John D. Cleary

Antifungal Susceptibility Survey of 2,000 Bloodstream Candida Isolates in the United States

ABSTRACT Candida bloodstream isolates (n = 2,000) from two multicenter clinical trials carried out by the National Institute of Allergy and Infectious Diseases Mycoses Study Group between 1995 and 1999 were tested against amphotericin B (AMB), flucytosine (5FC), fluconazole (FLU), itraconazole (ITR), voriconazole (VOR), posaconazole (POS), caspofungin (CFG), micafungin (MFG), and anidulafungin (AFG) using the NCCLS M27-A2 microdilution method. All drugs were tested in the NCCLS-specified RPMI 1640 medium except for AMB, which was tested in antibiotic medium 3. A sample of isolates was also tested in RPMI 1640 supplemented to 2% glucose and by using the diluent polyethylene glycol (PEG) in lieu of dimethyl sulfoxide for those drugs insoluble in water. Glucose supplementation tended to elevate the MIC, whereas using PEG tended to decrease the MIC. Trailing growth occurred frequently with azoles. Isolates were generally susceptible to AMB, 5FC, and FLU. Rates of resistance to ITR approached 20%. Although no established interpretative breakpoints are available for the candins (CFG, MFG, and AFG) and the new azoles (VOR and POS), they all exhibited excellent antifungal activity, even for those strains resistant to the other aforementioned agents.

Voriconazole versus a regimen of amphotericin B followed by fluconazole for candidaemia in non-neutropenic patients: a randomised non-inferiority trial.

BACKGROUND Voriconazole has proven efficacy against invasive aspergillosis and oesophageal candidiasis. This multicentre, randomised, non-inferiority study compared voriconazole with a regimen of amphotericin B followed by fluconazole for the treatment of candidaemia in non-neutropenic patients. METHODS Non-neutropenic patients with a positive blood culture for a species of candida and clinical evidence of infection were enrolled. Patients were randomly assigned, in a 2:1 ratio, either voriconazole (n=283) or amphotericin B followed by fluconazole (n=139). The primary efficacy analysis was based on clinical and mycological response 12 weeks after the end of treatment, assessed by an independent data-review committee unaware of treatment assignment. FINDINGS Of 422 patients randomised, 370 were included in the modified intention-to-treat population. Voriconazole was non-inferior to amphotericin B/fluconazole in the primary efficacy analysis, with successful outcomes in 41% of patients in both treatment groups (95% CI for difference -10.6% to 10.6%). At the last evaluable assessment, outcome was successful in 162 (65%) patients assigned voriconazole and 87 (71%) assigned amphotericin B/fluconazole (p=0.25). Voriconazole cleared blood cultures as quickly as amphotericin B/fluconazole (median time to negative blood culture, 2.0 days). Treatment discontinuations due to all-cause adverse events were more frequent in the voriconazole group, although most discontinuations were due to non-drug-related events and there were significantly fewer serious adverse events and cases of renal toxicity than in the amphotericin B/fluconazole group. INTERPRETATION Voriconazole was as effective as the regimen of amphotericin B followed by fluconazole in the treatment of candidaemia in non-neutropenic patients, and with fewer toxic effects. RELEVANCE TO PRACTICE There are several options for treatment of candidaemia in non-neutropenic patients, including amphotericin B, fluconazole, voriconazole, and echinocandins. Voriconazole can be given both as initial intravenous treatment and as an oral stepdown agent.

A Randomized and Blinded Multicenter Trial of High-Dose Fluconazole plus Placebo versus Fluconazole plus Amphotericin B as Therapy for Candidemia and Its Consequences in Nonneutropenic Subjects

A randomized, blinded, multicenter trial was conducted to compare fluconazole (800 mg per day) plus placebo with fluconazole plus amphotericin B (AmB) deoxycholate (0.7 mg/kg per day, with the placebo/AmB component given only for the first 5-6 days) as therapy for candidemia due to species other than Candida krusei in adults without neutropenia. A total of 219 patients met criteria for a modified intent-to-treat analysis. The groups were similar except that those who were treated with fluconazole plus placebo had a higher mean (+/- standard error) Acute Physiology and Chronic Health Evaluation II score (16.8+/-0.6 vs. 15.0+/-0.7; P=.039). Success rates on study day 30 by Kaplan-Meier time-to-failure analysis were 57% for fluconazole plus placebo and 69% for fluconazole plus AmB (P=.08). Overall success rates were 56% (60 of 107 patients) and 69% (77 of 112 patients; P=.043), respectively; the bloodstream infection failed to clear in 17% and 6% of subjects, respectively (P=.02). In nonneutropenic subjects, the combination of fluconazole plus AmB was not antagonistic compared with fluconazole alone, and the combination trended toward improved success and more-rapid clearance from the bloodstream.

Effect of Candida glabrata FKS1 and FKS2 Mutations on Echinocandin Sensitivity and Kinetics of 1,3-β-d-Glucan Synthase: Implication for the Existing Susceptibility Breakpoint

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

Reduced Candida glabrata susceptibility secondary to an FKS1 mutation developed during candidemia treatment.

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

Antifungal Therapy During Pregnancy

Careful consideration of the benefit to the mother and the risk to the fetus is required when prescribing antifungal therapy in pregnancy. Imidazoles are considered safe as topical therapy for fungal skin infections during pregnancy. Nystatin is minimally absorbed and is effective for vaginal therapy. Although vaginal use of the imidazoles is probably safe during the later stages of pregnancy, their systemic absorption is higher than when applied to the skin. The systemic antifungal drug with which there has been the most experience in pregnancy is amphotericin B. There have been no reports of teratogenesis attributed to this agent. There is evidence to suggest that fluconazole exhibits dose-dependent teratogenic effects; however, it appears to be safe at lower doses (150 mg/day). Ketoconazole, flucytosine, and griseofulvin have been shown to be teratogenic and/or embryotoxic in animals. Iodides have been associated with congenital goiter and should not be used during pregnancy.

Voriconazole: A New Triazole Antifungal Agent

OBJECTIVE: To review the pharmacology, in vitro susceptibility, pharmacokinetics, clinical efficacy, and adverse effects of voriconazole, a triazole antifungal agent. DATA SOURCES: A MEDLINE search, restricted to English language, was conducted from 1990 to June 2002. Supplementary sources included program abstracts from the Interscience Conference on Antimicrobial Agents and Chemotherapy and the Infectious Diseases Society of America from 1996 to 2001 and manufacturer information available through the Food and Drug Administrations Web site. DATA EXTRACTION: All published and unpublished trials and abstracts citing voriconazole were selected. DATA SYNTHESIS: Voriconazole has shown in vitro activity against many yeasts and a variety of mold and dermatophyte isolates. Voriconazole can be administered either orally or parenterally. It exhibits good oral bioavailability, wide tissue distribution including distribution into the central nervous system, and hepatic metabolism. Drug interactions occur through inhibition of the CYP2C9, CYP2C19, and CYP3A4 isoenzymes, resulting in alterations in kinetic parameters of either voriconazole or the interacting agent. Efficacy has been illustrated in open, noncomparative studies of aspergillosis in immunocompromised patients. Human case reports describe successful treatment of rare fungal pathogens. The most commonly reported adverse events include visual disturbances and elevations in liver function tests. CONCLUSIONS: Voriconazole is at least as effective as amphotericin B in the treatment of acute invasive aspergillosis in immunocompromised patients. It has similar efficacy as fluconazole in treatment of esophageal candidiasis. Voriconazole did not achieve statistical non-inferiority to liposomal amphotericin B for empirical therapy in patients with neutropenia and persistent fever, diminishing enthusiasm for use in this indication until additional trials are completed. Based on case reports and in vitro efficacy, voriconazole may prove to be a clinically useful agent in the treatment of other fungal disease.

Amphotericin B Activation of Human Genes Encoding for Cytokines

Amphotericin B has been shown to cause release of cytokines, including interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), from monocytes and macrophages. Human and murine monocytic cell lines were used to evaluate the effects of amphotericin B on the transcription of IL-1alpha, IL-1beta, and TNF-alpha and the transcription and production of soluble IL-1 receptor antagonist (sIL-1Ra). The effects of inhibitors of transcription and translation on amphotericin B-induced IL-1beta expression in a human monocytic cell line were also evaluated. Amphotericin B markedly increased IL-1beta and TNF-alpha mRNA levels, with peak levels occurring by 4 h. Amphotericin B induced production of sIL-1Ra in a dose-dependent fashion and induced sIL-1Ra mRNA, with peak levels at 24 h. Cycloheximide and actinomycin D resulted in a dose-dependent decrease in amphotericin B-induced IL-1beta expression at 2 h. Thus, amphotericin B induces gene expression for IL-1beta, TNF-alpha, and IL-1Ra in human and murine monocytic cells.

Pharmacologic modulation of interleukin-1 expression by amphotericin B-stimulated human mononuclear cells.

Fever and chills occur frequently with amphotericin B (AB) administration, but the mechanism that causes these reactions has not been definitively established. A variety of proinflammatory cytokines, including interleukin-1 (IL-1) and tumor necrosis factor, have been shown to be important mediators of fever. In order to clarify the cellular and biochemical responses associated with AB-induced fever, the experiments described sought to (i) establish whether human mononuclear cells exposed to AB in vitro expressed IL-1 beta, (ii) evaluate whether clinically used premedications for fever prophylaxis in AB-treated patients were effective in down-regulating IL-1 beta expression in vitro, (iii) evaluate whether methylxanthine agents with immunomodulatory actions effected in vitro IL-1 beta expression, and (iv) define the dose and time dependency of the modulating effects. Peripheral blood mononuclear cells were isolated by density centrifugation and resuspended to 10(6) cells per ml in culture wells of Linbro plates. When cocultured for 2 h with human mononuclear cells, both Escherichia coli lipopolysaccharide and AB stimulated IL-1 beta expression in a dose-related fashion. AB-induced IL-1 beta expression was suppressed by hydrocortisone (HC), pentoxifylline, and an investigational theobromine, A81-3138, in a linear, dose-related manner. In contrast, indomethacin, meperidine, and diphenhydramine had no effect on IL-1 beta expression. Our in vitro data indicate that serum HC concentrations of greater than 1 to 2 micrograms/ml may be sufficient to modulate IL-1 beta expression. Pentoxifylline and A81-3138 may also be effective in modulating IL-1 beta expression by mononuclear cells at concentrations achievable in serum. These new agents may prove to be effective alternatives to HC or may be added with HC to suppress febrile reactions secondary to AB administration. Clinical studies with pentoxifylline as a premedication for AB seem warranted. Images

Itraconazole in Antifungal Therapy

OBJECTIVE: This overview compares and contrasts the pharmacotherapy of itraconazole with that of other antifungal agents. DATA SOURCES: Primary literature on itraconazole was identified through a medical literature search from 1976 through 1991. This search included journal articles, abstracts, conference proceedings, and reports of animal and human research published in the English language. STUDY SELECTION: All primary literature was reviewed regardless of the study design or outcome. Literature evaluations of efficacy were ranked using a literature rating scale (Dalen JE, Hirsh J. Arch Intern Med 1986;146:462–72), which was slightly modified to include case reports and observations. DATA EXTRACTION: All data were collected and represented with a primary focus on itraconazoles mechanism of action, pharmacokinetics, clinical efficacy in systemic mycotic infections, drug interactions, and adverse reactions. All articles were referenced in the final data presentation unless grouped data had been accurately reviewed and published. DATA SYNTHESIS: Despite the paucity of controlled comparative trials with itraconazole in patients with deep mycoses, results on efficacy are encouraging. It is still unclear what role itraconazole will have in the prophylaxis of fungal infections in immunocompromised hosts. The favorable pharmacokinetic profile permits once- or twice-daily administration and itraconazole appears to be safe and well tolerated. CONCLUSIONS: Itraconazole should prove to be a useful replacement for ketoconazole on hospital formularies. This recommendation is based on itraconazoles greater apparent safety and efficacy. Reevaluation of this agent will be necessary upon the release of newer imidazoles and triazoles.