Correlation of MIC with outcome for Candida species tested against voriconazole: analysis and proposal for interpretive breakpoints

Commercial Methods for Antifungal Susceptibility Testing of Yeasts: Strengths and Limitations as Predictors of Resistance

Susceptibility testing can yield variable results because it is method (commercial or reference), agent, and species dependent. Therefore, in order for results to be clinically relevant, MICs (minimal inhibitory concentrations) or MECs (minimal effective concentrations) should help in selecting the best treatment agent in the clinical setting. This is accomplished by categorical endpoints, ideally, breakpoints (BPs) and/or ECVs/ECOFFs (epidemiological cutoff values). BPs and ECVs are available by the reference methods (CLSI [Clinical and Laboratory Standards Institute] and EUCAST [European Committee on Antifungal Susceptibility Testing]) for a variety of species/agent combinations. The lack of clinical data precludes establishment of BPs for susceptibility testing by the commercial methods and ECVs have only been calculated for the Etest and SYO assays. The goal of this review is to summarize the variety of commercial methods for antifungal susceptibility testing and the potential value of Etest and SYO ECVs for detecting mutants/non-wild type (NWT) Candida isolates. Therefore, the literature search focused on publications where the commercial method, meaning MICs and ECVs, were reported for specific NWT isolates; genetic mutations have also been listed. For the Etest, the best performers recognizing the NWT were anidulafungin ECVs: 92% for the common species; 97% for C. glabrata and fluconazole ECVs, mostly for C. parapsilosis (45 NWT isolates). By the SYO, posaconazole ECVs recognized 93% of the C. albicans and 96% of the C. parapsilosis NWT isolates and micafungin ECVs 94% (mostly C. albicans and C. glabrata). Smaller sets, some with clinical data, were also listed. These are promising results for the use of both commercial methods to identify antifungal resistance (NWT isolates). However, ECVs for other species and methods need to be defined, including the C. neoformans complex and emerging species.

Co-Administration with Voriconazole Doubles the Exposure of Ruxolitinib in Patients with Hematological Malignancies

Background

Ruxolitinib is newly approved for glucocorticoid-refractory acute graft-versus-host disease (GVHD) in patients undergoing allo-geneic hematopoietic stem-cell transplantation (allo-HSCT), and voriconazole is commonly used in allo-HSCT recipients for the prophylaxis or treatment of invasive fungal infections (IFIs). Drug–drug interaction (DDI) may occur between them because their metabolic pathways overlap and can be inhibited by voriconazole, including cytochrome P450 (CYP) isozymes 3A4 and 2C9.

Objective

In the present study, we aimed to investigate the DDI between ruxolitinib and voriconazole in patients with hematological malignancies.

Methods

A total of 12 patients with hematologic malignancies were enrolled in this single-arm, single-center, Phase I/II, fixed sequence self-control study. All subjects received 5 mg ruxolitinib alone, followed by the co-administration of ruxolitinib and voriconazole. The plasma concentrations of the two drugs were determined by two well-validated high-performance liquid chromatography-tandem mass spectrometry methods. Phoenix WinNonlin software was used to compare the differences in maximum plasma concentration (C_max), time to C_max (T_max), terminal elimination half-life (T_1/2), and apparent plasma clearance (CL/F), as well as area under the curve from time zero to last (AUC_last) and AUC from time zero to infinity (AUC_inf) between the two periods.

Results

After pre-treatment with voriconazole, no significant change existed in T_max, while C_max, T_1/2, AUC_last, and AUC_inf of ruxolitinib were significantly increased by 50.4%, 81.3%, 110.1%, and 118.3%, respectively, and CL/F was significantly decreased to 43.6% compared with patients receiving ruxolitinib alone.

Conclusion

Our findings confirmed a moderate inhibitory DDI between ruxolitinib and voriconazole as voriconazole decreased the elimination and increased the exposure of ruxolitinib in patients with hematologic malignancies. We recommended a dose reduction regimen when voriconazole and ruxolitinib were coadministered. Drug monitoring might help determine the ruxolitinib treatment concentration for aGVHD patients, improve efficacy, and reduce toxicity.

Epidemiology and Prevalence of Oral Candidiasis in HIV Patients From Chad in the Post-HAART Era

Oral candidiasis remains a common problem in HIV-infected individuals, especially in sub-Saharan Africa. Here, we performed the first study in Chad on the prevalence of oral yeasts carriage and oral candidiasis in HIV-positive subjects from southern Chad and analyzed the influence of HAART, CD4⁺ T-cell numbers, and antimycotics in 589 patients. These patients were recruited from a specialized medical center for HIV patients in Sarh and from a rural medical health dispensary in the vicinity, including a total of 384 HIV-positive and 205 HIV-negative individuals. Yeasts obtained from oral specimen were identified by MALDI-TOF MS and their antifungal susceptibility profiles determined. The overall prevalence of yeast colonization and symptomatic oral candidiasis in HIV-infected patients was 25.1%. The prevalence of oral candidiasis was higher in untreated than in HAART-treated HIV-positive patients (16% vs. 2%; p < 0.01). Oral candidiasis was furthermore associated with high fungal burdens of Candida albicans and a CD4⁺ T-cell number <200/μl. A shift toward non-albicans Candida species was observed under nucleoside-based HAART therapy. Azole antifungal drug resistance was only observed for the intrinsically resistant species Candida krusei and Candida glabrata. Prevalence of oral candidiasis in the studied area was very low. The species distribution was similar to other countries around the world, with C. albicans being dominant. Candida dubliniensis was not isolated. Nucleoside-based HAART therapy significantly reduced oral colonization as well as occurrence of oral candidiasis caused by C. albicans and led to a species shift toward non-albicans species. Antifungal resistance was not yet a concern in Chad.

Antifungal Susceptibility Testing: A Primer for Clinicians

Clinicians treating patients with fungal infections may turn to susceptibility testing to obtain information regarding the activity of different antifungals against a specific fungus that has been cultured. These results may then be used to make decisions regarding a patient's therapy. However, for many fungal species that are capable of causing invasive infections, clinical breakpoints have not been established. Thus, interpretations of susceptible or resistant cannot be provided by clinical laboratories, and this is especially true for many molds capable of causing severe mycoses. The purpose of this review is to provide an overview of susceptibility testing for clinicians, including the methods used to perform these assays, their limitations, how clinical breakpoints are established, and how the results may be put into context in the absence of interpretive criteria. Examples of when susceptibility testing is not warranted are also provided.

Oral candidiasis in HIV-uninfected pediatric population in areas with limited fungal diagnosis: A case study from a tertiary hospital, Tanzania

Background

Oral candidiasis (OC) is an indirect indicator of cell-mediated immunodeficiency with a high predictive value of disseminated candidiasis. Here, we report the prevalence and factors associated with laboratory-confirmed OC in human immunodeficiency virus (HIV)-uninfected children with clinical OC attending the outpatient clinic or admitted in pediatric wards of the Bugando Medical Center (BMC).

Methods

A cross-sectional study was conducted between January and June 2017. Social demographic and clinical data were collected using a pre-tested data collection tool. Oral swabs were collected using a sterile cotton swab and mycological culture was done to detect Candida spp. followed by susceptibility testing as per European Committee on Antimicrobial Testing (EUCAST) guidelines. Data were analyzed using STATA version 13 following study objectives.

Results

A total of 325 non-repetitive oral swabs from HIV-uninfected children aged between 2 and 156 months were collected. Candida spp. were detected in 123 (37.8%) children. One (1.8%) C. albicans isolate was resistant to fluconazole, voriconazole, and posaconazole with minimum inhibitory concentrations (MIC) of 256 μg/ml, 32 μg/ml, and 0.31 μg/ml, respectively. Upon multivariate logistic regression analysis, being a male child (OR 2, 95% CI 1.2-3.2, p = 0.008) and having a history of antibiotic use (OR 1.8, 95% CI 1.1-2.8, p = 0.017) independently predicted laboratory-confirmed OC among HIV-uninfected children.

Conclusion

Only a third of children with clinical OC were laboratory confirmed, and this was more likely in male children with a history of antibiotic use. Most of the isolates were highly susceptible to commonly used antifungal agents like fluconazole. Treatment of children at risk should be prioritized to reduce associated morbidity.

Toward Harmonization of Voriconazole CLSI and EUCAST Breakpoints for Candida albicans Using a Validated In Vitro Pharmacokinetic/Pharmacodynamic Model

CLSI and EUCAST susceptibility breakpoints for voriconazole and Candida albicans differ by one dilution (≤0.125 and ≤0.06 mg/liter, respectively) whereas the epidemiological cutoff values for EUCAST (ECOFF) and CLSI (ECV) are the same (0.03 mg/liter). We therefore determined the pharmacokinetic/pharmacodynamic (PK/PD) breakpoints of voriconazole against C. albicans for both methodologies with an in vitro PK/PD model, which was validated using existing animal PK/PD data. Four clinical wild-type and non-wild-type C. albicans isolates (voriconazole MICs, 0.008 to 0.125 mg/liter) were tested in an in vitro PK/PD model. For validation purposes, mouse PK were simulated and in vitro PD were compared with in vivo outcomes. Human PK were simulated, and the exposure-effect relationship area under the concentration-time curve for the free, unbound fraction of a drug from 0 to 24 h (fAUC_0-24)/MIC was described for EUCAST and CLSI 24/48-h methods. PK/PD breakpoints were determined using the fAUC_0-24/MIC associated with half-maximal activity (EI₅₀) and Monte Carlo simulation analysis. The in vitro 24-h PD EI₅₀ values of voriconazole against C. albicans were 2.5 to 5 (1.5 to 17) fAUC/MIC. However, the 72-h PD were higher at 133 (51 to 347) fAUC/MIC for EUCAST and 94 (35 to 252) fAUC/MIC for CLSI. The mean (95% confidence interval) probability of target attainment (PTA) was 100% (95 to 100%), 97% (72 to 100%), 83% (35 to 99%), and 49% (8 to 91%) for EUCAST and 100% (97 to 100%), 99% (85 to 100%), 91% (52 to 100%), and 68% (17 to 96%) for CLSI for MICs of 0.03, 0.06, 0.125, and 0.25 mg/liter, respectively. Significantly, >95% PTA values were found for EUCAST/CLSI MICs of ≤0.03 mg/liter. For MICs of 0.06 to 0.125 mg/liter, trough levels 1 to 4 mg/liter would be required to attain the PK/PD target. A PK/PD breakpoint of C. albicans voriconazole at the ECOFF/ECV of 0.03 mg/liter was determined for both the EUCAST and CLSI methods, indicating the need for breakpoint harmonization for the reference methodologies.

Expression of ERG11 and efflux pump genes CDR1, CDR2 and SNQ2 in voriconazole susceptible and resistant Candida glabrata strains

Candida glabrata causes difficult to treat invasive candidiasis due to its antifungal resistance, mainly to azoles. The aim of the present work was to study the role of the genes ERG11, CDR1, CDR2, and SNQ2 on the resistance to voriconazole (VRC) in a set of C. glabrata strains with known in vitro and in vivo susceptibility to this drug. Eighteen clinical isolates of C. glabrata were exposed in vitro to VRC, and the expression of the cited genes was quantified by real time quantitative polymerase chain reaction (q-PCR). In addition, the ERG11 gene was amplified and sequenced to detect possible mutations. Ten synonymous mutations were found in 15 strains, two of them being reported for the first time; however, no amino acid changes were detected. ERG11 and CDR1 were the most expressed genes in all the strains tested, while the expression of CDR2 and SNQ2 was modest. Our results show that gene expression does not directly correlate with the VRC MIC. In addition, the expression profiles of ERG11 and efflux pump genes did not change consistently after exposure to VRC. Although individual analysis did not result in a clear correlation between MIC and gene expression, we did observe an increase in ERG11 and CDR1 expression in resistant strains. It is of interest that considering both in vitro and in vivo results, the slight increase in such gene expression correlates with the observed resistance to VRC.

Virulence and susceptibility patterns of clinical Candida spp. isolates from a tertiary hospital, Tanzania

Despite the increased burden of human immunodeficiency virus (HIV) and other comobidities in developing countries, information regarding antifungal susceptibility patterns of Candida spp. and their virulence potential are still limited. Here, we report the virulence and antifungal susceptibility patterns of Candida spp. from varieties spectrum of candidiasis in a tertiary hospital, Tanzania. The study was conducted from March to December 2017. Candida spp. from clinical samples were characterized. Antifungal susceptibility patterns based on EUCAST guidelines and virulence activities (phospholipase, protease, hemolysin, and coagulase activity) were determined. A total of 399 Candida spp. isolates were obtained, of these, 278, 51 and 47 were C. albicans, C. tropicalis, and C. glabrata, respectively. Phospholipase 193/268, protease 32/51 and coagulase 25/47 were the most frequently detected virulence activities in C. albicans, C. tropicalis, and C. glabrata, respectively. Protease and phospholipase were frequently detected virulence activities from C. albicans from blood and esophageal brushes. The median zone diameter of protease activities was significantly larger among C. tropicalis than C. albicans. C. albicans, and C. tropicalis isolates were 100% sensitive to caspofungin. The proportions of C. albicans isolate resistant to fluconazole, voriconazole and posaconazole were 3.1, 3.6%, and 1.8%, respectively. In conclusion, the majority of Candida spp. isolates were sensitive to fluconazole. There are different phenotypes of C. albicans, C. glabrata and C. tropicalis based on susceptibility and virulence activities patterns, necessitating further molecular characterizations to place them in global perspective. Routine antifungal susceptibility testing to guide clinical therapy should be encouraged in developing countries.

Interpersonal Factors in the Pharmacokinetics and Pharmacodynamics of Voriconazole: Are CYP2C19 Genotypes Enough for Us to Make a Clinical Decision?

Background:

Invasive mycoses are serious infections with high mortality and increasing inci-dence. Voriconazole, an important drug to treat invasive mycosis, is metabolized mainly by the cytochrome P450 family 2 subfamily C member 19 enzyme (CYP2C19) and is affected by the genotypes of CYP2C19.

Objective:

We reviewed studies on how genotypes affect the pharmacokinetics and pharmacodynamics of voriconazole, and attempted to determine a method to decide on dosage adjustments based on genotypes, after which, the main characteristic of voriconazole was clarified in details. The pharmacokinetics of voriconazole are influenced by various inter and intrapersonal factors, and for certain populations, such as geriatric patients and pediatric patients, these influences must be considered. CYP2C19 genotype represents the main part of the interpersonal variability related to voriconazole blood concentrations. Thus monitoring the concentration of voriconazole is needed in clinical scenarios to minimize the negative influences of inter and intrapersonal factors. Several studies provided evidence on the stable trough concentration range from 1-2 to 4-6 mg/L, which was combined to consider the efficacy and toxicity. However, the therapeutic drug concentration needs to be narrowed down and evaluated by large-scale clinical trials.

Conclusion:

Though there is insufficient evidence on the relationship between CYP2C19 genotypes and clinical outcomes, there is a great potential for the initial voriconazole dose selection to be guided by the CYP2C19 genotype. Finally, voriconazole therapeutic drug monitoring is essential to provide patient-specific dosing recommendations, leading to more effective anti-fungal regimens to increase clinical effica-cy and reduce adverse drug reactions.

Are In Vitro Susceptibilities to Azole Antifungals Predictive of Clinical Outcome in the Treatment of Candidemia?

The purpose of this review is to critically analyze published data evaluating the impact of azole pharmacokinetic and pharmacodynamic parameters, MICs, and Candida species on clinical outcomes in patients with candidemia. Clinical breakpoints (CBPs) for fluconazole and voriconazole, which are used to determine susceptibility, have been defined by the Clinical and Laboratory Standards Institute (CLSI) for Candida species. Studies evaluating the relationship between treatment efficacy and in vitro susceptibility, as well as the pharmacodynamic targets, have been conducted in patients treated with fluconazole for candidemia; however, for species other than Candida albicans and Candida glabrata, and for other forms of invasive candidiasis, data remain limited and randomized trials are not available. Limited data evaluating these relationships with voriconazole are available. While pharmacodynamic targets for posaconazole and isavuconazole have been proposed based upon studies conducted in murine models, CBPs have not been established by CLSI. Fluconazole remains an important antifungal agent for the treatment of candidemia, and data supporting its use based on in vitro susceptibility are growing, particularly for C. albicans and C. glabrata Further investigation is needed to establish the roles of voriconazole, posaconazole, and isavuconazole in the treatment of candidemia and for all agents in the treatment of other forms of invasive candidiasis.

Bioactive nano-metal-organic frameworks as antimicrobials against Gram-positive and Gram-negative bacteria

More effective antibiotics are needed to overcome the problem of multidrug resistance. The antibacterial efficacies of three Zn-based nano metal-organic frameworks (nMOFs) - IRMOF-3, MOF-5, and Zn-BTC - were explored, both alone and as mixtures with ampicillin and kanamycin. When tested against Escherichia coli, Staphylococcus aureus, Staphylococcus lentus, and Listeria monocytogenes, the nMOF/drug mixtures demonstrated synergistic (IRMOF-3/kanamycin) or additive (other nMOF/drug combinations) effects compared with the nMOFs or antibiotics alone. Zn-Based nMOFs can reduce the burden of the new discovery of antimicrobial pharmaceuticals by increasing the potency of existing antibiotics.

Oral candidiasis among African human immunodeficiency virus-infected individuals: 10 years of systematic review and meta-analysis from sub-Saharan Africa

Oral candidiasis (OC) is the most common opportunistic fungal infection among immunocompromised individuals. This systematic review and meta-analysis reports on the contribution of non-albicans Candida species in causing OC among human immunodeficiency virus (HIV)-infected individuals in sub-Saharan Africa between 2005 and 2015. Thirteen original research articles on oral Candida infection/colonization among HIV-infected African populations were reviewed. The prevalence of OC ranged from 7.6% to 75.3%. Pseudomembranous candidiasis was found to range from 12.1% to 66.7%. The prevalence of non-albicans Candida species causing OC was 33.5% [95% confidence interval (CI) 30.9–36.39%]. Of 458 non-albicans Candida species detected, C. glabrata (23.8%; 109/458) was the most common, followed by C. tropicalis (22%; 101/458) and C. krusei (10.7%; 49/458). The overall fluconazole resistance was 39.3% (95% CI 34.4–44.1%). Candida albicans was significantly more resistant than non-albicans Candida species to fluconazole (44.7% vs 21.9%; p < 0.001). One-quarter of the cases of OC among HIV-infected individuals in sub-Saharan Africa were due to non-albicans Candida species. Candida albicans isolates were more resistant than the non-albicans Candida species to fluconazole and voriconazole. Strengthening the capacity for fungal diagnosis and antifungal susceptibility testing in sub-Saharan Africa is mandatory in order to track the azole resistance trend.

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.

SUSCEPTIBILITY TEST FOR FUNGI: CLINICAL AND LABORATORIAL CORRELATIONS IN MEDICAL MYCOLOGY

During recent decades, antifungal susceptibility testing has become standardized and nowadays has the same role of the antibacterial susceptibility testing in microbiology laboratories. American and European standards have been developed, as well as equivalent commercial systems which are more appropriate for clinical laboratories. The detection of resistant strains by means of these systems has allowed the study and understanding of the molecular basis and the mechanisms of resistance of fungal species to antifungal agents. In addition, many studies on the correlation of in vitro results with the outcome of patients have been performed, reaching the conclusion that infections caused by resistant strains have worse outcome than those caused by susceptible fungal isolates. These studies have allowed the development of interpretative breakpoints for Candida spp. and Aspergillus spp., the most frequent agents of fungal infections in the world. In summary, antifungal susceptibility tests have become essential tools to guide the treatment of fungal diseases, to know the local and global disease epidemiology, and to identify resistance to antifungals.

Study of Pathogens of Fungal Keratitis and the Sensitivity of Pathogenic Fungi to Therapeutic Agents with the Disk Diffusion Method

PURPOSE/AIM OF THE STUDY

To identify the causative fungi of fungal keratitis, test their susceptibility to antifungal agents with the disk diffusion method and study the relationship between the organisms, the inhibition zones and the clinical outcomes.

MATERIALS AND METHODS

535 patients with fungal keratitis in one eye were included in this study. Pathogenic fungi were isolated by corneal scraping, identified by fungal cultivation and subjected to drug sensitivity tests conducted with the disk diffusion method. The patients were treated initially with voriconazole, terbinafine and natamycin eye drops for one week. Further treatment continued using the most effective drug according to the drug sensitivity results. The patients were followed up every week until three months after cured. The inhibition zones of fungi cultured with voriconazole, terbinafine and natamycin were compared. The relationship between inhibition zones and organism, organism and treatment results measure, and each treatment results measure and inhibition zones were evaluated.

RESULTS

Of 535 patients, 53.84%, 19.25% and 26.91% were infected with Aspergillus, Fusarium and other fungi, respectively. Keratitis patients infected with Aspergillus keratitis had the worst outcome. The size of the inhibition zones of Aspergillus spp., Fusarium spp. and other fungal genera differed significantly in response to voriconazole, terbinafine and natamycin. The inhibition zone associated with natamycin correlated significantly with the clinical outcome of fungal keratitis (OR = 0.925), but no other such correlations were found for the other drugs tested.

CONCLUSIONS

Aspergillus and Fusarium were the predominant pathogenic genera causing fungal keratitis in our patients. Among the causative fungi, infections due to Aspergillus spp. were associated with the worst outcomes. The inhibition zones of fungal isolates in response to natamycin significantly correlated with the treatment outcomes of keratitis. Specifically, the smaller the natamycin inhibition zone, the lower the probability that the fungal keratitis had been eliminated.

Therapeutic Drug Monitoring and Genotypic Screening in the Clinical Use of Voriconazole

Voriconazole is an antifungal triazole that is the first line agent for treatment of invasive aspergillosis. It is metabolized by CYP2C19, CYP2C9, and CYP3A4 and demonstrates wide interpatient variability in serum concentrations. Polymorphisms in CYP2C19 contribute to variability in voriconazole pharmacokinetics. Here, evidence is examined for the use of voriconazole therapeutic drug monitoring (TDM) and the role of CYP2C19 genotyping in voriconazole dosing. The majority of studies exploring the impact of voriconazole TDM on efficacy and safety have found TDM to be beneficial. However, most of these studies are observational, with only one being a randomized controlled trial. High-volume multicenter randomized controlled trials of TDM are currently not available to support definitive guidelines. There is a significant relationship in healthy volunteers between CYP2C19 genotype and voriconazole pharmacokinetics, but this association is markedly less visible in actual patients. While CYP2C19 genotype data may explain variability of voriconazole serum levels, they alone are not sufficient to guide initial dosing. The timeliness of availability of CYP2C19 genotype data in treatment of individual patients also remains challenging. Additional studies are needed before implementation of CYP2C19 genotyping for voriconazole dosing into routine clinical care.

Pharmacokinetics and pharmacodynamics of antifungals in children and their clinical implications

Invasive fungal infections are a significant cause of morbidity and mortality in children. Successful management of these systemic infections requires identification of the causative pathogen, appropriate antifungal selection, and optimisation of its pharmacokinetic and pharmacodynamic properties to maximise its antifungal activity and minimise toxicity and the emergence of resistance. This review highlights salient scientific advancements in paediatric antifungal pharmacotherapies and focuses on pharmacokinetic and pharmacodynamic studies that underpin current clinical decision making. Four classes of drugs are widely used in the treatment of invasive fungal infections in children, including the polyenes, triazoles, pyrimidine analogues and echinocandins. Several lipidic formulations of the polyene amphotericin B have substantially reduced the toxicity associated with the traditional amphotericin B formulation. Monotherapy with the pyrimidine analogue flucytosine rapidly promotes the emergence of resistance and cannot be recommended. However, when used in combination with other antifungal agents, therapeutic drug monitoring of flucytosine has been shown to reduce high peak flucytosine concentrations, which are strongly associated with toxicity. The triazoles feature large inter-individual pharmacokinetic variability, although this pattern is less pronounced with fluconazole. In clinical trials, posaconazole was associated with fewer adverse effects than other members of the triazole family, though both posaconazole and itraconazole display erratic absorption that is influenced by gastric pH and the gastric emptying rate. Limited data suggest that the clinical response to therapy may be improved with higher plasma posaconazole and itraconazole concentrations. For voriconazole, pharmacokinetic studies among children have revealed that children require twice the recommended adult dose to achieve comparable blood concentrations. Voriconazole clearance is also affected by the cytochrome P450 (CYP) 2C19 genotype and hepatic impairment. Therapeutic drug monitoring is recommended as voriconazole pharmacokinetics are highly variable and small dose increases can result in marked changes in plasma concentrations. For the echinocandins, the primary source of pharmacokinetic variability stems from an age-dependent decrease in clearance with increasing age. Consequently, young children require larger doses per kilogram of body weight than older children and adults. Routine therapeutic drug monitoring for the echinocandins is not recommended. The effectiveness of many systemic antifungal agents has been correlated with pharmacodynamic targets in in vitro and in murine models of invasive candidiasis and aspergillosis. Further study is needed to translate these findings into optimal dosing regimens for children and to understand how these agents interact when multiple antifungal agents are used in combination.

Antifungal pharmacokinetics and pharmacodynamics

Successful treatment of infectious diseases requires choice of the most suitable antimicrobial agent, comprising consideration of drug pharmacokinetics (PK), including penetration into infection site, pathogen susceptibility, optimal route of drug administration, drug dose, frequency of administration, duration of therapy, and drug toxicity. Antimicrobial pharmacokinetic/pharmacodynamic (PK/PD) studies consider these variables and have been useful in drug development, optimizing dosing regimens, determining susceptibility breakpoints, and limiting toxicity of antifungal therapy. Here the concepts of antifungal PK/PD studies are reviewed, with emphasis on methodology and application. The initial sections of this review focus on principles and methodology. Then the pharmacodynamics of each major antifungal drug class (polyenes, flucytosine, azoles, and echinocandins) is discussed. Finally, the review discusses novel areas of pharmacodynamic investigation in the study and application of combination therapy.

Multi-drug resistant oral Candida species isolated from HIV-positive patients in South Africa and Cameroon

Candida species are a common cause of infection in immune-compromised HIV-positive individuals, who are usually treated with the antifungal drug, fluconazole, in public hospitals in Africa. However, information about the prevalence of drug resistance to fluconazole and other antifungal agents on Candida species is very limited. This study examined 128 Candida isolates from South Africa and 126 Cameroonian Candida isolates for determination of species prevalence and antifungal drug susceptibility. The isolates were characterized by growth on chromogenic and selective media and by their susceptibility to 9 antifungal drugs tested using the TREK™ YeastOne9 drug panel (Thermo Scientific, USA). Eighty-three percent (82.8%) of South African isolates were Candida albicans (106 isolates), 9.4% were Candida glabrata (12 isolates), and 7.8% were Candida dubliniensis (10 isolates). Of the Cameroonian isolates, 73.02% were C. albicans (92 isolates); 19.05% C. glabrata (24 isolates); 3.2% Candida tropicalis (4 isolates); 2.4% Candida krusei (3 isolates); 1.59% either Candida kefyr, Candida parapsilopsis, or Candida lusitaneae (2 isolates); and 0.79% C. dubliniensis (1 isolate). Widespread C. albicans resistance to azoles was detected phenotypically in both populations. Differences in drug resistance were seen within C. glabrata found in both populations. Echinocandin drugs were more effective on isolates obtained from the Cameroon than in South Africa. A multiple-drug resistant C. dubliniensis strain isolated from the South African samples was inhibited only by 5-flucytosine in vitro on the YO9 panel. Drug resistance among oral Candida species is common among African HIV patients in these 2 countries. Regional surveillance of Candida species drug susceptibility should be undertaken to ensure effective treatment for HIV-positive patients.

Comparison of Tablet and Disk Diffusion Methods for Fluconazole and VoriconazoleIn VitroActivity Testing Against Clinical Yeast Isolates

We have compared a commercially available tablet diffusion method for the in vitro antifungal susceptibility testing of fluconazole (FCZ) and voriconazole (VCZ) with the disk diffusion method M44 (CLSI) with 282 clinical yeast isolates. The superior stability of antifungal agents in tablets can explain the differences for each category of susceptibility by both methods.Neo-Sensitabs tablets antifungal susceptibility testing showed an excellent correlation (0.98 for FCZ and 0.98 for VCZ at 24h and 0.96 for FCZ and 0.94 for VCZ at 48 h ), a reduced percentage of disagreements (4.6% and 8.2% for FCZ at 24h and 48 h respectively; 1.1% and 2.1% for VCZ at 24h and 48 h respectively) and the absence of statistically significant difference in comparison with the reference protocol for performing antifungal susceptibility testing with the agar diffusion method.

Yeasts isolated from nosocomial urinary infections: antifungal susceptibility and biofilm production

BACKGROUND

Urinary Candida infections in the hospital environment are frequent and need to be better understood.

AIMS

To compare the results of antifungal susceptibility profiles of yeasts isolated from patients with urinary infections obtained by broth microdilution method (BM) and by disk diffusion (DD), and also evaluate the capacity of these yeasts to form biofilms.

METHODS

Only yeasts obtained from pure urine cultures with counts higher than 10(5) colony-forming units per milliliter, without bacteria development, of symptomatic patients were included. The isolates were identified by classical methods and the antifungal susceptibility tests were performed with the following drugs: amphotericin B, ketoconazole, fluconazole, itraconazole, voriconazole and caspofungin. The biofilm studies were carried out in polystyrene microtitration plates.

RESULTS

Ninety-five yeasts isolates were analyzed, including 40 Candida albicans, 31 Candida glabrata, 24 Candida tropicalis. In general, the majority of the isolates were susceptible to the tested drugs but some resistance was observed, especially against fluconazole. Great variability in the antifungal susceptibility results was observed with the different tested drugs and a few discrepancies were observed between both methods. We suggest that in case of DD resistance this result should be confirmed by BM, the standard method. C. tropicalis isolates showed high biofilm production (91.7%) compared to C. albicans (82.5%) and C. glabrata (61.3%), with statistical significance (p=0.0129).

CONCLUSIONS

Candiduria in critical patients requires major attention and a better control. The different susceptibility results obtained in this study showed the need to identify yeasts up to the species level, especially in patients with urinary tract infection. The development of techniques of antifungal susceptibility tests can help the clinicians in the empiric treatment of candiduria.

Identification and antifungal susceptibility of a large collection of yeast strains isolated in Tunisian hospitals

In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used as a rapid method to identify yeasts isolated from patients in Tunisian hospitals. When identification could not be exstablished with this procedure, sequencing of the internal transcribed spacer with 5.8S ribosomal DNA (rDNA) (ITS1-5.8S-ITS2) and D1/D2 domain of large-subunit (LSU rDNA) were employed as a molecular approach for species differentiation. Candida albicans was the dominant species (43.37% of all cases), followed by C. glabrata (16.55%), C. parapsilosis (13.23%), C. tropicalis (11.34%), C. dubliniensis (4.96%), and other species more rarely encountered in human diseases such as C. krusei, C. metapsilosis, C. lusitaniae, C. kefyr, C. palmioleophila, C. guilliermondii, C. intermedia, C. orthopsilosis, and C. utilis. In addition, other yeast species were obtained including Saccharomyces cerevisiae, Debaryomyces hansenii (anamorph known as C. famata), Hanseniaspora opuntiae, Kodamaea ohmeri, Pichia caribbica (anamorph known as C. fermentati), Trichosporon spp. and finally a novel yeast species, C. tunisiensis. The in vitro antifungal activities of fluconazole and voriconazole were determined by the agar disk diffusion test and Etest, while the susceptibility to additional antifungal agents was determined with the Sensititre YeastOne system. Our results showed low incidence of azole resistance in C. albicans (0.54%), C. tropicalis (2.08%) and C. glabrata (4.28%). In addition, caspofungin was active against most isolates of the collection with the exception of two K. ohmeri isolates. This is the first report to describe caspofungin resistant isolates of this yeast.

Intravenous anidulafungin followed optionally by oral voriconazole for the treatment of candidemia in Asian patients: results from an open-label Phase III trial

Background

Candidemia is a significant cause of morbidity and mortality in hospitalized patients, particularly in Asia. Anidulafungin has been reported to be an effective treatment for candidemia in Western populations, but little is known about its efficacy in Asian patients, where the clinical presentation and epidemiology may be different.

Methods

An open-label study of anidulafungin for the treatment of candidemia was recently conducted in several Asian countries. Treatment was initiated with intravenous anidulafungin, given for at least 5 days, with the option to complete treatment with oral voriconazole. The primary endpoint was global (clinical and microbiological) response, and the primary analysis was the proportion of patients in the modified intent-to-treat population with successful global response at the end of therapy. Secondary analyses included proportion with successful global response in clinically relevant patient subgroups. The safety and tolerability profile of anidulafungin and voriconazole in this population was also investigated.

Results

Forty-three patients were studied, including 42 in the modified intent-to-treat population. Eighteen patients were > 65 years, the largest age subgroup, and 21 had central venous catheters. The most common Candida species causing infection were C. tropicalis (n = 18) and C. albicans (n = 10). In the primary analysis, 73.8% had a successful global response at end of therapy. Success rates in subgroups were: 72.2% for C. tropicalis and 71.4% for C. albicans infection, 58.8% for patients > 65 years, and 81.0% for patients with central venous catheters. Safety and tolerability were comparable with the known profiles for anidulafungin (and voriconazole).

Conclusions

Although the epidemiology of Candida infections was different in this open-label study, the efficacy of anidulafungin in Asian patients with documented candidemia was consistent with previous studies in Western populations. No new safety concerns were identified.

Trial registration

http://www.clinicaltrials.gov identifier NCT00537329

Non-albicans Candida species in blood stream infections in a tertiary care hospital at New Delhi, India

BACKGROUND & OBJECTIVES

During recent decades, there has been a change in the epidemiology of Candida infections, characterized by a progressive shift from a predominance of Candida albicans to non-albicans Candida species. This study was undertaken to analyze the change in the epidemiology of candidaemia and antifungal use at tertiary care hospital in New Delhi, India, over a period of 10 years.

METHODS

A retrospective review of candidaemia between 1999 and 2008 and antifungal use from 2000 to 2008 was performed at Sir Ganga Ram Hosptial, New Delhi. Initially (1999-2005), isolates were differentiated as C. albicans and non- albicans Candida species. Between 2006-2008, these were identified to the species level and antifungal susceptibility was performed.

RESULTS

The occurrence of candidaemia and total antifungal use increased significantly. Candidaemia due to non-albicans species increased and this was correlated with an increasing use of fluconazole. There was emergence and increased isolation of a novel species C. haemulonii with decreased susceptibility to both amphotericin B and azoles. Overall, sensitivities of 89.6, 90.9, 88.6, 68.8 and 54.3 per cent to amphotericin B, 5 flucytosine, voriconazole, fluconazole and itraconazole, respectively were observed. Cross-resistance or reduced susceptibility to both fluconazole (MIC >16 μg/ml) and voriconazole was observed in 11.3 per cent isolates.

INTERPRETATION & CONCLUSIONS

The study demonstrates a shift to non-albicans Candida species causing fungaemia and the emergence of amphotericin B and azole resistant novel species, C. haemulonii. Decreased susceptibility to fluconazole, as well as the threat of emergence of cross-resistance to voriconazole in the background of high azole consumption may limit the use of these agents as a presumptive therapy for Candida blood stream infections (BSI).

In vitro susceptibilities of yeast species to fluconazole and voriconazole as determined by the 2010 National China Hospital Invasive Fungal Surveillance Net (CHIF-NET) study

We conducted active, laboratory-based surveillance for isolates from patients with invasive infections across China from August 2009 to July 2010. DNA sequencing methods were used to define species, and susceptibility to fluconazole and voriconazole was determined by the Clinical and Laboratory Standards Institute M44-A2 disk diffusion method but using up-to-date clinical breakpoints or epidemiological cutoff values. Candida spp. made up 90.5% of the 814 yeast strains isolated, followed by Cryptococcus neoformans (7.7%) and other non-Candida yeast strains (1.7%). Bloodstream isolates made up 42.9% of the strains, isolates from ascitic fluid made up 22.1%, but pus/tissue specimens yielded yeast strains in <5% of the cases. Among the Candida isolates, Candida albicans was the most common species from specimens other than blood (50.1%) but made up only 23% of the bloodstream isolates (P < 0.001). C. parapsilosis complex species were the most common Candida isolates from blood (33.2%). Uncommon bloodstream yeast strains included Trichosporon spp., C. pelliculosa, and the novel species C. quercitrusa, reported for the first time as a cause of candidemia. Most (>94%) of the isolates of C. albicans, C. tropicalis, and the C. parapsilosis complex were susceptible to fluconazole and voriconazole, as were all of the Trichosporon strains; however, 12.2% of the C. glabrata sensu stricto isolates were fluconazole resistant and 17.8% had non-wild-type susceptibility to voriconazole. Seven C. tropicalis strains were cross-resistant to fluconazole and voriconazole; six were from patients in the same institution. Resistance to fluconazole and voriconazole was seen in 31.9% and 13.3% of the uncommon Candida and non-Candida yeast strains, respectively. Causative species and azole susceptibility varied with the geographic region. This study provided clinically useful data on yeast strains and their antifungal susceptibilities in China.

Comparative pharmacodynamics of the new oxazolidinone tedizolid phosphate and linezolid in a neutropenic murine Staphylococcus aureus pneumonia model

Tedizolid phosphate (TR-701) is a novel oxazolidinone prodrug (converted to the active form tedizolid [TR-700]) with potent Staphylococcus aureus activity. The current studies characterized and compared the in vivo pharmacokinetic/pharmacodynamic (PD) characteristics of TR-701/TR-700 and linezolid against methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in the neutropenic murine pneumonia model. The pharmacokinetic properties of both drugs were linear over a dose range of 0.625 to 40 mg/kg of body weight. Protein binding was 30% for linezolid and 85% for TR-700. Mice were infected with one of 11 isolates of S. aureus, including MSSA and community- and hospital-acquired MRSA strains. Each drug was administered by oral-gastric gavage every 12 h (q12h). The dosing regimens ranged from 1.25 to 80 mg/kg/12 h for linezolid and 0.625 to 160 mg/kg/12 h for TR-701. At the start of therapy, mice had 6.24 ± 0.40 log(10) CFU/lungs, which increased to 7.92 ± 1.02 log(10) CFU/lungs in untreated animals over a 24-h period. A sigmoid maximum-effect (E(max)) model was used to determine the antimicrobial exposure associated with net stasis (static dose [SD]) and 1-log-unit reduction in organism relative to the burden at the start of therapy. The static dose pharmacodynamic targets for linezolid and TR-700 were nearly identical, at a free drug (non-protein-bound) area under the concentration-time curve over 24 h in the steady state divided by the MIC (AUC/MIC ratio) of 19 and 20, respectively. The 1-log-unit kill endpoints were also similar, at 46.1 for linezolid and 34.6 for TR-700. The exposure targets were also comparable for both MSSA and MRSA isolates. These dosing goals support further clinical trial examination of TR-701 in MSSA and MRSA pneumonia.

Canadian clinical practice guidelines for invasive candidiasis in adults

Candidemia and invasive candidiasis (C/IC) are life-threatening opportunistic infections that add excess morbidity, mortality and cost to the management of patients with a range of potentially curable underlying conditions. The Association of Medical Microbiology and Infectious Disease Canada developed evidence-based guidelines for the approach to the diagnosis and management of these infections in the ever-increasing population of at-risk adult patients in the health care system. Over the past few years, a new and broader understanding of the epidemiology and pathogenesis of C/IC has emerged and has been coupled with the availability of new antifungal agents and defined strategies for targeting groups at risk including, but not limited to, acute leukemia patients, hematopoietic stem cell transplants and solid organ transplants, and critical care unit patients. Accordingly, these guidelines have focused on patients at risk for C/IC, and on approaches of prevention, early therapy for suspected but unproven infection, and targeted therapy for probable and proven infection.

Progress in antifungal susceptibility testing of Candida spp. by use of Clinical and Laboratory Standards Institute broth microdilution methods, 2010 to 2012

Antifungal susceptibility testing of Candida has been standardized and refined and now may play a useful role in managing Candida infections. Important new developments include validation of 24-h reading times for all antifungal agents and the establishment of species-specific epidemiological cutoff values (ECVs) for the systemically active antifungal agents and both common and uncommon species of Candida. The clinical breakpoints (CBPs) for fluconazole, voriconazole, and the echinocandins have been revised to provide species-specific interpretive criteria for the six most common species. The revised CBPs not only are predictive of clinical outcome but also provide a more sensitive means of identifying those strains with acquired or mutational resistance mechanisms. This brief review serves as an update on the new developments in the antifungal susceptibility testing of Candida spp. using Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BMD) methods.