Growth of Candida albicans on agar plates containing high concentrations of fluconazole: antifungal resistance or trailing?

Background: The increasing incidence of invasive forms of candidiasis and resistance to antifungal therapy leads us to seek new and more effective antifungal compounds. Objective: To investigate the antifungal activity and toxicity as well as to evaluate the potential targets of 2- cyclohexylidenhydrazo-4-phenyl-thiazole (CPT) in Candida albicans. Methods: The antifungal activity of CPT against the survival of C. albicans was investigated in Caenorhabditis elegans. Additionally, we determined the effect of CPT on the inhibition of C. albicans adhesion capacity to buccal epithelial cells (BECs), the toxicity of CPT in mammalian cells, and the potential targets of CPT in C. albicans. Results: CPT exhibited a minimum inhibitory concentration (MIC) value of 0.4-1.9 µg/mL. Furthermore, CPT at high concentrations (>60 x MIC) showed no or low toxicity in HepG2 cells and <1% haemolysis in human erythrocytes. In addition, CPT decreased the adhesion capacity of yeasts to the BECs and prolonged the survival of C. elegans infected with C. albicans. Analysis of CPT-treated cells showed that their cell wall was thinner than that of untreated cells, especially the glucan layer. We found that there was a significantly lower quantity of 1,3-β-D-glucan present in CPT-treated cells than that in untreated cells. Assays performed on several mutant strains showed that the MIC value of CPT was high for its antifungal activity on yeasts with defective 1,3-β-glucan synthase. Conclusion: In conclusion, CPT appears to target the cell wall of C. albicans, exhibits low toxicity in mammalian cells, and prolongs the survival of C. elegans infected with C. albicans.

Download Full-text

Paradoxical Effect of Caspofungin: Reduced Activity against Candida albicans at High Drug Concentrations

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.48.9.3407-3411.2004 ◽

2004 ◽

Vol 48 (9) ◽

pp. 3407-3411 ◽

Cited By ~ 167

Author(s):

David A. Stevens ◽

Marife Espiritu ◽

Rachana Parmar

Keyword(s):

Candida Albicans ◽

Resistance Mechanisms ◽

Paradoxical Effect ◽

Fungal Cell ◽

High Drug ◽

Minimum Fungicidal Concentration ◽

Drug Concentrations ◽

High Concentrations ◽

Glucan Synthesis

ABSTRACT Resistance problems with caspofungin, an echinocandin inhibitor of fungal cell wall glucan synthesis, have been rare. We noted paradoxical turbid growth of Candida albicans isolates in broth in some high (supra-MIC) concentrations. Among isolates submitted for susceptibility testing and screened at drug concentrations up to 12.5 μg/ml, the frequency was 16%. Analysis of the turbid growth indicated slowing of growth in the presence of drug but with numbers of CFU up to 72% those of drug-free controls. Clearing of growth again by the highest drug concentrations produced a quadriphasic pattern in a tube dilution series. Cells growing at high drug concentrations were not resistant on retesting but showed the paradoxical effect of the parent. Among a selected series of isolates tested at concentrations up to 50 μg/ml, an additional 53% showed a “mini-paradoxical effect”: no turbid growth but incomplete killing at high concentrations (supra-minimum fungicidal concentration). These effects were reproducible; medium dependent in extent; noted in macro- and microdilution, in the presence or absence of serum, and on agar containing drug (but not when drug concentrations were not constant, as in agar diffusion); not seen with other echinocandins and less commonly in other Candida species; and not due to destruction of drug in tubes showing the effect. Cooperative enhancement of inhibition by a second drug could eradicate the effect. We postulate that high drug concentrations derepress or activate resistance mechanisms. The abilities of subpopulations to survive at high drug concentrations could have in vivo consequences.

Download Full-text

Reversal of antifungal resistance mediated by ABC efflux pumps from Candida albicans functionally expressed in yeast

International Journal of Antimicrobial Agents ◽

10.1016/s0924-8579(03)00213-9 ◽

2003 ◽

Vol 22 (3) ◽

pp. 291-300 ◽

Cited By ~ 72

Author(s):

M Schuetzer-Muehlbauer

Keyword(s):

Candida Albicans ◽

Efflux Pumps ◽

Antifungal Resistance

Download Full-text

The Candida albicans plasma membrane protein Rch1p, a member of the vertebrate SLC10 carrier family, is a novel regulator of cytosolic Ca2+ homoeostasis

Biochemical Journal ◽

10.1042/bj20112166 ◽

2012 ◽

Vol 444 (3) ◽

pp. 497-502 ◽

Cited By ~ 26

Author(s):

Linghuo Jiang ◽

Joerg Alber ◽

Jihong Wang ◽

Wei Du ◽

Xuexue Yang ◽

...

Keyword(s):

Functional Analysis ◽

Candida Albicans ◽

Plasma Membrane ◽

Membrane Protein ◽

Solute Carrier Family ◽

Plasma Membrane Protein ◽

Cellular Functions ◽

Downstream Target ◽

Solute Carrier ◽

High Concentrations

Candida albicans RCH1 (regulator of Ca2+ homoeostasis 1) encodes a protein of ten TM (transmembrane) domains, homologous with human SLC10A7 (solute carrier family 10 member 7), and Rch1p localizes in the plasma membrane. Deletion of RCH1 confers hypersensitivity to high concentrations of extracellular Ca2+ and tolerance to azoles and Li+, which phenocopies the deletion of CaPMC1 (C. albicans PMC1) encoding the vacuolar Ca2+ pump. Additive to CaPMC1 mutation, lack of RCH1 alone shows an increase in Ca2+ sensitivity, Ca2+ uptake and cytosolic Ca2+ level. The Ca2+ hypersensitivity is abolished by cyclosporin A and magnesium. In addition, deletion of RCH1 elevates the expression of CaUTR2 (C. albicans UTR2), a downstream target of the Ca2+/calcineurin signalling. Mutational and functional analysis indicates that the Rch1p TM8 domain, but not the TM9 and TM10 domains, are required for its protein stability, cellular functions and subcellular localization. Therefore Rch1p is a novel regulator of cytosolic Ca2+ homoeostasis, which expands the functional spectrum of the vertebrate SLC10 family.

Download Full-text

Submicellar complexes may initiate the fungicidal effects of cationic amphiphilic compounds on Candida albicans.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.41.3.544 ◽

1997 ◽

Vol 41 (3) ◽

pp. 544-550 ◽

Cited By ~ 31

Author(s):

B Ahlström ◽

M Chelminska-Bertilsson ◽

R A Thompson ◽

L Edebo

Keyword(s):

Candida Albicans ◽

Membrane Damage ◽

Hydrocarbon Chain ◽

Hexadecyltrimethylammonium Bromide ◽

Tetradecyltrimethylammonium Bromide ◽

Low Concentrations ◽

Hydrocarbon Chains ◽

Absorbing Material ◽

High Concentrations ◽

Chain Lengths

The killing of Candida albicans by a series of amphiphilic quaternary ammonium compounds (QACs) with different hydrocarbon chain lengths was closely related to the binding of the compounds to the cells and damage of the cell membranes. The membrane damage was measured as the level of release of the UV-absorbing material into the medium in which the cells were suspended and as the level of uptake of propidium iodide in individual cells by flow cytometry. It was shown that of the compounds tested, hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide [CTAB]) bound most efficiently. Tetradecyl betainate chloride (B14), tetradecanoylcholine bromide (C14), tetradecyltrimethylammonium bromide (TTAB), and dodecyltrimethylammonium bromide (DTAB) followed and had declining degrees of binding efficiency. The proportion of CTAB bound was almost total at concentrations up to the critical micelle concentration (CMC) of the compound, whereas that of B14 was somewhat smaller. For the two remaining tetradecyl compounds (C14 and TTAB), still smaller proportions were bound at low concentrations, but the proportions rose disproportionally at increasing concentrations to a distinct maximum at concentrations of 0.2 to 0.5 times the CMC. We propose that interfacial micelle-like aggregates are formed at the cell surface as a step in the binding process. An analogous, but less conspicuous, maximum was seen for DTAB. Thus, great differences in the binding affinity of QACs with different hydrocarbon chains at different concentrations to C. albicans were observed. These differences were related to the CMC of the compound. In contrast, the binding of TTAB to Salmonella typhimurium 395 MS was almost total at low as well as high concentrations until saturation was attained, indicating fundamental differences between binding to the yeast and binding to gram-negative bacteria. The importance of lipid-type complexes or aggregates to the antifungal effect of membrane-active substances are discussed.

Download Full-text

Antifungal resistance-modifying multiplexing action of Momordica charantia protein and phosphorylated derivatives on the basis of growth-dependent gene coregulation in Candida albicans

Medical Mycology ◽

10.1093/mmy/myaa070 ◽

2020 ◽

Author(s):

Qiao Yuan-Biao ◽

Zhang Lan-Fang ◽

Qiao Qi ◽

Niu Jia-Hui ◽

Ren Ze-Mei ◽

...

Keyword(s):

Candida Albicans ◽

Translation Initiation ◽

Low Dose ◽

Fungal Growth ◽

Momordica Charantia ◽

Antifungal Resistance ◽

Translation Initiation Factor ◽

Initiation Factor ◽

High Dose ◽

Rrna Processing

Abstract Fungal growth-dependent gene coregulation is strongly implicated in alteration of gene-encoding target proteases ruling with an antifungal resistance niche and biology of resistant mutants. On the basis of multi-alterative processes in this platform, the resistance-modifying strategy is designed in ketoconazole resistant Candida albicans and evaluated with less selective Momordica charantia protein and allosterically phosphorylated derivatives at the Thr102, Thr24 and Thr255 sites, respectively. We demonstrate absolutely chemo-sensitizing efficacy regarding stepwise-modifying resistance in sensitivity, by a load of only 26.23–40.00 μg/l agents in Sabouraud's dextrose broth. Five successive modifying-steps realize the decreasing of ketoconazole E-test MIC50 from 11.10 to a lower level than 0.10 mg/l. With the ketoconazole resistance-modifying, colony undergoes a high-frequency morphological switch between high ploidy (opaque) and small budding haploid (white). A cellular event in the first modifying-step associates with relatively slow exponential growth (ie, a 4-h delay)-dependent action, mediated by agents adsorption. Moreover, multiple molecular roles are coupled with intracellularly and extracellularly binding to ATP-dependent RNA helicase dbp6; the 0.08–2.45 fold upregulation of TATA-box-binding protein, rRNA-processing protein and translation initiation factor 5A; and the 7.52–55.33% decrease of cytochrome P450 lanosterol 14α-demethylase, glucan 1, 3-β glucosidase, candidapepsin-1 and 1-acylglycerol-3-phosphate O-acyltransferase. Spatial and temporal gene coregulation, in the transcription and translation initiation stages with rRNA-processing, is a new coprocessing platform enabling target protease attenuations for resistance-impairing. An updated resistance-modifying measure of these agents in the low-dose antifungal strategic design may provide opportunities to a virtually safe therapy that is in high dose-dependency. Lay Summary A new platform to modify resistance is fungal growth-dependent gene coregulation. MAP30 and phosphorylated derivatives are candidate resistance-modifying agents. Low-dose stepwise treatment absolutely modifies azole resistance in model fungus.

Download Full-text

The yeast, the antifungal, and the wardrobe: a journey into antifungal resistance mechanisms of Candida tropicalis

Canadian Journal of Microbiology ◽

10.1139/cjm-2019-0531 ◽

2020 ◽

Vol 66 (6) ◽

pp. 377-388

Author(s):

Jonathas Sales de Oliveira ◽

Vandbergue Santos Pereira ◽

Débora de Souza Collares Maia Castelo-Branco ◽

Rossana de Aguiar Cordeiro ◽

José Júlio Costa Sidrim ◽

...

Keyword(s):

Candida Albicans ◽

Intensive Care ◽

Candida Tropicalis ◽

Clinical Management ◽

Candida Species ◽

Genetic Basis ◽

Antifungal Susceptibility ◽

Resistance Mechanisms ◽

Antifungal Resistance ◽

Resistant Strains

Candida tropicalis is a prominent non-Candida albicans Candida species involved in cases of candidemia, mainly causing infections in patients in intensive care units and (or) those presenting neutropenia. In recent years, several studies have reported an increase in the recovery rates of azole-resistant C. tropicalis isolates. Understanding C. tropicalis resistance is of great importance, since resistant strains are implicated in persistent or recurrent and breakthrough infections. In this review, we address the main mechanisms underlying C. tropicalis resistance to the major antifungal classes used to treat candidiasis. The main genetic basis involved in C. tropicalis antifungal resistance is discussed. A better understanding of the epidemiology of resistant strains and the mechanisms involved in C. tropicalis resistance can help improve diagnosis and assessment of the antifungal susceptibility of this Candida species to improve clinical management.

Download Full-text

Ras1 involved in the antifungal resistance of Candida albicans and the inhibition of farnesol on the resistance of biofilms

10.21203/rs.2.13264/v1 ◽

2019 ◽

Author(s):

Xin Wei ◽

Lulu Zuo ◽

Shengyan Chen ◽

Zhenzhen Zhang ◽

Liuliu Jiang

Keyword(s):

Candida Albicans ◽

Molecular Mechanisms ◽

Hyphal Growth ◽

Antifungal Resistance ◽

Morphological Observation ◽

Inhibitory Effects ◽

Wild Strains ◽

Almost All ◽

Candida Albicans Biofilms

Abstract Background: Farnesol enhances the susceptibility of Candida albicans biofilms to antifungals, while the molecular mechanisms of this behavior are poorly understood. RAS1 regulates the hyphal growth of C. albicans, and farnesol inhibited hyphal growth by RAS1 regulation, while the role of RAS1 in the resistance of C. albicans biofilms and the molecular mechanism of the RAS1 in the farnesol-relevant antifungal capacity to C. albicans biofilms is still unknown. The study hypothesized that Ras1 involved in the antifungal resistance of C. albicans and the inhibition of farnesol on the resistance of biofilms. Results: The susceptibility assays showed that RAS1 over-expressing strain (RAS1OE) increased the resistance of C.albicans in both planktonic and biofilm form to antifungals, while RAS1 deletion strain (ras1Δ/Δ) reduced that to antifungals. The SMIC50 of the antifungals were increased with the mature of the biofilms formed from the mutant and the wild strains. Exogenous farnesol decreased the resistance of RAS1OE to antifungals, including fluconazole, amphotericin B, itraconazole, caspofungin, terbinafine, 5-flurocytosine and nystatin. The inhibitory effects of farnesol on the antifungal resistance of the biofilms from the RAS1OE were in accordance to almost all of the growth phases. Moreover, exogenous farnesol decreased the resistance of biofilms from RAS1OE more obviously than that from the wild strains (P<0.05). In addition, Morphological observation showed that that RAS1OE increased hyphal growth the biofilms, while ras1Δ/Δ reduced that of the biofilms. Compare to the wild-type strain, the inhibitory effects of farnesol on hyphal growth were more obvious to the RAS1OE, while less obvious to the ras1Δ/Δ. Furthermore, farnesol reduced the level of Ras1 and the expression of RAS1 of the biofilms formed from the RAS1OE strain compared with those of the untreated controls at all studied phases. Moreover, farnesol reduced the level of Ras1 and the expression of RAS1 of the biofilms formed from RAS1OE more obviously than that from the wild strains. Conclusions: Ras1 involved in the antifungal resistance of Candida albicans, and the inhibition of farnesol on the resistance of biofilm.

Download Full-text

Novel Bi-Factorial Strategy against Candida albicans Viability Using Carnosic Acid and Propolis: Synergistic Antifungal Action

Microorganisms ◽

10.3390/microorganisms8050749 ◽

2020 ◽

Vol 8 (5) ◽

pp. 749

Author(s):

Alejandra Argüelles ◽

Ruth Sánchez-Fresneda ◽

José P. Guirao-Abad ◽

Cristóbal Belda ◽

José Antonio Lozano ◽

...

Keyword(s):

Candida Albicans ◽

Pathogenic Fungi ◽

Carnosic Acid ◽

Moderate Degree ◽

Drastic Reduction ◽

Fungicidal Action ◽

Natural Extracts ◽

Antifungal Action ◽

High Concentrations

The potential fungicidal action of the natural extracts, carnosic acid (obtained from rosemary) and propolis (from honeybees’ panels) against the highly prevalent yeast Candida albicans, used herein as an archetype of pathogenic fungi, was tested. The separate addition of carnosic acid and propolis on exponential cultures of the standard SC5314 C. albicans strain caused a moderate degree of cell death at relatively high concentrations. However, the combination of both extracts, especially in a 1:4 ratio, induced a potent synergistic pattern, leading to a drastic reduction in cell survival even at much lower concentrations. The result of a mathematical analysis by isobologram was consistent with synergistic action of the combined extracts rather than a merely additive effect. In turn, the capacity of SC5314 cells to form in vitro biofilms was also impaired by the simultaneous presence of both agents, supporting the potential application of carnosic acid and propolis mixtures in the prevention and treatment of clinical infections as an alternative to antibiotics and other antifungal agents endowed with reduced toxic side effects.

Download Full-text