Variation in susceptibility of bloodstream isolates of Candida glabrata to fluconazole according to patient age and geographic location in the United States in 2001 to 2007

Epidemiology and Risk Factors for Echinocandin Nonsusceptible Candida glabrata Bloodstream Infections: Data From a Large Multisite Population-Based Candidemia Surveillance Program, 2008-2014

Background. Echinocandins are first-line treatment for Candida glabrata candidemia. Echinocandin resistance is concerning due to limited remaining treatment options. We used data from a multisite, population-based surveillance program to describe the epidemiology and risk factors for echinocandin nonsusceptible (NS) C glabrata candidemia.

Methods. The Centers for Disease Control and Prevention's Emerging Infections Program conducts population-based laboratory surveillance for candidemia in 4 metropolitan areas (7.9 million persons; 80 hospitals). We identified C glabrata cases occurring during 2008–2014; medical records of cases were reviewed, and C glabrata isolates underwent broth microdilution antifungal susceptibility testing. We defined echinocandin-NS C glabrata (intermediate or resistant) based on 2012 Clinical and Laboratory Standards Institute minimum inhibitory concentration breakpoints. Independent risk factors for NS C glabrata were determined by stepwise logistic regression.

Results. Of 1385 C glabrata cases, 83 (6.0%) had NS isolates (19 intermediate and 64 resistant); the proportion of NS isolates rose from 4.2% in 2008 to 7.8% in 2014 (P < .001). The proportion of NS isolates at each hospital ranged from 0% to 25.8%; 3 large, academic hospitals accounted for almost half of all NS isolates. In multivariate analysis, prior echinocandin exposure (adjusted odds ratio [aOR], 5.3; 95% CI, 2.6–1.2), previous candidemia episode (aOR, 2.5; 95% CI, 1.2–5.1), hospitalization in the last 90 days (aOR, 1.9; 95% CI, 1.0–3.5, and fluconazole resistance [aOR, 3.6; 95% CI, 2.0–6.4]) were significantly associated with NS C glabrata. Fifty-nine percent of NS C glabrata cases had no known prior echinocandin exposure.

Conclusion. The proportion of NS C glabrata isolates rose significantly during 2008–2014, and NS C glabrata frequency differed across hospitals. In addition to acquired resistance resulting from prior drug exposure, occurrence of NS C glabrata without prior echinocandin exposure suggests possible transmission of resistant organisms.

In vitro activity of essential oils extracted from condiments against fluconazole-resistant and -sensitive Candida glabrata

In the present study, the antifungal activity of essential oils obtained from Origanum vulgare (oregano), Cinnamomum zeylanicum (cinnamon), Lippia graveolens (Mexican oregano), Thymus vulgaris (thyme), Salvia officinalis (sage), Rosmarinus officinalis (rosemary), Ocimum basilicum (basil) and Zingiber officinale (ginger) were assessed against Candida glabrata isolates. One group contained 30 fluconazole-susceptible C. glabrata isolates, and the second group contained fluconazole-resistant isolates derived from the first group after the in vitro induction of fluconazole-resistance, for a total of 60 tested isolates. The broth microdilution methodology was used. Concentrations of 50μg/mL, 100μg/mL, 200μg/mL, 400μg/mL, 800μg/mL, 1600μg/mL and 3200μg/mL of the essential oils were used, and the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined. Thyme, sage, rosemary, basil and ginger essential oils showed no antifungal activity at the tested concentrations. Antimicrobial activity less than or equal to 3200μg/mL was observed for oregano, Mexican oregano and cinnamon essential oils. Both the oregano and Mexican oregano essential oils showed high levels of antifungal activity against the fluconazole-susceptible C. glabrata group, whereas the cinnamon essential oil showed the best antifungal activity against the fluconazole-resistant C. glabrata isolates.

Isavuconazole, micafungin, and 8 comparator antifungal agents' susceptibility profiles for common and uncommon opportunistic fungi collected in 2013: temporal analysis of antifungal drug resistance using CLSI species-specific clinical breakpoints and proposed epidemiological cutoff values

The in vitro activities of isavuconazole, micafungin, and 8 comparator antifungal agents were determined for 1613 clinical isolates of fungi (1320 isolates of Candida spp., 155 of Aspergillus spp., 103 of non-Candida yeasts, and 35 non-Aspergillus molds) collected during a global survey conducted in 2013. The vast majority of the isolates of the 21 different species of Candida, with the exception of Candida glabrata (MIC90, 2 μg/mL), Candida krusei (MIC90, 1 μg/mL), and Candida guilliermondii (MIC90, 8 μg/mL), were inhibited by ≤0.25 μg/mL of isavuconazole. C. glabrata and C. krusei were largely inhibited by ≤1 μg/mL of isavuconazole. Resistance to fluconazole was seen in 0.5% of Candida albicans isolates, 11.1% of C. glabrata isolates, 2.5% of Candida parapsilosis isolates, 4.5% of Candida tropicalis isolates, and 20.0% of C. guilliermondii isolates. Resistance to the echinocandins was restricted to C. glabrata (1.3-2.1%) and C. tropicalis (0.9-1.8%). All agents except for the echinocandins were active against 69 Cryptococcus neoformans isolates, and the triazoles, including isavuconazole, were active against the other yeasts. Both the mold active triazoles as well as the echinocandins were active against 155 Aspergillus spp. isolates belonging to 10 species/species complex. In general, there was low resistance levels to the available systemically active antifungal agents in a large, contemporary (2013), global collection of molecularly characterized yeasts and molds. Resistance to azoles and echinocandins was most prominent among isolates of C. glabrata, C. tropicalis, and C. guilliermondii.

Micafungin in premature and non-premature infants: a systematic review of 9 clinical trials

BACKGROUND

Invasive fungal infections cause excessive morbidity and mortality in premature neonates and severely ill infants.

METHODS

Safety and efficacy outcomes of micafungin were compared between prematurely and non-prematurely born infants <2 years of age. Data were obtained from all completed phase I-III clinical trials with micafungin that had enrolled infants (<2 years of age) that were listed in the Astellas Clinical Study Database. Demographics, adverse events, hepatic function tests and treatment success data were extracted and validated by the Astellas biostatistical group for all micafungin-treated patients, <2 years of age, using the unique patient identifier.

RESULTS

One-hundred and sixteen patients included in 9 clinical trials, 48% premature [birth weight (BW) <2500 g and/or gestational age <37 weeks], 52% non-premature, received ≥ 1 dose of micafungin. Among premature patients, 14.5% were low BW (1500-2499 g), 36.4% very low BW (1000-1499 g) and 49.1% extremely low BW (<1000 g). Ninety patients (78%) completed the studies; 13 [11% (4 premature)] died. Significantly more non-premature than premature patients discontinued treatment (P = 0.003). Treatment-related adverse events were recorded in 23% of patients with no difference between groups. More extremely low BW (n = 4, 15%) and very low BW (n = 8, 40%) infants experienced treatment-related adverse events than low BW (n = 0) and there was no relation to micafungin dose or duration. For a subgroup of 30 patients with invasive candidiasis, treatment success was achieved in 73% in both premature and non-premature groups. Prophylaxis was successful in 4/5 non-premature hematopoietic stem cell transplant patients.

CONCLUSION

Micafungin has a safe profile in premature and non-premature infants with substantial efficacy.

Emerging drugs and vaccines for candidemia

Candidemia and other forms of invasive candidiasis are important causes of morbidity and mortality. The evolving challenge of antimicrobial resistance among fungal pathogens continues to highlight the need for potent, new antifungal agents. MEDLINE, EMBASE, Scopus and Web of Science searches (up to January 2014) of the English-language literature were performed with the keywords 'Candida' or 'Candidemia' or 'Candidiasis' and terms describing investigational drugs with activity against Candida spp. Conference abstracts and the bibliographies of pertinent articles were also reviewed for relevant reports. ClinicalTrials.gov was searched for relevant clinical trials. Currently available antifungal agents for the treatment of candidemia are summarised. Investigational antifungal agents with potential activity against Candida bloodstream infections and other forms of invasive candidiasis and vaccines for prevention of Candida infections are also reviewed as are selected antifungal agents no longer in development. Antifungal agents currently in clinical trials include isavuconazole, albaconazole, SCY-078, VT-1161 and T-2307. Further data are needed to determine the role of these compounds in the treatment of candidemia and other forms of invasive candidiasis. The progressive reduction in antimicrobial drug development may result in a decline in antifungal drug discovery. Still, there remains a critical need for new antifungal agents to treat and prevent invasive candidiasis and other life-threatening mycoses.

Changes in genotype and fluconazole susceptibility of isolates from patients with Candida glabrata in Tunisia

Candida glabrata has emerged as an opportunistic pathogen of considerable importance in invasive and superficial infections.

AIMS

To analyze the development of fluconazole resistance in patients under treatment through epidemiological survey in our hospital.

PATIENTS AND METHODS

Twenty two patients (89 clinical strains) were collected. Molecular typing of isolates was performed by polymorphic markers. Analysis of gene expression was realized by reverse transcriptase-real time polymerase chain reactions (RT-qPCR).

RESULTS

Genetic analysis showed that 63% persists with apparently unchanged strains (n=14). Among them, four showed fluconazole resistance development. A strain replacement was observed in 6 patients and two patients selected more resistant isolates during the course of treatment. An analysis of Candida glabrata cerebellar degeneration-related protein 1 (CgCDR1), Candida glabrata cerebellar degeneration-related protein 2 (CgCDR2) and Candida glabrata sterol 14 alpha-demetylase Erg 11 (CgERG11) expression revealed an over-expression in 10 resistant isolates.

CONCLUSION

This study demonstrated that C. glabrata strain undergo frequent changes in vivo. The increase in CgCDR1 and CgCDR2 expression was the most mechanism associated with fluconazole resistance.

Epidemiology and outcomes of invasive candidiasis due to non-albicans species of Candida in 2,496 patients: data from the Prospective Antifungal Therapy (PATH) registry 2004-2008

This analysis describes the epidemiology and outcomes of invasive candidiasis caused by non-albicans species of Candida in patients enrolled in the Prospective Antifungal Therapy Alliance (PATH Alliance) registry from 2004 to 2008. A total of 2,496 patients with non-albicans species of Candida isolates were identified. The identified species were C. glabrata (46.4%), C. parapsilosis (24.7%), C. tropicalis (13.9%), C. krusei (5.5%), C. lusitaniae (1.6%), C. dubliniensis (1.5%) and C. guilliermondii (0.4%); 111 infections involved two or more species of Candida (4.4%). Non-albicans species accounted for more than 50% of all cases of invasive candidiasis in 15 of the 24 sites (62.5%) that contributed more than one case to the survey. Among solid organ transplant recipients, patients with non-transplant surgery, and patients with solid tumors, the most prevalent non-albicans species was C. glabrata at 63.7%, 48.0%, and 53.8%, respectively. In 1,883 patients receiving antifungal therapy on day 3, fluconazole (30.5%) and echinocandins (47.5%) were the most frequently administered monotherapies. Among the 15 reported species, 90-day survival was highest for patients infected with either C. parapsilosis (70.7%) or C. lusitaniae (74.5%) and lowest for patients infected with an unknown species (46.7%) or two or more species (53.2%). In conclusion, this study expands the current knowledge of the epidemiology and outcomes of invasive candidiasis caused by non-albicans species of Candida in North America. The variability in species distribution in these centers underscores the importance of local epidemiology in guiding the selection of antifungal therapy.

Systematic phenotyping of a large-scale Candida glabrata deletion collection reveals novel antifungal tolerance genes

The opportunistic fungal pathogen Candida glabrata is a frequent cause of candidiasis, causing infections ranging from superficial to life-threatening disseminated disease. The inherent tolerance of C. glabrata to azole drugs makes this pathogen a serious clinical threat. To identify novel genes implicated in antifungal drug tolerance, we have constructed a large-scale C. glabrata deletion library consisting of 619 unique, individually bar-coded mutant strains, each lacking one specific gene, all together representing almost 12% of the genome. Functional analysis of this library in a series of phenotypic and fitness assays identified numerous genes required for growth of C. glabrata under normal or specific stress conditions, as well as a number of novel genes involved in tolerance to clinically important antifungal drugs such as azoles and echinocandins. We identified 38 deletion strains displaying strongly increased susceptibility to caspofungin, 28 of which encoding proteins that have not previously been linked to echinocandin tolerance. Our results demonstrate the potential of the C. glabrata mutant collection as a valuable resource in functional genomics studies of this important fungal pathogen of humans, and to facilitate the identification of putative novel antifungal drug target and virulence genes.

Clinical infections by the yeast-like pathogen Candida glabrata have been ever-increasing over the past years. Importantly, C. glabrata is one of the most prevalent causes of drug-refractory fungal infections in humans. We have generated a novel large-scale collection encompassing 619 bar-coded C. glabrata mutants, each lacking a single gene. Extensive profiling of phenotypes reveals a number of novel genes implicated in tolerance to antifungal drugs that interfere with proper cell wall function, as well as genes affecting fitness of C. glabrata both during normal growth and under environmental stress. This fungal deletion collection will be a valuable resource for the community to study mechanisms of virulence and antifungal drug tolerance in C. glabrata, which is particularly relevant in view of the increasing prevalence of infections caused by this important human fungal pathogen.

Regional data analysis of Candida non-albicans strains collected in United States medical sites over a 6-year period, 2006-2011

Limited data are available on temporal and geographic variation of occurrence and antifungal resistance of non-C. albicans Candida species (non-CA-CSP) from the USA. The objective of this study was to evaluate the occurrence and antifungal resistance of 1694 isolates of non-CA-CSP collected during the period 2006-2011. Isolates were recovered in 33 hospitals located in four regions: Northcentral, North-east, South-east and West and tested using CLSI reference broth microdilution methods. Non-CA-CSP represented 55.6% of all Candida. C. glabrata was most predominant (39-42% of non-CA-CSP). Infections due to C. glabrata, C. krusei and C. dubliniensis increased over the 6 years. Anidulafungin (3.6%) and caspofungin (5.7%) resistance were prominent among C. glabrata from the North-east and West regions respectively. Resistance to micafungin was detected in 2.0% and 2.9% of C. glabrata from the West and North-east regions respectively. Echinocandin resistance was low, except for C. dubliniensis. Azole resistance was most prominent among C. glabrata from the South-east (13.6% fluconazole R) and the West (18.0%). Cross-resistance among three tested azoles was observed in C. glabrata from all regions. Whereas differences in species distribution and antifungal R varied across geographic regions, there was little evidence of temporal increase in resistance to azoles or echinocandins in the monitored non-CA-CSP.

What's new in the clinical and diagnostic management of invasive candidiasis in critically ill patients

Invasive candidiasis (IC) is a severe complication in the ICU setting. A high proportion of ICU patients become colonized with Candida species, but only 5-30 % develop IC. Progressive colonization and major abdominal surgery are well-known risk factors for Candida infection. IC is difficult to predict and early diagnosis remains a major challenge. In addition, microbiological documentation often occurs late in the course of infection. Delays in initiating appropriate treatment have been associated with increased mortality. In an attempt to decrease Candida-related mortality, an increasing number of critically ill patients without documented IC receive empirical systemic antifungal therapy, leading to concern for antifungal overuse. Scores/predictive rules permit the stratification and selection of IC high-risk patients who may benefit from early antifungal therapy. However, they have a far better negative predictive value than positive predictive value. New IC biomarkers [mannan, anti-mannan, (1,3)-β-D-glucan, and polymerase chain reaction] are being increasingly used to enable earlier diagnosis and, ideally, to provide prognostic information and/or therapeutic monitoring. Although reasonably sensitive and specific, these techniques remain largely investigational, and their clinical usefulness has yet to be established.

Association of clinical and demographic factors in invasive candidiasis caused by fluconazole-resistant Candida species: a study in 15 hospitals, Medellín, Colombia 2010-2011

Candida is the most important agent of fungal infections. Several risk factors have been described associated with invasive infection by fluconazole-resistant Candida spp. A prospective cross-sectional study with case-control analysis was conducted. Case group patients with fluconazole-resistant Candida isolate were included; control group were patients with fluconazole-susceptible Candida spp. A multivariate logistic regression model was performed. Three hundred isolates of Candida spp. were analyzed. Most frequent species were Candida albicans/Candida dubliniensis (48.3%) and Candida tropicalis (22.3%). Posaconazole susceptibility was 93.7%; voriconazole, 84%; and fluconazole, 78.7%. Susceptibility to anidulafungin and caspofungin was 92.7% and 92.3%, respectively. Neutropenia (adjusted odds ratio [aOR] 6.5, 95% confidence interval [CI] 1.0-43.1), antifungal exposure (aOR 5.1, 95% CI 2.3-11.2), and antituberculosis therapy (aOR 7.7, 95% CI 1.4-43.2) were associated to fluconazole resistance. Susceptibility results are useful to guide the selection of empiric antifungal treatment and the design of local therapeutic guidelines. Previous antifungal exposure suggests possible resistance to fluconazole, pointing towards the selection of a different class of antifungal agents.

Development of a Luminex-based multiplex assay for detection of mutations conferring resistance to Echinocandins in Candida glabrata

Echinocandins are the recommended treatment for invasive candidiasis due to Candida glabrata. Resistance to echinocandins is known to be caused by nonsynonymous mutations in the hot spot-1 (HS1) regions of the FKS1 and FKS2 genes, which encode a subunit of the β-1,3-glucan synthase, the target of echinocandins. Here, we describe the development of a microsphere-based assay using Luminex MagPix technology to identify mutations in the FKS1 HS1 and FKS2 HS1 domains, which confer in vitro echinocandin resistance in C. glabrata isolates. The assay is rapid and can be performed with high throughput. The assay was validated using 102 isolates that had FKS1 HS1 and FKS2 HS1 domains previously characterized by DNA sequencing. The assay was 100% concordant with DNA sequencing results. The assay was then used for high-throughput screening of 1,032 C. glabrata surveillance isolates. Sixteen new isolates with mutations, including a mutation that was new to our collection (del659F), were identified. This assay provides a rapid and cost-effective way to screen C. glabrata isolates for echinocandin resistance.

Interactions between copy number and expression level of genes involved in fluconazole resistance in Candida glabrata

Objectives: This study aimed to elucidate the relative involvement of drug resistance gene copy number and overexpression in fluconazole resistance in clinical C. glabrata isolates using a population-based approach.

Methods: Fluconazole resistance levels were quantified using the minimal inhibitory concentration (MIC) via Etest method. Both gene expression levels and gene copy number of CgCDR1, CgPDH1, CgERG11, and CgSNQ2 were assessed via quantitative real-time PCR. The influence of the main effects and first-level interactions of both the expression level and copy number of these genes on fluconazole resistance levels were analyzed using a multivariate statistical model.

Results: Forty-three C. glabrata isolates were collected from 30 patients during in a hospital survey. In the multivariate analysis, C. glabrata fluconazole MICs were independently increased by CgSNQ2 overexpression (p < 10⁻⁴) and the interaction between CgPDH1 gene copy number and CgPDH1 expression level (p = 0.038). In contrast, both CgPDH1 overexpression (p = 0.049) and the interaction between CgSNQ2 and CgERG11 expression (p = 0.003) led to a significant decrease in fluconazole MICs.

Conclusion: Fluconazole resistance in C. glabrata involves complex interactions between drug resistance gene expression and/or copy number. The population-based multivariate analysis highlighted the involvement of the CgSNQ2 gene in fluconazole resistance and the complex effect of the other genes such as PDH1 for which overexpression was associated with reduced fluconazole resistance levels, while the interaction between PDH1 overexpression and copy number was associated with increased resistance levels.

Candidemia in the critically ill: initial therapy and outcome in mechanically ventilated patients

Background

Mortality among critically ill patients with candidemia is very high. We sought to determine whether the choice of initial antifungal therapy is associated with survival among these patients, using need for mechanical ventilatory support as a marker of critical illness.

Methods

Cohort analysis of outcomes among mechanically ventilated patients with candidemia from the 24 North American academic medical centers contributing to the Prospective Antifungal Therapy (PATH) Alliance registry. Patients were included if they received either fluconazole or an echinocandin as initial monotherapy.

Results

Of 5272 patients in the PATH registry at the time of data abstraction, 1014 were ventilated and concomitantly had candidemia, with 689 eligible for analysis. 28-day survival was higher among the 374 patients treated initially with fluconazole than among the 315 treated with an echinocandin (66% versus 51%, P < .001). Initial fluconazole therapy remained associated with improved survival after adjusting for non-treatment factors in the overall population (hazard ratio .75, 95% CI .59–.96), and also among patients with albicans infection (hazard ratio .62, 95% CI .44–.88). While not statistically significant, fluconazole appeared to be associated with higher mortality among patients infected with glabrata (HR 1.13, 95% CI .70–1.84).

Conclusions

Among ventilated patients with candidemia, those receiving fluconazole as initial monotherapy were significantly more likely to survive than those treated with an echinocandin. This difference persisted after adjustment for non-treatment factors.

Antifungal activity of fused Mannich ketones triggers an oxidative stress response and is Cap1-dependent in Candida albicans

We investigated the antifungal activity of fused Mannich ketone (FMK) congeners and two of their aminoalcohol derivatives. In particular, FMKs with five-membered saturated rings were shown to have minimum inhibitory concentration (MIC90s) ranging from 0.8 to 6 µg/mL toward C. albicans and the closely related C. parapsilosis and C. krusei while having reduced efficacy toward C. glabrata and almost no efficacy against Aspergillus sp. Transcript profiling of C. albicans cells exposed for 30 or 60 min to 2-(morpholinomethyl)-1-indanone, a representative FMK with a five-membered saturated ring, revealed a transcriptional response typical of oxidative stress and similar to that of a C. albicans Cap1 transcriptional activator. Consistently, C. albicans lacking the CAP1 gene was hypersensitive to this FMK, while C. albicans strains overexpressing CAP1 had decreased sensitivity to 2-(morpholinomethyl)-1-indanone. Quantitative structure-activity relationship studies revealed a correlation of antifungal potency and the energy of the lowest unoccupied molecular orbital of FMKs and unsaturated Mannich ketones thereby implicating redox cycling-mediated oxidative stress as a mechanism of action. This conclusion was further supported by the loss of antifungal activity upon conversion of representative FMKs to aminoalcohols that were unable to participate in redox cycles.

Nationwide study of candidemia, antifungal use, and antifungal drug resistance in Iceland, 2000 to 2011

Candidemia is often a life-threatening infection, with highly variable incidence among countries. We conducted a nationwide study of candidemia in Iceland from 2000 to 2011, in order to determine recent trends in incidence rates, fungal species distribution, antifungal susceptibility patterns, and concurrent antifungal consumption. A total of 208 infection episodes in 199 patients were identified. The average incidence during the 12 years was 5.7 cases/100,000 population/year, which was significantly higher than that from 1990 to 1999 (4.3/100,000/year; P = 0.02). A significant reduction in the use of blood cultures was noted in the last 3 years of the study, coinciding with the economic crisis in the country (P < 0.001). Age-specific incidence rates were highest among patients at the extremes of age, 20.7/100,000 for <1 year of age and 18.1/100,000 for >60 years, and varied by gender. Age-specific incidence among males >80 years old was 28.6/100,000/year, and it was 8.3/100,000/year for females in this age group (P = 0.028). The 30-day survival rate among adult patients remained unchanged compared to that from 1990 to 1999 (70.4% versus 69.5%, P = 0.97). Candida albicans was the predominant species (56%), followed by C. glabrata (16%) and C. tropicalis (13%). The species distribution remained stable compared to that from previous decades. Fluconazole use increased 2.4-fold from 2000 to 2011, with no increase in resistance. In summary, the incidence of candidemia in Iceland has continued to increase but may have reached a steady state, and no increase in antifungal drug resistance has been noted. Decreased use of blood cultures toward the end of the study may have influenced detection rates.

Optimizing Echinocandin dosing and susceptibility breakpoint determination via in vivo pharmacodynamic evaluation against Candida glabrata with and without fks mutations

Echinocandins are a preferred therapy for invasive candidiasis due to their potency and broad spectrum. Resistance, especially in Candida glabrata, is an emerging threat to their use. Pharmacodynamic (PD) studies examining reduced susceptibility secondary to fks mutations in C. glabrata are lacking. The current study explored PD targets for anidulafungin, caspofungin, and micafungin in an in vivo invasive candidiasis model against 11 C. glabrata isolates with known or putative fks mutations. The PD targets were compared to those of 8 wild-type (WT) isolates. The MIC ranges in the WT group were 0.03 to 0.25 mg/liter for anidulafungin, 0.03 to 0.25 mg/liter for caspofungin, and 0.01 to 0.06 mg/liter for micafungin. The MIC ranges for mutants were 0.06 to 4, 0.25 to 16, and 0.13 to 8 mg/liter for the same compounds, respectively. The mean free drug 24-h area under the concentration-time curve (AUCf)/MIC ratio associated with a stasis endpoint for the WT group was 13.2 for anidulafungin, 2.04 for caspofungin, and 6.78 for micafungin. Comparative values for mutants were 3.43, 2.67, and 0.90, respectively. Pharmacokinetic data from patients suggest that the C. glabrata PD targets needed for success in this model could be achieved based on MIC values of 0.25 mg/liter for anidulafungin, 2 mg/liter for caspofungin, and 0.5 mg/liter for micafungin. These values are higher than recently identified epidemiology cutoff values (ECVs). The results suggest that drug-specific MIC breakpoints could be increased for caspofungin and micafungin against C. glabrata and could include organisms with mutations in fks-1 and fks-2. While identification of genetic mutants is epidemiologically important, the phenotype (MIC) provides a better predictor of therapeutic efficacy.

The effect of biomaterials and antifungals on biofilm formation by Candida species: a review

Candida albicans, C. glabrata, C. parapsilosis, and C. tropicalis are able to form biofilms on virtually any biomaterial implanted in a human host. Biofilms are a primary cause of mortality in immunocompromised and hospitalized patients, as they cause recurrent and invasive candidiasis, which is difficult to eradicate. This is due to the fact that the biofilm cells show high resistance to antifungal treatments and the host defense mechanisms, and exhibit an excellent ability to adhere to biomaterials. Elucidation of the mechanisms of antifungal resistance in Candida biofilms is of unquestionable importance; therefore, this review analyzes both the chemical composition of biomaterials used to fabricate the medical devices, as well as the Candida genes and proteins that confer drug resistance.

Frequency of decreased susceptibility and resistance to echinocandins among fluconazole-resistant bloodstream isolates of Candida glabrata

The echinocandin class of antifungal agents is considered to be the first-line treatment of bloodstream infections (BSI) due to Candida glabrata. Recent reports of BSI due to strains of C. glabrata resistant to both fluconazole and the echinocandins are of concern and prompted us to review the experience of two large surveillance programs, the SENTRY Antimicrobial Surveillance Program for the years 2006 through 2010 and the Centers for Disease Control and Prevention population-based surveillance conducted in 2008 to 2010. The in vitro susceptibilities of 1,669 BSI isolates of C. glabrata to fluconazole, voriconazole, anidulafungin, caspofungin, and micafungin were determined by CLSI broth microdilution methods. Fluconazole MICs of ≥64 μg/ml were considered resistant. Strains for which anidulafungin and caspofungin MICs were ≥0.5 μg/ml and for which micafungin MICs were ≥0.25 μg/ml were considered resistant. A total of 162 isolates (9.7%) were resistant to fluconazole, of which 98.8% were nonsusceptible to voriconazole (MIC > 0.5 μg/ml) and 9.3%, 9.3%, and 8.0% were resistant to anidulafungin, caspofungin, and micafungin, respectively. There were 18 fluconazole-resistant isolates that were resistant to one or more of the echinocandins (11.1% of all fluconazole-resistant isolates), all of which contained an acquired mutation in fks1 or fks2. By comparison, there were no echinocandin-resistant strains detected among 110 fluconazole-resistant isolates of C. glabrata tested in 2001 to 2004. These data document the broad emergence of coresistance over time to both azoles and echinocandins in clinical isolates of C. glabrata.

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.

Bloodstream and non-invasive isolates of Candida glabrata have similar population structures and fluconazole susceptibilities

We have compared multilocus sequence typing (MLST) and fluconazole susceptibility profiles of Candida glabrata bloodstream isolates obtained during active, population-based surveillance to those obtained from non-sterile sites of individuals with no evidence of fungal disease (i.e., non-invasive isolates) in the same US city during an overlapping time period. In each of the two populations, different proportions of the same six major sequence types (STs) encompassed 82% of the isolates. One ST was more prevalent in the candidemia population and two other STs were more prevalent in the non-invasive population, but the overall allelic frequencies within the groups suggested little, if any, genotypic diversity between them. Fluconazole susceptibility profiles of isolates from the patients in the two groups were not significantly different and were not associated with a particular sequence type. Our results support the hypothesis that C. glabrata strains causing bloodstream infections are genetically indistinguishable from those normally residing in/on the host, suggesting that relative pathogenicity may be closely tied to commensalism.

Current concepts in antifungal pharmacology

The introduction of new antifungal agents (eg, echinocandins, second-generation triazoles) in the past decade has transformed the management of invasive mycoses to the point that drug toxicity is no longer the major limiting factor in treatment. Yet, many of these newer antifungal agents have important limitations in their spectrum of activity, pharmacokinetics, and unique predisposition for pharmacokinetic drug-drug interactions and unusual toxicities associated with long-term use. This article reviews key pharmacological aspects of systemic antifungal agents as well as evolving strategies, such as pharmacokinetic-pharmacodynamic optimization and therapeutic drug monitoring, to improve the safety and efficacy of systemic antifungal therapy.

Candida bloodstream infections in intensive care units: analysis of the extended prevalence of infection in intensive care unit study

OBJECTIVES

To provide a global, up-to-date picture of the prevalence, treatment, and outcomes of Candida bloodstream infections in intensive care unit patients and compare Candida with bacterial bloodstream infection.

DESIGN

A retrospective analysis of the Extended Prevalence of Infection in the ICU Study (EPIC II). Demographic, physiological, infection-related and therapeutic data were collected. Patients were grouped as having Candida, Gram-positive, Gram-negative, and combined Candida/bacterial bloodstream infection. Outcome data were assessed at intensive care unit and hospital discharge.

SETTING

EPIC II included 1265 intensive care units in 76 countries.

PATIENTS

Patients in participating intensive care units on study day.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

Of the 14,414 patients in EPIC II, 99 patients had Candida bloodstream infections for a prevalence of 6.9 per 1000 patients. Sixty-one patients had candidemia alone and 38 patients had combined bloodstream infections. Candida albicans (n = 70) was the predominant species. Primary therapy included monotherapy with fluconazole (n = 39), caspofungin (n = 16), and a polyene-based product (n = 12). Combination therapy was infrequently used (n = 10). Compared with patients with Gram-positive (n = 420) and Gram-negative (n = 264) bloodstream infections, patients with candidemia were more likely to have solid tumors (p < .05) and appeared to have been in an intensive care unit longer (14 days [range, 5-25 days], 8 days [range, 3-20 days], and 10 days [range, 2-23 days], respectively), but this difference was not statistically significant. Severity of illness and organ dysfunction scores were similar between groups. Patients with Candida bloodstream infections, compared with patients with Gram-positive and Gram-negative bloodstream infections, had the greatest crude intensive care unit mortality rates (42.6%, 25.3%, and 29.1%, respectively) and longer intensive care unit lengths of stay (median [interquartile range]) (33 days [18-44], 20 days [9-43], and 21 days [8-46], respectively); however, these differences were not statistically significant.

CONCLUSION

Candidemia remains a significant problem in intensive care units patients. In the EPIC II population, Candida albicans was the most common organism and fluconazole remained the predominant antifungal agent used. Candida bloodstream infections are associated with high intensive care unit and hospital mortality rates and resource use.

Comparison of in vitro susceptibility characteristics of Candida species from cases of invasive candidiasis in solid organ and stem cell transplant recipients: Transplant-Associated Infections Surveillance Network (TRANSNET), 2001 to 2006

Invasive fungal infections (IFI) are a major cause of morbidity and mortality among both solid organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) recipients. Candida is the most common cause of IFI in SOT recipients and the second most common cause of IFI in HSCT recipients. We determined susceptibilities to fluconazole, voriconazole, itraconazole, posaconazole, amphotericin B, and caspofungin for 383 invasive Candida sp. isolates from SOT and HSCT recipients enrolled in the Transplant-Associated Infection Surveillance Network and correlated these results to clinical data. Fluconazole resistance in C. albicans, C. tropicalis, and C. parapsilosis isolates was low (1%), but the high percentage of C. glabrata and C. krusei isolates within this group of patients increased the overall percentage of fluconazole resistance to 16%. Voriconazole resistance was 3% overall but was 8% among C. glabrata isolates. On multivariable analysis, among HSCT recipients fluconazole nonsusceptibility was independently associated with C. glabrata, non-Hodgkin's lymphoma, cytomegalovirus (CMV) antigenemia, diabetes active at the time of the IFI, and any prior amphotericin B use; among SOT recipients, fluconazole nonsusceptibility was independently associated with any fluconazole use in the 3 months prior to the IFI, C. glabrata, ganciclovir use in the 3 months prior to the IFI, diabetes acquired since the transplant, and gender.

FKS mutations and elevated echinocandin MIC values among Candida glabrata isolates from U.S. population-based surveillance

Candida glabrata is the second leading cause of candidemia in the United States. Its high-level resistance to triazole antifungal drugs has led to the increased use of the echinocandin class of antifungal agents for primary therapy of these infections. We monitored C. glabrata bloodstream isolates from a population-based surveillance study for elevated echinocandin MIC values (MICs of ≥0.25 μg/ml). From the 490 C. glabrata isolates that were screened, we identified 16 isolates with an elevated MIC value (2.9% of isolates from Atlanta and 2.0% of isolates from Baltimore) for one or more of the echinocandin drugs caspofungin, anidulafungin, and micafungin. All of the isolates with elevated MIC values had a mutation in the previously identified hot spot 1 of either the glucan synthase FKS1 (n = 2) or FKS2 (n = 14) gene. No mutations were detected in hot spot 2 of either FKS1 or FKS2. The predominant mutation was mutation of FKS2-encoded serine 663 to proline (S663P), found in 10 of the isolates with elevated echinocandin MICs. Two of the mutations, R631G for FKS1 and R665G for FKS2, have not been reported previously for C. glabrata. Multilocus sequence typing indicated that the predominance of the S663P mutation was not due to the clonal spread of a single sequence type. With a rising number of echinocandin therapy failures reported, it is important to continue to monitor rates of elevated echinocandin MIC values and the associated mutations.