Effect of progesterone on Candida albicans vaginal pathogenicity

Candida albicans is responsible for the majority of cases of vulvovaginal candidiasis (VVC), an infection which occurs mainly during the luteal phase of the menstrual cycle or during the pregnancy, when levels of progesterone are elevated. One of the most important candidal virulence factors is the ability to adhere to host surfaces and form biofilms.The aim of this study was to determine the influence of progesterone on C. albicans virulence, namely biofilm formation and colonisation/invasion of a reconstituted human vaginal epithelium (RHVE). Biofilm formation on the RHVE was evaluated by enumeration of culturable cells, total mass quantification and scanning electron microscopy. The capacity of C. albicans strains to invade and colonise the tissue was examined by fluorescence microscopy using species-specific peptide nucleic acid (PNA) probe hybridisation, and quantitatively evaluated by RT-PCR Candida quantification methodology. Furthermore, gene (BCR1 and HWP1) expression of biofilm and RHVE-colonising cells was evaluated by quantitative RT-PCR. Results confirmed that progesterone reduced the capacity of C. albicans strains to form biofilms and to colonise and invade RHVE. Additionally, it was demonstrated that progesterone decreased expression of BCR1 and HWP1, which are important virulence determinants of C. albicans. In conclusion, it was evident that progesterone can have a major influence on C. albicans pathogenicity on vaginal epithelial cells and may partly explain susceptibility of women to VVC at different stages of the menstrual cycle.     

Symbiotic Relationship between Streptococcus mutans and Candida albicans Synergizes Virulence of Plaque Biofilms In Vivo

Streptococcus mutans is often cited as the main bacterial pathogen in dental caries, particularly in early-childhood caries (ECC). S. mutans may not act alone; Candida albicans cells are frequently detected along with heavy infection by S. mutans in plaque biofilms from ECC-affected children. It remains to be elucidated whether this association is involved in the enhancement of biofilm virulence. We showed that the ability of these organisms together to form biofilms is enhanced in vitro and in vivo. The presence of C. albicans augments the production of exopolysaccharides (EPS), such that cospecies biofilms accrue more biomass and harbor more viable S. mutans cells than single-species biofilms. The resulting 3-dimensional biofilm architecture displays sizeable S. mutans microcolonies surrounded by fungal cells, which are enmeshed in a dense EPS-rich matrix. Using a rodent model, we explored the implications of this cross-kingdom interaction for the pathogenesis of dental caries. Coinfected animals displayed higher levels of infection and microbial carriage within plaque biofilms than animals infected with either species alone. Furthermore, coinfection synergistically enhanced biofilm virulence, leading to aggressive onset of the disease with rampant carious lesions. Our in vitro data also revealed that glucosyltransferase-derived EPS is a key mediator of cospecies biofilm development and that coexistence with C. albicans induces the expression of virulence genes in S. mutans (e.g., gtfB, fabM). We also found that Candida-derived β1,3-glucans contribute to the EPS matrix structure, while fungal mannan and β-glucan provide sites for GtfB binding and activity. Altogether, we demonstrate a novel mutualistic bacterium-fungus relationship that occurs at a clinically relevant site to amplify the severity of a ubiquitous infectious disease.     

Involvement of amyloid proteins in the formation of biofilms in the pathogenic yeast Candida albicans

Candida species represent a major fungal threat for human health. Within the Candida genus, the yeast Candida albicans is the most frequently incriminated species during episodes of candidiasis or candidemia. Biofilm formation is used by C. albicans to produce a microbial community that is important in an infectious context. The cell wall, the most superficial cellular compartment, is of paramount importance regarding the establishment of biofilms. C. albicans cell wall contains proteins with amyloid properties that are necessary for biofilm formation due to their adhesion properties. This review focuses on these amyloid proteins during biofilm formation in the yeast C. albicans.     

Thymus vulgaris essential oil and thymol inhibit biofilms and interact synergistically with antifungal drugs against drug resistant strains of Candida albicans and Candida tropicalis

Role of biofilm in disease development and enhance tolerance to antifungal drugs among Candida species has necessitated search for new anti-fungal treatment strategy. Interference in pathogenic biofilm development by new antifungal compounds is considered as an attractive anti-infective strategy. Therefore, the objective of this study was to evaluate Thymus vulgaris essential oil and its major active compound, thymol for their potential to inhibit and eradicate biofilms alone and in combination with antifungal drugs against Candida spp. with especial reference to Candida tropicalis. Anti-candidal efficacy of T. vulgaris and thymol in terms of minimum inhibitory concentration (MIC) was first determined to select the sub-MICs against C. albicans and C. tropicalis. Biofilm formation in the presence and absence of test agents was determined in 96-well microtiter plate by XTT reduction assay and effect of essential oils at sub-MICs of the test agents on biofilm development on glass surface was analysed by light and scanning electron microscopy. Synergistic interaction between essential oils and antifungal drugs were studied by checkerboard method. Effect of sub-MIC of T. vulgaris (0.5 × MIC) and thymol (0.5 × MIC) on biofilm formation showed a significant reduction (P < 0.05) in biofilms. Light microscopy and SEM studies revealed disaggregation and deformed shape of C. albicans biofilm cells and reduced hyphae formation in C. tropicalis biofilm cells at sub-MICs of thymol. Significant effect of T. vulgaris and thymol was also recorded on pre-formed biofilms of both C. albicans and C. tropicalis. T. vulgaris and thymol also showed synergy with fluconazole against both in planktonic and biofilm mode of growth of C. albicans and C. tropicalis. However, synergy with amphotericin B is clearly evident only in planktonic Candida cells. Thyme oil and thymol alone or in combination with antifungal drugs can act as promising antibiofilm agent against drug resistant strains of Candida species and needs further in vivo study to synergise its therapeutic efficacy.     

Changing Virulence Factors among Vaginal Non-albicans Candida species

Background: Vulvovaginal candidiasis (VVC) is caused by overgrowth of Candida species in the female lower genital tract and most commonly caused by Candida albicans. The production of various virulence factors may attribute to their pathogenicity. Hence, this study was aimed to determine the production of various virulence factors of Candida spp. causing VVC. Materials and Methods: A total of 51 Candida spp. were isolated prospectively from 50 patients among 211 clinically suspected cases of VVC. The haemolytic activity, biofilm production, proteinase activity, phospholipase activity and esterase activity were detected by standard methods. Statistical analysis was performed using OpenEpi version 3.01. Results: Haemolytic activity was observed in 42 Candida isolates (82.4%), biofilm activity in 21 Candida isolates (41.2%), proteinase and esterase activity in 19 Candida isolates (37.3%) each and phospholipase activity in 15 Candida isolates (29.4%). Phospholipase activity was observed in all of the C. albicans strains, whereas all strains of Candida krusei were able to produce biofilm. All strains of Candida parapsilosis and 87% strains of Candida glabrata were haemolytic. Five of the eight C. glabrata strains were found to produce strong proteinase (Pr_z score ≤0.63). About 30.4% strains of C. glabrata and 20% strains of C. krusei were found to be positive for esterase activity. This is one of the few studies which revealed esterase activity among C. glabrata and C. krusei strains. Conclusions: This study highlighted that there is a change in the virulence factors among the non-albicans Candida species, especially C. glabrata strains which were haemolytic and produce strong proteinase activity and esterase activity. It may be one of the explanation of the most common causative agent of VVC in our study. Multicentric studies from this area might be required to get a more generalised conclusion.     

Detection of phospholipase activity of Candida albicans and non albicans isolated from women of reproductive age with vulvovaginal candidiasis in rural area

Background: Vulvovaginal candidiasis (VVC) is most common accounting for 17 to 39% of symptomatic women. Both Candida albicans and non albicans Candida species are involved in VVC. Amongst various virulence factors proposed for Candida, extracellular phospholipases is one of the virulence factor implicated in its pathogenicity. With this background the present study was carried out to find the prevalence of different Candida species and to detect phospholipase producing strains isolated from symptomatic women with VVC. Materials and Methods: At least two vaginal swabs from 156 women of reproductive age with abnormal vaginal discharge were collected. Direct microscopy and Gram’s stained smear examined for presence of budding yeast and pseudo mycelia followed by isolation and identification of Candida species. Extracellular phospholipase activity was studied by inoculating all isolates on Sabouraud’s dextrose egg yolk agar (SDA) medium. Results: Of the 156 women with curdy white discharge alone or in combination with other signs, 59 (37.82%) women showed laboratory evidence of VVC. A total of 31 (52.54%) women had curdy white discharge followed by 12 (20.33%) with other signs and symptoms. C. albicans (62.59%) and non albicans Candida (37.28%) in a ratio of 1.68:1 were isolated. Of the 37 strains of C. albians 30 (81.08%) showed the enzyme activity. Seventeen (56.66%) strains showed higher Pz value of < 0.70 (++++). Conclusion: Although there may be typical clinical presentation of Candidiasis. all the patients did not show laboratory evidence of infection. Pregnancy was found to be major risk factor for development of VVC. C. albicans was prevalent species but non albicans species were also frequently isolated. Extracellular phospholipase activity was seen in C. albicans and not in non albicans Candida isolates.     

In vitro and in vivo activity of a possible novel antifungal small molecule against Candida albicans

Nosocomial infections by fungi are important causes of morbidity and mortality, and the adhesion capacity of yeast on abiotic and biotic surfaces has been considered an important step in this process. Als3 proteins are widely studied for their ability to allow Candida albicans to bind to various surfaces. The objective of the present study was to verify, with more details, the action of F2768-0318 in relation to its antifungal activity as well as its ability to act on C. albicans virulence factors related to adhesion and biofilm formation in vitro and in vivo by inhibiting the Als3 protein. F2768-0318 was assessed in tests of biofilm formation and adhesion on abiotic surfaces (polystyrene plates) and adherence on biotic surfaces, including human endocervical (HeLa) cells, human umbilical vein endothelial cells (HUVECs), and fresh buccal epithelial cells (BEC). Our results showed F2768-0318 was useful in reducing the adhesion and biofilm formation of C. albicans on abiotic surfaces, indicating the possibility of treating hospital materials and preventing biofilm formation on these types of equipment. Further studies are still needed, including optimization of the molecule to allow this molecule to be effective on other types of surfaces, such as human cells.     

Carnosol inhibits the growth and biofilm of Candida albicans

ObjectiveThis study was to explore the inhibitory effects of carnosol on the growth and biofilm of Candida albicans.ResultsOur results showed that carnosol inhibited the planktonic growth of C. albicans with a MIC of 100 μg/mL. Carnosol can also inhibit the biofilm formation and development of C. albicans. 25–100 μg/mL of carnosol can obviously inhibit the yeast-to-hyphal transition in four kinds of hyphal-inducing media and the adhesion of C. albicans to polystyrene surfaces. Results from PI staining indicated that carnosol may disrupt cell membrane of C. albicans.ConclusionCarnosol can inhibit the planktonic growth and virulence factors of C. albicans, such as biofilm formation, adhesion and hyphal growth. The antifungal mechanism may involve the increase in cell membrane permeability.     

Antivirulence activity and in vivo efficacy of a thiazole derivative against candidiasis

Candida albicans is a pathogen equipped with a variety of commensal and virulence traits that help it colonize the microbiota and invade host tissue during infection. In this study, we investigated the potential anticandidal activity of 3-[2-(4-(4-methoxyphenyl)thiazol-2-yl)hydrazino)]butan-1-ol (MT), a thiazolylhydrazone compound synthesized by our group, and identified it as a promising antifungal agent. The activity of MT was evaluated in vitro and in vivo against C. albicans as well as its ability to inhibit virulence factors. For this, the ability of MT to inhibit the adhesion of C. albicans to human buccal epithelial cells and biofilm formation and filamentation was tested. In addition, the potential in vivo activity of MT was evaluated in murine models of oral candidiasis.Our results confirmed the antifungal activity of MT, with a minimal inhibitory concentration range of 0.5–2 µg/mL. Indeed, MT treatment in vitro decreased the expression of C. albicans genes involved in biofilm formation and morphogenesis and encoding hydrolytic enzymes, which was also confirmed through phenotypic observations. In addition, MT promoted a decrease in the colony forming units recovered from the tongues of mice with oral candidiasis. In this work, we present a potent antivirulence compound that shows potential for candidiasis therapy, especially for topical use.     

Candida albicans Aro1 affects cell wall integrity,biofilm formation and virulence

BackgroundCandida albicans is an opportunistic pathogen capable of causing life-threatening systemic infections. The C. albicans ARO1 gene encodes an arom multifunctional enzyme, which can possibly catalyze reactions of the shikimate pathway to synthesize aromatic amino acids. However, the functions of C. albicans Aro1 have not been extensively characterized.MethodsARO1 knockdown mutant strain was constructed, using a tetracycline-regulated (TR) expression system. Cell growth of the mutant strain was compared with wild type. Effects of the ARO1 gene knockdown on cell wall properties, adhesion to polystyrene and biofilm formation were further investigated. Finally, Galleria mellonella was used as a model host to study the role of ARO1 in virulence of C. albicans.ResultsWe showed that defective growth in the ARO1 knockdown strain was rescued by supplemental aromatic amino acids. In addition, the ARO1 knockdown strain was easily aggregated and precipitated. The knockdown of ARO1 also caused changes in cell wall properties and compositions and promoted C. albicans cell adhesion to polystyrene and biofilm formation. Finally, the ARO1 knockdown strain showed attenuation of C. albicans virulence.ConclusionThis work provides new insights into C. albicans metabolism, cell wall and virulence.     

Host Intestinal Signal-Promoted Biofilm Dispersal Induces Vibrio cholerae Colonization

Vibrio cholerae causes human infection through ingestion of contaminated food and water, leading to the devastating diarrheal disease cholera. V. cholerae forms matrix-encased aggregates, known as biofilms, in the native aquatic environment. While the formation of V. cholerae biofilms has been well studied, little is known about the dispersal from biofilms, particularly upon entry into the host. In this study, we found that the exposure of mature biofilms to physiologic levels of the bile salt taurocholate, a host signal for the virulence gene induction of V. cholerae, induces an increase in the number of detached cells with a concomitant decrease in biofilm mass. Scanning electron microscopy micrographs of biofilms exposed to taurocholate revealed an altered, perhaps degraded, appearance of the biofilm matrix. The inhibition of protein synthesis did not alter rates of detachment, suggesting that V. cholerae undergoes a passive dispersal. Cell-free media from taurocholate-exposed biofilms contains a larger amount of free polysaccharide, suggesting an abiotic degradation of biofilm matrix by taurocholate. Furthermore, we found that V. cholerae is only able to induce virulence in response to taurocholate after exit from the biofilm. Thus, we propose a model in which V. cholerae ingested as a biofilm has coopted the host-derived bile salt signal to detach from the biofilm and go on to activate virulence.     

Environmental pH influences Candida albicans biofilms regarding its structure,virulence and susceptibility to fluconazole

Candida albicans colonizes sites with different environmental pH. However, it is unclear how these conditions can interfere on biofilms. This study aimed to evaluate the influence of environmental pH on behavior of C. albicans regarding its structure, virulence and susceptibility to fluconazole (FLZ). Minimal inhibitory concentration, minimal fungicidal concentration and time kill were used to evaluate the susceptibility to FLZ in planktonic cells under three pH values (4.0, 5.5, 7.0). These pH values were used for biofilms analysis. C. albicans ATCC 90028 was developed on poly(methlymethacrylate) resin for 48 h. Then, 2.56 μg/mL of FLZ was added to experimental groups for 24 h, and biofilms were analyzed by cell quantification, bioactivity, secretion of proteinases and phospholipases and structure. All data were analyzed by two-way ANOVA, followed by Tukey's test (α = 0.05). For planktonic cells, changes in environmental pH decreased the susceptibility to FLZ. C. albicans biofilms developed at pH 5.5 showed higher cell counts, bioactivity, bio-volume, average thickness and roughness coefficient (p < 0.05). In contrast, the presence of FLZ at pH 4.0 did not influence the structural parameters (p > 0.05), but increased secretion of proteinase and phospholipase (p < 0.05). Within the conditions studied, it was shown that environmental pH modulates the structure, virulence and susceptibility of C. albicans to FLZ.     

Escherichia coli enhances the virulence factors of Candida albicans,the cause of vulvovaginal candidiasis,in a dual bacterial/fungal biofilm

Co-infection with other microorganisms can promote the Candida albicans to be invasive. In this study, Escherichia coli and C. albicans were co-isolated from the women with candidiasis symptoms. The in vitro effects of E. coli on C. albicans hypha development, biofilm formation, antibiotic susceptibility, dispersion from the biofilm, expression of Als3, Hwp1, and Tup1 genes, and pathogenesis in Galleria mellonella were investigated. Electron microscopic images revealed that hypha induction was markedly increased in the bacteria-fungi co-culture. Biofilm formation was increased 2.2 fold in the presence of E. coli. The minimum inhibitory concentration of nystatin against Candida was increased from (μg mL^?1) 25 to 50 in the dual biofilm. Candida dissemination was increased up to 2.7 fold from the mixed fungi/bacteria biofilm. The expression of ALS3 and HWP1 genes was increased (5.9 and 2.0 fold, respectively) while the TUP1 gene expression was decreased (0.4 fold) when C. albicans was incubated with E. coli. The simultaneous injection of C. albicans and E. coli to the insect larvae increased Galleria mortality up to 40%. This study demonstrated the effects of E. coli to promote fungi virulence factors, which suggest polymicrobial interaction should be considered during treatment of fungal infections.     

Candida albicans biofilms formed into catheters and probes and their resistance to amphotericin B

In Algeria, many bacterial biofilms have been studied but those of fungal origin, particularly those due to the yeast Candida albicans remained unidentified. The present study was performed at the Chabane Hamdoune hospital in Maghnia (Algeria), where 51 strains of C. albicans representing 16.94% of all taken samples were isolated. They were collected from catheters and probes used in different hospital services with variable rates; the most concerned service was ICU (40.74%) followed by gynecology department (17.39%), while general surgery came third (15.79%). Testing the antifungal property of amphotericin B (AmB) we showed clearly that the sessile cells of C. albicans were much more resistant than their planktonic counterparts (suspended cells), especially when the resistance increased during the different phases of biofilm formation until it reached its threshold at the ripening stage (at 48 h). Furthermore, scanning electron microscopy of the isolated strains in the laboratory revealed the formation of biofilms on catheters by C. albicans. Surprisingly, observations revealed the presence of a new structure in these biofilms: a chlamydospore?