Virulence factors and antifungal susceptibility of Candida albicans isolates from oral candidosis patients and control individuals

Comparison of proteinase activity, hemolysin production, and adherence ability of Candida albicans isolates obtained from gastroesophageal lesions and urinary tract infections

Background:

Adhesion of Candida to host cell receptors, hemolysin production, and proteinase activity are assumed as principal virulence factors and infection establishment. These virulence factors are essential for colonization, biofilm formation, and attack on the host cells.

Materials and Methods:

A total of 97 Candida albicans isolates obtained from gastroesophageal lesions and urinary tract infections were included in the study. Adhesion assay, proteinase activity, and hemolysin production were measured. Statistical analysis was performed using the independent t-test and Chi-square test to compare quantitative and qualitative data between the two groups.

Results:

The adherence ability to the buccal epithelial cells was the same in the two groups. Proteinase activity was seen in all clinical isolates. Hemolytic activities were not statistically significant in the two groups.

Conclusion:

Our results recommend that the pathogenicity of C. albicans in the mucous membranes cannot be connected to the infected site.

Antifungal photodynamic activities of phthalocyanine derivatives on Candida albicans

Antimicrobial resistance is one of the most important causes of morbidity and mortality in the treatment of infectious diseases worldwide. Candida albicans is one of the most virulent and common species of fungi to cause invasive fungal infections on humans. Alternative treatment strategies, including photodynamic therapy, are needed for controlling these infectious diseases. The aim of this study was to investigate the antifungal photodynamic activities of phthalocyanine derivatives on C. albicans. The minimum inhibitory concentration (MIC) values of compounds were determined by the broth microdilution method. Uptake of the compounds in C. albicans and dark toxicity of the compounds were also investigated. Photodynamic inhibition of growth experiments was performed by measuring the colony-forming unit/mL (CFU/mL) of the strain. Maximum uptake into the cells was observed in the presence of 64 μg/mL concentration for each compound except for ZnPc. Compounds did not show dark toxicity/inhibitory effects at sub-MIC concentrations on C. albicans when compared to the negative control groups. Zn(II)Pc, ZnPc, and ZnPc-TiO₂ showed fungicidal effect after irradiation with the light dose of 90 J/cm² in the presence of the compounds. In addition to the fungicidal effects, SubPc, SubPc-TiO₂, Es-SiPc, and Es-SubPc compounds were also found to have inhibitory effects on the growth of yeast cells after irradiation.

Photodithazine-mediated antimicrobial photodynamic therapy against fluconazole-resistant Candida albicans in vivo

This study evaluated the efficacy of antimicrobial Photodynamic Therapy (aPDT) against fluconazole-resistant Candida albicans in a murine model of oral candidosis. Mice were inoculated with two clinical isolates (R10, R15) and one reference strain (ATCC) of resistant C. albicans to produce oral candidosis. After inoculation, aPDT mediated by Photodithazine® (PDZ) and LED light was performed. The use of PDZ or light only was also investigated. Additional animals were treated with Nystatin (NYS). Untreated or healthy mice were also evaluated. Microbiological evaluation was performed by recovering C. albicans from the tongue via colony-forming units. Animals were killed 24 hours after treatments, and the tongues were removed for histological analysis. Data were analyzed by one-way ANOVA and Tukey test (P < .05). The results demonstrated that all strains showed the same behavior after aPDT and NYS treatment. A significant reduction in C. albicans viability was achieved after both treatments for R15 and ATCC. No significant reduction was verified for C. albicans R10 submitted to aPDT or NYS. The histological analysis revealed that aPDT did not cause side effects on tissues. aPDT was effective for inactivation of two fluconazole-resistant C. albicans of the three strains evaluated.

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.

First report of Candida bracarensis in Mexico: hydrolytic enzymes and antifungal susceptibility pattern

Candida bracarensis is an emerging cryptic species within the Candida glabrata clade. To date, little is known about its epidemiology, virulence, and antifungal susceptibility. This study documents the occurrence of C. bracarensis for the first time in Mexico and focuses on its in vitro production of hydrolytic enzymes, as well as antifungal susceptibility to echinocandins. This strain was isolated from a vaginal swab of a female with vulvovaginal candidosis; exhibited a very strong activity of aspartyl proteinase, phospholipase, and hemolysin; and was susceptible to caspofungin, anidulafungin, and micafungin (MIC = 0.031 μg/mL). Data obtained could contribute to the knowledge of the epidemiology and virulence attributes of this yeast as a fungal opportunistic human pathogen.

Phenotypical characterization and molecular identification of clinical isolates of Candida tropicalis

BACKGROUND

Candida tropicalis is an increasingly important human pathogen which usually affects neutropenic oncology patients with common hematogenous seeding to peripheral organs and high mortality rates. Candida pathogenicity is facilitated by several virulence attributes, including secretion of hydrolytic enzymes; however, little is known regarding the C. tropicalis ability to secrete them and their role in the disease.

AIMS

To confirm by molecular means the identification of 187 clinical isolates (127 from blood, 52 from urine, and 8 from diverse clinical origins) phenotypically identified as C. tropicalis, and to investigate their in vitro aspartyl proteinase, phospholipase, esterase, hemolysin, DNase and coagulase activities.

METHODS

The molecular confirmation was performed by ITS sequencing, and the enzymatic determinations were conducted using plate assays with specific substrates, with the exception of coagulase, which was determined by the classical tube test.

RESULTS

The majority of the strains exhibited a very strong or strong activity of aspartyl proteinase, phospholipase and esterase. A 4.7% of the bloodstream isolates were hemolysin producers, and all were negative for the coagulase and DNase assays.

CONCLUSIONS

Very strong activities of aspartyl proteinase, phospholipase and esterase profiles were detected, and a statistical association between phospholipase production and blood and urine isolates was found.

Investigations of the prevalence and virulence of Candida albicans in periodontal and endodontic lesions in diabetic and normoglycemic patients

Pulpal and periodontal tissues have similar microbiota that allows cross-contamination between the pulp and periodontal tissues.

The Synergistic Effect of Azoles and Fluoxetine against Resistant Candida albicans Strains Is Attributed to Attenuating Fungal Virulence

This study evaluated the synergistic effects of the selective serotonin reuptake inhibitor, fluoxetine, in combination with azoles against Candida albicans both in vitro and in vivo and explored the underlying mechanism. MICs, sessile MICs, and time-kill curves were determined for resistant C. albicans Galleria mellonella was used as a nonvertebrate model for determining the efficacy of the drug combinations against C. albicans in vivo For the mechanism study, gene expression levels of the SAP gene family were determined by reverse transcription (RT)-PCR, and extracellular phospholipase activities were detected in vitro by the egg yolk agar method. The combinations resulted in synergistic activity against C. albicans strains, but the same effect was not found for the non-albicans Candida strains. For the biofilms formed over 4, 8, and 12 h, synergism was seen for the combination of fluconazole and fluoxetine. In addition, the time-kill curves confirmed the synergism dynamically. The results of the G. mellonella studies agreed with the in vitro analysis. In the mechanism study, we observed that fluconazole plus fluoxetine caused downregulation of the gene expression levels of SAP1 to SAP4 and weakened the extracellular phospholipase activities of resistant C. albicans The combinations of azoles and fluoxetine showed synergistic effects against resistant C. albicans may diminish the virulence properties of C. albicans.

Estudo comparativo entre a produção de fosfolipases extracelulares e proteinases do gênero Candida isoladas a partir de infecções de cavidade oral

Resumo Introdução A habilidade da Candida spp. em produzir enzimas proteolíticas, tais como fosfolipase e proteinases, tem um papel importante na patogenicidade destas leveduras. Objetivo Determinar as espécies causadoras das infecções orais por Candida spp., além de investigar a atividade in vitro das fosfolipases e proteinases em isolados clínicos do gênero Candida, provenientes de pacientes com candidíase oral. Material e método Isolados de Candida spp., pertencentes à Coleção de Cultivos Fúngicos do Laboratório de Microbiologia e Patologia Oral do Departamento de Odontologia da Faculdade da Serra Gaúcha, foram analisados. Produção de fosfolipases foi analisada utilizando-se Ágar gema de ovo. Liberação de proteinases foi medida utilizando-se extrato de levedura adicionado à albumina bovina. Resultado Um total de 35 isolados clínicos do gênero Candida foi testado. C. albicans foi a espécie predominante (77%). Os demais isolados identificados foram: C. parapsilosis (20%) e C. tropicalis (2%). Ao comparar a atividade de fosfolipase do grupo C. albicans com o grupo Candida não-albicans, foi encontrada diferença significativa (P=0,04). Não foi encontrada diferença significativa entre a C. albicans e a C. não-albicans, para a produção de proteinase. A liberação de proteinase foi significativamente maior quando comparada à produção de fosfolipase para o gênero Candida (P=0,04). Diferença estatisticamente significativa foi encontrada quando a atividade de fosfolipase e proteinase da C. albicans foi comparada à atividade das espécies de C. não-albicans (P=0,02). Conclusão Diferentes quantificações de fosfolipase extracelular e atividade de proteinase têm sido atribuídas aos isolados clínicos de C. albicans quando comparados a outras espécies de Candida.

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.

Evaluation of in vivo pathogenicity of Candida parapsilosis, Candida orthopsilosis, and Candida metapsilosis with different enzymatic profiles in a murine model of disseminated candidiasis

Six isolates of the Candida parapsilosis complex with different enzymatic profiles were used to induce systemic infection in immunocompetent BALB/c mice. Fungal tissue burden was determined on days 2, 5, 10, and 15 post challenge. The highest fungal load irrespective of post-infection day was detected in the kidney, followed by the spleen, lung, and liver, with a tendency for the fungal burden to decrease by day 15 in all groups. Significant differences among the strains were not detected, suggesting that the three species of the "psilosis" group possess a similar pathogenic potential in disseminated candidiasis regardless of their enzymatic profiles.

Enzymatic activity profile of a Brazilian culture collection of Candida albicans isolated from diabetics and non-diabetics with oral candidiasis

The secretion of hydrolytic enzymes is a fundamental virulence factor of Candida albicans to develop disease. The objective of this study was to characterise the virulence of 148 clinical isolates of C. albicans from oral candidiasis by assessing the expression of phospholipase (PL) and secreted aspartyl proteinase (SAP). Isolates were obtained from healthy subjects (HS) and diabetics (DOC) and non-diabetics with oral candidiasis (NDOC). An aliquot (5 μl) of each cell suspension was inoculated on PL and SAP agar plates and incubated. Enzymes secretion was detected by the formation of an opaque halo around the colonies and enzymatic activity (PZ) was determined by the ratio between colony diameter and colony diameter plus the halo zone. Statistical comparisons were made by a one-way anova followed by Tukey's post hoc test (α = 0.05). The clinical sources of C. albicans had significant effect (P < 0.001) on the PZ values of both enzymes. For PL, clinical isolates from NDOC and DOC had highest enzymatic activity than those from HS (P < 0.05), with no significant differences between them (P = 0.506). For SAP, C. albicans from NDOC showed the lower enzymatic activity (P < 0.001). There were no significant differences between isolates from HS and DOC (P = 0.7051). C. albicans isolates from NDOC and DOC patients showed an increased production of PL.

Susceptibility profile of a Brazilian yeast stock collection of Candida species isolated from subjects with Candida-associated denture stomatitis with or without diabetes

OBJECTIVE

This study investigated the susceptibility of 198 clinical isolates of Candida species against caspofungin, amphotericin B, itraconazole, and fluconazole.

STUDY DESIGN

Suspensions of the microorganisms were spread on Roswell Park Memorial Institute (RPMI) agar plates. Etest strips were placed on the plates, and the minimal inhibitory concentration (MIC) was read after incubation (48 h at 37 °C). Data were analyzed by a factorial analysis of variance and a 2 × 2 post hoc test (α = .05).

RESULTS

C glabrata showed the highest MIC values (P < .001) against caspofungin, itraconazole, and fluconazole. For amphotericin B, the MIC values of C tropicalis and C glabrata (P = .0521) were higher than those of C albicans (P < .001). Itraconazole was the least effective antifungal; 93.3% of the C glabrata isolates, 3.3% of the C albicans, and 1.3% of the C tropicalis were resistant. All microorganisms were susceptible to caspofungin and amphotericin B.

CONCLUSIONS

Caspofungin and amphotericin B should be recommended as an effective alternative for the management of oral Candida infections when treatment with topical or other systemic drugs has definitely failed.

Aspartyl proteinase, phospholipase, esterase and hemolysin activities of clinical isolates of the Candida parapsilosis species complex

Candida parapsilosis is considered as an important emerging fungal pathogen and was recently found to be a complex that include three species, i.e., Candida parapsilosis sensu stricto, Candida orthopsilosis and Candida metapsilosis. The aim of this study was to determine the in vitro aspartyl proteinase, phospholipase, esterase and hemolysin activities of 65 clinical isolates of the C. parapsilosis complex, which had been previously identified by RFLP-BanI analysis. Of the enzymes evaluated, aspartyl proteinase was the least produced by the C. parapsilosis species complex. Phospholipase and esterase were strongly expressed by C. orthopsilosis (67% of isolates), while 10% and 13% of C. parapsilosis sensu stricto isolates were strong producers, respectively, of these two enzymes. In contrast, high production of both enzymes was not detected in C. metapsilosis. Hemolysin activity was significantly more abundant in C. orthopsilosis (87%) than C. parapsilosis sensu stricto (67%). Overall, C. orthopsilosis isolates were statistically associated with the production of hemolysins (P= 0.048) and phospholipases (P< 0.0001) compared to isolates of C. parapsilosis sensu stricto or C. metapsilosis. Furthermore, a statistical association was found between isolates recovered from blood and phospholipase production (P= 0.017). The distribution of isolates obtained from blood was 30% of C. parapsilosis sensu stricto, 67% of C. orthopsilosis and 20% of C. metapsilosis.

Opportunistic microorganisms in patients undergoing antibiotic therapy for pulmonary tuberculosis

Antimicrobial therapy may cause changes in the resident oral microbiota, with the increase of opportunistic pathogens. The aim of this study was to compare the prevalence of Candida, Staphylococcus, Pseudomonas and Enterobacteriaceae in the oral cavity of fifty patients undergoing antibiotic therapy for pulmonary tuberculosis and systemically healthy controls. Oral rinsing and subgingival samples were obtained, plated in Sabouraud dextrose agar with chloramphenicol, mannitol agar and MacConkey agar, and incubated for 48 h at 37°C. Candida spp. and coagulase-positive staphylococci were identified by phenotypic tests, C. dubliniensis, by multiplex PCR, and coagulase-negative staphylococci, Enterobacteriaceae and Pseudomonas spp., by the API systems. The number of Candida spp. was significantly higher in tuberculosis patients, and C. albicans was the most prevalent specie. No significant differences in the prevalence of other microorganisms were observed. In conclusion, the antimicrobial therapy for pulmonary tuberculosis induced significant increase only in the amounts of Candida spp.

Candida albicans strain-dependent modulation of pro-inflammatory cytokine release by in vitro oral and vaginal mucosal models

Candida albicans is a commensal organism at several sites and is a versatile, opportunistic pathogen. The underlying factors of pathogen and host associated with commensalism and pathogenicity in C. albicans are complex and their importance is largely unknown. We aimed to study the responses of oral epithelial (OEM) and vaginal epithelial models (VEM) to infection by oral and vaginal C. albicans strains to obtain evidence of inter-strain differences in pathogenicity and of site-specificity. Following inoculation of models, proinflammatory cytokines IL-1α, IL-1β, IL-6, IL-8 and prostaglandin E2 (PGE2) release were monitored and histological staining undertaken. Striking differences in strain behaviour and epithelial responses were observed. IL-1α, IL-1β and IL-8 release were significantly increased from the OEM in response to denture stomatitis strain NCYC 1467. Increased IL-8 release also followed infection of the OEM with both vaginal strains. Overall the VEM was relatively unresponsive to infection with either oral or vaginal strains under these conditions. Adherence and hyphal development were observed for all strains on both models although extensive, uniform tissue penetration was seen only with stomatitis strain NCYC 1467 on the OEM. Candidal strains were assayed for phospholipase (PL) and secreted aspartyl proteinase (SAP) activities where phospholipase (PL) activity was highest for strain NCYC 1467 although highest SAP activity was observed for vaginal strain NCPF 8112 in this assay. This is the first study to concurrently investigate cytokine production from oral and epithelial models using candidal strains originating from these respective mucosal sites from healthy and disease states. These data demonstrate significant differences in inflammatory responses of host epithelia to individual C. albicans strains.

Genetic and phenotypic evaluation of Candida albicans strains isolated from subgingival biofilm of diabetic patients with chronic periodontitis

Candida spp. are commensal microorganisms that are part of the microflora of different sites within the oral cavity. In healthy subjects, who have an unaltered immunological status, these yeasts do not cause disease. However, in immunosuppressed individuals whose condition may have been caused by diabetes mellitus, Candida spp. can express different virulence factors and may consequently become pathogenic. Studies have detected the presence of Candida spp. in periodontal sites of patients with chronic periodontitis, especially those that are immunologically compromised. However, the role of these microorganisms in the pathogenesis of periodontal disease is still unknown. The objectives of this study were: (1) to isolate and identify Candida albicans strains from subgingival sites of diabetic patients with chronic periodontitis; (2) to evaluate the following virulence factors; colony morphology, proteinase, phospholipase and hemolysin activities and cell surface hydrophobicity (CSH) under different atmospheric conditions; and (3) to determine the genetic patterns of these C. albicans isolates. Microbial samples were collected from subgingival sites and seeded on CHROMagar for subsequent identification of C. albicans by polymerase chain reaction (PCR). For the phenotypic tests, all strains of C. albicans were grown under reduced oxygen (RO) and anaerobiosis (ANA) conditions. Genotypes were defined by the identification through PCR of the transposable introns in the 25S rDNA. The results obtained relative to virulence factors were analyzed according to the atmospheric condition or genetic group, using Chi-square and Wilcoxon non-parametric tests. In this study, 128 strains were identified as C. albicans and of these, 51.6% were genotype B, 48.4% were genotype A and Genotype C was not found. Most of the strains were alpha-hemolytic in both atmospheric conditions, without a statistical difference. However, when comparing the genotypes, 46.1% of the genotype A strains were beta-hemolytic. In relation to colony morphology, 100% of the strains under ANA showed rough colonies, which were especially prevalent in genotype A isolates. In contrast, most of the colonies were smooth under RO. C. albicans strains did not produce proteinase and phospholipase activity in the total absence of oxygen. In RO, most strains had high proteinase activity and were positive by phospholipase tests (P < 0.05). Hydrophobicity was higher in anaerobiosis and was noted mainly for genotype A isolates. In conclusion, environmental oxygen concentration influenced the virulence factors of C. albicans strains isolated from subgingival sites of diabetic and periodontal patients. In addition, genotype A seems to be more virulent based on the phenotypic tests evaluated in this study.

Virulence attributes and genetic variability of oral Candida albicans and Candida tropicalis isolates

The wide spectrum of candidiasis and its clinical importance encourage the research with the purpose of clarifying the mechanisms of pathogenicity and identification of virulence factors of Candida sp. Therefore, the aim of this study was to verify the adhesion capacity, protease activity and genotypic diversity of oral C. albicans and C. tropicalis isolates. The adhesion ability to the extracellular matrix glycoproteins laminin and fibronectin was evaluated using the ELISA technique. The research of proteases was carried out in agar plate containing bovine albumin and through a quantitative method in buffer solution containing haemoglobin. Intra and interspecies polymorphisms was verified through random amplified polymorphic DNA (RAPD) technique. All C. albicans and C. tropicalis isolates binded to immobilised laminin and fibronectin. Ca33 and Ct13 isolates had relative adhesion index significantly higher than the other isolates for both glycoproteins (P < 0.001). Protease activity was observed in all isolates of C. albicans using either the semi-quantitative or quantitative assay. The protease activity of C. tropicalis was better detected through the quantitative assay. The genotypic diversity by RAPD revealed a heterogeneous population in both species. Nevertheless, C. tropicalis presented higher genetic variability than C. albicans strains.

Proteinase and phospholipase activities and development at different temperatures of yeasts isolated from bovine milk

The presence of yeasts in milk may cause physical and chemical changes limiting the durability and compromising the quality of the product. Moreover, milk and dairy products contaminated by yeasts may be a potential means of transmission of these microorganisms to man and animals causing several kinds of infections. This study aimed to determine whether different species of yeasts isolated from bovine raw milk had the ability to develop at 37°C and/or under refrigeration temperature. Proteinase and phospholipase activities resulting from these yeasts were also monitored at different temperatures. Five genera of yeasts (Aureobasidium sp., Candida spp., Geotrichum spp., Trichosporon spp. and Rhodotorula spp.) isolated from bovine raw milk samples were evaluated. All strains showed one or a combination of characteristics: growth at 37°C (99·09% of the strains), psychrotrophic behaviour (50·9%), proteinase production (16·81% of the strains at 37°C and 4·09% under refrigeration) and phospholipase production (36·36% of the isolates at 37°C and 10·9% under refrigeration), and all these factors may compromise the quality of the product. Proteinase production was similar for strains incubated at 37°C (16·81% of the isolates) and room temperature (17·27%) but there was less amount of phospholipase-producing strains at room temperature (15·45% of the isolates were positive) when compared with incubation at 37°C (36·36%). Enzymes production at 37°C by yeasts isolated from milk confirmed their pathogenic potential. The refrigeration temperature was found to be most efficient to inhibit enzymes production and consequently ensure better quality of milk. The viability of yeasts and the activity of their enzymes at different temperatures are worrying because this can compromise the quality of dairy products at all stages of production and/or storage, and represent a risk to the consumer.

Investigating biofilm production, coagulase and hemolytic activity in Candida species isolated from denture stomatitis patients

OBJECTIVE

Oral candidiasis, in the form of Candida-associated denture stomatitis, represents a common disease in a large percentage of denture wearers, and Candida albicans remains the most commonly isolated species. In this study, we aimed to evaluate biofilm production, coagulase and hemolytic activity of Candida species isolated from denture stomatitis patients.

MATERIALS AND METHODS

This study included 70 patients (31 female, 39 male). Forty-eight of the patients were found to have a positive culture. A total of 48 Candida isolates representing five species, C. albicans (n=17), C. glabrata (n=10), C. krusei (n=9), C. kefyr (n=7) and C. parapsilosis (n=5), were tested. Their coagulase activities were evaluated by a classical tube coagulase test with rabbit plasma. A blood plate assay on 3% enriched sheep blood Sabouraud-dextrose agar (SDA) was used to determine their in vitro hemolytic activities. Biofilm production was determined by a visual tube method.

RESULTS

Twenty-one Candida isolates exhibited coagulase activity, and the coagulase activities of the C. albicans (64.7%) isolates were higher than other species. C. albicans, C. glabrata, C. kefyr and C. krusei species demonstrated beta hemolysis. C. parapsilosis strains failed to demonstrate any hemolytic activities. Fifteen (88.0%) of the C. albicans strains were biofilm positive. Six (35.2%) of these strains were strongly positive, 8 (47.0%) C. albicans strains were moderately positive and 1 (5.8%) C. albicans strain was weakly positive. Sixteen (51.6%) of the non-albicans Candida strains were biofilm positive while 15 (48.3%) did not produce biofilms.

CONCLUSION

The results of this present study indicate coagulase, hemolytic activity and biofilm production by Candida spp. isolated from patients with denture stomatitis. Investigations of these virulence factors might be helpful in gaining information about the possible virulence of oral Candida species related to denture stomatitis.

Adherence to buccal epithelial cells, enzymatic and hemolytic activities of Candida isolates from HIV-infected individuals

Candida spp., along with other microorganisms are usually found in the normal flora of the human oral mucosa. However in HIV-infected individuals these yeasts can become opportunistic pathogens and lead to mucosal infections. The transformation from a harmless commensal to a virulent pathogen under conditions of dysfunctional host defense system is attributable to an extensive repertoire of selectively expressed virulence determinants. The present study was undertaken to analyze the production of four important virulence factors viz. adherence to buccal epithelial cells (BEC), proteinase activity, phospholipase activity and hemolysis, and to evaluate the correlation between these virulence factors in 65 Candida isolates from HIV-infected individuals with oral candidiasis. A total of 95.3%, 67.7%, 41.5% and 100% of the Candida isolates showed adherence to BEC, and proteinase, phospholipase and hemolytic activities, respectively. Production of proteinase and phospholipase enzymes was seen in 89.7% and 59.0% of C. albicans isolates and 34.6% and 15.4% of non-Candida albicans Candida (NAC) isolates, respectively. C. albicans showed significantly greater level of virulence factor expression with regards to adherence to BEC (P < 0.001), phospholipase production (P < 0.044) and hemolysis (P = 0.037) as compared to NAC. A correlative relationship between proteinase activity and adherence to BEC, as well as phospholipase production was noted.

[Cell surface hydrophobicity as an indicator of other virulence factors in Candida albicans]

OBJECTIVE

To evaluate virulence factors involved in the adhesion process, such as cell surface hydrophobicity (CSH), adherence to plastic capacity, adherence capacity to buccal epithelial cells (BEC), and biofilm formation, in 17 strains of C. albicans isolated from bronchial aspirates of critically ill patients.

METHOD

The CSH of the strains of C. albicans was determined using the MATH method, a microbial adhesion to hydrocarbons test. The study of adherence to plastic was performed in microtitre plates in accordance with Christensen's technique. Biofilm formation was studied in polystyrene microtitre plates, according to the method of Ramage. Adherence to BEC was evaluated by quantifying the percentage of adhered yeasts to cells.

RESULTS

All the strains studied showed factors directly involved in adhesion, with variability in the degree of expression among them. Medium-high levels of CSH were found in 52.9% of the strains. The percentage of strains with high values in adherence to plastic was 35.3%. The most hydrophobic strains were the most adherent to plastic, with a correlation coefficient of 0.76. Of the 12 biofilm-producing strains, 6 were high producers. These strains had also high levels of CSH and adherence to plastic, with significant results. All the strains studied adhered to BEC, with results ranging widely from 45 to 157 yeasts/100 BEC, with no significant correlation with the rest of the parameters studied, although CSH was seen to be an indispensable prior requisite for adherence to cells.

CONCLUSION

CSH is a variable characteristic in C. albicans and is directly related to adherence to plastic and biofilm formation. Ease in evaluating CSH permits its quantification, and could be used as an indicator of the presence of other determinants of pathogenicity.

Differences in exoenzyme production and adherence ability of Candida spp. isolates from catheter, blood and oral cavity

Phospholipase and proteinase production and the ability of adhesion to buccal epithelial cells (BEC) of 112 Candida isolates originated from oral cavity of HIV infected patients and from blood and catheter of intensive care unit patients were investigated. The proteinase production was detected by inoculation into bovine serum albumin (BSA) agar and the phospholipase activity was performed using egg yolk emulsion. A yeast suspension of each test strain was incubated with buccal epithelial cells and the number of adherence yeast to epithelial cells was counted. A percentage of 88.1% and 55.9% of Candida albicans and 69.8% and 37.7% of non-albicans Candida isolates produced proteinase and phospholipase, respectively. Non-albicans Candida isolated from catheter were more proteolytic than C. albicans isolates. Blood isolates were more proteolytic than catheter and oral cavity isolates while oral cavity isolates produced more phospholipase than those from blood and catheter. C. albicans isolates from oral cavity and from catheter were more adherent to BEC than non-albicans Candida isolates, but the adhesion was not different among the three sources analyzed. The results indicated differences in the production of phospholipase and proteinase and in the ability of adhesion to BEC among Candida spp. isolates from different sources. This study suggests that the pathogenicity of Candida can be correlated with the infected site.

Epidemiology and phospholipase activity of oral Candida SPP. Among patients with central nervous system diseases before and after dental cleaning procedure

Patients suffering of diseases that affect central nervous system may be considered more susceptible to the infectious diseases of mouth. Sixty-nine patients suffering of cerebral palsy, Down's syndrome and metal retardation were submitted to saliva examination for the presence of Candida spp. before and after a procedure of dental cleaning. The isolates were submitted to assay for verifying phospholipase production. 55.10% of the patients provided isolation of Candida spp. The frequency of isolation obtained before dental procedure was: C. albicans (83.33%), C. krusei (8.33%) and C. kefyr, C. parapsilosis and C. glabrata (2.78% each). The frequency after the procedure was: C. albicans (68.57%), C. parapsilosis (11.43%), C. krusei and C. kefyr (8.57% each) and Candida glabrata (2.86%). We verified significantly difference (p < 0.01) between populations obtained at the two examinations. Phospholipase production was verified only among C. albicans strains and the proportion of producers was higher when testing isolates obtained after dental cleaning procedure. Studies focused on Candida spp. isolation are useful for better comprehension of the role of these yeasts on the oral flora from patients with cerebral palsy, Down's syndrome and metal retardation.

Phospholipase and proteinase activities of Candida isolates from denture wearers

The aim of the present study was to characterise phospholipase and proteinase activities of oral Candida isolates from 100 denture wearers and to study the relationship of these activities with denture stomatitis. Of 100 patients studied, 44 suffered from denture stomatitis. Specimens were collected by swabbing the denture and underlying mucosa. Isolates were previously identified by conventional mycological and genotypic methods. The phospholipase and proteinase activities were evaluated by agar plate methods. A total of 152 isolates were recovered from denture and underlying mucosa, including 101 Candida albicans, 18 Candida tropicalis, 14 Candida glabrata, 11 Candida guilliermondii, four Candida parapsilosis, two Saccharomyces cerevisiae and one isolate each of Candida dubliniensis and Candida krusei. Most C. albicans (97%) showed phospholipase activity; furthermore, the unique C. dubliniensis isolate showed a moderate phospholipase activity. The isolation of C. albicans (chi-square test, P = 0.0016) and phospholipase production by Candida spp. (chi-square test, P = 0.0213) was found to be significantly associated with denture stomatitis. Proteinase production was observed in <30% of isolates, and it was not related to the presence of denture stomatitis (P = 0.7675). Candida albicans isolates may produce both virulence factors, although the proteinase production was only observed in <30% of the isolates. Phospholipase production was exclusive of C. albicans and C. dubliniensis.

Identification of Candida species isolated from bovine mastitic milk and their in vitro hemolytic activity in Western Turkey

In this study, identification of 207 Candida isolates, previously isolated from mastitic bovine quarter milk samples at the level of genus, was made using API 20 C AUX system. The most frequently isolated species were Candida krusei (34.8%), followed by Candida rugosa (16.4%), Candida kefyr (12.6%), Candida albicans (10.1%), and Candida tropicalis (9.2%). Less common isolates were Candida zeylanoides (5.8%), Candida parapsilosis (4.3%), Candida guilliermondii (3.4%), Candida famata (1.9%), and Candida glabrata (1.5%). Additionally, in vitro hemolytic activity of all Candida strains were also examined in the present study. C. krusei (72 isolates), C. kefyr (26), C. albicans (21), C. tropicalis (19), C. zeylanoides (12), and C. glabrata (3) demonstrated both alpha and beta hemolysis at 48-h postinoculation. Only alpha hemolysis was detected in C. rugosa (34), C. guilliermondii (7), and C. famata (4), while C. parapsilosis (9) did not show any hemolytic activity after incubation for 72 h. Statistically significant difference (P < 0.001) was determined between the beta-hemolytic activities of Candida strains. The hemolytic activities of C. zeylanoides, C. albicans and C. kefyr were higher than other strains. This is the first study to describe variable hemolysis types exhibited by different Candida strains isolated from bovine mastitic milk in Turkey.

The effect of Dodonaea viscosa var. angustifolia on Candida albicans proteinase and phospholipase production and adherence to oral epithelial cells

AIM OF THE STUDY

This study investigated effect of a crude extract of Dodonaea viscosa on the proteinase and phospholipase production and adherence to epithelial cells by Candida albicans isolated from HIV positive and HIV negative patients.

MATERIALS AND METHODS

Twenty Candida albicans strains isolated from HIV positive and 20 from HIV negative patients were investigated. The isolates were exposed to subinhibitory concentration of crude plant extract and adherence, proteinase and phospholipase production were assessed. The results were analysed using Student's t-test and a two-way ANOVA.

RESULTS

Dodonaea viscosa var. angustifolia inhibited the adherence of Candida albicans to oral epithelial cells (p=<0.01) but no significant effect of the plant extract on proteinase and phospholipase production was observed. Results from Candida albicans strains isolated from HIV positive and HIV negative patients were similar.

CONCLUSIONS

Dodonaea viscosa var. angustifolia inhibited the adherence of Candida albicans to oral epithelial cells, which is the initial step of colonization in the infection process. This plant has a therapeutic potential at subinhibitory concentration.

Phospholipase, proteinase and haemolytic activities of Candida albicans isolated from oral cavities of patients with type 2 diabetes mellitus

The aim of this study was to biotype and characterize phospholipase, proteinase and haemolytic activities of oral Candida albicans isolates from 210 Chinese patients with type 2 diabetes mellitus (DM) and 210 age- and sex-matched healthy controls. Seventy-six and 50 C. albicans isolates were obtained from type 2 DM patients and controls, respectively, using the oral rinse technique. The isolates were characterized with a biotyping system based on enzyme profiles, carbohydrate assimilation patterns and boric acid resistance of the yeasts, and the isolates were further tested for in vitro phospholipase, proteinase and haemolytic activities. The major biotypes of C. albicans isolates from the type 2 DM and control groups were A1R (42.1 %) and J1R (36.0 %), respectively. Significantly higher proteinase and haemolytic activities were found in the isolates from the type 2 DM group (P<0.05). Proteinase activity was higher in isolates from patients with > or =10 years of DM history than those with <10 years (P<0.05). Haemolytic activity was significantly higher in isolates from female DM patients than in those from male counterparts (P<0.05). These data provide evidence of increased extracellular enzyme activity in Candida isolates taken from DM patients.

Distribution and phospholipase activity of Candida species in different denture stomatitis types

The aim of this study was to evaluate the correlation between frequency and phospholipase activity of Candida species and denture stomatitis according to Newton's classification. Seventy-five complete denture wearers were evaluated for the presence of yeasts on the palatal mucosa by culture method. In addition, the number of yeast isolates producing phospholipase and amount of this enzyme were determined using egg yolk agar plate method. According to Newton's classification, 25 denture wearers were with healthy palatal mucosa while 50 were with any types of denture stomatitis. The frequency of yeasts was linked to whether subjects had Type II or Type III, but not Type I denture stomatitis. Candida albicans was the most frequently isolated species in denture wearers with and without clinical signs of denture stomatitis and it was the only species produced phospholipase. Although the amount of phospholipase produced by the C. albicans isolates from denture wearers in control and Type II and III DS groups was not significantly different, there was statistically significant difference in the number of C. albicans isolates producing phospholipase between patients with and without clinical signs of DS.

Phospholipase activity of Candida albicans isolates from patients with denture stomatitis: the influence of chlorhexidine gluconate on phospholipase production

BACKGROUND AND OBJECTIVES

The extracellular phospholipases of Candida albicans are considered to play a significant role in the pathogenesis of human infections. Therefore 23 clinical oral isolates of C. albicans from patients with denture stomatitis and 22 commensal oral isolates obtained from the palatal mucosa of healthy subjects were assayed for phospholipase activity. It is generally accepted that chlorhexidine gluconate is an appropriate adjunct or an alternative to antimycotic therapy in the management of oral candidiasis. However, the intraoral concentrations of this antiseptic fluctuate considerably due to the dynamics of the oral cavity. So the second main objective of this study was to investigate the effect of brief exposure (30 min) to two sub-therapeutic concentrations (0.002% and 0.0012%) of chlorhexidine gluconate on the value of phospholipase production (Pz) of C. albicans.

METHOD

An in vitro phospholipase production was done by plate assay method using an egg yolk-agar medium.

RESULTS

No significant differences were found in the number of C. albicans isolates producing phospholipase between two groups. However, the mean value of Pz produced by the isolates from patients with denture stomatitis was significantly (p<0.05) higher than the commensals. Exposure of the isolates to 0.002% and 0.0012% chlorhexidine led to a significant (p<0.001 and p<0.01, respectively) reduction in the amount of phospholipase.

CONCLUSION

The results of this study imply that sub-therapeutic levels of chlorhexidine may modulate candidal phospholipase activity, thereby suppressing pathogenicity of C. albicans.