Mrr2 mutations and upregulation are associated with increased fluconazole resistance in Candida albicans isolates from patients with vulvovaginal candidiasis

Roles of Nucleolar Factor RCL1 in Itraconazole Resistance of Clinical Candida albicans Under Different Stress Conditions

Purpose

RNA terminal phosphate cyclase like 1 (RCL1) undergoes overexpression during the immune response of Candida albicans following drug treatment. This study aims to investigate the expression levels of RCL1 in C. albicans under various stress conditions.

Methods

Fifteen itraconazole (ITR)-resistant strains of clinical C. albicans, and one standard strain were employed for RCL1 sequencing, and mutations in RCL1 were analyzed. Subsequently, 14 out of the 15 ITR-resistant clinical strains and 14 clinical strains sensitive to ITR, fluconazole (FCA) as well as voriconazole (VRC) were cultured under diverse conditions. The expression of RCL1 ITR-resistant and sensitive C. albicans was then assessed using real-time quantitative PCR (RT-qPCR) assays.

Results

Compared to the standard strain, three missense mutations (C6A, G10A, and A11T) were identified in the RCL1 gene of ITR-resistant C. albicans through successful forward sequencing. Additionally, using successful reverse sequencing, one synonymous mutation (C1T) and four missense mutations (C1T, A3T, A7G, and T8G) were found in the RCL1 gene of ITR-resistant C. albicans. RCL1 expression was significantly higher in ITR-resistant C. albicans than in sensitive strains under standard conditions (37°C, 0.03% CO2, pH 4.0). Low temperature (25°C) increased RCL1 expression in sensitive C. albicans while decreasing it in ITR-resistant strains. Elevated CO2 concentrations (5% CO2) had a negligible effect on RCL1 expression in sensitive C. albicans, but effectively reduced RCL1 level in ITR-resistant strains. Furthermore, a medium with a pH of 7 decreased the expression of RCL1 in both resistant and sensitive C. albicans.

Conclusion

This study demonstrated that RCL1 mutations in ITR-resistant C. albicans, and variations in culture conditions significantly influence RCL1 expression in both ITR-resistant and sensitive C. albicans, thereby inducing alterations in the dimorphism of C. albicans.

Autophagy of Candida albicans cells after the action of earthworm Venetin-1 nanoparticle with protease inhibitor activity

The present studies show the effect of the Venetin-1 protein-polysaccharide complex obtained from the coelomic fluid of the earthworm Dendrobaena veneta on Candida albicans cells. They are a continuation of research on the mechanisms of action, cellular targets, and modes of cell death. After the action of Venetin-1, a reduced survival rate of the yeast cells was noted. The cells were observed to be enlarged compared to the controls and deformed. In addition, an increase in the number of cells with clearly enlarged vacuoles was noted. The detected autophagy process was confirmed using differential interference contrast, fluorescence microscopy, and transmission electron microscopy. Autophagic vesicles were best visible after incubation of fungus cells with the Venetin-1 complex at a concentration of 50 and 100 µg mL-1. The changes in the vacuoles were accompanied by changes in the size of mitochondria, which is probably related to the previously documented oxidative stress. The aggregation properties of Venetin-1 were characterized. Based on the results of the zeta potential at the Venetin-1/KCl interface, the pHiep = 4 point was determined, i.e. the zeta potential becomes positive above pH = 4 and is negative below this value, which may affect the electrostatic interactions with other particles surrounding Venetin-1.

Draft genome sequence and probiotic functional property analysis of Lactobacillus gasseri LM1065 for food industry applications

Probiotics are defined as live organisms in the host that contribute to health benefits. Lactobacillus gasseri LM1065, isolated from human breast milk, was investigated for its probiotic properties based on its genome. Draft genome map and de novo assembly were performed using the PacBio RS II system and hierarchical genome assembly process (HGAP). Probiotic properties were determined by the resistance to gastric conditions, adherence ability, enzyme production, safety assessment and mobile genetic elements. The fungistatic effect and inhibition of hyphae transition were studied using the cell-free supernatant (CFS). L. gasseri LM1065 showed high gastric pepsin tolerance and mild tolerance to bile salts. Auto-aggregation and hydrophobicity were measured to be 61.21% and 61.55%, respectively. The adherence to the human intestinal epithelial cells was measured to be 2.02%. Antibiotic-resistance genes and putative virulence genes were not predicted in the genomic analysis, and antibiotic susceptibility was satisfied by the criteria of the European Food Safety Authority. CFS showed a fungistatic effect and suppressed the tricarboxylic acid cycle in Candida albicans (29.02%). CFS also inhibited the transition to true hyphae and damaged the blastoconidia. This study demonstrates the essential properties of this novel probiotic, L. gasseri LM1065, and potential to inhibit vaginal C. albicans infection.

Atypical changes in Candida albicans cells treated with the Venetin-1 complex from earthworm coelomic fluid

In the present research, the effect of a protein-polysaccharide complex Venetin-1 obtained from the coelomic fluid of Dendrobaena veneta earthworm on Candida albicans cells was characterized. The compound destroyed fungal cells without showing cytotoxicity to human skin fibroblasts, which was demonstrated in earlier studies. Since it had an effect on the fungal cell wall and membrane, this complex was compared with the known antifungal antibiotic fluconazole. Both preparations disturbed the division of yeast cells and resulted in the formation of aggregates and chains of unseparated cells, which was illustrated by staining with fluorochromes. Fluorescent staining of the cell wall with Calcofluor white facilitated comparison of the types of aggregates formed after the action of both substances. The analysis performed with the use of Congo red showed that Venetin-1 exposed deeper layers of the cell wall, whereas no such effect was visible after the use of fluconazole. The FTIR analysis confirmed changes in the mannoprotein layer of the cell wall after the application of the Venetin-1 complex. Staining with Rhodamine 123 and the use of flow cytometry allowed comparison of changes in the mitochondria. Significantly elongated mitochondria were observed after the Venetin-1 application, but not after the application of the classic antibiotic. Phase contrast microscopy revealed vacuole enlargement after the Venetin-1 application. The flow cytometry analysis of C. albicans cells treated with Venetin-1 and fluconazole showed that both substances caused a significant decrease in cell viability.

Distribution and antifungal susceptibility pattern of Candida species from mainland China: A systematic analysis

Antifungal resistance to Candida pathogens increases morbidity and mortality of immunosuppressive patients, an emerging crisis worldwide. Understanding the Candida prevalence and antifungal susceptibility pattern is necessary to control and treat candidiasis. We aimed to systematically analyse the susceptibility profiles of Candida species published in the last ten years (December 2011 to December 2021) from mainland China. The studies were collected from PubMed, Google Scholar, and Science Direct search engines. Out of 89 included studies, a total of 44,716 Candida isolates were collected, mainly comprising C. albicans (49.36%), C. tropicalis (21.89%), C. parapsilosis (13.92%), and C. glabrata (11.37%). The lowest susceptibility was detected for azole group; fluconazole susceptibilities against C. parapsilosis, C. albicans, C. glabrata, C. tropicalis, C. guilliermondii, C. pelliculosa, and C. auris were 93.25%, 91.6%, 79.4%, 77.95%, 76%, 50%, and 0% respectively. Amphotericin B and anidulafungin were the most susceptible drugs for all Candida species. Resistance to azole was mainly linked with mutations in ERG11, ERG3, ERG4, MRR1-2, MSH-2, and PDR-1 genes. Mutation in FKS-1 and FKS-2 in C. auris and C. glabrata causing resistance to echinocandins was stated in two studies. Gaps in the studies' characteristics were detected, such as 79.77%, 47.19 %, 26.97%, 7.86%, and 4.49% studies did not mention the mortality rates, age, gender, breakpoint reference guidelines, and fungal identification method, respectively. The current study demonstrates the overall antifungal susceptibility pattern of Candida species, gaps in surveillance studies and risk-reduction strategies that could be supportive in candidiasis therapy and for the researchers in their future studies.

Single nucleotide polymorphisms and chromosomal copy number variation may impact the Sporothrix brasiliensis antifungal susceptibility and sporotrichosis clinical outcomes

Feline-transmitted sporotrichosis has garnered attention due to the recent high incidence and the lack of efficient control in the epicenter of the epidemic, Rio de Janeiro, Brazil. Sporothrix brasiliensis is the major pathogen involved in feline-to-human sporotrichosis in Brazil and displays more virulent genotypes than the closely related species S. schenckii. Over the last two decades, several reports of antifungal-resistant strains have emerged. Sequencing and comparison analysis of the outbreak strains allowed us to observe that the azole non-wild-type S. brasiliensis strain CFP 1054 had significant chromosomal variations compared to wild-type strains. One of these variants includes a region of 231 Kb containing 75 duplicated genes, which were overrepresented for lipid and isoprenoid metabolism. We also identified an additional strain (CFP 1055) that was resistant to itraconazole and amphotericin B, which had a single nucleotide polymorphism in the tac1 gene. The patients infected with these two strains showed protracted clinical course and sequelae. Even though our sample size is modest, these results suggest the possibility of identifying specific point mutations and large chromosomal duplications potentially associated with antifungal resistance and clinical outcomes of sporotrichosis.

Photodynamic therapy-mediated hypericin-loaded nanostructured lipid carriers against vulvovaginal candidiasis

INTRODUCTION AND AIM

The indiscriminate use and adverse effects of the main conventional antifungal agents compromise the effectiveness of treating vulvovaginal candidiasis (VVC), mainly caused by the species Candida albicans. This study evaluated the effectiveness of photodynamic therapy (PDT) and the in vitro and in vivo anti-candida potential of the hypericin (HYP)-loaded nanostructured lipid carriers (NLC).

MATERIALS AND METHODS

Empty NLC and NLC-HYP were characterized by the dynamic light scattering technique and transmission electron microscopy to evaluate the average particle size distribution and its morphologies. The in vitro inhibition photodynamic effect of the systems was tested to reduce the planktonic viability of C. albicans. The therapeutic assay photodynamic of the systems was performed to treat VVC in mice.

RESULTS

Empty NLC and NLC-HYP presented values of average hydrodynamic diameter, polydispersity index, and ζ-potential from 136 to 133 nm, 0.16 to 0.22, and -18 to -30 mV, respectively, on day 30. Microscopically, the systems showed spherical morphologies and nanoscale particles. Furthermore, in the in vitro inhibition assay, the treatment of PDT with NLC-HYP (NLC-HYP+) showed a significant reduction of the C. albicans planktonic viability compared to YNB negative control after 5 min of LED light irradiation. In the in vivo therapeutic assay, the antifungal group (vaginal antifungal cream) and NLC-HYP+ evaluated in the dark and by PDT, respectively, had a significant log₁₀ reduction in fungal burden compared to the infected group on day 8 of the VVC treatment.

CONCLUSION

Due to the in vitro and in vivo anti-candida potential, PDT-mediated systems can be an effective strategy in VVC therapy.

Vulvovaginal candidiasis: An overview of mycological, clinical, and immunological aspects

AIM

To provide an overview of clinical, immunological, and mycological aspects of vulvovaginal candidiasis (VVC).

METHODS

A literature search was conducted to find relevant articles about different aspects of VVC. Related data from retrieved articles were summarized in different headings.

RESULTS

VVC has a global distribution and Candida albicans is the leading cause of infection except for specific patient groups like postmenopausal, diabetic, or immunocompromised women. VVC has a range of clinical presentations, accordingly, its diagnosis should be based on clinical examination coupled with laboratory investigations. The best therapeutic regimen depends on the patient's conditions and the causative agent. Moreover, factors like drug resistance of the causative agents and different mutations in the immunity-related genes could affect the treatment outcome.

CONCLUSION

As a globally distributed disease, VVC needs further attention, especially in areas related to the treatment failure and recurrence of the disease.

Cotreatment with Aspirin and Azole Drugs Increases Sensitivity of Candida albicans in vitro

Purpose

This study aimed to investigate the effects of aspirin (acetyl salicylic acid [ASA]) combined with fluconazole (FCA), itraconazole (ITR), or voriconazole (VRC) on Candida albicans under planktonic and biofilm conditions.

Methods

A total of 39 clinical C. albicans strains were used to perform the in vitro drug sensitivity assay under different conditions using the M27-A4 broth microdilution method. The minimal inhibitory concentrations (MICs) and fractional inhibitory concentration index (FICI) values were calculated. C. albicans ZY23 was chosen for the further analyses.

Results

Under planktonic conditions, the half maximal MIC (MIC₅₀) values of FCA, ITR, and VRC were 64-0.5 μg/mL, 32-0.0625 μg/mL, and 16-0.125 μg/mL, respectively, when applied, whereas in combination with ASA, the values decreased to 32-0.25 μg/mL, 8-0.0313 μg/mL, and 8-0.0313 μg/mL, respectively. Under biofilm conditions, FCA, ITR, or VRC alone showed MIC₅₀ values of 128-8 μg/mL, 32-4 μg/mL, and 32-0.5 μg/mL, whereas in combination with ASA the values were decreased to 32-0.5 μg/mL, 16-0.5 μg/mL, and 8-0.0625 μg/mL, respectively. Analysis of the FICI showed that the sensitization rate of ASA to FCA, ITR, and FCA under planktonic conditions was 43.59%, whereas the sensitization rates of ASP to FCA, ITR, and FCA under biofilm conditions were 46.15%, 46.15%, and 48.72%, respectively. Additionally, the time-growth and time-kill curves of C. albicans ZY23 further verified the synergistic effects of ASA on azole drugs.

Conclusion

ASA may act as an enhancer of the inhibitory effects of azole drugs on the growth of clinical C. albicans under planktonic and biofilm conditions.

Silver nanoparticles offer a synergistic effect with fluconazole against fluconazole-resistant Candida albicans by abrogating drug efflux pumps and increasing endogenous ROS

OBJECTIVES

A frequent emergence of drug resistance has been observed and posed great threat to global public health recently. This work aimed to investigate the potential synergistic effect and the underlying mechanisms of AgNPs-fluconazole combination more extensively through 2 clinically isolated fluconazole-resistant Candida albicans (C. albicans) strains.

METHODS

Antifungal properties of AgNPs and fluconazole alone or together against planktonic cells and biofilms were tested. Cellular and molecular targets associated with fluconazole resistance were monitored after AgNPs treatment. Antifungal potential of AgNPs-fluconazole combination was also explored in vivo using a mouse model of disseminated candidiasis. Tissue burden and survival rate were analyzed.

RESULTS

The results indicated that AgNPs worked synergistically with fluconazole against both planktonic cells of fluconazole-resistant C. albicans and biofilms formed <12 h. AgNPs treatment down-regulated ERG1, ERG11, ERG25, and CDR2, decreased membrane ergosterol levels and membrane fluidity, reduced membrane content of Cdr1p, Cdr2p, and thus efflux bump activity. The elevated ROS production was also a likely cause of the synergistic effect. In vivo, AgNPs and fluconazole combination significantly decreased the fungal burden and improved the survival rate of infected mice.

CONCLUSION

In conclusion, these results further confirm that AgNPs-fluconazole combination is a hopeful strategy for the treatment of fluconazole-resistant fungal infections.

The effects of secreted aspartyl proteinase inhibitor ritonavir on azoles-resistant strains of Candida albicans as well as regulatory role of SAP2 and ERG11

BACKGROUND

Candida albicans, the main human fungal pathogen, can cause fungal infection and seriously affect people's health and life. This study aimed to investigate the effects of ritonavir (RIT) on C. albicans and the correlation between SAP2 as well as ERG11 and drug resistance.

RESULTS

Secreted aspartyl proteinases (Saps) activities and pathogenicity of C. albicans with different drug resistance were measured. M27-A4 broth microdilution method was used to analyze the drug sensitivity of RIT combined with fluconazole (FCA) on C. albicans. After that, SAP2 and ERG11 mutations were examined by polymerase chain reaction (PCR) and sequencing, and quantitative real-time PCR was utilized to determine the expression of the two genes. By analyzing pz values, the Saps activity of cross-resistant strains was the highest, followed by voriconazole (VRC)-resistant strains, FCA-resistant strains, itraconazole (ITR)-resistant strains, and sensitive strains. The pathogenicity of C. albicans in descending order was as follows: cross-resistant strains, VRC-resistant strains, ITR-resistant strains, FCA-resistant strains, and sensitive strains. With the increase of RIT concentrations, the Saps activity was gradually inhibited. Drug sensitivity results showed that there was no synergistic effect between RIT and FCA. Additionally, no gene mutation sites were found in SAP2 sequencing, and 17 synonymous mutations and 6 missense mutations occurred in ERG11 sequencing. Finally, the expression of SAP2 and ERG11 was significantly higher in the resistant strains compared with the sensitive strains, and there was a positive liner correlation between SAP2 and ERG11 messenger RNA expression (r = .6655, p < .001).

CONCLUSION

These findings may help to improve our understanding of azole-resistant mechanisms of C. albicans and provide a novel direction for clinical therapeutics of C. albicans infection.

Whole genome sequencing of a clinical drug resistant Candida albicans isolate reveals known and novel mutations in genes involved in resistance acquisition mechanisms

Candida albicans is an opportunistic pathogen accounting for the majority of cases of Candida infections. Currently, C. albicans are developing resistance towards different classes of antifungal drugs and this has become a global health burden that does not spare Lebanon. This study aims at determining point mutations in genes known to be involved in resistance acquisition and correlating resistance to virulence and ergosterol content in the azole resistant C. albicans isolate CA77 from Lebanon. This pilot study is the first of its kind to be implemented in Lebanon. We carried out whole genome sequencing of the azole resistant C. albicans isolate CA77 and examined 18 genes involved in antifungal resistance. To correlate genotype to phenotype, we evaluated the virulence potential of this isolate by injecting it into BALB/c mice and we quantified membrane ergosterol. Whole genome sequencing revealed that eight out of 18 genes involved in antifungal resistance were mutated in previously reported and novel residues. These genotypic changes were associated with an increase in ergosterol content but no discrepancy in virulence potential was observed between our isolate and the susceptible C. albicans control strain SC5314. This suggests that antifungal resistance and virulence potential in this antifungal resistant isolate are not correlated and that resistance is a result of an increase in membrane ergosterol content and the occurrence of point mutations in genes involved in the ergosterol biosynthesis pathway.

Virulence of "white-gray-opaque" tri-stable transformation in clinical Candida albicans in vitro and in vivo

The study aimed to induce the white-opaque-gray tri-stable transformation in clinical C. albicans and to explore their potential pathogenicity. Sixty-four clinical strains were used to induce the white, opaque and gray cells of C. albicans. Secreted aspartyl proteinases (Sap) activity of the three phenotypes was then measured, and a vulvovaginal candidiasis (VVC) animal model was constructed. Of the 64 clinical strains, only 3 strains successfully underwent white-gray-opaque tri-stable transformation, and the three strains all belonged to MTL homozygous strains. Pz values in white, opaque and gray phenotypes were 0.834 ± 0.012, 0.707 ± 0.036, and 0.628 ± 0.002, respectively, which indicated that the cells with gray phenotype had higher Sap activity. After inoculation of different fungal suspension, the fungal colony count in descending order was as follows: gray phenotype, opaque phenotype and white phenotype. After treated with fluconazole for 3 days or 10 days, the fungal colony counts were significantly decreased compared with that before treatment (P < 0.05). The Sap activity and pathogenicity of gray cells in C. albicans were the strongest, followed by opaque cells and white cells. Additionally, white, gray and opaque phenotypic cells were all susceptible to fluconazole.

Aspirin and verapamil increase the sensitivity of Candida albicans to caspofungin under planktonic and biofilm conditions

OBJECTIVES

This study aimed to investigate the effects of caspofungin (CAS) combined with aspirin (ASP) or verapamil (VPL) on the sensitivity of Candida albicans under planktonic and biofilm conditions.

METHODS

A total of 39 C. albicans clinical strains were used to construct biofilms. Sensitivity to ASP or VPL combined with CAS was analysed by broth microdilution. MIC₅₀ values were obtained and the fractional inhibitory concentration index (FICI) was calculated. Subsequently, C. albicans ZY22 was selected for time-growth curve analysis and strains ZY15 and ZY22 were used for time-kill curve analysis.

RESULTS

Under planktonic condition the MIC₅₀ of CAS was 0.0313-8 μg/mL following treatment with CAS alone, whereas it decreased to 0.0313-4 μg/mL following CAS combined with ASP or VPL. Under biofilm condition the MIC₅₀ of CAS was 0.125-16 μg/mL following treatment with CAS alone, whereas it decreased to 0.0625-16 μg/mL or 0.0625-8 μg/mL following CAS combined with ASP or VPL. FICI results showed synergistic interactions between CAS and ASP under planktonic and biofilm conditions in 17 and 16 strains, respectively. However, synergistic interactions between CAS and VPL under planktonic and biofilm conditions were observed in 19 and 23 strains, respectively. Additionally, 8000 μg/mL ASP or 8 μg/mL VPL combined with CAS had better inhibitory effects on C. albicans.

CONCLUSION

ASP and VPL may be a sensitiser for CAS, and the antifungal effects of CAS may be sensitised by 8000 μg/mL ASP or 8 μg/mL VPL against C. albicans under planktonic and biofilm conditions.