. albicans SC5314 possessed a biofilm-forming ability significantly higher (p < 0.001) than non-albicans Candida strains, after 6 h 37 °C. The total C. albicans CFU from a dual-species biofilm was less than the total CFU of a monospecies C. albicans biofilm. In contrast to the profuse hyphae verified in monospecies C. albicans biofilms, micrographies showed that the C. albicans/non-albicans Candida biofilms consisted of sparse yeast forms and profuse budding yeast cells that generated a network. These results suggested that C. albicans and the tested Candida species could co-exist in biofilms displaying apparent antagonism. The study provide the first description of C. albicans/C. rugosa mixed biofilm.

Competitive Interactions between C. albicans, C. glabrata and C. krusei during Biofilm Formation and Development of Experimental Candidiasis

In this study, we evaluated the interactions between Candida albicans, Candida krusei and Candida glabrata in mixed infections. Initially, these interactions were studied in biofilms formed in vitro. CFU/mL values of C. albicans were lower in mixed biofilms when compared to the single biofilms, verifying 77% and 89% of C. albicans reduction when this species was associated with C. glabrata and C. krusei, respectively. After that, we expanded this study for in vivo host models of experimental candidiasis. G. mellonella larvae were inoculated with monotypic and heterotypic Candida suspensions for analysis of survival rate and quantification of fungal cells in the haemolymph. In the groups with single infections, 100% of the larvae died within 18 h after infection with C. albicans. However, interaction groups achieved 100% mortality after 72 h of infection by C. albicans-C. glabrata and 96 h of infection by C. albicans-C. krusei. C. albicans CFU/mL values from larvae hemolymph were lower in the interacting groups compared with the monoespecies group after 12 h of infection. In addition, immunosuppressed mice were also inoculated with monotypic and heterotypic microbial suspensions to induce oral candidiasis. C. albicans CFU/mL values recovered from oral cavity of mice were higher in the group with single infection by C. albicans than the groups with mixed infections by C. albicans-C. glabrata and C. albicans-C. krusei. Moreover, the group with single infection by C. albicans had a higher degree of hyphae and epithelial changes in the tongue dorsum than the groups with mixed infections. We concluded that single infections by C. albicans were more harmful for animal models than mixed infections with non-albicans species, suggesting that C. albicans establish competitive interactions with C. krusei and C. glabrata during biofilm formation and development of experimental candidiasis.