Development of interpretive breakpoints for antifungal susceptibility testing: conceptual framework and analysis of in vitro-in vivo correlation data for fluconazole, itraconazole, and candida infections. Subcommittee on Antifungal Susceptibility Testing of the National Committee for Clinical Laboratory Standards

The effect of cumulative length of hospital stay on the antifungal resistance of Candida strains isolated from critically ill surgical patients

Fluconazole is the first line of therapy for the management of candidiasis. However, fluconazole-resistant strains pose an emerging challenge in everyday clinical practice. In this study, we sought to determine whether cumulative length of hospital stay (CLOS) is a predictive factor for the acquisition of non-susceptible Candida strains to fluconazole. Thirty-three critically ill emergency surgery patients with 56 Candida isolates were enrolled in this prospective study. We divided our isolates according to their minimum inhibitory concentration (MIC) to fluconazole using 8 mcg/ml as a cutoff. We then compared the two groups with respect to basic demographics, antifungal agents prescribed, number of wide-spectrum antibiotics, duration of central venous catheter placement, elapsed time to positive culture, duration of prior hospital stay, and length of hospital stay. Non-susceptible fluconazole samples belonged to patients with a significantly longer prior hospital stay and a longer CLOS (P = 0.02 and 0.01, respectively). The difference between the 2 groups regarding non-albicans strains was statistically significant (P < 0.001). By fitting a non-parametric receiver-operating characteristics (ROC) curve into our analysis, a CLOS ≥ 29 days predicted the occurrence of non-susceptible strains with 90% sensitivity and 79.6% specificity (correct classification 81.5%). A CLOS ≥ 29 days is a strong predictor for the isolation of non-susceptible Candida isolates to fluconazole among critically ill emergency surgery patients. Clinicians should consider the duration of previous hospital stay when deciding on empiric antifungal therapy.

Itraconazole for invasive fungal infection with pediatric malignancies

BACKGROUND

Invasive fungal infection (IFI) is an increasingly common and often fatal infection in children with hematological malignancies and solid tumor. Prophylactic therapy with anti-fungal agents is very important for these patients, because the early diagnosis of IFI is very difficult.

PROCEDURE

A total of 0.5 mL/kg per day of itraconazole oral solution (ITCZ-OS) was administered in twice-daily doses to 22 children with hematological malignancies who had received chemotherapy, and its usefulness and safety regarding the prevention of IFI were examined.

RESULT

Prophylactic therapy with ITCZ-OS was completed in 18 (81.8%) of the 22 children. Of these, IFI was not strongly suspected in any child. Side-effects included non-alcoholic steatohepatitis in two children, syndrome of inappropriate anti-diuretic hormone secretion in one, and liver dysfunction in one. The administration of ITCZ-OS was discontinued in these cases. These four children had received vincristine sulfate (VCR) or irinotecan hydrochloride, which were reported to interact with ITCZ. In most children the plasma levels of ITCZ were satisfactory. The plasma levels, however, were slightly increased in VCR-treated children; ITCZ should be carefully administered.

CONCLUSION

Although the number of subjects was small in the present study, the plasma concentrations of ITCZ-OS favorably increased in the children with hematological malignancies, suggesting that this agent exhibits prophylactic effects on IFI. It must be considered, however, that some combined agents cause side-effects via their interactions with ITCZ.

A simple, sensitive high-performance liquid chromatography -ultraviolet method for the quantification of concentration and steady-state pharmacokinetics of itraconazole and hydroxyitraconazole

Background

A steady-state trough plasma itraconazole concentration greater than 500 ng/mL is a therapeutic target for itraconazole. A simple, rapid and sensitive high-performance liquid chromatography-based method was developed for quantitation of itraconazole and hydroxyitraconazole in human plasma.

Methods

Itraconazole and hydroxyitraconazole were separated using a mobile phase of 0.5% KH2PO4 (pH 6.0)-acetonitrile (30:70, v/v) on a CAPCELLPAK C18 MGII column at a flow rate of 0.5 mL/min and ultraviolet absorbance at 260 nm.

Results

The analysis required 200 μL of plasma and involved a rapid, simple solid-phase extraction with an Oasis HLB cartridge, which resulted in recoveries of 87–92% for itraconazole and 91–94% for hydroxyitraconazole. The lower limit of quantification for itraconazole and hydroxyitraconazole was 5 ng/mL each. Intra- and interday coefficients of variation for itraconazole and hydroxyitraconazole were less than 11.3% and 12.2%, respectively, and accuracies were within 11.7% and 4.5% over the linear range, respectively. Although the steady-state plasma concentrations of itraconazole and hydroxyitraconazole ranged from 506 to 2482 ng/mL and from 766 to 2444 ng/mL, respectively, after a two-day loading dose of 400 mg/day intravenous itraconazole followed by the administration of 200 mg/day itraconazole oral solution, calibration curves of itraconazole and hydroxyitraconazole showed positive linearity in a concentration range of 5–2500 and 50–2500 ng/mL, respectively.

Conclusions

Our results indicate that this method is applicable for the monitoring of plasma levels of itraconazole and hydroxyitraconazole in a clinical setting. Furthermore, the regimen presented here might also be effective in preventing infection, but further studies with large sample sizes are necessary to investigate this avenue.

Conazoles

This review provides a historical overview of the analog based drug discovery of miconazole and its congeners, and is focused on marketed azole antifungals bearing the generic suffix “conazole”. The antifungal activity of miconazole, one of the first broad-spectrum antimycotic agents has been mainly restricted to topical applications. The attractive in vitro antifungal spectrum was a starting point to design more potent and especially orally active antifungal agents such as ketoconazole, itraconazole, posaconazole, fluconazole and voriconazole. The chemistry, in vitro and in vivo antifungal activity, pharmacology, and clinical applications of these marketed conazoles has been described.

In vivo comparison of the pharmacodynamic targets for echinocandin drugs against Candida species

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

Evaluation by data mining techniques of fluconazole breakpoints established by the Clinical and Laboratory Standards Institute (CLSI) and comparison with those of the European Committee on Antimicrobial Susceptibility Testing (EUCAST)

The EUCAST and the CLSI have established different breakpoints for fluconazole and Candida spp. However, the reference methodologies employed to obtain the MICs provide similar results. The aim of this work was to apply supervised classification algorithms to analyze the clinical data used by the CLSI to establish fluconazole breakpoints for Candida infections and to compare these data with the results obtained with the data set used to set up EUCAST fluconazole breakpoints, where the MIC for detecting failures was >4 mg/liter, with a sensitivity of 87%, a false-positive rate of 8%, and an area under the receiver operating characteristic (ROC) curve of 0.89. Five supervised classifiers (J48 and CART decision trees, the OneR decision rule, the naïve Bayes classifier, and simple logistic regression) were used to analyze the original cohort of patients (Rex's data set), which was used to establish CLSI breakpoints, and a later cohort of candidemia (Clancy's data set), with which CLSI breakpoints were validated. The target variable was the outcome of the infections, and the predictor variable was the MIC or dose/MIC ratio. For Rex's data set, the MIC detecting failures was >8 mg/liter, and for Clancy's data set, the MIC detecting failures was >4 mg/liter, in close agreement with the EUCAST breakpoint (MIC > 4 mg/liter). The sensitivities, false-positive rates, and areas under the ROC curve obtained by means of CART, the algorithm with the best statistical results, were 52%, 18%, and 0.7, respectively, for Rex's data set and 65%, 6%, and 0.72, respectively, for Clancy's data set. In addition, the correlation between outcome and dose/MIC ratio was analyzed for Clancy's data set, where a dose/MIC ratio of >75 was associated with successes, with a sensitivity of 93%, a false-positive rate of 29%, and an area under the ROC curve of 0.83. This dose/MIC ratio of >75 was identical to that found for the cohorts used by EUCAST to establish their breakpoints (a dose/MIC ratio of >75, with a sensitivity of 91%, a false-positive rate of 10%, and an area under the ROC curve of 0.90).

MALDI-TOF MS-based drug susceptibility testing of pathogens: the example of Candida albicans and fluconazole

MALDI-TOF MS can be used for the identification of microorganism species. We have extended its application to a novel assay of Candida albicans susceptibility to fluconazole, based on monitoring modifications of the proteome of yeast cells grown in the presence of varying drug concentrations. The method was accurate, and reliable, and showed full agreement with the Clinical Laboratory Standards Institute's reference method. This proof-of-concept demonstration highlights the potential for this approach to test other pathogens.

Design, synthesis and determination of antifungal activity of 5(6)-substituted benzotriazoles

In an effort to find inhibitors that are effective against both Candida and Aspergillus spp., a series of 5(6)-(un)substituted benzotriazole analogs, represented by compounds 3a-3h and 3b'-3f', were prepared using a crystalline oxirane intermediate 1 previously synthesized in our laboratory. All the compounds were evaluated for inhibitory activity against various species of Candida and Aspergillus. Compounds 3b' (5,6-dimethylbenzotriazol-2-yl derivative), 3d (5-chlorobenzotriazol-1-yl derivative) and 3e' (6-methylbenzotriazol-1-yl derivative) exhibited potent antifungal activity, with the MICs for Candida spp. and Aspergillus niger, ranging from 1.6 microg/mL to 25 microg/mL and 12.5 microg/mL to 25 microg/mL, respectively. The present work describes the design, synthesis, regioisomer characterization (through COSY and NOESY 2D-NMR spectroscopy and single molecule X-ray crystallography), antifungal evaluation, molecular docking, and structure-activity relationships of the various 5(6)-(un)substituted benzotriazole analogs.

Antifungal activity of alpha-mangostin against Candida albicans

This study was conducted to examine the activity of alpha-mangostin against Candida albicans, the most important microorganism implicated in oral candidiasis. Its activity was compared to Clotrimazole and Nystatin. Results showed that alpha-mangostin was effective against C. albicans, the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were 1,000 and 2,000 microg/ml, respectively. The C. albicans killing activity of alpha-mangostin was more effective than Clotrimazole and Nystatin. The cytotoxicity of alpha-mangostin was determined and it was found that alpha-mangostin at 4,000 microg/ml was not toxic to human gingival fibroblast for 480 min. The strong antifungal activity and low toxicity of alpha-mangostin make it a promising agent for treatment of oral candidiasis.

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.

Acquisition of flucytosine, azole, and caspofungin resistance in Candida glabrata bloodstream isolates serially obtained from a hematopoietic stem cell transplant recipient

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

Safety of triazole antifungal drugs in patients with cancer

Triazole drugs are widely used in cancer patients for prophylaxis and treatment of life-threatening invasive fungal infections. Fluconazole, available for over two decades, is safe and effective in patients with cancer; however, the excellent safety profile of fluconazole may not be applicable to the newer triazoles. Itraconazole, voriconazole and posaconazole are associated with adverse events, and drug interactions frequently occur, particularly in cancer patients, since the triazoles and many drugs used in cancer chemotherapy are metabolized via a common metabolic pathway, the hepatic cytochrome P450 system. Close monitoring for drug interactions is needed when triazoles are used with anti-neoplastic drugs and dosage modification of the triazole or its discontinuation may be required. Monitoring of triazole serum concentrations is becoming an important aspect of management to minimize toxicity and ensure efficacy.

Antifungal drug resistance mechanisms in fungal pathogens from the perspective of transcriptional gene regulation

Fungi are primitive eukaryotes and have adapted to a variety of niches during evolution. Some fungal species may interact with other life forms (plants, insects, mammals), but are considered as pathogens when they cause mild to severe diseases. Chemical control strategies have emerged with the development of several drugs with antifungal activity against pathogenic fungi. Antifungal agents have demonstrated their efficacy by improving patient health in medicine. However, fungi have counteracted antifungal agents in several cases by developing resistance mechanisms. These mechanisms rely on drug resistance genes including multidrug transporters and drug targets. Their regulation is crucial for the development of antifungal drug resistance and therefore transcriptional factors critical for their regulation are being characterized. Recent genome-wide studies have revealed complex regulatory circuits involving these genetic and transcriptional regulators. Here, we review the current understanding of the transcriptional regulation of drug resistance genes from several fungal pathogens including Candida and Aspergillus species.

Characterization of Hwp2, a Candida albicans putative GPI-anchored cell wall protein necessary for invasive growth

Various factors are thought to be responsible for Candida albicans virulence, such as lipases, proteases and adhesins. Many of these factors are GPI-anchored cell surface proteins responsible for pathogenicity. Hwp2 is a putative GPI-anchored protein. The purpose of this study is to characterize the role of Hwp2 regarding filamentation on various filamentation-inducing and non-inducing solid and liquid media, virulence in a mouse model of disseminated candidiasis, and drug resistance to six widely used antifungal agents, by creating a homozygous null hwp2 strain and comparing it with the parental and a revertant HWP2(+)strain. It was observed that an hwp2Delta strain was highly filamentation-deficient on solid agar media as opposed to most liquid media tested. Furthermore, the mutant strain was slightly reduced in virulence compared to the wild strain since all mice infected with the control strain died after 6 days of injection compared with 11 days for the mutant. These results indicate a possible role for Hwp2 in adhesion and invasiveness. Finally a previously unidentified 37-amino-acid-long, stretch of Hwp2, possibly involved in protein aggregation, was found to align with high sequence identity and exclusively to C. albicans cell wall proteins.

Determinants of mortality in non-neutropenic ICU patients with candidaemia

INTRODUCTION

Candidaemia in critically-ill intensive care unit (ICU) patients is associated with high crude mortality. Determinants of mortality--particularly those amenable to potential modification--are incompletely defined.

METHODS

A nationwide prospective clinical and microbiological cohort study of all episodes of ICU-acquired candidaemia occurring in non-neutropenic adults was undertaken in Australian ICUs between 2001 and 2004. Multivariate Cox regression analyses were performed to determine independently significant variables associated with mortality.

RESULTS

183 episodes of ICU-acquired candidaemia occurred in 183 patients during the study period. Of the 179 with microbiological data, Candida albicans accounted for 111 (62%) episodes and Candida glabrata, 32 (18%). Outcome data were available for 173: crude hospital mortality at 30 days was 56%. Host factors (older age, ICU admission diagnosis, mechanical ventilation and ICU admission diagnosis) and failure to receive systemic antifungal therapy were significantly associated with mortality on multivariate analysis. Among the subset who received initial fluconazole therapy (n = 93), the crude mortality was 52%. Host factors (increasing age and haemodialysis receipt), but not organism- (Candida species, fluconazole MIC), pharmacokinetic- (fluconazole dose, time to initiation), or pharmacodynamic-related parameters (fluconazole dose:MIC ratio) were associated with mortality. Process of care measures advocated in recent guidelines were implemented inconsistently: follow-up blood cultures were obtained in 68% of patients, central venous catheters removed within five days in 80% and ophthalmological examination performed in 36%.

CONCLUSIONS

Crude mortality remains high in Australian ICU patients with candidaemia and is overwhelmingly related to host factors but not treatment variables (the time to initiation of antifungals or fluconazole pharmacokinetic and pharmacodynamic factors). The role and timing of early antifungal intervention in critically-ill ICU patients requires further investigation.

Bulky 1,4-benzoxazine derivatives with antifungal activity

For many years the development of new azole antifungals has been quite empirically based. More recently, the publication of the crystal structure of CYP51 of Mycobacterium tuberculosis (MT-CYP51) provided new opportunities to rationalize the knowledge about antifungal action of this class of compounds. Recent studies reported that a 'channel 2 opened' conformation of the enzyme could better explain the interaction with ketoconazole (KTZ)-like drugs. Conformational changes were made on our model of Candida albicans CYP51 (CA-CYP51) previously reported and docking experiments were performed. The results allowed new KTZ analogues to be designed, by predicting that the 1,4-benzoxazine moiety could replace the KTZ aryl-piperazinyl chain. The synthesis of derivatives 12 and 13 was planned. The in vitro antifungal activity was evaluated against different Candida species and low and high capsulated strains of Cryptococcus neoformans. Since the in vitro activity do not necessarily correlate with the in vivo antifungal activity the newly synthesized compounds were also tested in a murine model of systemic C. albicans infection. The therapeutic effect was evaluated in terms of animal survival and of fungal growth in the kidneys, the target organ in systemic candidiasis.

[Epidemiology of candidemia: a one-year prospective observational study in the west of France]

OBJECTIVE

A one-year prospective, observational study was conducted in the west of France, to evaluate the epidemiology of candidemia.

METHOD

During the year 2004, each patient with at least one blood culture yielding Candida sp. was included. For each episode of candidemia, mycological, demographical, clinical, and therapeutic data, as well as outcome, were collected.

RESULTS

One hundred and ninety-three strains of Candida sp. were isolated in 186 patients, Candida albicans accounting for 54.9%, Candida glabrata for 18.7%, Candida parapsilosis for 12.9%, Candida tropicalis for 4.7% and Candida krusei for 4.1% of these isolates. A percentage of 84% of the Candida isolates were fully susceptible to fluconazole in vitro. Dose-dependent susceptibility or resistance to fluconazole was detected in more than one third of the Candida glabrata strains, of which 36% were also resistant to voriconazole. Two-thirds of the patients were males, and the mean age was 61.5 years. A percentage of 37% of patients were hospitalized in intensive care units. The main predisposing factors for candidemia were broad-spectrum antibiotics (75.8%), central venous catheter (72.6%), cancer or hematologic malignancy (47.3%), recent surgery (42.5%), total parenteral nutrition (37.6%). One hundred and fifty-four patients were treated with antifungal therapy, two-thirds of whom received fluconazole as first-line agent. Mortality was 49% overall, and was significantly higher in case of septic shock, advanced age, and absence of catheter removal.

Therapeutic drug monitoring for triazoles

PURPOSE OF REVIEW

Invasive fungal infections are a leading cause of morbidity and mortality in immunocompromised patients, and mechanisms to optimize therapeutic outcomes are urgently required. Therapeutic drug monitoring represents an important component for the routine use of the triazoles.

RECENT FINDINGS

Triazoles have revolutionized the prevention and treatment of invasive fungal infections. Increasing data suggest that this class displays important concentration-effect and concentration-toxicity relationships. There has been an increased understanding of the pharmacokinetics and pharmacodynamics of triazoles, and this has facilitated the identification of concentrations (or drug exposures) that are both effective and nontoxic. This review discusses the application of therapeutic drug monitoring to fluconazole, itraconazole, voriconazole and posaconazole.

SUMMARY

Therapeutic drug monitoring represents an important mechanism to optimize the outcome of immunocompromised patients receiving triazoles.

Dermaseptins from Phyllomedusa oreades and Phyllomedusa distincta: Secondary structure, antimicrobial activity, and mammalian cell toxicity

The present study reports the structural characteristics, the biological activities, and preliminary clinical investigations of three synthetic members of the dermaseptin family of antimicrobial peptides. The three peptides showed similar tendencies to form alpha-helical structures in non-polar media. The antimicrobial activity towards bacteria and fungi was determined in the micromolar concentration and the peptides did not influenced peritoneal cells viability. One of the peptides was intravenously administered in mice at concentrations similar to those of antibiotics employed in bacterial/fungal infections and it did not cause any detectable changes in cells and tissues.

Synthesis and antifungal activity of new thienyl and aryl conazoles

Recent studies reported that an first generation azole (tioconazole) was active against Candida glabrata petite mutants, a fluconazole- and voriconazole- resistant strain of fungi characterized as most azole resistant yeast by an overexpression of the efflux pumps. Therefore, monosubstituted 1-[2-(2,4-dichlorophenyl)ethyl]-1H-imidazoles differing from tioconazole by the nature of the linker and of the aromatic ring in their side-chain were synthesized and evaluated against the mutant and the wild-type strain of C. glabrata. New 2-aryl-1-azolyl-3-thienylbutan-2-ols were then designed and synthesized, and their antifungal activity was evaluated against both strains of C. glabrata and two other major human pathogenic fungi, C. albicans and Aspergillus fumigatus. These new compounds exhibited a broad spectrum activity, as well as good efficiency against the petite mutant, suggesting that they may overcome the increased expression of the efflux pumps usually observed in clinical yeast isolates resistant to current azoles.

Relationship between susceptibility of Candida spp. isolates to amphotericin B and death or survival of patients with candidemia episodes

In this study, the susceptibility to amphotericin B of Candida spp. isolates obtained from patients with candidemia was related to their respective clinical outcomes. The susceptibility tests were carried out in three culture media: RPMI 1640, Antibiotic medium 3 and Yeast Nitrogen Base dextrose. We have found that minimal inhibitory concentrations and minimal fungicidal concentrations obtained using AM3 and YNBd media were significantly higher for Candida spp. from patients who died than for those from patients who survived the candidemia (P < 0.05). The assays with RPMI 1640 medium did not show these differences.

Rationale for reading fluconazole MICs at 24 hours rather than 48 hours when testing Candida spp. by the CLSI M27-A2 standard method

We investigated if CLSI M27-A2 Candida species breakpoints for fluconazole MIC are valid when read at 24 h. Analysis of a data set showed good correlation between 48- and 24-h MICs, as well as similar outcomes and pharmacodynamic efficacy parameters, except for isolates in the susceptible dose-dependent category, such as Candida glabrata.

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.

Susceptibility testing of Cryptococcus diffluens against amphotericin B, flucytosine, fluconazole, itraconazole, voriconazole and posaconazole

Cryptococcus diffluens is a recently re-established species that shares several phenotypic features with Cryptococcus neoformans. We evaluated the application of the Clinical Laboratory Standards Institute (CLSI, formerly NCCLS) macro- and microbroth dilution methods and the E-test agar diffusion method to determine the in vitro susceptibilities of known strains of C. diffluens against amphotericin B (AMB), flucytosine (5-FC), fluconazole (FLC), itraconazole (ITC) and the novel triazoles, voriconazole (VRC) and posaconazole (PSC). Seven strains were found to be resistant in vitro to AMB (MICs >/=2 microg/ml), five were resistant to 5-FC (MICs of >/=32 microg/ml), four were resistant to FLC (MICs of FLC >/=32 microg/ml) and nine were resistant to ITC (MICs of ITC >1 microg/ml). In contrast, VRC and PSC showed good in vitro activity against C.diffluens strains, even those with elevated MICs to amphotericin B and/or established azoles. Most of the isolates were inhibited by 0.5 microg/ml of both VRC and PSC. A clinical isolate showing phenotypic switching exhibited elevated MICs to both agents, i.e., VRC (>16 microg/ml) and PSC (>8 microg/ml).

In vivo pharmacodynamic target investigation for micafungin against Candida albicans and C. glabrata in a neutropenic murine candidiasis model

Previous studies using in vivo candidiasis models have demonstrated that the concentration-associated pharmacodynamic indices, the maximum concentration of a drug in serum/MIC and 24-h area under the curve (AUC)/MIC, are associated with echinocandin treatment efficacy. The current investigations used a neutropenic murine model of disseminated Candida albicans and C. glabrata infection to identify the 24-h AUC/MIC index target associated with a stasis and killing endpoint for the echinocandin, micafungin. The kinetics after intraperitoneal micafungin dosing were determined in neutropenic infected mice. Peak levels and AUC values were linear over the 16-fold dose range studied. The serum drug elimination half-life ranged from 7.5 to 16 h. Treatment studies were conducted with 4 C. albicans and 10 C. glabrata isolates with micafungin MICs varying from 0.008 to 0.25 microg/ml to determine whether similar 24-h AUC/MIC ratios were associated with efficacy. The free drug AUC/MICs associated with stasis and killing (1-log) endpoints were near 10 and 20, respectively. The micafungin exposures associated with efficacy were similar for the two Candida species. Furthermore, the free drug micafungin exposures required to produce stasis and killing endpoints were similar to those recently reported for another echinocandin, anidulafungin, against the identical Candida isolates in this model.

Therapeutic drug monitoring of antifungals: pharmacokinetic and pharmacodynamic considerations

Therapeutic drug monitoring of any pharmacologic agent should be considered when there is both significant pharmacokinetic variability and strong, clinically relevant, exposure-effect relationships. Many antifungal drugs exhibit marked variability in drug concentration as a result of inconsistent absorption, metabolism, elimination, or interaction with concomitant medications. For each of the available antifungal drugs, both preclinical and clinical trials have exhibited a relationship between serum concentrations and treatment efficacy. For a smaller subset of compounds, a similar relationship has been identified for the toxicity. The kinetic variability among patients falls outside the therapeutic window for a group of four antifungal compounds. This review summarizes the current literature on therapeutic drug monitoring for these antifungal agents.

Association of fluconazole pharmacodynamics with mortality in patients with candidemia

Recent studies of nonneutropenic patients with candidemia or candidiasis suggest that fluconazole pharmacodynamic parameters correlate with clinical outcomes; however, additional data of correlation to mortality in patients with candidemia would be valuable. We assessed the impact of MICs for Candida, fluconazole pharmacodynamics, and patient characteristics on all-cause mortality with use of a prospective cohort of 96 hospitalized patients with candidemia. Among 84 patients for whom Candida isolates were available for testing, the most frequent Candida species isolated were Candida albicans (44%), followed by Candida parapsilosis (20.2%), and Candida glabrata (20.2%). Fluconazole resistance (MIC of >or=64 microg/ml) was present in 7 (8.3%) to 10 (11.9%) of 84 isolates, depending on the MIC endpoint determination method (50% or 80% inhibition read at 24 or 48 h). Overall mortality occurred in 27 (28.1%) of 96 patients, and nonsurvivors were more likely to have fluconazole-resistant isolates (25% versus 6.7%; P = 0.02). Multivariable analysis demonstrated an association between fluconazole resistance and mortality, but it did not reach statistical significance (odds ratio, 5.3; 95% confidence interval, 0.8 to 33.4; P = 0.08). By pharmacodynamic analysis, a fluconazole area under the concentration-time curve/MIC of <11.5 or MIC of >or=64 was associated with increased patient mortality (P <or= 0.09). These data support previous findings of an antifungal exposure-response relationship to mortality in patients with candidemia. In addition, similar MICs were obtained using a 24- or 48-h MIC endpoint determination, thus providing the opportunity to assess earlier the impact of isolate susceptibility on therapy.