In vitro evaluation of virulence factors of Candida species isolated from oral cavity

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.

In Vitro Evaluation of the Virulence Attributes of Oropharyngeal Candida Species Isolated from People Living with Human Immunodeficiency Virus with Oropharyngeal Candidiasis on Antiretroviral Therapy

Background

Oropharyngeal Candida species are part commensal microflora in the the oral cavity of health individuals. Commensal Candida species can become opportunist and transition to pathogenic causes of oropharyngeal candidiasis (OPC) in individuals with impaired immunity through ecological cues and expression of virulence factors. Limited studies have evaluated virulence attributes of oropharyngeal Candida species among people living with human immunodeficiency virus (PLHIV) with OPC on antiretroviral therapy (ART) in Uganda.

Objective

Evaluation of the Virulence Attributes of Oropharyngeal Candida Species Isolated from People Living with Human Immunodeficiency Virus with Oropharyngeal Candidiasis on Antiretroviral Therapy.

Methods

Thirty-five (35) Candida isolates from PLHIV with OPC on ART were retrieved from sample repository and evaluated for phospholipase activity using the egg yolk agar method, proteinase activity using the bovine serum albumin agar method, hemolysin activity using the blood agar plate method, esterase activity using the Tween 80 opacity test medium method, coagulase activity using the classical tube method and biofilm formation using the microtiter plate assay method in vitro.

Results

Phospholipase and proteinase activities were detected in 33/35 (94.3%) and 31/35 (88.6%) of the strains, respectively. Up to 25/35 (71.4%) of the strains exhibited biofilm formation while esterase activity was demonstrated in 23/35 (65.7%) of the strains. Fewer isolates 21/35 (60%) of the strains produced hemolysin and coagulase production was the least virulence activity detected in 18/35 (51.4%).

Conclusion

Phospholipase and proteinase activities were the strongest virulence attributes of oropharyngeal Candida species.

Chitosan nanogel aqueous treatment improved blood biochemicals, antioxidant capacity, immune response, immune-related gene expression and infection resistance of Nile tilapia

Candida albicans is a pathogenic yeast recently associated with diverse diseases in aquaculture. The present study investigated the efficacy of chitosan nanogel (CNG) in ameliorating effects of C. albicans on Nile tilapia (Oreochromis niloticus). Fish were randomly distributed into four groups (control, waterborne CNG at 75 μg/L, intraperitoneally challenged with C. albicans (1.8 × 107 CFU/mL), and waterborne CNG at 75 μg/L + C. albicans at 1.8 × 107 CFU/mL). Results showed that C. albicans infection reduced survival rate (57.5%) and caused marked clinical symptoms in fish among all infected groups. Substantial declines in immunological (complement 3, lysozyme, and immunoglobulin M), protein (total protein and non-albumin protein), and antioxidant (catalase, glutathione peroxidase, and superoxide dismutase) biochemical endpoints were exhibited, The C. albicans infected group also showed marked down-regulation in the expression of immune-related genes, including toll-like receptor 2 (TLR-2), transforming growth factor beta2, tumor necrosis factor alpha, interleukins (IL-1β, IL-6, and IL-10), and antiapoptotic gene (B-cell lymphoma, BCL-2). The expression of the apoptotic gene (Bcl-2 associated X protein, BAX) was up-regulated in fish challenged by C. albicans. The application of waterborne CNG to fish challenged with C. albicans infection improved fish survival (79.5%) and all other measured parameters. The main finding of this work was that CNG is a nanotechnology with potential for preventing degraded health status by C. albicans infection in tilapia, and thus has promise as an intervention in aquaculture settings.

In-vitro evaluation of virulence markers and antifungal resistance of clinical Candida albicans strains isolated from Karachi, Pakistan

Candidiasis is a significant fungal infection with high mortality and morbidity rates worldwide. Candida albicans is the most dominant species responsible for causing different manifestations of candidiasis. Certain virulence traits as well as its resistance to antifungal drugs contribute to the pathogenesis of this yeast. This study was designed to determine the production of some virulence factors, such as biofilm formation and extracellular hydrolytic enzymes (esterase, coagulase, gelatinase, and catalase) by this fungus, as well as its antifungal resistance profile. A total of 304 clinical C. albicans isolates obtained from different clinical specimens were identified by a conventional diagnostic protocol. The antifungal susceptibility of C. albicans strains was determined by disk diffusion technique against commercially available antifungal disks, such as nystatin 50 μg, amphotericin B 100 unit, fluconazole 25 μg, itraconazole 10 μg, ketoconazole 10 μg, and voriconazole 1 μg. The assessment of biofilm formation was determined by the tube staining assay and spectrophotometry. Gelatinase, coagulase, catalase, and esterase enzyme production was also detected using standard techniques. A total of 66.1% (201/304) and 28.9% (88/304) of C. albicans strains were susceptible-dose dependent (SDD) to nystatin and itraconazole, respectively. Among the antifungal drugs, C. albicans strains showed high resistance to ketoconazole 24.7% (75/304); however, no statistically significant relationship between the clinical origin of C. albicans isolates and antifungal drug resistance pattern was detected. For virulence factors, the majority of the C. albicans strains actively produced biofilm and all hydrolytic enzymes. Biofilm formation was demonstrated by 88% (267/304) of the strains with a quantitative mean value 0.1762 (SD ± 0.08293). However, 100% (304/304) of isolates produced catalase enzyme, 69% (211/304) produced coagulase, 66% (197/304) produced gelatinase, and 52% (157/304) produced esterase enzyme. A significant relationship between the source of specimens and biofilm formation by C. albicans was observed; nevertheless, there was no significant relationship between different sources of C. albicans strains and the production of different enzymatic virulence factors. The study found that C. albicans strains have excellent potential to produce virulence markers and resistance to antifungals, which necessitates surveillance of these opportunistic pathogens to minimize the chances of severe invasive infections.

Profiling of potential pathogenic candida species in obesity

PURPOSE OF RESEARCH

The aim of the current study was gut profiling of culturable Candida species and their possible pathogenic potential to asses role in obesity.

METHODS

This case control study includes stool samples from 75 obese individuals and 50 controls. Isolation and identification of various Candida species was carried out by standard microbiological techniques. For pathogenic profiling, extracellular enzymatic assays, biofilm forming ability and resistance to azole were analyzed.

RESULTS

Culturable gut profiling identified comparative higher abundance and diversity of Candida species among obese compared to controls. The most abundant specie among both groups was C.kefyr. A comparatively higher pathogenic potential as more hydrolases expression was detected in C.kefyr, C.albicans and Teunomyces krusei from obese group. Majority isolates from obese group were strong biofilm formers (47.1%) compared to control group (35.4%) suggesting it as strong risk factor for obesity. Fluconazole resistance was highest among C.kefyr (51%) followed by Teunomyces krusei and C.albicans. All the isolates from different species were voriconazole sensitive except C.kefyr displaying a 4.2% resistance in obese group only. A significant association of dominant colonizing species with meat, fruit/vegetable consumption and residence area was present (p < 0.05).

CONCLUSION

The presence of hydrolytic enzymes in gut Candida species showed strong association with protein's degradation and enhanced pathogenicity. C.kefyr and Teunomyces krusei has emerged as potential pathogen showing increased colonization as result of protein rich and low carb diet. Thus presenting it as a bad choice for weight loss in obese individuals.

Biofilm formation of Candida isolates from xerostomic post-radiotherapy head and neck cancer patients

Oral candidiasis is a common problem in post-radiation head and neck cancer (HNC) patients. While biofilm formation is a crucial virulence factor for Candida colonization, existing information on biofilm formation capability of Candida in cancer patients is scarce.

OBJECTIVE

To evaluate biofilm formation capability of Candida spp. colonized in xerostomic post-radiotherapy HNC patients.

DESIGN

Candida albicans and non-albicans Candida species were previously isolated from xerostomic post-radiation cancer patients and healthy individuals. Biofilm mass and biofilm metabolic activity were investigated by crystal violet and MTT assays, respectively. Their relationship with clinical parameters was analyzed using Mann-Whitney U and Chi-square tests.

RESULTS

A total of 109 and 45 Candida isolates from 64 cancer patients and 34 controls, respectively, were evaluated. Both biofilm mass and metabolic activity of Candida isolates from cancer patients were higher than those from controls. The between-group differences were statistically significant in C. albicans (p < 0.001) for biofilm mass, and in C. tropicalis (p = 0.01) for biofilm metabolic activity. Overall, C. tropicalis was the best biofilm producers in both groups. Additionally, we found that higher biofilm formation among C. albicans was associated with low saliva buffering capacity.

CONCLUSIONS

C. albicans and C. tropicalis isolated from xerostomic post-radiation cancer patients had higher biofilm formation capability than those from healthy individuals. Our findings suggest that, in addition to compromised host factors, higher biofilm formation capability may also contribute to the pathogenesis of oral candidiasis in HNC patients. This novel information potentially adds to proper management for these patients.

Impeding Virulence of Candida albicans by Candesartan and Domperidone

Candida albicans is the most common human fungal pathogen that has developed extensive virulence factors which allows successful colonization and infection of the host. Anti-virulence agents can alleviate the pathogenesis of fungi and help the immune system to eradicate them easily. This study aimed to explore the anti-virulence effect of domperidone and candesartan against C. albicans standard strain. Sub-inhibitory concentrations (1/4 and 1/8 of minimum inhibitory concentration) of domperidone and candesartan significantly inhibited the virulence factors hemolysin, lipase, protease, phospholipase, and bioflim formation. It was found that candesartan inhibited biofilm formation by 60.48-67.91%, hemolysin activity (61.21-74.14%), phospholipase activity (40-49.67%), lipase activity (58.97-73%), and protease activity (52.63%), while domperidone was found to inhibit biofilm formation by 70.54-77.49%, hemolysin activity (64.84-69.84%), phospholipase activity (49.67-60%), lipase activity (50-54.87%), and protease activity (52.63-57.9%). Quantitative real time-PCR confirmed the anti-virulence activity of domperidone and candesartan as both drugs significantly reduce the expression of the virulence genes SAP2, SAP6, PLB1, PLB2, LIP4, LIP5. In conclusion, domperidone and candesartan could serve as anti-virulence agents for treatment of C. albicans infections.

Opportunistic yeast pathogen Candida spp.: Secreted and membrane-bound virulence factors

Candidiasis is a fungal infection caused by Candida spp. especially Candida albicans, C. glabrata, C. parapsilosis and C. tropicalis. Although the medicinal therapeutic strategies have rapidly improved, the mortality rate due to candidiasis has continuously increased. The secreted and membrane-bound virulence factors (VFs) are responsible for fungal invasion, damage and translocation through the host enterocytes besides the evasion from host immune system. VFs such as agglutinin-like sequences (Als), heat shock protein 70, phospholipases, secreted aspartyl proteinases (Sap), lipases, enolases and phytases are mostly hydrolases which degrade the enterocyte membrane components except for candidalysin, the VF acts as a peptide toxin to induce necrotic cell lysis. To date, structural studies of the VFs remain underexplored, hindering their functional analyses. Among the VFs, only secreted aspartyl proteinases and agglutinin-like sequences have their structures deposited in Protein Data Bank (PDB). Therefore, this review scrutinizes the mechanisms of these VFs by discussing the VF-deficient studies of several Candida spp. and their abilities to produce these VFs. Nonetheless, their latest reported sequential and structural analyses are discussed to impart a wider perception of the host-pathogen interactions and potential vaccine or antifungal drug targets. This review signifies that more VFs structural investigations and mining in the emerging Candida spp. are required to decipher their pathogenicity and virulence mechanisms compared to the prominent C. albicans.

LAY ABSTRACT

Candida virulence factors (VFs) including mainly enzymes and proteins play vital roles in breaching the human intestinal barrier and causing deadly candidiasis. Limited VFs' structural studies hinder deeper comprehension of their mechanisms and thus the design of vaccines and antifungal drugs against fungal infections.

Role of Candida glabrata as nosocomial pathogen and its susceptibility to Fluconazole, Voriconazole, Caspofungin, Micafungin and Amphotericin B

Candida has different types that could cause bloodstream infections. A total number of 150 samples were collected from candidemia patients and examined. The Candida spp. Species isolated from blood samples were analysed. These were identified by culturing the species using different media, namely the chromogenic agar test. Then, the virulence factors of all samples were tested. The Candida glabrata isolates were tested with six commercial antifungal drugs. C. glabrata 67 (44.6%), C. albicans 34 (22.6%), C. krusei 18 (12%), C. tropicalis 17 (11.3%), and C. parasilosis 14 (9.3%). the production of phospholipase ranged between 0.63-0.99 mm. It was found that 96% of the species showed phospholipase activity in aerobic conditions. The protease activities of Candida spp. Isolates were experimentally tested by area of inhibition around the colonies, where 59.3% had the double (++) protease activity, 31.4% with (+) grade, and 9.3% had (–) grade or clear zone around the colony. The hemolytic capacity ranged from 0.69-0.89 in the optimum aerobic environments. Finally, 38.33% of the isolated Candida spp. were positive and 61.67% negative for biofilm formation. Out of the total positive Candida spp. for biofilm formation, 21.73% were strong biofilm producers, and 78.27% were weak. Minimum fungicidal concentration (MFC) of Fluconazole for C. glabrata isolates was not appropriate (NA) due to the occurrence of low inhibition tested for species. Micafungin exhibited the lowest fungicidal activity against C. glabrata ranging from 0.03 - 0.125, while Fluconazole showed the highest.

Candida Pathogenicity and Interplay with the Immune System

Candida species are opportunistic fungal pathogens that are part of the normal skin and mucosal microflora. Overgrowth of Candida can cause infections such as thrush or life-threatening invasive candidiasis in immunocompromised patients. Though Candida albicans is highly prevalent, several non-albicans species are also isolated from nosocomial infections. Candida sp. are over presented in the gut of people with Crohn's disease and certain types of neurological disorders, with hyphal form and biofilms being the most virulent states. In addition, Candida uses several secreted and cell surface molecules such as pH related antigen 1, High affinity glucose transporter, Phosphoglycerate mutase 1 and lipases to establish pathogenicity. A strong innate immune response is elicited against Candida via dendritic cells, neutrophils and macrophages. All three complement pathways are also activated. Production of proinflammatory cytokines IL-10 and IL-12 signal differentiation of CD4⁺ cells into Th1 and Th2 cells, whereas IL-6, IL-17 and IL-23 induce Th17 cells. Importance of T-lymphocytes is reflected in depleted T-cell count patients being more prone to Candidiasis. Anti- Candida antibodies also play a role against candidiasis using various mechanisms such as targeting virulent enzymes and exhibiting direct candidacidal activity. However, the significance of antibody response during infection remains controversial. Furthermore, some of the Candida strains have evolved molecular strategies to evade the sophisticated host attack by proteolysis of components of immune system and interfering with immune signalling pathways. Emergence of several non-albicans species that are resistant to current antifungal agents makes treatment more difficult. Therefore, deeper insight into interactions between Candida and the host immune system is required for discovery of novel therapeutic options.

Mechanism of Candida pathogenesis: revisiting the vital drivers

Candida is the most implicated fungal pathogen in the clinical setting. Several factors play important roles in the pathogenesis of Candida spp. Multiple transcriptional circuits, morphological and phenotypic switching, biofilm formation, tissue damaging extracellular hydrolytic enzymes, metabolic flexibility, genome plasticity, adaptation to environmental pH fluctuation, robust nutrient acquisition system, adherence and invasions (mediated by adhesins and invasins), heat shock proteins (HSPs), cytolytic proteins, escape from phagocytosis, evasion from host immune system, synergistic coaggregation with resident microbiota, resistance to antifungal agents, and the ability to efficiently respond to multiple stresses are some of the major pathogenic determinants of Candida species. The existence of multiple connections, in addition to the interactions and associations among all of these factors, are distinctive features that play important roles in the establishment of Candida infections. This review describes all the underlying factors and mechanisms involved in Candida pathogenesis by evaluating pathogenic determinants of Candida species. It reinforces the already available pool of data on the pathogenesis of Candida species by providing a clear and simplified understanding of the most important factors implicated in the pathogenesis of Candida species. The Candida pathogenesis network, an illustration linking all the major determinants of Candida pathogenesis, is also presented. Taken together, they will further improve our current understanding of how these factors modulate virulence and consequent infection(s). Development of new antifungal drugs and better therapeutic approaches to candidiasis can be achieved in the near future with continuing progress in the understanding of the mechanisms of Candida pathogenesis.

Isolation of pathogenic Candida species from oral cavity of postpartum females, and its association with obstetric and dental problems

OBJECTIVE

The aim of the current study was to investigate pathogenic Candida spp. Colonization in oral cavity of postpartum females and its association with adverse pregnancy outcomes (APOs) and dental issues.

METHODS

Saliva samples and clinico-demographic data were collected from 267 postpartum females along with 54 non-pregnant females (Jan 2016-March 2018). Isolation of Candida was carried out by using standard microbiological methods and different virulence factors (Esterase activity, phospholipase activity and biofilm formation) were evaluated.

RESULTS

Candidacolonization was high in postpartum females (p<0.001, OR = 4.28). This colonization was not significant among females with APOs, however, one to three folds risk was seen with different obstetric and dental factors. High esterase activity was seen among Candida isolates from postpartum females in comparison to control group (p = 0.01). Phospholipase activity of C.albicans isolates from this group was also high (p = 0.001). Majority of the Candida isolates (66.87%) from postpartum females were biofilm formers. Increase in antifungal activity was seen among isolates from postpartum females, with 85% isolates resistant to Fluconazole and Voriconazole (p<0.001) and Amphotericin B resistance was present in 64.38% isolates (p<0.001).

CONCLUSION

Postpartum females are more susceptible to oral Candida colonization, which exhibit enhanced virulence characteristics and its carriage are associated with increased risk for development of APOs and dental problems.

The frequency, antifungal susceptibility and enzymatic profiles of Candida species in cases of onychomycosis infection

Although the frequency of candidal onychomycosis is increasing daily, there is little information in literature about the epidemiology, pathogenesis, and antifungal susceptibility of this dermatological disease. This study aimed to provide information about the epidemiology, pathogenesis, and azole susceptibility of Candida species isolated from patients living in a region with continental climate. After identification of the isolated strains using conventional methods, proteinase and phospholipase activities were determined by a plate method and biofilm-forming ability was determined using the microplate method. Susceptibility of the same species to fluconazole (FLU), voriconazole (VRC), miconazole (MNZ), itraconazole (ITZ), and ketoconazole (KTZ) were determined by microdilution method. The 50 Candida isolates included 23 C. parapsilosis (46%), 13 C. albicans (26%), 4 C. guilliermondii(8%), 4 C.tropicalis (8%), 2 C.krusei(2%), 1 C.lusitaniae (2%), 1 C. sake (2%), and 1 C. kefyr (2%) isolates. The geometric mean (GM) of the minimum inhibitory concentration (MIC) for FLU, KTZ, VRC, MNZ, and ITZ was 0.4 μg/mL, 0.08 μg/mL, 0.08 μg/mL, 0.2 μg/mL, and 0.6 μg/mL, respectively. Proteinase, phospholipase, and biofilm-forming ability were detected in 18%(9/50), 20%(10/50), and 6%(3/50) of the Candida isolates, respectively. We found that the most frequently isolated species is C.parapsilosis. On the basis of the GM values, the most effective azoles are ketoconazole and voriconazole. The isolated Candida species exhibited low phospholipase, proteinase, and biofilm formation activities.