Selection of a surrogate agent (fluconazole or voriconazole) for initial susceptibility testing of posaconazole against Candida spp.: results from a global antifungal surveillance program

Screening the in vitro susceptibility of posaconazole in clinical isolates of Candida spp. and Aspergillus spp. and analyzing the sequence of ERG11 or CYP51A in non-wild-type isolates from China

The present study was to determine the in vitro activity of posaconazole (POS) against 385 Candida and 268 Aspergillus clinical isolates from China. We found that POS was active against 85.5% Candida and 94.4% Aspergillus isolates. Non-wild-type (non-WT) phenotype was found in a subset of Candida albicans (15.4%), Candida tropicalis (11.9%), Aspergillus fumigatus (4.1%), and Aspergillus flavus (17.4%) isolates. Cross-resistance to POS and other triazoles was seen. Gene sequencing showed that 4 C. albicans, 1 C. tropicalis, and 9 A. fumigatus isolates with cross-resistance to POS and other triazoles had mutations in ERG11 or CYP51A. In conclusion, POS has potent in vitro activity against most of Candida and Aspergillus isolates from China. Non-WT phenotype and those with cross-resistance to POS and other triazoles exist, frequently driven by mutations of ERG11 in Candida spp. and CYP51A in Aspergillus spp.

Cysteine-Rich Antifungal Proteins from Filamentous Fungi are Promising Bioactive Natural Compounds in Anti-Candida Therapy

The emerging number of life-threatening invasive fungal infections caused by drug-resistant Candida strains urges the need for the development and application of fundamentally new and safe antifungal strategies in the clinical treatment. Recent studies demonstrated that the extracellular cysteine-rich and cationic antifungal proteins (crAFPs) originating from filamentous fungi, and de novo designed synthetic peptide derivatives of these crAFPs provide a feasible basis for this approach. This mini-review focuses on the global challenges of the anti-Canidia therapy and on the crAFPs as potential drug candidates to overcome existing problems. The advantages and limitations in the use of crAFPs and peptide derivatives compared to those of conventional antifungal drugs will also be critically discussed.

Drug susceptibility profile of Candida glabrata clinical isolates from Iran and genetic resistant mechanisms to caspofungin

BACKGROUND

Candida glabrata is a yeast that can cause hazardous fungal infections with high mortality and drug resistance.

AIMS

The aim of this study was to determine the profile of drug susceptibility in clinical isolates of C. glabrata and review the resistance mechanisms to caspofungin.

METHODS

A total of 50 C. glabrata clinical isolates from Iran were tested for in vitro susceptibilities to amphotericin B, caspofungin, fluconazole and voriconazole. To investigate the mechanism of resistance to caspofungin, hotspot areas of FKS1 and FKS2 genes were sequenced and gene expression profile was evaluated.

RESULTS

All the isolates were susceptible to amphotericin B and caspofungin. Fluconazole resistance was exhibited in four isolates. In addition, only one isolate was resistant to voriconazole. FKS2 with 12 point mutations showed more mutations compared to FKS1 that had only two mutations. All substitutions were synonymous. FKS genes were expressed at comparable levels (no statistical significance) in caspofungin-treated and non-treated cultures.

CONCLUSIONS

The silent mutations in the hotspot areas of FKS genes and inconsiderable changes in gene expression were not associated with increased MIC (0.25μg/ml). Other mechanisms of resistance which include mutations outside the hotspot area of FKS genes could be involved in a slight increase of MIC, and they should be identified through complete FKS gene sequencing.

Activity of Combined Antifungal Agents Against Multidrug-Resistant Candida glabrata Strains

In this study, we evaluated the in vitro activity of echinocandins, azoles, and amphotericin B alone and in combination against echinocandin/azole-sensitive and echinocandin/azole-resistant Candida glabrata isolates. Susceptibility tests were performed using the broth microdilution method in accordance with the Clinical and Laboratory Standards Institute document M27-A3. The checkerboard method was used to evaluate the fractional inhibitory concentration index of the interactions. Cross-resistance was observed among echinocandins; 15% of the isolates resistant to caspofungin were also resistant to anidulafungin and micafungin. Synergistic activity was observed in 70% of resistant C. glabrata when anidulafungin was combined with voriconazole or posaconazole. Higher (85%) synergism was found in the combination of caspofungin and voriconazole. The combinations of caspofungin with fluconazole, posaconazole and amphotericin B, micafungin with fluconazole, posaconazole and voriconazole, and anidulafungin with amphotericin B showed indifferent activities for the majority of the isolates. Anidulafungin combined with fluconazole showed the same percentage of synergism and indifference (45%). Antagonism was detected in 50% of isolates when micafungin was combined with amphotericin B. Combinations of echinocandins and antifungal azoles have great potential for in vivo assays which are required to evaluate the efficacy of these combinations against multidrug-resistant C. glabrata strains.

In Vitro Antifungal Susceptibility of Oral Candida Isolates from Patients Suffering from Caries and Chronic Periodontitis

Caries and chronic periodontitis are common oral diseases where a higher Candida colonization is reported. Antifungal agents could be adjuvant drugs for the therapy of both clinical conditions. The aim of the current study has been to evaluate the in vitro activities of conventional and new antifungal drugs against oral Candida isolates from patients suffering from caries and/or chronic periodontitis. In vitro activities of amphotericin B, fluconazole, itraconazole, miconazole, nystatin, posaconazole and voriconazole against 126 oral Candida isolates (75 Candida albicans, 18 Candida parapsilosis, 11 Candida dubliniensis, six Candida guilliermondii, five Candida lipolytica, five Candida glabrata, four Candida tropicalis and two Candida krusei) from 61 patients were tested by the CLSI M27-A3 method. Most antifungal drugs were highly active, and resistance was observed in less than 5% of tested isolates. Miconazole was the most active antifungal drug, being more than 98% of isolates susceptible. Fluconazole, itraconazole, and the new triazoles, posaconazole and voriconazole, were also very active. Miconazole, fluconazole and voriconazole have excellent in vitro activities against all Candida isolates and could represent suitable treatment for a hypothetically adjunctive therapy of caries and chronic periodontitis.

Parallel and cross-resistances of clinical yeast isolates determined by susceptibility pattern analysis

For calculated initial antifungal therapy, knowledge on parallel and cross-resistances are vitally important particularly in the case of multiresistant isolates. Based on a strain collection of 1,062 yeast isolates from a German/Austrian multicentre study, susceptibility pattern analysis (SPA) was used to determine the proportion of parallel and cross-resistances to eight antifungal agents (AFAs) encompassing flucytosine, amphotericin B, azoles (fluconazole, voriconazole and posaconazole) and echinocandins (caspofungin, micafungin and anidulafungin). A total of 414 (39.0%) isolates were resistant for one or more of the AFAs. Resistance to one AFA was shown for 18.1% of all isolates. For 222 isolates (20.9%), resistance to two to seven AFAs was noted (7.7%; 7.7%; 3.6%; 1.0%; 0.7% and 0.2% to 2, 3, 4, 5, 6 and 7 antifungal compounds, respectively). Partial parallel resistances within the azole and echinocandin classes, respectively, were found for 81 (7.6%) and 70 (6.6%) isolates. Complete parallel resistances for azoles, echinocandins and combined for both classes were exhibited by 93 (8.8%), 18 (1.7%) and 6 (0.6%) isolates, respectively. Isolates displaying cross-resistances between azoles and echinocandins were infrequently found. Highly resistant isolates (resistance to ≥6 AFAs) were almost exclusively represented by Candida albicans. Highly standardized testing of AFAs in parallel and from the same inocula followed by SPA allows detailed insights in the prevalence and distribution of susceptibility patterns of microbial isolates.

Clotrimazole Drug Resistance in Candida glabrata Clinical Isolates Correlates with Increased Expression of the Drug:H(+) Antiporters CgAqr1, CgTpo1_1, CgTpo3, and CgQdr2

For years, antifungal drug resistance in Candida species has been associated to the expression of ATP-Binding Cassette (ABC) multidrug transporters. More recently, a few drug efflux pumps from the Drug:H(+) Antiporter (DHA) family have also been shown to play a role in this process, although to date only the Candida albicans Mdr1 transporter has been demonstrated to be relevant in the clinical acquisition of antifungal drug resistance. This work provides evidence to suggest the involvement of the C. glabrata DHA transporters CgAqr1, CgQdr2, CgTpo1_1, and CgTpo3 in the clinical acquisition of clotrimazole drug resistance. A screening for azole drug resistance in 138 C. glabrata clinical isolates, from patients attending two major Hospitals in Portugal, was performed. Based on this screening, 10 clotrimazole susceptible and 10 clotrimazole resistant isolates were selected for further analysis. The transcript levels of CgAQR1, CgQDR2, CgTPO1_1, and CgTPO3 were found to be significantly up-regulated in resistant isolates when compared to the susceptible ones, with a level of correlation that was found to be similar to that of CgCDR2, an ABC gene known to be involved in the clinical acquisition of resistance. As a proof-of-concept experiment, the CgTPO3 gene was deleted in an azole resistant C. glabrata isolate, exhibiting high levels of expression of this gene. The deletion of CgTPO3 in this isolate was found to lead to decreased resistance to clotrimazole and fluconazole, and increased accumulation of azole drugs, thus suggesting the involvement of this transporter in the manifestation of azole resistance.

In Vitro Susceptibilities of Candida albicans Isolates to Antifungal Agents in Tokat, Turkey

Background:

Candida albicans is the pathogenic species most commonly isolated from fungal infections. Management of these infections depends on the immune status of the host, severity of disease, and the choice of antifungal drug. In spite of the development of new antifungal drugs, epidemiological studies have shown that resistance to antifungal drugs in C. albicans strains is becoming a serious problem.

Objectives:

The aim of this study was to evaluate the in vitro susceptibility of C. albicans isolates to ketoconazole, fluconazole, itraconazole, voriconazole, posaconazole, amphotericin B, caspofungin, and anidulafungin.

Materials and Methods:

A total of 201 C. albicans isolates were collected from clinical specimens. Antifungal susceptibility tests were performed using the Etest.

Results:

All the tested C. albicans isolates were found to be susceptible to amphotericin B and anidulafungin. Although none of the isolates showed resistance to caspofungin, 15% of the isolates were classified as showing intermediate resistance. The resistance rates of C. albicans isolates to ketoconazole, fluconazole, itraconazole, voriconazole and posaconazole were 32%, 34%, 21%, 14% and 14%, respectively.

Conclusions:

Our findings indicate that resistance of C. albicans strains to azoles is more common in Tokat, Turkey. Therefore, a strategy to control the inappropriate and widespread use of antifungal drugs is urgently needed. Fungal culturing and antifungal susceptibility testing will be useful in patient management as well as resistance surveillance.

In Vitro Susceptibilities of Candida albicans Isolates to Antifungal Agents in Tokat, Turkey

BACKGROUND

Candida albicans is the pathogenic species most commonly isolated from fungal infections. Management of these infections depends on the immune status of the host, severity of disease, and the choice of antifungal drug. In spite of the development of new antifungal drugs, epidemiological studies have shown that resistance to antifungal drugs in C. albicans strains is becoming a serious problem.

OBJECTIVES

The aim of this study was to evaluate the in vitro susceptibility of C. albicans isolates to ketoconazole, fluconazole, itraconazole, voriconazole, posaconazole, amphotericin B, caspofungin, and anidulafungin.

MATERIALS AND METHODS

A total of 201 C. albicans isolates were collected from clinical specimens. Antifungal susceptibility tests were performed using the Etest.

RESULTS

All the tested C. albicans isolates were found to be susceptible to amphotericin B and anidulafungin. Although none of the isolates showed resistance to caspofungin, 15% of the isolates were classified as showing intermediate resistance. The resistance rates of C. albicans isolates to ketoconazole, fluconazole, itraconazole, voriconazole and posaconazole were 32%, 34%, 21%, 14% and 14%, respectively.

CONCLUSIONS

Our findings indicate that resistance of C. albicans strains to azoles is more common in Tokat, Turkey. Therefore, a strategy to control the inappropriate and widespread use of antifungal drugs is urgently needed. Fungal culturing and antifungal susceptibility testing will be useful in patient management as well as resistance surveillance.

Isavuconazole, a broad-spectrum triazole for the treatment of systemic fungal diseases

The prodrug isavuconazonium sulfate (BAL8557) is an extended-spectrum water-soluble triazole, developed for the treatment of severe invasive and life-threatening fungal diseases. Its active moiety, BAL4815, is a potent inhibitor of ergosterol biosynthesis, resulting in the disruption of fungal membrane structure and function. The active compound shows broad-spectrum of activity and potency against all major opportunistic fungi, such as Aspergillus spp., Candida spp., Cryptococcus spp., Mucorales, Black yeasts and their filamentous relatives and the true pathogenic fungi, including Histoplasma capsulatum and Blastomyces dermatitidis. It is currently in Phase III clinical development for treatment of aspergillosis, candidiasis and mucormycosis, as well as other rare fungi infections. We reviewed the pharmacokinetic and pharmacodynamic characteristics of isavuconazole, and its microbiological and clinical investigation progress in advanced stages of development.

Advances in the treatment of invasive neonatal candidiasis

INTRODUCTION

Invasive candidiasis is responsible for ∼ 10% of nosocomial sepsis in very-low-birth-weight infants and is associated with substantial morbidity and mortality. Over the last two decades, the antifungal armamentarium against Candida spp. has increased; however, efficacy and safety studies in this population are lacking.

AREAS COVERED

We reviewed the medical literature and extracted information on clinical and observational studies evaluating the use of antifungal agents in neonates with invasive candidiasis.

EXPERT OPINION

Efficacy and safety data for antifungals in neonates are lacking, and the majority of studies conducted to date have concentrated on pharmacokinetic/pharmacodynamic evaluations. Unlike other anti-infective agents, efficacy data in the setting of neonatal candidiasis cannot be extrapolated from adult studies due to differences in the pathophysiology of the disease in this population relative to older children and adults. Data for amphotericin B deoxycholate, fluconazole, and micafungin suggest that these are the current agents of choice for this disease in neonates until data for newer antifungal agents become available. For prophylaxis, data from fluconazole randomized controlled trials will be submitted to the regulatory agencies for labeling. Ultimately, the field of therapeutics for neonatal candidiasis will require multidisciplinary collaboration given the numerous challenges associated with conducting clinical trials in neonates.

Use of linezolid susceptibility test results as a surrogate for the susceptibility of Gram-positive pathogens to tedizolid, a novel oxazolidinone

Background

Tedizolid is a novel oxazolidinone antibacterial with potent activity against a wide range of Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. Although tedizolid is approved by the US Food and Drug Administration (FDA) for treatment of patients with acute bacterial skin and skin structure infection, commercial susceptibility testing products for tedizolid are not currently available. This study evaluated the usefulness of applying linezolid susceptibility test results as a surrogate for predicting susceptibility to tedizolid in clinically significant Gram-positive pathogens.

Methods

Gram-positive isolates (N = 10,702) were obtained from annual surveillance programs conducted between 2009 and 2012, from 3 tedizolid clinical trials, and from a preclinical study of the antibacterial activity of tedizolid. Susceptibility testing of linezolid and tedizolid was performed using the reference broth microdilution method in accordance with Clinical and Laboratory Standards Institute methods.

Results

The minimum inhibitory concentration (MIC) distribution for tedizolid and linezolid against this set of isolates was consistent with that of previous reports. Scatter plot analysis of relevant subsets of organisms was performed and showed high categorical agreement between linezolid and tedizolid MIC results (>99% for staphylococci and streptococci; >98% for enterococci). Very major error rates (ie, tedizolid false-susceptible errors) were very low and within acceptable limits for a surrogate agent: S. aureus and other staphylococcal species, 0%; Enterococcus spp, 0.2%; and Streptococcus spp, 0%.

Conclusions

High categorical agreement between MIC values for tedizolid and linezolid and low very major error rates were shown for all organism groups tested, supporting the use of linezolid as a reliable surrogate for tedizolid susceptibility testing.

Isavuconazole and nine comparator antifungal susceptibility profiles for common and uncommon Candida species collected in 2012: application of new CLSI clinical breakpoints and epidemiological cutoff values

The in vitro activity of isavuconazole and nine antifungal comparator agents was assessed using reference broth microdilution methods against 1,421 common and uncommon species of Candida from a 2012 global survey. Isolates were identified using CHROMagar, biochemical methods and sequencing of ITS and/or 28S regions. Candida spp. were classified as either susceptible or resistant and as wild type (WT) or non-WT using CLSI clinical breakpoints or epidemiological cutoff values, respectively, for the antifungal agents. Isolates included 1,421 organisms from 21 different species of Candida. Among Candida spp., resistance to all 10 tested antifungal agents was low (0.0-7.9 %). The vast majority of each species of Candida, with the exception of Candida glabrata, Candida krusei, and Candida guilliermondii (modal MICs of 0.5 µg/ml), were inhibited by ≤0.12 µg/ml of isavuconazole (99.0 %; range 94.3 % [Candida tropicalis] to 100.0 % [Candida lusitaniae and Candida dubliniensis]). C. glabrata, C. krusei, and C. guilliermondii were largely inhibited by ≤1 µg/ml of isavuconazole (89.7, 96.9 and 92.8 %, respectively). Decreased susceptibility to isavuconazole was most prominent with C. glabrata where the modal MIC for isavuconazole was 0.5 µg/ml for those strains that were SDD to fluconazole or WT to voriconazole, and was 4 µg/ml for those that were either resistant or non-WT to fluconazole or voriconazole, respectively. In conclusion, these data document the activity of isavuconazole and generally the low resistance levels to the available antifungal agents in a large, contemporary (2012), global collection of molecularly characterized species of Candida.

Impact of new antifungal breakpoints on antifungal resistance in Candida species

We reviewed our antifungal susceptibility data for micafungin, anidulafungin, fluconazole, and voriconazole against Candida species and compared resistance rates determined by the previous and recently revised CLSI antifungal breakpoints. With the new breakpoints, resistance was significantly increased for micafungin (from 0.8% to 7.6%), anidulafungin (from 0.9% to 7.3%), and voriconazole (from 6.1% to 18.4%) against Candida glabrata. Resistance was also increased for fluconazole against Candida albicans (from 2.1% to 5.7%).

Prevention of infection in cancer patients

Patients with cancer vary regarding the nature and level of immunocompromise. Both the underlying malignancy and therapy can influence risk of infectious complications. Therefore, decisions about antimicrobial prophylaxis must be guided by a number of factors: (1) the risk of infection; (2) the potential severity of infection and the likelihood of response to therapy; and (3) the safety and efficacy of antimicrobial prophylaxis. The potential for selection for antibiotic-resistant pathogens should also inform decisions about prophylaxis. When assessing clinical trial data on antimicrobial prophylaxis, two major criteria should be considered: the quality of studies supporting prophylaxis (randomized, blinded studies are optimal) and the expected benefit of prophylaxis, measured in terms of prevention of morbidity and potentially mortality. This chapter reviews the epidemiology and clinical trial data on prophylaxis against the major bacterial, viral, and fungal diseases in patients with cancer. Gaps in knowledge and alternative approaches, such as the use of newer diagnostics, are discussed.

Use of micafungin as a surrogate marker to predict susceptibility and resistance to caspofungin among 3,764 clinical isolates of Candida by use of CLSI methods and interpretive criteria

Due to unacceptably high interlaboratory variation in caspofungin MIC values, we evaluated the use of micafungin as a surrogate marker to predict the susceptibility of Candida spp. to caspofungin using reference methods and species-specific interpretive criteria. The MIC results for 3,764 strains of Candida (eight species), including 73 strains with fks mutations, were used. Caspofungin MIC values and species-specific interpretive criteria were compared with those of micafungin to determine the percent categorical agreement (%CA) and very major error (VME), major error (ME), and minor error rates as well as their ability to detect fks mutant strains of Candida albicans (11 mutants), Candida tropicalis (4 mutants), Candida krusei (3 mutants), and Candida glabrata (55 mutants). Overall, the %CA was 98.8% (0.2% VMEs and MEs, 0.8% minor errors) using micafungin as the surrogate marker. Among the 60 isolates of C. albicans (9 isolates), C. tropicalis (5 isolates), C. krusei (2 isolates), and C. glabrata (44 isolates) that were nonsusceptible (either intermediate or resistant) to both caspofungin and micafungin, 54 (90.0%) contained a mutation in fks1 or fks2. An additional 10 C. glabrata mutants, two C. albicans mutants, and one mutant each of C. tropicalis and C. krusei were classified as susceptible to both antifungal agents. Using the epidemiological cutoff values (ECVs) of 0.12 μg/ml for caspofungin and 0.03 μg/ml for micafungin to differentiate wild-type (WT) from non-WT strains of C. glabrata, 80% of the C. glabrata mutants were non-WT for both agents (96% concordance). Micafungin may serve as an acceptable surrogate marker for the prediction of susceptibility and resistance of Candida to caspofungin.

Echinocandin and triazole antifungal susceptibility profiles for clinical opportunistic yeast and mold isolates collected from 2010 to 2011: application of new CLSI clinical breakpoints and epidemiological cutoff values for characterization of geographic and temporal trends of antifungal resistance

The SENTRY Antimicrobial Surveillance Program monitors global susceptibility and resistance rates of newer and established antifungal agents. We report the echinocandin and triazole antifungal susceptibility patterns for 3,418 contemporary clinical isolates of yeasts and molds. The isolates were obtained from 98 laboratories in 34 countries during 2010 and 2011. Yeasts not presumptively identified by CHROMagar, the trehalose test, or growth at 42°C and all molds were sequence identified using internal transcribed spacer (ITS) and 28S (yeasts) or ITS, translation elongation factor (TEF), and 28S (molds) genes. Susceptibility testing was performed against 7 antifungals (anidulafungin, caspofungin, micafungin, fluconazole, itraconazole, posaconazole, and voriconazole) using CLSI methods. Rates of resistance to all agents were determined using the new CLSI clinical breakpoints and epidemiological cutoff value criteria, as appropriate. Sequencing of fks hot spots was performed for echinocandin non-wild-type (WT) strains. Isolates included 3,107 from 21 Candida spp., 146 from 9 Aspergillus spp., 84 from Cryptococcus neoformans, 40 from 23 other mold species, and 41 from 9 other yeast species. Among Candida spp., resistance to the echinocandins was low (0.0 to 1.7%). Candida albicans and Candida glabrata that were resistant to anidulafungin, caspofungin, or micafungin were shown to have fks mutations. Resistance to fluconazole was low among the isolates of C. albicans (0.4%), Candida tropicalis (1.3%), and Candida parapsilosis (2.1%); however, 8.8% of C. glabrata isolates were resistant to fluconazole. Among echinocandin-resistant C. glabrata isolates from 2011, 38% were fluconazole resistant. Voriconazole was active against all Candida spp. except C. glabrata (10.5% non-WT), whereas posaconazole showed decreased activity against C. albicans (4.4%) and Candida krusei (15.2% non-WT). All agents except for the echinocandins were active against C. neoformans, and the triazoles were active against other yeasts (MIC90, 2 μg/ml). The echinocandins and triazoles were active against Aspergillus spp. (MIC90/minimum effective concentration [MEC90] range, 0.015 to 2 μg/ml), but the echinocandins were not active against other molds (MEC90 range, 4 to >16 μg/ml). Overall, echinocandin and triazole resistance rates were low; however, the fluconazole and echinocandin coresistance among C. glabrata strains warrants continued close surveillance.

Posaconazole for the Treatment of Oropharyngeal Candidiasis, Including Triazole-Resistant Disease, in HIV-positive patients

Oropharyngeal candidiasis is a common affliction in HIV-positive patients worldwide. Although the incidence has decreased with the advent of potent antiviral combinations, it continues to be a cause of significant morbidity. Historically, fluconazole or itraconazole was the treatment of choice for oropharyngeal candidiasis, but increasing incidence of resistance and high recurrence rates mandate the use of alternative therapies. Posaconazole, a broad-spectrum second-generation triazole antifungal agent, has been studied in both first-line and salvage settings for treatment of oropharyngeal candidiasis. Posaconazole is well-tolerated, yields high response rates and demonstrates durable response rates with long-term use. This review will provide state-of-the-art knowledge of pharmacology and therapeutics of posaconazole focusing on the indication for oropharyngeal candidiasis in HIV-positive patients.

Prototheca wickerhamii as a cause of neuroinfection in a child with congenital hydrocephalus. First case of human protothecosis in Poland

This report describes a rare case of neuroinfection due to Prototheca wickerhamii in a child with severe, congenital hydrocephalus. The infection resolved completely after the patient was treated with oral ketoconazole, followed by intravenous fluconazole and amphotericin B. A probable source of infection was contamination during ventriculoperitoneal drain care procedures.

The cellular and molecular defense mechanisms of the Candida yeasts against azole antifungal drugs

The molecular mechanisms supporting resistance to azole antifungals have attracted a great interest during the last decades because of the emergence of clinical resistance to the treatment of fungal infections. The availability of genome sequencing data, of molecular biology tools, and of a large set of clinical and laboratory azole-resistant strains, made the yeasts Candida the biological material of choice to decipher azole resistance mechanisms. The yeast Candida albicans has several cellular ways to resist to azole drugs: decreased affinity of the target protein Erg11p for the drugs, increased biosynthesis of Erg11p, and efflux of the drugs outside the fungal cells. At the molecular level, two main mechanisms are operating: point mutation in the target gene or in transcriptional activator factors, eventually associated to a loss of heterozygosity, and gene duplication that results from the extraordinary plasticity of the genome. This review proposes to explore the different molecular strategies that are used by Candida yeasts to fight azole antifungals.

Fluconazole exposure rather than clonal spreading is correlated with the emergence of Candida glabrata with cross-resistance to triazole antifungal agents

The emergence of antifungal resistance in Candida species has raised concern in recent years, especially resistance toward triazole. Several newer triazole antifungal agents have been introduced which have a broader spectrum for fungal infections, such as voriconazole. However, cross-resistance among triazoles is a major concern with regard to their clinical application. Antifungal susceptibility was performed using E-test for 166 clinical isolates (29 blood and 137 nonblood isolates) in 2003 and 2004. We applied pulsed-field gel electrophoresis for genotyping. Ninety isolates of C. albicans, 47 isolates of C. tropicalis, 27 isolates of C. glabrata, and two isolates of C. krusei were included. All isolates were susceptible to amphotericin B. Eleven (40.7%) of the 27 C. glabrata had intermediate resistance to caspofungin. Forty-seven (28.3%) of the 166 isolates were not susceptible to fluconazole, including two C. albicans, 16 C. tropicalis, 27 C. glabrata, and two C. krusei isolates. All except seven of the C. glabrata isolates were susceptible to voriconazole. All the triazole drugs had a positive correlation among their minimum inhibitory concentrations (MICs). Fluconazole MIC was a good predictor for susceptibility to voriconazole, as determined using a receiver operating characteristic curve. Furthermore, a high diversity of pulsotypes for the 27 clinical isolates of C. glabrata was observed. Previous fluconazole exposure within 3 months was associated with reduced triazole susceptibility for C. glabrata. We demonstrated a significant positive correlation of MIC values among the four tested triazole drugs. No amphotericin B and caspofungin resistant isolates were found in this study. The cross-resistance to triazole among C. glabrata isolates was associated with previous fluconazole exposure as opposed to clonal spreading. Selection pressure due to fluconazole use may play a major role in triazole cross-resistance.

Antifungal drug resistance: mechanisms, epidemiology, and consequences for treatment

Antifungal resistance continues to grow and evolve and complicate patient management, despite the introduction of new antifungal agents. In vitro susceptibility testing is often used to select agents with likely activity for a given infection, but perhaps its most important use is in identifying agents that will not work, i.e., to detect resistance. Standardized methods for reliable in vitro antifungal susceptibility testing are now available from the Clinical and Laboratory Standards Institute (CLSI) in the United States and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) in Europe. Data gathered by these standardized tests are useful (in conjunction with other forms of data) for calculating clinical breakpoints and epidemiologic cutoff values (ECVs). Clinical breakpoints should be selected to optimize detection of non-wild-type (WT) strains of pathogens, and they should be species-specific and not divide WT distributions of important target species. ECVs are the most sensitive means of identifying strains with acquired resistance mechanisms. Various mechanisms can lead to acquired resistance of Candida species to azole drugs, the most common being induction of the efflux pumps encoded by the MDR or CDR genes, and acquisition of point mutations in the gene encoding for the target enzyme (ERG11). Acquired resistance of Candida species to echinocandins is typically mediated via acquisition of point mutations in the FKS genes encoding the major subunit of its target enzyme. Antifungal resistance is associated with elevated minimum inhibitory concentrations, poorer clinical outcomes, and breakthrough infections during antifungal treatment and prophylaxis. Candidemia due to Candida glabrata is becoming increasingly common, and C glabrata isolates are increasingly resistant to both azole and echinocandin antifungal agents. This situation requires continuing attention. Rates of azole-resistant Aspergillus fumigatus are currently low, but there are reports of emerging resistance, including multi-azole resistant isolates in parts of Europe.

Posaconazole in the management of refractory invasive fungal infections

The rising incidence of invasive fungal infections due to the expanding population of immunocompromised hosts and the increasing prevalence of fungal resistance has led to the need for novel antifungal agents. Posaconazole, a new member of the triazole class has demonstrated in vitro activity against a broad spectrum of fungi and clinical activity against various fungal pathogens, including Aspergillus spp., Candida spp., zygomycetes, and Fusarium spp. To date, posaconazole has been approved for prophylaxis of invasive fungal infections in stem cell transplant recipients with acute graft versus host disease (GVHD) and neutropenic patients receiving intensive induction chemotherapy for acute myelogenous leukemia and myelodys-plastic syndrome. In addition, it has been licensed for use in oropharyngeal candidiasis and for salvage therapy in invasive aspergillosis, fusariosis, coccidioidomycosis, chromoblastomycosis, and mycetoma. Posaconazole is the only azole with activity against zygomycetes and other difficult-to-treat fungi, representing a potential treatment option for refractory invasive mycosis. This article reviews available preclinical and clinical data of posaconazole, focusing on its role in the teatment of refractory invasive fungal infections.

Multicenter comparison of the Vitek 2 antifungal susceptibility test with the CLSI broth microdilution reference method for testing caspofungin, micafungin, and posaconazole against Candida spp

The performance of the automated Vitek 2 (bioMérieux, Inc., Marcy l'Etoile, France) antifungal susceptibility system was compared to that of broth microdilution (BMD) for the determination of MICs of various antifungal drugs. A total of 112 challenge strains and 755 clinical isolates of Candida spp. were tested against caspofungin and micafungin. An additional 452 clinical isolates of Candida albicans were tested against posaconazole. Reference BMD MIC endpoints were established after 24 h of incubation for caspofungin and micafungin and after 48 h of incubation for posaconazole. Essential agreements (EAs) between the Vitek 2 and BMD methods for caspofungin and micafungin were 99.5% and 98.6%, respectively. EA between the Vitek 2 and BMD methods was 95.6% for posaconazole. The overall categorical agreements (CAs) between the Vitek 2 system and BMD were 99.8% for caspofungin, 98.2% for micafungin, and 98.1% for posaconazole. The Vitek 2 system reliably determined caspofungin and micafungin MICs among Candida spp. and posaconazole MICs among C. albicans isolates and demonstrated excellent quantitative and qualitative agreement with the reference BMD method.

Antifungal prophylaxis and therapy in patients with hematological malignancies and hematopoietic stem cell transplant recipients

Patients with acute leukemia and hematopoietic stem cell transplant recipients are at risk of a spectrum of invasive fungal diseases corresponding to the type and intensity of immunosuppression. The development of newer antifungal agents has broadened therapeutic options. In the 1990s, lipid formulations of amphotericin B became widely used as safer alternatives to amphotericin B deoxycholate. In addition, fluconazole was shown to be beneficial as a yeast-active prophylaxis in hematopoietic stem cell transplant recipients. In the past decade, the antifungal armamentarium was further enhanced with the availability of extended-spectrum azoles and echinocandins. The development of effective broad-spectrum antifungal agents has led to their use as prophylaxis rather than delaying treatment until clinical signs of infection manifest. Antigen-based and PCR-based diagnostic adjuncts facilitate earlier detection of invasive fungal diseases compared with conventional culture, and have been incorporated into strategies in which initiation or modification of an antifungal regimen is targeted to patients with the highest likelihood of having fungal disease. Here, we review the pharmacological data and major clinical trials that guide the use of antifungals, as well as areas of uncertainty and future perspectives.

Validation of 24-hour posaconazole and voriconazole MIC readings versus the CLSI 48-hour broth microdilution reference method: application of epidemiological cutoff values to results from a global Candida antifungal surveillance program

We performed 24- and 48-h MIC determinations of posaconazole and voriconazole against more than 16,000 clinical isolates of Candida species. By using the 24- and 48-h epidemiological cutoff values (ECVs), the categorical agreement between the 24-h and reference 48-h broth microdilution results ranged from 97.1% (C. parapsilosis and voriconazole) to 99.8% (C. krusei and voriconazole), with 0.0 to 2.9% very major discrepancies (VMD). The essential agreement (within 2 log(2) dilutions) between the 24- and 48-h results was 99.6% for both posaconazole and voriconazole. The MIC results obtained for both posaconazole and voriconazole after only 24 h of incubation may be used to determine the susceptibilities of Candida spp. to these important antifungal agents. The applications of ECVs to this large collection of Candida isolates suggests the potential to develop 24-h species-specific clinical breakpoints for both posaconazole and voriconazole.

Comparison of the broth microdilution (BMD) method of the European Committee on Antimicrobial Susceptibility Testing with the 24-hour CLSI BMD method for testing susceptibility of Candida species to fluconazole, posaconazole, and voriconazole by use of epidemiological cutoff values

The antifungal broth microdilution (BMD) method of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) was compared with CLSI BMD method M27-A3 for fluconazole, posaconazole, and voriconazole susceptibility testing of 1,056 isolates of Candida. The isolates were obtained in 2009 from more than 60 centers worldwide and included 560 isolates of C. albicans, 175 of C. glabrata, 162 of C. parapsilosis, 124 of C. tropicalis, and 35 of C. krusei. The overall essential agreement (EA) between EUCAST and CLSI results ranged from 96.9% (voriconazole) to 98.6% (fluconazole). The categorical agreement (CA) between methods and species of Candida was assessed using previously determined epidemiological cutoff values (ECVs). The ECVs (expressed as μg/ml) for fluconazole, posaconazole, and voriconazole, respectively, were as follows: 0.12, 0.06, and 0.03 for C. albicans; 32, 2, and 0.5 for C. glabrata; 2, 0.25, and 0.12 for C. parapsilosis; 2, 0.12, and 0.06 for C. tropicalis; 64, 0.5, and 0.5 for C. krusei. Excellent CA was observed for all comparisons between the EUCAST and CLSI results for fluconazole, posaconazole, and voriconazole, respectively, for each species: 98.9%, 93.6%, and 98.6% for C. albicans; 96.0%, 98.9%, and 93.7% for C. glabrata; 90.8%, 98.1%, and 98.1% for C. parapsilosis; 99.2%, 99.2%, and 96.8% for C. tropicalis; 97.1%, 97.1%, and 97.1% for C. krusei. We demonstrate high levels of EA and CA between the CLSI and EUCAST BMD methods for testing of triazoles against Candida when the MICs were determined after 24 h and ECVs were used to differentiate wild-type (WT) from non-WT strains. These results provide additional data in favor of the harmonization of these two methods.

Wild-type MIC distributions and epidemiological cutoff values for posaconazole and voriconazole and Candida spp. as determined by 24-hour CLSI broth microdilution

We tested 16,191 strains of Candida against posaconazole and voriconazole, using the CLSI M27-A3 broth microdilution (BMD) method (24-h incubation), in order to define wild-type (WT) populations and epidemiological cutoff values (ECVs). From 2001 to 2009, 8,619 isolates of Candida albicans, 2,415 isolates of C. glabrata, 2,278 isolates of C. parapsilosis, 1,895 isolates of C. tropicalis, 508 isolates of C. krusei, 205 isolates of C. lusitaniae, 177 isolates of C. guilliermondii, and 93 isolates of C. kefyr were obtained from over 100 centers worldwide. The modal MICs (μg/ml) for posaconazole and voriconazole, respectively, were as follows: for C. albicans, 0.016 and 0.007; for C. glabrata, 0.5 and 0.06; for C. parapsilosis, 0.06 and 0.007; for C. tropicalis, 0.03 and 0.015; for C. krusei, 0.25 and 0.12; for C. lusitaniae, 0.03 and 0.007; for C. guilliermondii, 0.12 and 0.03; and for C. kefyr, 0.06 and 0.007. The ECVs (μg/ml [% of isolates that had MICs equal to or less than the ECV]) for posaconazole and voriconazole, respectively, were as follows: 0.06 (98.5) and 0.03 (98.9) for C. albicans, 2 (96.2) and 0.5 (90.4%) for C. glabrata, 0.25 (99.3) and 0.12 (97.9) for C. parapsilosis, 0.12 (97.6) and 0.06 (97.2) for C. tropicalis, 0.5 (99.8) and 0.5 (99.4) for C. krusei, 0.12 (95.6) and 0.03 (96.6) for C. lusitaniae, 0.5 (98.9) and 0.25 (98.3) for C. guilliermondii, and 0.25 (100.0) and 0.015 (100.0) for C. kefyr. In the absence of clinical breakpoints (CBPs) for posaconazole, these WT distributions and ECVs will be useful in surveillance for emergence of reduced susceptibility to posaconazole among Candida spp. Whereas a CBP for susceptibility of ≤ 1 μg/ml has been established for voriconazole and all species of Candida, it is notable that ECVs for this agent range from 10- to >100-fold lower than the CBP, depending on the species of Candida. The CBP is inadequate in detecting the emergence of voriconazole resistance among most Candida species encountered clinically. The CBPs for voriconazole should be reassessed, with consideration for development of species-specific CBPs.

Epidemiology of invasive mycoses in North America

The incidence of invasive mycoses is increasing, especially among patients who are immunocompromised or hospitalized with serious underlying diseases. Such infections may be broken into two broad categories: opportunistic and endemic. The most important agents of the opportunistic mycoses are Candida spp., Cryptococcus neoformans, Pneumocystis jirovecii, and Aspergillus spp. (although the list of potential pathogens is ever expanding); while the most commonly encountered endemic mycoses are due to Histoplasma capsulatum, Coccidioides immitis/posadasii, and Blastomyces dermatitidis. This review discusses the epidemiologic profiles of these invasive mycoses in North America, as well as risk factors for infection, and the pathogens' antifungal susceptibility.

New triazoles and echinocandins: mode of action, in vitro activity and mechanisms of resistance

Different types of mycoses, especially invasive mycoses caused by yeasts and molds, are a growing problem in healthcare. The most notable explanation for this increase is a rise in the number of immunocompromised patients owing to advances in transplantation, the emergence of AIDS and a rise in the number of invasive surgical procedures. Despite advances in medical practice, some therapeutic problems remain. In addition, intrinsic or acquired antifungal resistance may pose a serious problem to antifungal therapy. A new generation of triazole agents (voriconazole, posaconazole, isavuconazole, ravuconazole and albaconazole) and the recent class of the echinocandins (caspofungin, micafungin and anidulafungin) have become available, and represent an alternative to conventional antifungals for serious fungal infection management. Currently, only two of the recent triazole generation (voriconazole and posaconazole) and all three echinocandins are available for clinical use. More precisely, voriconazole and posaconazole are indicated for the treatment of invasive fungal infections and the echinocandins for the treatment of specific candidiasis. Voriconazole and posaconazole have a very broad spectrum of antifungal activity that includes Candida species, and filamentous and dimorphic fungi. Their activity extends to both fluconazole- and itraconazole-resistant strains of Candida. A major difference between posaconazole and voriconazole is that posaconazole has activity against Zygomycetes including Mucor spp., Rhizopus spp. and Cunninghamella spp., and voriconazole has no activity against this class of fungi. Ravuconazole, isavuconazole and albaconazole have shown very potent in vitro activity against species of Candida, Cryptococcus and Aspergillus, and they are currently in various stages of development. All three echinocandin agents, caspofungin, micafungin and anidulafungin, are similar in their spectrum of activity. Echinocandins do not possess in vitro activity against important basidiomycetes, including Cryptococcus, Rhodotorula and Trichosporon. This review attempts to deliver the most up-to-date knowledge on the mode of action and mechanisms of resistance to triazoles and echinocandins in fungal pathogens. In addition, the in vitro activity data available on triazoles and echinocandins are reported.

Effect of Candida glabrata FKS1 and FKS2 mutations on echinocandin sensitivity and kinetics of 1,3-beta-D-glucan synthase: implication for the existing susceptibility breakpoint

Thirteen Candida glabrata strains harboring a range of mutations in hot spot regions of FKS1 and FKS2 were studied. The mutations were linked to an echinocandin reduced susceptibility phenotype. Sequence alignments showed that 11 out of the 13 mutants harbored a mutation in FKS1 or FKS2 not previously implicated in echinocandin reduced susceptibility in C. glabrata. A detailed kinetic characterization demonstrated that amino acid substitutions in Fks1p and Fks2p reduced drug sensitivity in mutant 1,3-beta-D-glucan synthase by 2 to 3 log orders relative to that in wild-type enzyme. These mutations were also found to reduce the catalytic efficiency of the enzyme (Vmax) and to influence the relative expression of FKS genes. In view of the association of FKS mutations and reduced susceptibility of 1,3-beta-D-glucan synthase, an evaluation of the new CLSI echinocandin susceptibility breakpoint was conducted. Only 3 of 13 resistant fks mutants (23%) were considered anidulafungin or micafungin nonsusceptible (MIC > 2 microg/ml) by this criterion. In contrast, most fks mutants (92%) exceeded a MIC of >2 microg/ml with caspofungin. However, when MIC determinations were performed in the presence of 50% serum, all C. glabrata fks mutants showed MICs of > or = 2 microg/ml for the three echinocandin drugs. As has been observed with Candida albicans, the kinetic inhibition parameter 50% inhibitory concentration may be a better predictor of FKS-mediated resistance. Finally, the close association between FKS1/FKS2 hot spot mutations provides a basis for understanding echinocandin resistance in C. glabrata.

Evaluating the resistance to posaconazole by E-test and CLSI broth microdilution methodologies of Candida spp. and pathogenic moulds

E-test methodology was compared with Clinical and Laboratory Standards Institute (CLSI) broth microdilution, particularly concerning the detection of resistance to posaconazole among clinical fungal isolates. The susceptibility of a large set of fungal strains (n = 300) was evaluated following 24 and 48 h in two different culture media (RPMI 1640 and Sabouraud agar). Fungal strains were highly susceptible to posaconazole; however, few less susceptible strains were found, mostly regarding Candida albicans, Candida glabrata, Acremonium sp., Cladosporium sp. and Scedosporium apiospermum. Broth microdilution and E-test methods provided similar results for posaconazole-susceptible strains, while the less susceptible fungal strains (10.3% of the strains showed MIC > or =2 microg/mL) resulted in higher discrepancies between the two methodologies, particularly concerning Candida spp. E-test susceptibility values were critically affected by the pH of the culture media. Sabouraud medium provided similar susceptibility results for moulds to those for RPMI, soon after 24 h. Posaconazole resistance was rare in this study, but routine susceptibility methods, such as the E-test, should be able to detect fungal strains with reduced susceptibility. E-test methodology still needs improvements to recognise accurately strains less susceptible to posaconazole.

Efflux-mediated antifungal drug resistance

Fungi cause serious infections in the immunocompromised and debilitated, and the incidence of invasive mycoses has increased significantly over the last 3 decades. Slow diagnosis and the relatively few classes of antifungal drugs result in high attributable mortality for systemic fungal infections. Azole antifungals are commonly used for fungal infections, but azole resistance can be a problem for some patient groups. High-level, clinically significant azole resistance usually involves overexpression of plasma membrane efflux pumps belonging to the ATP-binding cassette (ABC) or the major facilitator superfamily class of transporters. The heterologous expression of efflux pumps in model systems, such Saccharomyces cerevisiae, has enabled the functional analysis of efflux pumps from a variety of fungi. Phylogenetic analysis of the ABC pleiotropic drug resistance family has provided a new view of the evolution of this important class of efflux pumps. There are several ways in which the clinical significance of efflux-mediated antifungal drug resistance can be mitigated. Alternative antifungal drugs, such as the echinocandins, that are not efflux pump substrates provide one option. Potential therapeutic approaches that could overcome azole resistance include targeting efflux pump transcriptional regulators and fungal stress response pathways, blockade of energy supply, and direct inhibition of efflux pumps.

Abc1p is a multidrug efflux transporter that tips the balance in favor of innate azole resistance in Candida krusei

Most Candida krusei strains are innately resistant to fluconazole (FLC) and can cause breakthrough candidemia in immunocompromised individuals receiving long-term prophylactic FLC treatment. Although the azole drug target, Erg11p, of C. krusei has a relatively low affinity for FLC, drug efflux pumps are also believed to be involved in its innate FLC resistance. We describe here the isolation and characterization of Abc1p, a constitutively expressed multidrug efflux pump, and investigate ERG11 and ABC1 expression in C. krusei. Examination of the ERG11 promoter revealed a conserved azole responsive element that has been shown to be necessary for the transcription factor Upc2p mediated upregulation by azoles in related yeast. Extensive cloning and sequencing identified three distinct ERG11 alleles in one of two C. krusei strains. Functional overexpression of ERG11 and ABC1 in Saccharomyces cerevisiae conferred high levels of resistance to azoles and a range of unrelated Abc1p pump substrates, while small molecule inhibitors of Abc1p chemosensitized C. krusei to azole antifungals. Our data show that despite the presence of multiple alleles of ERG11 in some, likely aneuploid, C. krusei strains, it is mainly the low affinity of Erg11p for FLC, together with the constitutive but low level of expression of the multidrug efflux pump Abc1p, that are responsible for the innate FLC resistance of C. krusei.

Correlating echinocandin MIC and kinetic inhibition of fks1 mutant glucan synthases for Candida albicans: implications for interpretive breakpoints

A detailed kinetic characterization of echinocandin inhibition was performed for mutant 1,3-beta-d-glucan synthase enzymes from clinical isolates of Candida albicans with nine different FKS1 mutations resulting in high MICs. Among 14 mutant Fks1p enzymes studied, the kinetic parameters 50% inhibitory concentration and K(i) increased 50-fold to several thousandfold relative to those for the wild type. Enzymes with mutations at Ser645 (S645P, S645Y, and S645F) within hot spot 1 showed the most prominent decrease in sensitivity, while those with mutations at the N- and C-terminal ends of hot spot 1 generally retained greater sensitivity to all three drugs. Kinetic inhibitions by caspofungin, micafungin, and anidulafungin were comparable among the fks1 mutant enzymes, although absolute values did vary with specific mutations. Amino acid substitutions in Fks1p did not alter K(m) values, although some mutations decreased the V(max). Given the association of FKS1 mutations with clinical resistance, an evaluation of the kinetic parameters for the inhibition of mutant 1,3-beta-D-glucan synthase as a function of the MIC enabled an independent evaluation of the recently adopted susceptibility breakpoint for echinocandin drugs. Overall, a breakpoint MIC of >or=2 microg/ml for caspofungin captured nearly 100% of fks1 C. albicans strains when a kinetic inhibition rise threshold of <or=50-fold for the K(i) was used as a measure of susceptibility. A similar MIC breakpoint for micafungin and anidulafungin was less inclusive, and a projected MIC of >or=0.5 microg/ml was required for >95% coverage of clinical isolates. However, when MIC determinations were performed in the presence of 50% serum, all fks1 mutants showed MIC values of >or=2 microg/ml for the three echinocandin drugs. The 1,3-beta-D-glucan synthase kinetic inhibition data support the proposed susceptibility breakpoint for caspofungin in C. albicans, but a lower susceptibility breakpoint (<or=0.5 microg/ml) may be more appropriate for anidulafungin and micafungin. Overall, the data indicate that MIC testing with caspofungin may serve as a surrogate marker for resistance among the class of echinocandin drugs.

Validation of 24-hour fluconazole MIC readings versus the CLSI 48-hour broth microdilution reference method: results from a global Candida antifungal surveillance program

We performed 24- and 48-h MIC determinations and disk diffusion testing of fluconazole against more than 11,000 clinical isolates of Candida species. By using the reference MIC breakpoints, the categorical agreement between the 24-h and reference 48-h broth microdilution results ranged from 93.8% (all Candida species) to 94.9% (all Candida species minus Candida krusei), with only 0.1% very major errors (VME). The essential agreement (within 2 log(2) dilutions) between the 24-h and 48-h results was 99.6%. The categorical agreement between the 24-h disk diffusion results and the 24-h MIC results, using the previously established breakpoints, was 94.4%, with 0.1% VME. Both the MIC and the disk diffusion results obtained for fluconazole after only 24 h of incubation may be used to determine the susceptibilities of Candida spp. to this widely used antifungal agent.

Activity of amphotericin B, anidulafungin, caspofungin, micafungin, posaconazole, and voriconazole against Candida albicans with decreased susceptibility to fluconazole from APECED patients on long-term azole treatment of chronic mucocutaneous candidiasis

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED, APS-I) is exceptionally common in Finland. Most patients have chronic oral candidiasis since childhood. Thus, most patients receive repeated courses of antifungals throughout their life. Eleven of our patients (31.4%) have become colonized with Candida albicans with decreased sensitivity to fluconazole. A total of 43 isolates of C. albicans from 23 APECED patients isolated during the years 1994 to 2004 were divided into 2 groups: fluconazole-susceptible dose-dependent (MIC, 16-32 microg/mL, 18 isolates) and fluconazole-susceptible (MIC <or=8 microg/mL, 25 isolates) groups. Antifungal activity of amphotericin B, echinocandins, and azoles was determined by the Clinical and Laboratory Standards Institute M27-A2 methodology. All isolates were highly susceptible to amphotericin B and echinocandins. Posaconazole and voriconazole were active against all isolates. Our data suggest that topical amphotericin B could continue to be a safe and active drug for daily administration for APECED patients. Posaconazole, voriconazole, and echinocandins may be useful in some complicated cases.

Posaconazole against Candida glabrata isolates with various susceptibilities to fluconazole

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.