Determination of germ tube, phospholipase, and proteinase production by bloodstream isolates of Candida albicans

Improvement of a low-cost protocol for a simultaneous comparative evaluation of hydrolytic activity between sessile and planktonic cells: Candida albicans as a study model

Candida albicans is often implicated in nosocomial infections with fatal consequences. Its virulence is contributed to hydrolytic enzymes and biofilm formation. Previous research focused on studying these virulence factors individually. Therefore, this study aimed to investigate the impact of biofilm formation on the hydrolytic activity using an adapted low-cost method. Eleven strains of C. albicans were used. The biofilms were formed on pre-treated silicone discs using 24-well plates and then deposited on the appropriate agar to test each enzyme, while the planktonic cells were conventionally seeded. Biofilms were analysed using Raman spectroscopy, fluorescent and scanning electron microscopy. The adapted method provided an evaluation of hydrolytic enzymes activity in C. albicans biofilm and showed that sessile cells had a higher phospholipase and proteinase activities compared with planktonic cells. These findings were supported by spectroscopic and microscopic analyses, which provided valuable insights into the virulence mechanisms of C. albicans during biofilm formation.

Photodynamic impact of curcumin enhanced silver functionalized graphene nanocomposites on Candida virulence

Candida species are escalating resistance to conventional antifungal treatments, intensifying their virulence, and obstructing the effectiveness of antifungal medications. Addressing this challenge is essential for effectively managing Candida infections. The overarching objective is to advance the development of more efficient and precise therapies tailored to counter Candida infections. This study focuses on developing antifungal combined drugs using curcumin-enhanced silver-functionalized graphene nanocomposites (Cur-AgrGO) to effectively target key virulence factors of C. albicans, C. tropicalis, and C. glabrata (Candida spp.). The green reduction of graphene oxide (GO) using bioentities and active molecules makes this approach cost-effective and environmentally friendly. The nanocomposites were characterized using various techniques. Combining Cur-AgrGO with photodynamic therapy (PDT) demonstrated effective antifungal and antibiofilm activity with delayed growth and metabolism. The nanocomposites effectively suppressed hyphal transition and reduced key virulence factors, including proteinases, phospholipases, ergosterol levels, and cell membrane integrity. The findings suggest that Cur-AgrGO + PDT has potential as a treatment option for Candida infections. This innovative approach holds promise for treating Candida infections.

Characterization of Virulence Factors in Candida Species Causing Candidemia in a Tertiary Care Hospital in Bangkok, Thailand

Candidemia is often associated with high mortality, and Candida albicans, Candida tropicalis, Candida glabrata, and Candida parapsilosis are common causes of this disease. The pathogenicity characteristics of specific Candida spp. that cause candidemia in Thailand are poorly understood. This study aimed to characterize the virulence factors of Candida spp. Thirty-eight isolates of different Candida species from blood cultures were evaluated for their virulence properties, including exoenzyme and biofilm production, cell surface hydrophobicity, tissue invasion, epithelial cell damage, morphogenesis, and phagocytosis resistance; the identity and frequency of mutations in ERG11 contributing to azole-resistance were also determined. C. albicans had the highest epithelial cell invasion rate and phospholipase activity, with true hyphae formation, whereas C. tropicalis produced the most biofilm, hydrophobicity, protease activity, and host cell damage and true hyphae formation. ERG11 mutations Y132F and S154F were observed in all azole-resistant C. tropicalis. C. glabrata had the most hemolytic activity while cell invasion was low with no morphologic transition. C. glabrata was more easily phagocytosed than other species. C. parapsilosis generated pseudohyphae but not hyphae and did not exhibit any trends in exoenzyme production. This knowledge will be crucial for understanding the pathogenicity of Candida spp. and will help to explore antivirulence-based treatment.

Unraveling the anti-virulence potential and antifungal efficacy of 5-aminotetrazoles using the zebrafish model of disseminated candidiasis

Candida albicans remains the main causal agent of candidiasis, the most common fungal infection with disturbingly high mortality rates worldwide. The limited diversity and efficacy of clinical antifungal drugs, exacerbated by emerging drug resistance, have resulted in the failure of current antifungal therapies. This imposes an urgent demand for the development of innovative strategies for effective eradication of candidal infections. While the existing clinical drugs display fungicidal or fungistatic activity, the strategy specifically targeting C. albicans filamentation, as the most important virulence trait, represents an attractive approach for overcoming the drawbacks related to clinical antifungals. The results acquired in this study revealed the significant potential of 5-aminotetrazoles as a new class of effective and safe anti-virulence agents. Moreover, these novel agents were active when applied both alone and in combination with clinically approved polyenes. Complete prevention of C. albicans morphogenetic yeast-to-hyphae transition was achieved at doses as low as 1.3 μM under conditions mimicking various filamentation-responsive stimuli in the human body, while no cardio- or hepatotoxicity was observed at doses as high as 200 μM. The treatment of C. albicans-infected zebrafish embryos with nystatin alone had low efficacy, while the combination of nystatin and selected 5-aminotetrazoles prevented fungal filamentation, successfully eliminating the infection and rescuing the infected embryos from lethal disseminated candidiasis. In addition, the most potent anti-virulence 5-aminotetrazole prevented C. albicans in developing the resistance to nystatin when applied in combination, keeping the fungus sensitive to the antifungal drug.

The genotypes and virulence attributes of C. albicans isolates from oral leukoplakia

Background

There is a debate as to whether some types of oral leucoplakias (OL) are caused by Candida species, and whether they contribute to the malignant transformation, associated with a minority of such lesions. As no detailed population analysis of yeast isolates from OL is available, we evaluated the virulence attributes, and genotypes of 35 C. albicans from OL, and compared their genotypes with 18 oral isolates from healthy individuals.

Material and Methods

The virulence traits evaluated were esterase, phospholipase, proteinase, haemolysin and coagulase production, and phenotypic switching activity, and yeast adherence and biofilm formation. DNA from OL and control yeasts were evaluated for A, B or C genotype status.

Results

Phospholipase, proteinase, and coagulase activity and biofilm formation was observed in 80%, 66%, 97 % and 77 % of the isolates, respectively. Phenotypic switching was detected in 8.6%, while heamolytic, and esterase activity and adherence were noted in all isolates.

Conclusions

The genotype A was predominant amongst both the OL and control groups. Due to the small sample size of our study a larger investigation to define the role of candidal virulent attributes in the pathogenicity of OL is warranted, and the current data should serve as a basis until then.

Key words:C. albicans, oral cavity, leukoplakia, virulence factors, genotyping.

Virulence Factors and Azole-Resistant Mechanism of Candida Tropicalis Isolated from Candidemia

BACKGROUND

Limited knowledge exists on the virulence factors of Candida tropicalis and the mechanisms of azole resistance that lead to an intensified pathogenicity and treatment failure. We aimed to evaluate the virulence factors and molecular mechanisms of azole resistance among C. tropicalis isolated from patients with candidemia.

MATERIALS AND METHODS

Several virulence factors, including extracellular enzymatic activities, cell surface hydrophobicity (CSH), and biofilm formation, were evaluated. Antifungal susceptibility pattern and expression level of ERG11, UPC2, MDR1, and CDR1 genes of eight (4 fluconazole resistance and 4 fluconazole susceptible) clinical C. tropicalis isolates were assessed. The correlation between the virulence factors and antifungal susceptibility patterns was analyzed.

RESULTS

During a 4 year study, forty-five C. tropicalis isolates were recovered from candidemia patients. The isolates expressed different frequencies of virulence determinants as follows: coagulase 4 (8.9%), phospholipase 5 (11.1%), proteinase 31 (68.9%), esterase 43 (95.6%), hemolysin 44 (97.8%), biofilm formation 45 (100%) and CSH 45(100%). All the isolates were susceptible to amphotericin B and showed the highest resistance to voriconazole. There was a significant positive correlation between micafungin minimum inhibitory concentrations (MICs) and hemolysin production (r_s = 0.316). However, we found a negative correlation between fluconazole MICs and esterase production (r_s = -0.383). We observed the high expression of ERG11 and UPC2 genes in fluconazole-resistant C. tropicalis isolates.

CONCLUSION

C. tropicalis isolated from candidemia patients extensively displayed capacities for biofilm formation, hemolysis, esterase activity, and hydrophobicity. In addition, the overexpression of ERG11 and UPC2 genes was considered one of the possible mechanisms of azole resistance.

Aspartyl Proteinase and Phospholipase Activities of Candida albicans Isolated From Oropharyngeal Candidiasis in Head and Neck Cancer Patients

Background: Candida albicans is one of the most important members of the human normal flora that can cause opportunistic fungal infections. Hydrolytic enzymes are one of the main virulence factors in the pathogenesis of Candida species. Objectives: This study was carried out to determine proteolytic activities, and their related gene expressions in C. albicans isolates obtained from oropharyngeal candidiasis in head and neck cancer patients. Methods: Thirty-two C. albicans clinical isolates were included in this study. Secreted aspartyl protease and phospholipase activities were analyzed by appropriate agar media and precipitation zones. The expression levels of SAP1, 3 and PLB1, 2 genes were evaluated by real-time PCR. Results: All the 32 isolates exhibited proteinase activity while 28 of them showed phospholipase activity. All the strains possessed all SAPs genes; however, PLBs genes were not expressed in four isolates. Conclusions: Our findings demonstrated that the clinical strains of C. albicans had strong proteolytic activity and high expression levels of the pertaining genes.

Secreted aspartyl peptidases by the emerging, opportunistic and multidrug-resistant fungal pathogens comprising the Candida haemulonii complex

The opportunistic pathogens comprising the Candida haemulonii complex (C. haemulonii, C. duobushaemulonii and C. haemulonii var. vulnera) are notable for their intrinsic resistance to different antifungal classes. Little is known about the virulence attributes in this emerging fungal complex. However, it is well-recognized that enzymes play important roles in virulence/pathogenesis of candidiasis. Herein, we aimed to identify aspartyl-type peptidases in 12 clinical isolates belonging to the C. haemulonii complex. All isolates were able to grow in a chemically defined medium containing albumin as the sole nitrogen source, and a considerable consumption of this protein occurred after 72-96 h. C. haemulonii var. vulnera isolates showed the lowest albumin degradation capability and the poorest growth rate. The measurement of secreted aspartyl peptidase (Sap) activity, using the cathepsin D fluorogenic substrate, varied from 91.6 to 413.3 arbitrary units and the classic aspartyl peptidase inhibitor, pepstatin A, significantly blocked the Sap released by C. haemulonii complex. No differences were observed in the Sap activity among the three fungal species. Flow cytometry, using a polyclonal antibody against Sap1-3 of C. albicans, detected homologous proteins at the surface of C. haemulonii complex (anti-Sap1-3-labeled cells ranged from 24.6 to 79.1%). Additionally, the immunoblotting assay, conducted with the same Sap1-3 antibody, recognized a protein of ∼50 kDa in all fungal isolates. A glimpse in the genome of these fungi revealed several potential proteins containing Sap1-3-like conserved domain. Altogether, our results demonstrated the potential of C. haemulonii species complex to produce Saps, an important virulence factor of Candida spp.

Molecular Identification of Candida Species in the Oral Microbiota of Individuals with Down Syndrome: A Case-Control Study

Candida species are common in the human oral microbiota and may cause oral candidiasis (OC) when the microbiota equilibrium is disturbed. Immunosuppressed individuals are susceptible to oral infections as individuals with Down syndrome (IDS) due to particularities of their mouth morphoanatomy, saliva and comorbidities. This study aimed to analyze the molecular epidemiology of Candida spp. from the oral cavity of IDS and their relatives. A case-control study with 80 IDS and 80 non-syndromic (non-DS) was evaluated by oral swab collection for culture on Sabouraud dextrose agar, selection of yeast colonies to Gram staining and culturing on chromogenic media. DNA extraction was performed with the phenol/chloroform method for screening of 6 Candida species medically important in PCR, applying SPSS for statistics. We confirmed four species in 46 IDS without use of antimicrobials (57.54%), with a high prevalence of C. albicans/Ca (93.48%/43) and 3 C. glabrata/Cg (6.52%), being 25 of these IDS (31.25%) colonized by species other than C. albicans: Ca + Cg (16), Ca + C. tropicalis/Ct (7) and Ca + C. krusei/Ck (2). Only 10 non-DS were colonized by one species (11.25%): 6 C. albicans, 2 C. glabrata, 1 C. tropicalis and 1 C. krusei. Previous OC was reported by 39 IDS (48.75%), being 33 positives for Candida spp. (84.61%) and 17 with active OC (21.25%). Five non-DS reported OC previously and had no active lesions. Behavioral changes and buccal health programs directed to IDS may help prevent OC and its recurrence, providing information on oral hygiene for self-care.

Resensitization of Fluconazole-Resistant Urinary Candida spp. Isolates by Amikacin through Downregulation of Efflux Pump Genes

The contribution of fluconazole-resistant Candida spp. isolates to urinary tract infections in Egypt has become a nationwide problem. A recent approach to overcome such disaster is combining conventional antifungals with non-antifungals. This study investigated the interaction of amikacin with fluconazole against resistant Candida strains isolated from the urine culture of patients admitted to Alexandria Main University Hospital. Among the collected Candida spp. isolates, 42.9% were resistant to fluconazole with MICs ranging between 128 and 1,024 μg/ml. The resistance-modifying activity of amikacin (4,000 μg/ml) was studied against fluconazole-resistant isolates where amikacin sensitized 91.7 % of resistant Candida spp. isolates to fluconazole with a modulation factor ranging between 32 and 256. The rhodamine efflux assay was performed to examine the impact of amikacin on efflux pump activity. After 120 minutes of treatment, amikacin affected the efflux pump activity of the isolates tested with a percentage of reduction in the fluorescence intensity of 8.9%. Quantitative real-time PCR was applied to assess the amikacin effect on the expression of the efflux pump genes MDR1, CDR1, and CDR2. The downregulatory effect of amikacin on the expression of the studied genes caused a percentage of reduction in the expression level ranging between 42.1 and 94%. In conclusion, amikacin resensitized resistant Candida spp. isolates to fluconazole and could be used in combination in the management of candiduria with a higher efficiency or at lower administration doses. To the best of our knowledge, this is the first study evaluating the enhancement of fluconazole activity in combination with amikacin against Candida spp.

The contribution of fluconazole-resistant Candida spp. isolates to urinary tract infections in Egypt has become a nationwide problem. A recent approach to overcome such disaster is combining conventional antifungals with non-antifungals. This study investigated the interaction of amikacin with fluconazole against resistant Candida strains isolated from the urine culture of patients admitted to Alexandria Main University Hospital. Among the collected Candida spp. isolates, 42.9% were resistant to fluconazole with MICs ranging between 128 and 1,024 μg/ml. The resistance-modifying activity of amikacin (4,000 μg/ml) was studied against fluconazole-resistant isolates where amikacin sensitized 91.7 % of resistant Candida spp. isolates to fluconazole with a modulation factor ranging between 32 and 256. The rhodamine efflux assay was performed to examine the impact of amikacin on efflux pump activity. After 120 minutes of treatment, amikacin affected the efflux pump activity of the isolates tested with a percentage of reduction in the fluorescence intensity of 8.9%. Quantitative real-time PCR was applied to assess the amikacin effect on the expression of the efflux pump genes MDR1, CDR1, and CDR2. The downregulatory effect of amikacin on the expression of the studied genes caused a percentage of reduction in the expression level ranging between 42.1 and 94%. In conclusion, amikacin resensitized resistant Candida spp. isolates to fluconazole and could be used in combination in the management of candiduria with a higher efficiency or at lower administration doses. To the best of our knowledge, this is the first study evaluating the enhancement of fluconazole activity in combination with amikacin against Candida spp.

Extracellular hydrolytic enzyme activities of the different Candida spp. isolated from the blood of the Intensive Care Unit-admitted patients

BACKGROUND

Candida spp. secretes various extracellular hydrolytic enzymes. These enzymes are the important virulence factor for the pathogenesis of Candida. We assessed four different enzymatic activities of Candida isolates obtained from bloodstream infections.

MATERIALS AND METHODS

We isolated 79 strains of different Candida species from the blood of the Intensive Care Unit-admitted patients. Species were identified by conventional methods including culture characteristic, germ tube, sugar assimilation, and Dalmau's culture technique. Phospholipase, proteinase, hemolysin, and esterase enzymatic activities were determined by the Plate method.

RESULTS

Non albicans candida were the most common isolates from the blood of the ICU admitted patient with a predominance of Candida tropicalis. Hemolytic activity was the most prominent enzyme activity followed by the proteinase activity. Candida albicans (89.86%) was the major proteinase producer, while 95.8% of C. tropicalis produced hemolysin. No esterase activity was shown by the Candida glabrata and Candida krusei.

CONCLUSION

No significant difference was observed between the two most common causative agents of candidemia: C. albicans and C. tropicalis.

Relationship between antifungal susceptibility profile and virulence factors in Candida albicans isolated from nail specimens

INTRODUCTION

The aim of this study was to evaluate some virulence factors in Candida albicans isolates from patients with onychomycosis and determine the correlation between these factors and the antifungal resistance profile.

METHODS

Seventy species of C. albicans were confirmed using polymerase chain reaction amplification of the HWP1 gene. According to the Clinical & Laboratory Standards Institute guidelines, the susceptibility profile of four antifungal agents was investigated, and the production of aspartyl protease, phospholipase, haemolysin, and biofilm was determined. The correlation between these profiles was also investigated.

RESULTS

The isolates indicated different levels of resistance and production of virulence factors. Significant correlations were observed between the minimum inhibitory concentration (MIC) of fluconazole/itraconazole and biofilm production, between phospholipase production and fluconazole/itraconazole MIC, and between fluconazole MIC and hemolytic activity in C. albicans isolates. The results also showed significant correlations between phospholipase activity and biofilm production.

CONCLUSIONS

Our findings will contribute to a better understanding of the pathogenesis of C. albicans and characterize the relationship between virulence factors and antifungal resistance, which may suggest new therapeutic strategies considering the possible involvement of the virulence mechanism in the effectiveness of treatment.

Virulence and biofilms as promising targets in developing antipathogenic drugs against candidiasis

Candida albicans has remained the main etiological agent of candidiasis, challenges clinicians with high mortality and morbidity. The emergence of resistance to antifungal drugs, toxicity and lower efficacy have all contributed to an urgent need to develop alternative drugs aiming at novel targets in C. albicans. Targeting the production of virulence factors, which are essential processes for infectious agents, represents an attractive substitute for the development of newer anti-infectives. The present review highlights the recent developments made in the understanding of the pathogenicity of C. albicans. Production of hydrolytic enzymes, morphogenesis and biofilm formation, along with their molecular and metabolic regulation in Candida are discussed with regard to the development of novel antipathogenic drugs against candidiasis.

Over the last decade, candidiasis has remained a major problematic disease worldwide. In spite of the existence of many antifungal drugs, the treatment of such diseases has still remained unsuccessful due to drug inefficacy. Therefore, there is a need to discover antifungals with different modes of action, such as antipathogenic drugs against Candida albicans. Here, we describe how various types of virulence factors such as proteinase, phospholipase, hemolysin, adhesion, morphogenesis and biofilm formation, could be targeted to develop novel therapeutics. We can inhibit production of these virulence factors by controlling their molecular/metabolic regulation.

Clinical characteristics and risk factors for complications of candidaemia in adults: Focus on endophthalmitis, endocarditis, and osteoarticular infections

OBJECTIVES

This study evaluated the incidence, risk factors, and clinical characteristics of complications of candidaemia in adults, with a focus on endophthalmitis, endocarditis, and osteoarticular infections.

METHODS

All patients ≥18 years old with candidaemia in two Korean tertiary hospitals from 2007 to 2016 were investigated. Complications of candidaemia were defined as the presence of endophthalmitis, endocarditis, or osteoarticular infections documented in patients with candidaemia. The clinical characteristics and risk factors for candidaemia with complications were analysed in the patients who underwent ophthalmological examinations.

RESULTS

Of 765 adult patients with candidaemia, 34 (4.4%) met the definition of complications, including endophthalmitis in 29 (3.8%), endocarditis in 4 (0.5%), and osteoarticular infections in 3 (0.4%). Of the 225 patients who underwent ophthalmological examinations, 29 (12.9%) had endophthalmitis. Candida albicans was an independent risk factor for complicated candidaemia (OR, 5.12; 95% CI, 2.17-12.09; P < 0.001). Although the mortality rate was no higher in complicated candidaemia, the duration of antifungal therapy was longer (23.1 ± 17.6 vs. 16.4 ± 10.8 days, P = 0.042), and 13 patients (39.3%) underwent additional procedures or surgery.

CONCLUSIONS

Complications of candidaemia occurred in 4.4% of adult patients. C. albicans was an independent risk factor for complicated candidaemia in adults. Complications of candidaemia might need prolonged treatment and additional procedures or surgery. Therefore, careful evaluation and active treatment of candidaemia with complications should be encouraged.

Upregulation of secreted aspartyl proteinase genes of fluconazole-sensitive Candida albicans isolates

Candida albicans infection development depends on several factors associated with this etiological agent, including secreted aspartyl protease (Sap) production. Sap expression commonly occurs under selective pressure caused by the presence of antifungals. Fluconazole is the main antifungal drug used for treatment or prophylaxis. This study investigated the influence of inhibitory and sub-inhibitory fluconazole concentrations on Sap activity and their gene transcription for three clinical C. albicans isolates. Two isolates presented significant increases in Sap activity and transcription of SAP 1-8 genes in the presence of 1 MIC₈₀ of fluconazole compared to the absence of the antifungal agent. The results suggest that the increase in Sap activity occurs due to an upregulation of the SAP gene transcription influenced by fluconazole. This suggests the importance of all SAP genes in the progression of bloodstream infections compared to primary tissue infection. However, this phenomenon does not occur everywhere, and it is multifactorial. This may be related to the selective pressure effect on transcription modulators. Although preliminary, these results open a new perspective for the study of virulence factors.

A Predominance of Clade 17 Candida albicans Isolated From Hemocultures in a Tertiary Care Hospital in Thailand

Candida albicans is one of the most common human fungal pathogens. Candidemia has significant mortality globally. No epidemiological study of C. albicans based on multilocus sequence typing (MLST) has been conducted in Thailand. Therefore, MLST was used to study the molecular epidemiology of C. albicans blood strains in a large Thai teaching hospital. In vitro virulence phenotypes and antifungal susceptibility testing by broth microdilution were also conducted. Forty-six C. albicans blood strains from 37 patients were collected from the Department of Microbiology, Siriraj Hospital, in 2016 and 2017. Most patients (71.8%) were more than 60 years old, and the case fatality rate was 54.8%. The male-to-female ratio was 5:3. Thirty-four diploid sequence types (DSTs), including six new DSTs, were identified, with DST2514 (8.7%) and DST2876 (8.7%) as the most common DSTs. Strains were clustered into nine clades. Unlike other studies of C. albicans blood strains in Asia, clade 17 was the most common (13 strains, 28.3%). Sequential allelic changes were evident in sequential strains from one patient. All strains produced phospholipase and hemolysin, while none produced proteinase. The ability to form biofilm was found in 82.6% of the strains. Clade 17 strains showed significantly stronger hemolytic activity than non–clade 17 strains (69.2% versus 27.3%; p = 0.022). However, no significant association existed between clades and patient mortalities. All were susceptible or wild type to anidulafungin (MIC range = 0.015–0.12 and GM = 0.030), micafungin (MIC range = ≤ 0.008–0.015 and GM = 0.008), caspofungin (MIC range = 0.008–0.12 and GM = 0.036), and amphotericin B (MIC range = 0.25–0.5 and GM = 0.381). Only one strain was resistant to voriconazole (MIC range = ≤ 0.008 to ≥ 8 and GM = 0.010) and fluconazole (MIC range = 0.12–16 and GM = 0.398). In conclusion, a high prevalence of clade 17 C. albicans blood strains was found in Thailand, in contrast to other Asian countries. This unique finding might be explained by the strong hemolytic activity that is required for bloodstream infection of C. albicans.

Comparative analysis of proteinase, phospholipase, hydrophobicity and biofilm forming ability in Candida species isolated from clinical specimens

Candida species are the commensal organisms of human and animal mucosa that cause a wide range of debilitating diseases in immunocompromised patients and other susceptible individuals. The present study aimed to investigate the ability of clinical isolates of various Candida species to produce proteinase and phospholipase, hydrophobicity and biofilm forming ability that assumed to have a vital role in Candida pathogenicity. Eighty-four Candida strains belonged to Candida albicans (44.1%), C. glabrata (5.9%), C. guilliermondii (5.9%), C. krusei (10.8%), C. parapsilosis (26.2%), and C. tropicalis (7.1%) were examined for proteinase and phospholipase production, cell surface hydrophobicity and biofilm forming ability. The production of proteinase and phospholipase was detected in 81 (96.4%) and 79 (94.1%) of the strains, respectively. C. albicans showed the highest proteinase and phospholipase activity (mean Pz values of 0.42±0.25 and 0.72±0.28) and biofilm formation ability (0.66±0.22). C. parapsilosis had the highest hydrophobicity (42.97±16.1), which showed a good correlation with biofilm formation ability. A considerable percentage of non-albicans Candida strains produced significant amounts of proteinase and phospholipase with a good ability of biofilm formation in vitro. Taken together, our results further substantiated that enzymatic activity, hydrophobicity and the ability for biofilm formation are important virulence factors which may be account for pathogenicity of various Candida species distributed in albicans and non-albicans groups.

Anticandidal activity of bioinspired ZnO NPs: effect on growth, cell morphology and key virulence attributes of Candida species

The pathogenicity of Candida species in human is dependent on a variety of virulence factor such as adhesion factors, germ tube and hyphal formation, secretion of hydrolytic phospholipases and proteinases and drug resistance biofilm. ZnO NPs have been synthesized by using leaf extract of Crinum latifolium and were characterized by UV-Vis spectrophotometer, FTIR, SEM, EDX and TEM. In this study for the first time, potent inhibitory effects of ZnO NPs on principal virulence factors of Candida albicans and non-albicans such as germ tube formation, secretion of hydrolytic phospholipases and proteinases and biofilm formation has been investigated. ZnO NPs remarkably reduced the germ tube formation of C. albicans at 1 (86.4%), 0.5 (75.0%), 0.25 (61.4%), 0.125 (34.1%) and 0.062 mg/ml (11.4%). ZnO NPs significantly lowered the phospholipase and proteinase secretion by 58.8 and 95.2% at 0.25 mg/ml, respectively. CSLM results showed that ZnO NPs suppressed biofilm formation up to 85% at 0.25 mg/ml. SEM and TEM micrograph showed that ZnO NPs penetrated inside the cell and causes extensive damaged in cell wall and cell membrane. Inhibition of Candida growth and various virulent factors by ZnO NPs provides an insight towards their therapeutic application for the treatment of Candida-associated infections.

Prevalence, virulence factors and antifungal susceptibility of Candida spp. isolated from bloodstream infections in a tertiary care hospital in Brazil

Candida spp. are responsible for 80% of all systemic fungal infections and are associated with high mortality rates. This study characterised 79 bloodstream isolates of C. albicans, C. glabrata, C. orthopsilosis, C. parapsilosis and C. tropicalis from patients in a Brazilian hospital. The susceptibility to amphotericin B, caspofungin, fluconazole and voriconazole was determined; virulence factor production was assessed based on haemolysin, phospholipase and proteinase activities, and the patients' clinical characteristics were analysed. C. albicans was the predominant species (44%), followed by C. glabrata (19%), C. tropicalis (19%), C. parapsilosis (14%) and C. orthopsilosis (4%). The candidemia incidence was 1.52 per 1000 admissions, and the crude mortality rate was 52%. One C. albicans isolate was resistant to fluconazole and voriconazole. Moreover, 20.2%, 2.5% and 3.8% of the isolates exhibited dose-dependent susceptibility to fluconazole, voriconazole and caspofungin, respectively. In conclusion, although the C. glabrata incidence was higher than that usually described in Brazil, its increase was previously observed in studies conducted worldwide. Furthermore, the azole resistance of the C. albicans isolate could be due to previous exposure to these antifungals. These results highlight the importance of epidemiological studies and will facilitate an improved understanding of candidemia in the studied hospital.

Isolation and identification of Candida species in patients with orogastric cancer: susceptibility to antifungal drugs, attributes of virulence in vitro and immune response phenotype

Background

Because of the inherent immunosuppression of cancer patients opportunistic infections by Candida spp, occur frequently. This study aimed to identify Candida species in the oral mucosa of 59 patients with orogastric cancer (OGC) and to analyze the immunological phenotype of these patients.

Methods

The yeasts were identified by MALDI-TOF mass spectrometry (MS). For all isolates, we performed phospholipases and proteinases assays, in vitro adherence to buccal epithelial cells (BEC), minimum inhibitory concentration of antifungal drugs and determined the cytokine profile by Cytometric Bead Array flow citometry assay.

Results

C. albicans was the most prevalent species in OGC patients (51.6 %) and control group (66.7 %). Candida spp. strains isolated from OGC patients exhibited better adherence to BEC (p = 0.05) than did the control group. Phospholipases production by Candida strains from OGC patients was lower (51.6 %) than in the control group (61.9 %). Proteinases were detected in 41.9 % and 4.8 % of the yeasts from OGC patients and control group, respectively. Significant differences were found in the serum of OGC patients compared to the control group for IL-2, IL-10, TNF-α, IFN-γ and IL-17.

Conclusions

The results of this work suggest increased virulence of yeasts isolated from OGC patients and, that this may interfere with the immune phenotype.

Reliability of the agar based method to assess the production of degradative enzymes in clinical isolates of Candida albicans

The aim of this study was to establish a reproducible protocol using the methodology of hyaline zones around the colonies on specific agar plates for phospholipase and proteinase production. This was an in vitro double-blind experiment, in which the dependent variables were the enzymatic activity measurements (Pz) for the production of phospholipase (Pz-ph) and the production of secreted aspartyl proteinases (Pz-sap). Three independent variables give rise to different measurement protocols. All measurements were carried out at two different moments by four examiners (E1, E2, E3, and E4). The minimum sample size was 30 Candida albicans clinical isolates. Specific agar plates for phospholipase and SAPs production were prepared according the literature. The intra-and inter-examiner reproducibility for each protocol was estimated using the Intraclass Correlation Coefficient (ICC) and its confidence interval (95% CI). Based on the results obtained for both phospholipase and SAPs, there appears to be no consensus on the protocol chosen for each particular examiner. Measuring the colonies in triplicate may be the main factor associated with the increase in measurement accuracy and should therefore take precedence over measuring only one colony. When only one examiner is responsible for taking measurements, a standard protocol should be put in place and the statistical calibration of this researcher should be done prior to data collection. However, if two or more researchers are involved in the assessment of agar plates, our results suggest that the protocols using software to undertake plate reading is preferred.

Potential Targets for Antifungal Drug Discovery Based on Growth and Virulence in Candida albicans

Fungal infections, especially infections caused by Candida albicans, remain a challenging problem in clinical settings. Despite the development of more-effective antifungal drugs, their application is limited for various reasons. Thus, alternative treatments with drugs aimed at novel targets in C. albicans are needed. Knowledge of growth and virulence in fungal cells is essential not only to understand their pathogenic mechanisms but also to identify potential antifungal targets. This article reviews the current knowledge of the mechanisms of growth and virulence in C. albicans and examines potential targets for the development of new antifungal drugs.

Effect of the crude extract of Eugenia uniflora in morphogenesis and secretion of hydrolytic enzymes in Candida albicans from the oral cavity of kidney transplant recipients

Background

Candida albicans is a diploid yeast that in some circumstances may cause oral or oropharyngeal infections. Yeasts virulence factors contribute for both the maintenance of colonizing strains in addition to damage and cause tissue invasion, thus the establishment of infection occurs. The limited arsenal of antifungal drugs for the treatment of candidiasis turn the investigation of natural products mandatory for the discovery of new targets for antifungal drug development. Therefore, tropical countries emerge as important providers of natural products with potential antimicrobial activity. This study aimed to investigate morphogenesis and secretion of hydrolytic enzymes (phospholipase and proteinase) in the presence of the CE of Eugenia uniflora.

Methods

The isolates were tested for their ability to form hyphae in both solid and liquid media under three different conditions: YPD + 20% FBS, Spider medium and GlcNac and the ability to secrete phospholipase and proteinase in the presence of 2000 μg/mL of E. uniflora.

Results

The CE of E. uniflora inhibited hypha formation in both liquid and solid media tested. It also impaired hydrolytic enzymes production.

Conclusions

This was the first study to describe the interaction of a natural product with the full expression of three different factors in C. albicans. E. uniflora may be an alternative therapeutic for oral candidiasis in the future.