cancidas and Candidiasis

We previously reported medicinal chemistry efforts that identified MK-5204, an orally efficacious β-1,3-glucan synthesis inhibitor derived from the natural product enfumafungin. Further extensive optimization of the C2 triazole substituent identified 4-pyridyl as the preferred replacement for the carboxamide of MK-5204, leading to improvements in antifungal activity in the presence of serum, and increased oral exposure. Reoptimizing the aminoether at C3 in the presence of this newly discovered C2 substituent, confirmed that the (R) t-butyl, methyl aminoether of MK-5204 provided the best balance of these two key parameters, culminating in the discovery of ibrexafungerp, which is currently in phase III clinical trials. Ibrexafungerp displayed significantly improved oral efficacy in murine infection models, making it a superior candidate for clinical development as an oral treatment for Candida and Aspergillus infections.

Topics: Administration, Oral; Animals; Antifungal Agents; Aspergillosis; Aspergillus; beta-Glucans; Candida albicans; Candidiasis; Disease Models, Animal; Glycosides; Half-Life; Mice; Structure-Activity Relationship; Triterpenes

Fluconazole (FLC) is the drug of choice when it comes to treat fungal infections such as invasive candidiasis in humans. However, the widespread use of FLC has resulted in the development of resistance to this drug in various fungal strains and, simultaneously has occasioned the need for new antifungal agents. Herein, we report the synthesis of 27 new FLC derivatives along with their antifungal activity against a panel of 13 clinically relevant fungal strains. We also explore their toxicity against mammalian cells, their hemolytic activity, as well as their mechanism of action. Overall, many of our FLC derivatives exhibited broad-spectrum antifungal activity and all compounds displayed an MIC value of <0.03 μg/mL against at least one of the fungal strains tested. We also found them to be less hemolytic and less cytotoxic to mammalian cells than the FDA approved antifungal agent amphotericin B. Finally, we demonstrated with our best derivative that the mechanism of action of our compounds is the inhibition of the sterol 14α-demethylase enzyme involved in ergosterol biosynthesis.

Topics: Alkylation; Animals; Antifungal Agents; Azoles; Candida albicans; Candidiasis; Cell Line; Ergosterol; Fungi; Hemolysis; Humans; Mice; Microbial Sensitivity Tests; Mycoses

Echinocandins and pneumocandins are classes of lipocyclohexapeptides that are broad spectrum antifungal agents. They inhibit fungal specific 1,3-β-glucan synthase activity which is an essential component of the fungal cell wall. Chemical modifications of these two leads have produced three clinical agents namely caspofungin, micafungin and anidulafungin. The presence of hydroxy-glutamine versus threonine and unsaturated linear fatty acid versus branched chain saturated fatty acid differentiate the two classes of compounds with profound differences in their hemolytic properties. In the current study, we have replaced the side chain of the cyclohexapeptides with a common aromatic heterocyclic acyl side chain and compared the biological activities of the cores head-to-head and for the first time demonstrated the role played by the acyl chain and the hydroxy-glutamine for the antifungal potency.

Topics: Animals; Antifungal Agents; Candida; Candidiasis; Caspofungin; Cell Wall; Echinocandins; Glucosyltransferases; Glutamine; Isoxazoles; Lipopeptides; Mice; Microbial Sensitivity Tests; Protein Binding; Structure-Activity Relationship; Threonine

A detailed structure-activity relationship study of a novel series of pyridazine-based small molecule glucan synthase inhibitors is described. The optimization of the PK profile of this series led to the discovery of compound 11g, which demonstrated in vivo potency ip in a lethal fungal infection model.

Topics: Animals; Antifungal Agents; Candida; Candidiasis; Enzyme Inhibitors; Glucosyltransferases; Half-Life; Mice; Microbial Sensitivity Tests; Pyridazines; Rats; Structure-Activity Relationship; Sulfonamides

We describe the acquisition of flucytosine, azole, and caspofungin resistance in sequential Candida glabrata bloodstream isolates collected from a bone marrow transplant patient with clinical failure. Point mutations in C. glabrata FUR1 (CgFUR1) and CgFKS2 and overexpression of CgCDR1 and CgCDR2 were observed in resistant isolates.

Topics: Antifungal Agents; Azoles; Candida glabrata; Candidiasis; Caspofungin; Child; Drug Resistance, Fungal; Echinocandins; Female; Flucytosine; Fungal Proteins; Fungemia; Hematopoietic Stem Cell Transplantation; Humans; Lipopeptides; Microbial Sensitivity Tests; Point Mutation

Multilocus microsatellite polymorphisms in 27 clinical Candida albicans isolates were found to be clearly unrelated to in vitro paradoxical growth or trailing effect with caspofungin. These findings suggest that such in vitro phenotypes are either gained or lost too rapidly to be predicted by more stable genomic markers.

Topics: Antifungal Agents; Candida albicans; Candidiasis; Caspofungin; Echinocandins; Genotype; Humans; Lipopeptides; Microbial Sensitivity Tests; Microsatellite Repeats; Phenotype; Polymorphism, Genetic

We studied three clinical isolates of Candida spp. (one C. tropicalis isolate and two C. glabrata isolates) from patients with invasive candidiasis. The first isolate emerged during echinocandin treatment, while the others emerged after the same treatment. These strains harbored an amino acid substitution in Fksp never linked before with reduced echinocandin susceptibility in C. tropicalis or in C. glabrata. The molecular mechanism of reduced susceptibility was confirmed using a 1,3-beta-D-glucan synthase inhibition assay.

Topics: Adult; Antifungal Agents; Candida glabrata; Candida tropicalis; Candidiasis; Drug Resistance, Fungal; Echinocandins; Female; Glucosyltransferases; Humans; Male; Middle Aged; Mutation

We evaluated the prevalence of fks1 hot spot (HS) 1 mutations among 133 Candida strains from six species displaying various caspofungin MIC values (from < or =0.008 to >8 microg/ml). Only 4 (2.9%) strains displayed FKS1 HS1 amino acid substitutions: 1 C. albicans (F641Y) among 32 isolates tested (3.1%), 1 C. glabrata (S645P) among 34 isolates tested (2.9%), and 2 C. tropicalis (F641S) among 12 isolates tested (16.7%). The 4 isolates displaying FKS1 HS1 alterations showed elevated caspofungin MIC results (1 to >8 microg/ml) but lower anidulafungin and micafungin MIC values (0.12 to 4 microg/ml and 0.25 to 4 microg/ml, respectively) in some instances within the wild-type MIC population, as determined using the epidemiologic cutoff values (ECV). Candida krusei, C. parapsilosis, and C. guilliermondii isolates tested showed no FKS1 HS1 alterations regardless of echinocandin MIC result. We additionally analyzed 8 C. albicans and 7 C. glabrata strains for mutations on other HS regions of fks1 and fks2. Three C. glabrata strains showed alterations on FKS2 HS1 (two S645P and one L644W). In general, strains displaying S645P alteration showed higher echinocandin MIC values than strains harboring other mutations. Overall, Candida spp. strains showing caspofungin MIC values within the ECV did not display fks HS mutations. In contrast, strains showing alterations in this region displayed anidulafungin and/or micafungin MIC values within the wild-type population, suggesting that caspofungin could be the most sensitive agent for detection of these resistance mutations. Furthermore, results from this large, geographically diverse Candida spp. collection demonstrated that fks1 HS1 mutations remain uncommon among isolates with various echinocandin MIC levels.

Topics: Amino Acid Sequence; Amino Acid Substitution; Antifungal Agents; Base Sequence; Candida; Candida albicans; Candida glabrata; Candidiasis; DNA, Fungal; Drug Resistance, Fungal; Echinocandins; Fungal Proteins; Genes, Fungal; Humans; In Vitro Techniques; Microbial Sensitivity Tests; Molecular Sequence Data; Mutation; Sequence Homology, Amino Acid; Species Specificity

Previous pharmacodynamic studies using in vivo candidiasis models have demonstrated that the 24-h area under the concentration-time curve (AUC)/MIC is a good descriptor of the echinocandin exposure-response relationship. Further studies investigating the 24-h AUC/MIC target for a stasis endpoint identified free-drug 24-h AUC/MIC against Candida albicans and were similar for two echinocandins, anidulafungin and micafungin. The current studies expand investigation of a third echinocandin (caspofungin) and compare the pharmacodynamic target among C. albicans, Candida glabrata, and Candida parapsilosis. Treatment studies were conducted with six C. albicans, nine C. glabrata, and 15 C. parapsilosis strains with various MICs (anidulafungin, 0.015 to 4.0 microg/ml; caspofungin, 0.03 to 4.0 microg/ml; and micafungin, 0.008 to 1.0 microg/ml). Efficacy was closely tied to MIC and the 24-h AUC/MIC. Therapy against C. parapsilosis required more of each echinocandin on a mg/kg basis. Caspofungin required less drug on a mg/kg basis for efficacy against all of the organisms than did the other two drugs. However, the 24-h AUC/MIC targets were similar among the echinocandins when free drug concentrations were considered, suggesting the relevance of protein binding. The targets for C. parapsilosis (mean, 7) and C. glabrata (mean, 7) were significantly lower than those for C. albicans (mean, 20) for each echinocandin. The results suggest that current susceptibility breakpoints and the consideration of organism species in these determinations should be reexplored.

Topics: Anidulafungin; Animals; Antifungal Agents; Candida; Candida albicans; Candida glabrata; Candidiasis; Caspofungin; Echinocandins; Female; Kidney; Lipopeptides; Micafungin; Mice; Mice, Inbred ICR; Microbial Sensitivity Tests; Protein Binding; Species Specificity

Caspofungin is used for the treatment of acute invasive candidiasis and as salvage treatment for invasive aspergillosis. We report characteristics of isolates of Candida albicans and Aspergillus fumigatus detected in a patient with breakthrough infection complicating severe gastrointestinal surgery and evaluate the capability of susceptibility methods to identify candin resistance. The susceptibility of C. albicans to caspofungin and anidulafungin was investigated by Etest, microdilution (European Committee on Antibiotic Susceptibility Testing [EUCAST] and CLSI), disk diffusion, agar dilution, and FKS1 sequencing and in a mouse model. Tissue was examined by immunohistochemistry, PCR, and sequencing for the presence of A. fumigatus and resistance mutations. The MICs for the C. albicans isolate were as follows: >32 microg/ml caspofungin and 0.5 microg/ml anidulafungin by Etest, 2 microg/ml caspofungin and 0.125 microg/ml anidulafungin by EUCAST methods, and 1 microg/ml caspofungin and 0.5 microg/ml anidulafungin by CLSI methods. Sequencing of the FKS1 gene revealed a mutation leading to an S645P substitution. Caspofungin and anidulafungin failed to reduce kidney CFU counts in animals inoculated with this isolate (P > 0.05 compared to untreated control animals), while both candins completely sterilized the kidneys in animals infected with a control isolate. Disk diffusion and agar dilution methods clearly separated the two isolates. Immunohistochemistry and sequencing confirmed the presence of A. fumigatus without FSK1 resistance mutations in liver and lung tissues. Breakthrough disseminated aspergillosis and candidiasis developed despite an absence of characteristic FKS1 resistance mutations in the Aspergillus isolates. EUCAST and CLSI methodology did not separate the candin-resistant clinical isolate from the sensitive control isolate as well as did the Etest and agar methods.

Topics: Animals; Antifungal Agents; Aspergillosis; Aspergillus fumigatus; Candida albicans; Candidiasis; Caspofungin; Colony Count, Microbial; Echinocandins; Humans; Immunohistochemistry; Injections, Intraperitoneal; Lipopeptides; Mice; Mice, Inbred Strains; Microbial Sensitivity Tests; Polymerase Chain Reaction

This study retrospectively reviews the susceptibility of 135 baseline ICU candidemia isolates (from 1997 to 2007) to nine antifungals as determined by the AFST-EUCAST microdilution method and identifies the most frequent causative agents of confirmed point-source candidemia outbreaks in local intensive care units. A minority of common and rare Candida species displayed decreased susceptibility to all antifungals.

Topics: Antifungal Agents; Candida; Candidiasis; Data Collection; Disease Susceptibility; Greece; Humans; Intensive Care Units; Microbial Sensitivity Tests; Retrospective Studies

Candida dubliniensis commonly shows paradoxical or trailing growth effects in vitro in the presence of echinocandins. We tested the in vitro activities of anidulafungin, caspofungin, and micafungin against clinical isolates of C. dubliniensis and evaluated the efficacy of these drugs in two murine models of systemic infection. The three echinocandins were similarly effective in the treatment of experimental disseminated infections with C. dubliniensis strains showing or not showing abnormal growth in vitro.

Topics: Anidulafungin; Animals; Antifungal Agents; Candida; Candidiasis; Caspofungin; Echinocandins; Lipopeptides; Male; Micafungin; Mice

We evaluated the effects of sequential therapy with caspofungin (CAS) or amphotericin B (AMB) followed by posaconazole (POS) against Candida glabrata. The susceptibilities to POS of yeast cells pre-exposed to CAS or AMB were identical to those of untreated cells as shown by standard Clinical and Laboratory Standards Institute broth dilution, cell viability, and disk diffusion methods. We then investigated the activity of sequential regimens in an experimental model of disseminated candidiasis. CAS given at 1 mg/kg/day for 2 days followed by POS at either 15 or 30 mg/kg/day significantly reduced the counts compared to the controls, but this treatment was not superior to the use of CAS alone. Also, sequential regimens with AMB given at 1 mg/kg/day for 2 days followed by POS (AMB/POS) were effective at reducing the fungal burden against the controls. In addition, AMB/POS with both doses of the triazole were significantly more effective than AMB alone. Overall, our data showed that there is no therapeutic advantage in using CAS followed by POS, whereas an induction therapy with AMB followed by a maintenance regimen with POS might be a suitable strategy in managing C. glabrata infections.

Topics: Amphotericin B; Animals; Antifungal Agents; Candida glabrata; Candidiasis; Caspofungin; Colony Count, Microbial; Drug Administration Schedule; Echinocandins; Humans; Kidney; Lipopeptides; Male; Mice; Microbial Sensitivity Tests; Treatment Outcome; Triazoles

Mechanism-based pharmacokinetic-pharmacodynamic (PK-PD) models describing the fungistatic activity of fluconazole and the fungicidal activity of caspofungin were developed using dynamic in vitro models. Antifungal-drug pharmacokinetics was simulated in vitro, assuming a one-compartment model with an elimination half-life of 3 h and using a wide (1 to 10,000) range of initial concentrations. The number of CFUs over time was determined for up to 31 h and used for PK-PD modeling. A model incorporating first-order natural growth and natural death, plus a maximum number of viable Candida cells, was used to characterize Candida growth in the absence of a drug. Fluconazole was considered to inhibit Candida growth and caspofungin to stimulate Candida death according to an Emax pharmacodynamic model. The data were analyzed with Nonmem, using a population approach. A good fit of the data was obtained with satisfactory estimates of PK-PD parameters, especially with drug concentrations producing 50% of the maximal effect: 50% inhibitory concentrations for fluconazole growth inhibition and 50% effective concentrations for caspofungin death stimulation. In conclusion, mechanistic PK-PD models were successfully developed to describe, respectively, the fungistatic and fungicidal activities of fluconazole and caspofungin in vitro. These models provide much better information on the drug effects over time than the traditional PK-PD index based on MICs. However, they need to be further characterized.

Topics: Antifungal Agents; Candida albicans; Candidiasis; Caspofungin; Colony Count, Microbial; Dose-Response Relationship, Drug; Drug Resistance, Fungal; Echinocandins; Fluconazole; Humans; Lipopeptides; Microbial Sensitivity Tests; Models, Biological

We describe the prevalences and susceptibility profiles of two recently described species, Candida metapsilosis and Candida orthopsilosis, related to Candida parapsilosis in candidemia. The prevalences of these species (1.7% for C. metapsilosis and 1.4% for C. orthopsilosis) are significant. Differences observed in their susceptibility profiles could have therapeutic importance.

Topics: Antifungal Agents; Candida; Candidiasis; Fungemia; Humans; Microbial Sensitivity Tests; Population Surveillance; Prevalence; Spain; Species Specificity

We describe a case of recurring Candida glabrata infection in a 68-year-old African-American female on caspofungin therapy. The initial isolate was susceptible, but isolates recovered during following relapses were not. All isolates were clonal, and high-MIC strains contained a mutation in the highly conserved hot spot 1 region of Fks1p.

Topics: Aged; Antifungal Agents; Candida glabrata; Candidiasis; Caspofungin; Drug Resistance, Fungal; Echinocandins; Fatal Outcome; Female; Fungal Proteins; Fungemia; Glucosyltransferases; Humans; Lipopeptides; Membrane Proteins; Microbial Sensitivity Tests; Mutation

We tested the activity of anidulafungin against 30 Candida albicans isolates. The planktonic MICs for 50 and 90% of the isolates tested (MIC(50) and MIC(90)) were < or =0.03 and 0.125 microg/ml, respectively (MIC range, < or =0.03 to 2 microg/ml). The sessile MIC(50) and MIC(90) were < or =0.03 and < or =0.03 microg/ml, respectively (MIC range, < or =0.03 to >16 microg/ml).

Topics: Anidulafungin; Antifungal Agents; Biofilms; Candida albicans; Candidiasis; Drug Resistance, Fungal; Echinocandins; Humans; Microbial Sensitivity Tests

We investigated the in vitro activities of posaconazole (POS), fluconazole (FLC), amphotericin B (AMB), and caspofungin (CAS) against four clinical isolates of Candida glabrata with various susceptibilities to FLC (FLC MICs ranging from 1.0 to >64 microg/ml). POS MICs ranged from < or =0.03 to 0.5 microg/ml; AMB MICs ranged from 0.25 to 2.0 microg/ml, while CAS MICs ranged from 0.03 to 0.25 microg/ml. When FLC MICs increased, so did POS MICs, although we did not observe any isolate with a POS MIC greater than 0.5 mug/ml. Time-kill experiments showed that POS, FLC, and CAS were fungistatic against all isolates, while AMB at eight times the MIC was fungicidal against three out of four isolates of C. glabrata tested. Then, we investigated the activity of POS in an experimental model of disseminated candidiasis using three different isolates of C. glabrata: one susceptible to FLC (S; FLC MICs ranging from 1.0 to 4.0 microg/ml; POS MIC of < or =0.03 microg/ml), one susceptible in a dose-dependent manner (SDD; FLC MICs ranging from 32 to 64 microg/ml; POS MICs ranging from 0.125 to 0.25 microg/ml), and another one resistant to FLC (R; FLC MIC of >64 microg/ml; POS MIC of 0.5 microg/ml). FLC significantly reduced the kidney burden of mice infected with the S strain (P = 0.0070) but not of those infected with the S-DD and R strains. POS was significantly effective against all three isolates at reducing the kidney fungal burden with respect to the controls (P ranging from 0.0003 to 0.029). In conclusion, our data suggest that POS may be a useful option in the management of systemic infections caused by C. glabrata. Additionally, the new triazole may be a therapeutic option in those cases where an FLC-resistant isolate is found to retain a relatively low POS MIC.

Topics: Animals; Antifungal Agents; Candida glabrata; Candidiasis; Drug Resistance, Fungal; Fluconazole; Humans; Kidney; Male; Mice; Microbial Sensitivity Tests; Treatment Outcome; Triazoles

Candida parapsilosis has emerged as a common cause of invasive fungal infection, especially in Latin America and in the neonatal setting. C. parapsilosis is part of a closely related group of organisms that includes the species Candida orthopsilosis and Candida metapsilosis. All three species show elevated MICs for the new echinocandin class drugs caspofungin, micafungin, and anidulafungin relative to other Candida species. Despite potential impacts on therapy, the mechanism behind this reduced echinocandin susceptibility has not been determined. In this report, we investigated the role of a naturally occurring Pro-to-Ala substitution at amino acid position 660 (P660A), immediately distal to the highly conserved hot spot 1 region of Fks1p, in the reduced-echinocandin-susceptibility phenotype. Kinetic inhibition studies demonstrated that glucan synthase from the C. parapsilosis group was 1 to 2 logs less sensitive to echinocandin drugs than the reference enzyme from C. albicans. Furthermore, clinical isolates of C. albicans and C. glabrata which harbor mutations at this equivalent position also showed comparable 2-log decreases in target enzyme sensitivity, which correlated with increased MICs. These mutations also resulted in 2.4- to 18.8-fold-reduced V(max) values relative to those for the wild-type enzyme, consistent with kinetic parameters obtained for C. parapsilosis group enzymes. Finally, the importance of the P660A substitution for intrinsic resistance was confirmed by engineering an equivalent P647A mutation into Fks1p of Saccharomyces cerevisiae. The mutant glucan synthase displayed characteristic 2-log decreases in sensitivity to the echinocandin drugs. Overall, these data firmly indicate that a naturally occurring P660A substitution in Fks1p from the C. parapsilosis group accounts for the reduced susceptibility phenotype.

Topics: Amino Acid Sequence; Amino Acid Substitution; Antifungal Agents; Base Sequence; Candida; Candidiasis; DNA Primers; DNA, Fungal; Drug Resistance, Fungal; Echinocandins; Enzyme Inhibitors; Fungal Proteins; Gene Expression; Genes, Fungal; Glucosyltransferases; Humans; Membrane Proteins; Molecular Sequence Data; Mutagenesis, Site-Directed; Saccharomyces cerevisiae Proteins; Sequence Homology, Amino Acid; Species Specificity

This study assessed the tissue distribution of anidulafungin in rats. Anidulafungin rapidly distributed into tissues, achieving peak concentrations within 30 min, and maintained levels above MICs for common pathogens over 72 h. In tissues susceptible to fungal infection (liver, lung, spleen, kidney), exposure was 9- to 12-fold higher than in plasma.

Topics: Anidulafungin; Animals; Antifungal Agents; Autoradiography; Candidiasis; Carbon Radioisotopes; Echinocandins; Humans; Infusions, Intravenous; Kidney; Liver; Lung; Male; Rats; Rats, Inbred F344; Spleen; Tissue Distribution

We report a case of Candida glabrata invasive candidiasis that developed reduced susceptibility to caspofungin during prolonged therapy. Pre- and posttreatment isolates were confirmed to be isogenic, and sequencing of hot spots known to confer echinocandin resistance revealed an F659V substitution within the FKS2 region of the glucan synthase complex.

Topics: Adult; Amino Acid Substitution; Antifungal Agents; Base Sequence; Candida glabrata; Candidiasis; Caspofungin; DNA Primers; DNA, Fungal; Drug Resistance, Fungal; Echinocandins; Genes, Fungal; Glucosyltransferases; Humans; Lipopeptides

Pyrosequencing was compared to Sanger dideoxy sequencing to detect mutations in FKS1 responsible for reduced echinocandin susceptibility in Candida albicans. These methods were in complete agreement for 10 of 12 clinical isolates with elevated echinocandin MICs, supporting the potential feasibility of pyrosequencing to detect mutations within diploid fungi.

Topics: Anidulafungin; Antifungal Agents; Base Sequence; Candida albicans; Candidiasis; Caspofungin; DNA Mutational Analysis; DNA, Fungal; Drug Resistance, Fungal; Echinocandins; Genes, Fungal; Glucosyltransferases; Humans; Lipopeptides; Micafungin; Point Mutation

We identified three cases of C. tropicalis strains causing breakthrough fungemia in allogeneic stem cell recipients receiving caspofungin prophylaxis and treatment. Three genetically unrelated isolates with high echinocandin MICs were identified. Each strain carried a characteristic mutation conferring an amino acid substitution within Fks1p hot spot 1.

Topics: Aged; Aged, 80 and over; Antifungal Agents; Candida tropicalis; Candidiasis; Caspofungin; Drug Resistance, Fungal; Echinocandins; Fungemia; Hematologic Neoplasms; Humans; Lipopeptides; Male; Middle Aged

Little information is available about the molecular mechanisms responsible for polyene resistance in pathogenic yeasts. A clinical isolate of Candida glabrata with a poor susceptibility to polyenes, as determined by disk diffusion method and confirmed by determination of MIC, was recovered from a patient treated with amphotericin B. Quantitative analysis of sterols revealed a lack of ergosterol and an accumulation of late sterol intermediates, suggesting a defect in the final steps of the ergosterol pathway. Sequencing of CgERG11, CgERG6, CgERG5, and CgERG4 genes revealed exclusively a unique missense mutation in CgERG6 leading to the substitution of a cysteine by a phenylalanine in the corresponding protein. In addition, real-time reverse transcription-PCR demonstrated an overexpression of genes encoding enzymes involved in late steps of the ergosterol pathway. Moreover, this isolate exhibited a pseudohyphal growth whatever the culture medium used, and ultrastructural changes of the cell wall of blastoconidia were seen consisting in a thinner inner layer. Cell wall alterations were also suggested by the higher susceptibility of growing cells to Calcofluor white. Additionally, complementation of this isolate with a wild-type copy of the CgERG6 gene restored susceptibility to polyenes and a classical morphology. Together, these results demonstrated that mutation in the CgERG6 gene may lead to a reduced susceptibility to polyenes and to a pseudohyphal growth due to the subsequent changes in sterol content of the plasma membrane.

Topics: Antifungal Agents; Candida glabrata; Candidiasis; DNA Primers; Genes, Fungal; Genetic Complementation Test; Methyltransferases; Microbial Sensitivity Tests; Molecular Sequence Data; Mutation, Missense; Phenotype; Polyenes; Reverse Transcriptase Polymerase Chain Reaction; RNA, Fungal; RNA, Messenger; Sterols

Candida parapsilosis has emerged as an important nosocomial pathogen. In the present study, a checkerboard broth microdilution method was performed to investigate the in vitro activities of caspofungin (CAS) in combination with amphotericin B (AMB) against three clinical isolates of C. parapsilosis. Although there was a significant reduction of the MIC of one or both drugs used in combination, an indifferent interaction (fractional inhibitory concentration index greater than 0.50 and less than or equal to 4.0) was observed in 100% of cases. This finding was confirmed by killing curve studies. By a disk diffusion assay, the halo diameters produced by antifungal agents in combination were often significantly greater than those produced by each drug alone. Antagonism was never observed. In a murine model of systemic candidiasis, CAS at either 0.25 or 1 mg/kg/day combined with AMB at 1 mg/kg/day was significantly more effective than each single drug at reducing the colony counts in kidneys. Higher doses of the echinocandin (i.e., 5 and 10 mg/kg/day) combined with the polyene did not show any advantage over CAS alone. Overall, our study showed a positive interaction of CAS and AMB against C. parapsilosis.

Topics: Amphotericin B; Animals; Antifungal Agents; Candida; Candidiasis; Caspofungin; Colony Count, Microbial; Drug Combinations; Echinocandins; Kidney; Lipopeptides; Male; Mice; Microbial Sensitivity Tests; Peptides, Cyclic

In vitro studies have demonstrated that anidulafungin has greater potency than caspofungin against Candida glabrata. However, data from in vivo studies demonstrating that it has superior efficacy are lacking. The objective of this study was to compare the activities of anidulafungin and caspofungin against C. glabrata in a murine model of disseminated candidiasis. Two clinical C. glabrata isolates were used, including one with reduced caspofungin susceptibility. MICs were determined by broth microdilution in the presence and absence of sera. For the animal studies, mice were immunosuppressed with 5-fluorouracil one day prior to intravenous inoculation. Treatment with anidulafungin and caspofungin (0, 0.5, 1, 5, and 10 mg/kg of body weight per day) was begun 24 h later and was continued through day 7 postinoculation. The CFU were enumerated from kidney tissue. According to the standard microdilution methodology, anidulafungin had superior in vitro activity. However, this enhanced potency was attenuated by the addition of mouse and human sera. Caspofungin reduced the kidney fungal burden at lower doses compared to that achieved with anidulafungin in mice infected with the isolate with the lower MIC. Against the strain with the elevated caspofungin MIC, both anidulafungin and caspofungin were effective in reducing the kidney fungal burden at the higher doses studied. Despite the greater in vitro activity of anidulafungin in the absence of sera, both echinocandins were similarly effective in reducing the fungal burden in kidney tissue. The superior in vitro activity of anidulafungin did not confer enhanced in vivo efficacy against C. glabrata.

Topics: Anidulafungin; Animals; Antifungal Agents; Candida glabrata; Candidiasis; Caspofungin; Echinocandins; Lipopeptides; Mice; Mice, Inbred ICR; Microbial Sensitivity Tests; Peptides, Cyclic; Serum

Paradoxical growth of some Candida isolates occurs at concentrations above the MIC for echinocandins. In 60 Candida bloodstream isolates from cancer patients (20 C. albicans isolates and 10 isolates each of C. parapsilosis, C. tropicalis, C. krusei, and C. glabrata), paradoxical growth was more frequent with caspofungin than micafungin or anidulafungin, was unrelated to MIC, and was strikingly absent in C. glabrata isolates.

Topics: Antifungal Agents; Candida; Candidiasis; Culture Media; Fungemia; Humans; Microbial Sensitivity Tests; Neoplasms; Peptides, Cyclic; Species Specificity

The paradoxical growth (PG) of Candida sp. biofilms in the presence of high caspofungin (CAS) concentrations was previously unknown. We sought to characterize the PG at supra-MICs of CAS among clinical Candida sp. isolates grown as biofilms in 96-well polystyrene microtiter plates. The MICs of CAS were determined for 30 clinical Candida sp. isolates (4 Candida albicans, 6 C. tropicalis, 7 C. parapsilosis, 8 C. orthopsilosis, and 5 C. metapsilosis isolates) when they were grown as planktonic cells and biofilms and were defined as the lowest drug concentrations that resulted in a prominent decrease in growth and a 50% reduction in metabolic activity, respectively. PG was defined as a resurgence of growth (>50% of that in the drug-free growth control well) at drug concentrations above the MIC. With the exception of C. tropicalis, all isolates displayed PG more frequently when they were grown as biofilms than when they grown as planktonic cells. PG was undetectable among C. metapsilosis isolates in planktonic cell MIC tests but was present in 100% of the isolates in biofilm MIC tests. The drug concentration and the number of drug dilutions supporting PG were higher for biofilms than for planktonic cells. Microscopic changes in cell morphology were observed among both planktonic and biofilm cells with PG. Specifically, the accumulation of enlarged, globose cells was associated with PG, and we hypothesize that CAS-induced changes in the cell wall composition may be the explanation.

Topics: Antifungal Agents; Biofilms; Candida; Candidiasis; Caspofungin; Echinocandins; Lipopeptides; Microbial Sensitivity Tests; Risk; Tetrazolium Salts