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

Phenotypic and genotypic characterization of virulence markers and antifungal susceptibility of oral Candida species from diabetic and non-diabetic hemodialysis patients

BACKGROUND

Patients with chronic kidney disease undergoing hemodialysis are often colonized by Candida species with high possibility of fungal infections. The purposes of this study were to determine the prevalence of Candida species, evaluate antifungal susceptibility profile, biofilm formation, proteinase and phospholipase activities, and the frequency of virulence genes in the Candida species isolated from the oral mucosa of hemodialysis diabetic (DM) and non-diabetic (non-DM) patients.

METHODS

This study identified several species of Candida isolated from 69 DM and 58 non-DM patients on hemodialysis using phenotypic methods and PCR-RFLP technique. The identification of C. albicans and C. glabrata complex was performed by HWP1 gene and four oligonucleotides (UNI-5.8S, GLA-f, BRA-f, and NIV-f), respectively. Antifungal susceptibility to amphotericin B, fluconazole, itraconazole, voriconazole, and caspofungin was assessed according to CLSI M27-A3/S4. The biomass, metabolic activity of biofilm, proteinase (P_rz), phospholipase (P_z), and molecular study for virulence genes were assessed using crystal violet, XTT assay, agar-based hydrolytic enzyme, and PCR technique, respectively.

RESULTS

Candida prevalence was 44.9% with 47.8% and 41.4% among DM and non-DM patients, respectively (P = .045). The species identified were C. albicans (49.5%), C. glabrata (16.5%), C. tropicalis (12%), C. kefyr (8.8%), C. parapsilosis (6.6%), C. dubliniensis (3.3%), and C. lusitaniae (3.3%). The antifungal susceptibility profile showed that all Candida isolates were sensitive to amphotericin B, itraconazole, voriconazole, and caspofungin whereas fluconazole resistance was observed in 6.3% (MIC ≥ 64 μg/mL) of C. albicans and 6.6% of C. glabrata (MIC ≥ 64 μg/mL). The susceptible- dose-dependent rate was found in 10.5% of C. albicans. The P_rz values of C. albicans ranged from 0.37 to 0.66 for the DM and 0.44-0.73 for the non-DM group (P < 0.05). The non-albicans Candida (NAC) species produced higher degree of biomass and metabolic activity compared to C. albicans (P < 0.05). Furthermore, significant (p < 0.05) correlations were detected between the biofilm formation with P_rz values and fluconazole MICs. The most detected virulence factors were ALS3 and Sap5.

CONCLUSIONS

These results showed the importance of prevalence of NAC species in hemodialysis patients. Investigating antifungal susceptibility profile made a better understanding of the role of virulence markers in the pathogenesis of Candida strains.

Performance of Two Extracts Derived from Propolis on Mature Biofilm Produced by Candida albicans

Species of the Candida genus represent the third most common cause of onychomycosis, the most frequent and difficult to treat nail infection. Onychomycosis has been attributed to fungi organized in biofilm and some natural products have proved promising for its treatment. This study aimed to evaluate the antibiofilm activity of propolis extract (PE) and its by-product (WPE) on 7-day preformed biofilms produced by Candida albicans in polystyrene microplates, as well as in an ex vivo model on human nail fragments. The cytotoxicity and permeation capacity were also assessed. Firstly, multiple parameters were evaluated over 7 days to elucidate the dynamics of biofilm formation by C. albicans. The cell viability and total biomass did not vary much from the beginning; however, days 3 and 4 were crucial in terms of metabolic activity, which was significantly increased, and the levels of extracellular matrix components, wherein proteins and nucleic acids experienced an increase, but polysaccharide levels dropped. Architecturally, one-day biofilm showed a monolayer of organized cells (blastoconidia, hyphae, and pseudohyphae), while in the seven-day biofilm there was a three-dimensional well-structured and complex biofilm. This yeast was also able to form a biofilm on both surfaces of the nail, without an additional nutritional source. Both extracts showed excellent antibiofilm activity against the 7-day preformed biofilm and were not toxic to Vero cells at concentrations compatible with the antifungal and antibiofilm activities. Both extracts permeated the experimentally infected nail, with WPE being more efficient. The results of this study, taken together, reinforce the potential of these natural products, containing propolis, as a safe option for the topical treatment of onychomycosis.

Itraconazole-Loaded Ufasomes: Evaluation, Characterization, and Anti-Fungal Activity against Candida albicans

Numerous obstacles challenge the treatment of fungal infections, including the uprising resistance and the low penetration of available drugs. One of the main active agents against fungal infections is itraconazole (ITZ), with activity against a broad spectrum of fungi while having few side effects. The aim of this study was to design ufasomes, oleic acid-based colloidal carriers, that could encapsulate ITZ to improve its penetration power. Employing a 2²3¹ factorial design, the effect of three independent factors (oleic acid amount, cholesterol concentration, and ITZ amount) was investigated and evaluated for the percentage encapsulation efficiency (%EE), particle size (PS), and zeta potential (ZP). Optimization was performed using Design^® expert software and the optimized ITZ-loaded ufasomes obtained had %EE of 99.4 ± 0.7%, PS of 190 ± 1 nm, and ZP of -81.6 ± 0.4 mV, with spherical unilamellar morphology and no aggregation. An in vitro microbiological study was conducted to identify the minimum inhibitory concentration of the selected formula against Candida albicans, which was found to be 0.0625 μg/mL. Moreover, the optimized formula reduced the expression of toll-like receptors-4 and pro-inflammatory cytokine IL-1β secretion in the C. albicans-infected fibroblasts, indicating that the proposed ITZ-loaded ufasomes are a promising drug delivery system for ITZ.

Correlation Between Drug Resistance and Virulence of Candida Isolates from Patients with Candidiasis

Purpose

This article aims to provide a theoretical basis for new or adjuvant strategies to facilitate the early diagnosis and treatment of candidiasis and to determine if drug-resistant Candida would affect virulence.

Patients and Methods

Our strains were collected from patients diagnosed with candidiasis in our hospital. The strains were identified by MALDI-TOF system and ITS sequencing. Antifungal sensitivity testing in vitro was performed to evaluate susceptibility of these isolates to current widely used antifungal drugs. The Galleria mellonella larvae model infected by Candida spp. was used to compare the virulence of drug-resistant and susceptible Candida spp.

Results

A total of 206 Candida strains were collected from clinical specimens. Candida albicans was the most common species among them, and was predominantly isolated from male patients aged over 40 years in ICU environments suffering from pulmonary and/or cerebral conditions. The accuracy rate of MALDI TOF-MS identification was 92.72% when compared with ITS sequencing as the standard method. Most Candida species, except for C. tropicalis which showed high resistance to micafungin, showed high susceptibilities to voriconazole, itraconazole, amphotericin B and micafungin but were highly resistant to terbinafine. For each specific Candida species, the G. mellonella larvae model revealed that the virulence of drug-resistant Candida isolates did not markedly differ from that of the drug-susceptible isolates, however, the virulence was dose-dependent on inoculated fungal cells in this model.

Conclusion

The possibility of Candida infection should not be neglected in patients at critical care hospital settings and C. albicans is the most common causative agent. MALDI-TOF MS has the advantages of rapidity and high accuracy, and should be a preferred method for identification of Candida spp. in a clinical laboratory. Voriconazole, itraconazole, amphotericin B and micafungin can still be recommended as the first line antifungals to treat candidiasis.

Insights on the etiopathogenesis of onychomycosis by dermatophyte, yeast and non dermatophyte mold in ex vivo model

Fungal biofilms have been involved in the pathogenesis of onychomycosis, but the aspects contributing to this association need to be enlightened. This study aimed to investigate the ability of three different fungi to form biofilm on the nail. All evaluated fungi were able to grow on the nails, using them as the only nutritional source and formed a structure strongly suggestive of biofilms. However, their architecture and morphology were highly contrasting: Candida albicans showed dense growth, exhibited a well-structured community and a large amount of extracellular matrix (ECM), and FTIR-ATR spectroscopy reinforced these findings revealing components suggestive of the biofilm. For Fusarium oxysporum these events were also observed, but in lower intensity. Furthermore, while Trichophyton rubrum presented a well-organized architecture, the ECM was not visualized. We hypothesize that these findings are related to the symptomatology of onychomycosis. When it is caused by a non-dermatophyte, it usually is accompanied with paronychia, pain, edema, inflammation and few signals of keratolysis, while dermatophytes are more associated with intense onycholysis and absence of the inflammatory signals. Biofilm seems to be crucial for non-dermatophytes to cause onychomycosis, but not for T. rubrum.

In Vitro Production of Virulence Factors and Antifungal Susceptibility Pattern of Aspergillus Isolates from Clinical Samples in a Tertiary Care Center

Objectives This study was aimed to investigate the association between virulence factors and antifungal susceptibility pattern among Aspergillus species.

Materials and Methods This study was carried out in the Department of Microbiology, from May 2018 to June 2019. A total of 52 Aspergillus isolates obtained from various clinical samples were speciated based on microscopic identification by lacto phenol cotton blue (LPCB) mount and slide culture technique. The production of virulence factors such as biofilm, lipase, phospholipase, amylase, and hemolysin were detected using standard phenotypic methods with Aspergillus niger ATCC (American Type Culture Collection) 6275 as the control strain. Antifungal susceptibility patterns of all Aspergillus isolates to amphotericin B, itraconazole, voriconazole, and posaconazole were evaluated in line with the Clinical Laboratory Standards Institute (CLSI) M38-A2 guidelines.

Results The percentage of resistance was the highest in itraconazole (48.08%), followed by amphotericin B (28.85%) and voriconazole (9.62%). All amphotericin B-resistant isolates produced biofilm, itraconazole-resistant isolates exhibited phospholipase activity, and voriconazole-resistant isolates produced biofilm and demonstrated phospholipase and hemolytic activities. Regardless of the virulence factors produced, all isolates were susceptible to posaconazole.

Conclusion Understanding the relationship between virulence factors and antifungal resistance aids in the development of new therapeutic approaches involving virulence mechanisms as potential targets for effective antifungal drug development.

Relevant insights into onychomycosis' pathogenesis related to the effectiveness topical treatment

Onychomycosis (OM) is a fungal infection, responsible for about 50% of nail diseases. OM has been attributed to the ability of fungi to naturally organize themselves into biofilms on nail surfaces. However, little is known about the exact role of the biofilm in the etiopathogenesis of OM, as well as its influence in the permeation of a topical treatment. The objectives of this study were to review the literature for topical OM treatments in clinical trials, assess the efficiency of these treatments, and discuss factors that could affect the success of these treatments. First, a systematic search of articles published in the MEDLINE database (PubMed) between January 2010 and December 2019 was conducted, focusing on drugs under clinical trials for the topical treatment of OM. Of the publications selected, it was clear that none of them had considered the fungi organized in biofilm. Therefore, we reflected on some important variables involved in OM, such as the nail structure and the mechanism of fungal invasion. Some methods, such as histopathologic analysis and spectroscopy techniques, were found to be effective in the detection of nail biofilm, and could be used in future drug permeation studies. This review allowed us to conclude that novel antifungals for the topical treatment of OM must consider the drug to permeate through biofilm. Natural products, such as propolis, seem strong candidates in this respect.

The effect of antifungal resistance development on the virulence of Candida species

In recent years, the relevance of diseases associated with fungal pathogens increased worldwide. Members of the Candida genus are responsible for the greatest number of fungal bloodstream infections every year. Epidemiological data consistently indicate a modest shift toward non-albicans species, albeit Candidaalbicans is still the most recognizable species within the genus. As a result, the number of clinically relevant pathogens has increased, and, despite their distinct pathogenicity features, the applicable antifungal agents remained the same. For bloodstream infections, only three classes of drugs are routinely used, namely polyenes, azoles and echinocandins. Antifungal resistance toward all three antifungal drug classes frequently occurs in clinical settings. Compared with the broad range of literature on virulence and antifungal resistance of Candida species separately, only a small portion of studies examined the effect of resistance on virulence. These studies found that resistance to polyenes and echinocandins concluded in significant decrease in the virulence in different Candida species. Meanwhile, in some cases, resistance to azole type antifungals resulted in increased virulence depending on the species and isolates. These findings underline the importance of studies aiming to dissect the connections of virulence and resistance in Candida species.

Characterization of Aspergillus nidulans Biofilm Formation and Structure and Their Inhibition by Pea Defensin Psd2

Approximately four million people contract fungal infections every year in Brazil, primarily caused by Aspergillus spp. The ability of these fungi to form biofilms in tissues and medical devices complicates treatment and contributes to high rates of morbidity and mortality in immunocompromised patients. Psd2 is a pea defensin of 5.4 kDa that possesses good antifungal activity against planktonic cells of representative pathogenic fungi. Its function depends on interactions with membrane and cell wall lipid components such as glucosylceramide and ergosterol. In the present study, we characterized Aspergillus nidulans biofilm formation and determined the effect of Psd2 on A. nidulans biofilms. After 4 hours, A. nidulans conidia adhered to polystyrene surfaces and formed a robust extracellular matrix-producing biofilm at 24 h, increasing thickness until 48 h Psd2 inhibited A. nidulans biofilm formation in a dose-dependent manner. Most notably, at 10 μM Psd2 inhibited 50% of biofilm viability and biomass and 40% of extracellular matrix production. Psd2 significantly decreased the colonized surface area by the biofilm and changed its level of organization, causing a shortening of length and diameter of hyphae and inhibition of conidiophore formation. This activity against A. nidulans biofilm suggests a potential use of Psd2 as a prototype to design new antifungal agents to prevent biofilm formation by A. nidulans and related species.

Analysis of Biofilm-Related Genes and Antifungal Susceptibility Pattern of Vaginal Candida albicans and Non-Candida albicans Species

Background

Vulvovaginal candidiasis caused by Candida species is a prevalent fungal infection among women. It is believed that the pathogenesis of Candida species is linked with the production of biofilm which is considered a virulence factor for this organism. The aim of this study was molecular identification, antifungal susceptibility, biomass quantification of biofilm, and detection of virulence markers of Candida species.

Methods

We investigated the molecular identification of 70 vaginal isolates of Candida species, antifungal resistance to amphotericin B, fluconazole, itraconazole, and voriconazole according to CLSI M27-A3 and M27-S4, biofilm formation, and frequency analysis of biofilm-related ALS1, ALS3, and HWP1 genes.

Results

Our findings showed that the most common yeast isolated from vaginal discharge was C. albicans (67%), followed by the non-Candida albicans species (33%). All C. albicans complex isolates were confirmed as C. albicans by HWP-PCR, and all isolates of the C. glabrata complex were revealed to be C. glabrata sensu stricto using the multiplex PCR method. FLC resistance was observed in 23.4% of C. albicans and 7.7% of C. glabrata. The resistance rate to ITC was found in 10.6% of C. albicans. The frequency of ALS1, ALS3, and HWP1 genes among Candida species was 67.1%, 80%, and 81.4%, respectively. Biofilm formation was observed in 54.3% of Candida species, and the highest frequency detected as a virulence factor was for the ALS3 gene (97.3%) in biofilm-forming species. Discussion. Our results showed the importance of molecular epidemiology studies, investigating antifungal susceptibility profiles, and understanding the role of biofilm-related virulence markers in the pathogenesis of Candida strains.

Virulence and Antifungal Susceptibility of Microsporum canis Strains from Animals and Humans

The enzymatic and antifungal profiles of dermatophytes play an important role in causing infections in humans and animals. This study aimed to assess the virulence factors produced by Microsporum canis strains, in vitro antifungal profile and the relationship between virulence, antifungal profile and occurrence of lesions in animals and humans. A total of 100 M. canis strains from humans with tinea corporis (n = 10) and from animals presenting (n = 64) or not (n = 26) skin lesions was employed to evaluate phospholipase (Pz), hemolytic (Hz), lipase (Lz), catalase (Ca), and thermotolerance (GI) activities. In addition, in vitro antifungal profile was conducted using the CLSI broth microdilution method. A statistically significant difference (p < 0.05) in Lz and Ca values was revealed among strains from hosts with and without lesions. Voriconazole, terbinafine, and posaconazole were the most active drugs followed by ketoconazole, griseofulvin, itraconazole, and fluconazole in decreasing activity order. The significant positive correlation between azole susceptibility profile of M. canis and virulence factors (i.e., hemolysin and catalase) suggest that both enzyme patterns and antifungal susceptibility play a role in the appearance of skin lesions in animals and humans.

Diagnosis of biofilm infections: current methods used, challenges and perspectives for the future

The diagnosis of biofilms continues to be a challenge, and there is no standardized protocol for such a diagnosis in clinical practice. In addition, some proposed methodologies are expensive to require significant amounts of time and a high number of trained staff, making them impracticable for clinical practice. In recent years, mass spectrophotometry/matrix-assisted laser desorption ionization time of flight (MALDI-TOF) has been applied it in biofilm studies. However, due to several problems and limitations of the technique, MALDI-TOF is far from being the gold standard for identifying biofilm formation. The omics analysis may prove to be a promising strategy for the diagnosis of biofilms in clinical laboratories since it allows the identification of pathogens in less time than needed for conventional techniques and in a more specific manner. However, omic tools are expensive and require qualified technical expertise, and an analysis of the data obtained needs to be careful not to neglect subpopulations in the biofilm. More studies must therefore be developed for creating a protocol that guarantees rapid biofilm identification, ensuring greater chances of success in infection control. This review discusses the current methods of microbial biofilm detection and future perspectives for its diagnosis in clinical practice.

Immune Sensing of Candida albicans

Candida albicans infections range from superficial to systemic and are one of the leading causes of fungus-associated nosocomial infections. The innate immune responses during these various infection types differ, suggesting that the host environment plays a key role in modulating the host–pathogen interaction. In addition, C. albicans is able to remodel its cell wall in response to environmental conditions to evade host clearance mechanisms and establish infection in niches, such as the oral and vaginal mucosa. Phagocytes play a key role in clearing C. albicans, which is primarily mediated by Pathogen Associated Molecular Pattern (PAMP)–Pattern Recognition Receptor (PRR) interactions. PRRs such as Dectin-1, DC-SIGN, and TLR2 and TLR4 interact with PAMPs such as β-glucans, N-mannan and O-mannan, respectively, to trigger the activation of innate immune cells. Innate immune cells exhibit distinct yet overlapping repertoires of PAMPs, resulting in the preferential recognition of particular Candida morphotypes by them. The role of phagocytes in the context of individual infection types also differs, with neutrophils playing a prominent role in kidney infections, and dendritic cells playing a prominent role in skin infections. In this review, we provide an overview of the key receptors involved in the detection of C. albicans and discuss the differential innate immune responses to C. albicans seen in different infection types such as vulvovaginal candidiasis (VVC) and oral candidiasis.

Virulence Factors and Antifungal Susceptibility in Candida Species Isolated from Dermatomycosis Patients

Dermatomycoses caused by Candida spp. are increasingly common, however there are few reports in the literature regarding their epidemiology, pathogenesis and antifungal susceptibility of these fungal pathogens. This study aimed to identify, characterize virulence and determine the antifungal susceptibility of Candida species isolated from patients with dermatomycoses. We studied a total of 45 yeast samples isolated from dermal scrapings from patients treated at a public hospital, Bauru, São Paulo, Brazil. After identification, the samples were analyzed for protease activity, phospholipase, biofilm formation and antifungal susceptibility. The most common species was Candida albicans (40%), followed by C. krusei (22.22%), C. parapsilosis complex (22.22%) and C. famata (6.67%). Regarding virulence mechanisms, 57.78% and 28.89% of the samples showed enzymatic activity for protease and phospholipase, respectively. A total of 13.33% of the samples showed secretion of both enzymes. All isolates were biofilm producers, and a higher production was observed in C. tropicalis isolates. Regarding the antifungal susceptibility test, 97.78% of the samples had the highest levels of the minimal inhibitory concentration (MIC) for terbinafine, and one C. krusei sample showed intermediate susceptibility to fluconazole. The correct identification of dermatomycosis-related microorganisms, as well as a better knowledge of their pathogenicity and susceptibility against the antifungals used in the clinic, is extremely important for an efficient preventive and therapeutic action.

Genotypic and Phenotypic Changes in Candida albicans as a Result of Cold Plasma Treatment

We treated Candida albicans cells with a sublethal dose of nonequilibrium (cold) atmospheric-pressure He plasma and studied alterations in the genome of this fungus as well as changes in the phenotypic traits, such as assimilation of carbon from carbohydrates, hydrolytic enzyme activity, and drug susceptibility. There is a general problem if we use cold plasma to kill microorganism cells and some of them survive the process—whether the genotypic and phenotypic features of the cells are significantly altered in this case, and, if so, whether these changes are environmentally hazardous. Our molecular genetic studies have identified six single nucleotide variants, six insertions, and five deletions, which are most likely significant changes after plasma treatment. It was also found that out of 19 tested hydrolytic enzymes, 10 revealed activity, of which nine temporarily decreased their activity and one (naphthol-AS-BI- phosphohydrolase) permanently increased activity as a result of the plasma treatment. In turn, carbon assimilation and drug susceptibility were not affected by plasma. Based on the performed studies, it can be concluded that the observed changes in C. albicans cells that survived the plasma action are not of significant importance to the environment, especially for the drug resistance and pathogenicity of this fungus.

Marked virulence and azole resistance in Candida albicans isolated from patients with periodontal disease

Candida albicans is an opportunistic fungus frequently associated with periodontal diseases. The objective of this study was to determine the expression patterns of virulence genes associated with those of azole resistance among the strains of C. albicans isolated from patients with periodontal disease. We isolated 80 strains of C. albicans from patients with periodontal disease enrolled from two dental clinics and their antifungal susceptibilities were evaluated using the disc diffusion method. C. albicans and its virulence genes were identified using PCR. The expressions of the virulence genes of C. albicans were analyzed using real-time PCR post in vitro infection of the cell line A549. The phenotype for resistance against azoles such as ketoconazole and fluconazole was observed in all analyzed strains (n = 80), which coincided with the high frequency of occurrence of the genes CDR1 and MDR1 associated with resistance. The frequencies of detection and expression of the genes HWP1 (47/15), ALS1 (80/66), ALS3 (70/30), LIP1 (78/44), LIP4 (77/65), LIP5 (79/58), LIP6 (79/58), PLB1 (79/65), and PLB2 (80/66) were found to be higher in the strains of C. albicans isolated from patients with moderate periodontitis and different expression patterns associated with those for azole resistance were identified. It could be elucidated that the high expression of virulence markers associated with azole resistance in C. albicans might be contributing to the chronicity of periodontal infections.