Guidelines for Treatment of Candidiasis

Alternative dosing regimens of liposomal amphotericin B (AmBisome) effective in treating murine systemic candidiasis

OBJECTIVES

This study was done to determine whether high dose AmBisome (4-20 mg/kg), given intermittently, could reduce the frequency of dosing needed to treat murine systemic candidiasis when compared with conventional daily treatment.

METHODS

Mice were immunosuppressed with cyclophosphamide every 3 days, beginning day -3 before challenge with log(10) 5.0 cfu Candida albicans. Treatment was begun 48-72 h post-challenge with daily or intermittent dose regimens of AmBisome, followed by determination of kidney cfu for up to 1 month post-treatment.

RESULTS

A single AmBisome dose of 4 mg/kg was as effective as four daily, 1 mg/kg treatments. A total of 8 mg/kg, given as 4 mg/kg on days 2 and 4, or as 5 mg/kg on day 2 followed by 1 mg/kg on days 3, 4, and 5, also produced comparable efficacy. While 20 mg/kg given day 2, 4 and 6 post-challenge as a 1 week loading dose, followed by one 10 mg/kg treatment on day 13, decreased the fungal burden by up to 5 logs compared with controls (log(10) 2.3 cfu/g and log(10) 7.5 cfu/g, respectively), 20 mg/kg given Monday, Wednesday and Friday for 5 weeks, reduced the fungal burden to undetectable levels (i.e. log(10) 1.0 cfu).

CONCLUSIONS

Significant reduction or clearance of kidney cfu, following intermittent, high dose AmBisome treatment, indicated that non-daily dosing regimens could be successfully used instead of conventional daily dosing to treat established C. albicans infection in immunosuppressed mice.

A meta-analysis of medical versus surgical therapy for Candida endocarditis

OBJECTIVES

The optimal management of Candida infective endocarditis (IE) is unknown.

METHODS

We reviewed all 879 cases of Candida IE reported from 1966-2002 in the peer-reviewed literature to better understand the role of medical and surgical therapies. This review included 163 patients from 105 reports that met our inclusion criteria: 31 cases treated with antifungal monotherapy, 25 cases treated with medical antifungal combination therapy, and 107 cases treated with adjunctive surgical plus medical antifungal therapy. We also used meta-analytic techniques to evaluate 22 observational case-series (72 patients) of the 105 reports with two or more patients with definite Candida IE.

RESULTS

We found that in patients who underwent adjunctive surgery there was a lower reported proportion of deaths [prevalence odds ratio (POR)=0.56; 95% confidence interval (CI)=0.16, 1.99)]. Higher mortality was noted in patients treated prior to 1980 (POR=2.03; 95% CI=0.55, 7.61), treated with antifungal monotherapy (POR=1.49; 95% CI=0.39, 5.81), infected with Candida parapsilosis (POR=1.51; 95% CI=0.41, 5.52), or with left-sided endocarditis (POR=2.36; 95% CI=0.55, 10.07).

CONCLUSIONS

Medical antifungal therapy of Candida IE is poorly characterized, and recent antifungal developments lend promise for those patients who cannot undergo surgery.

Impact of real-time fungal susceptibility on clinical practices

PURPOSE OF REVIEW

In the past two decades standardized in-vitro antifungal susceptibility tests have been developed in response to increasing invasive fungal infections. Our purpose is to review the utility of real-time Candida antifungal susceptibility testing and its effects on clinical outcomes in the context of the new antifungal agents, existing antifungal susceptibility testing methods, and the changing epidemiology and susceptibilities of Candida spp.

RECENT FINDINGS

New antifungal agents active against Candida spp. are now available. Caspofungin is approved for the treatment of invasive candidiasis but standardized antifungal susceptibility testing has not been developed. The newer triazoles, such as voriconazole, posaconazole and ravuconazole, are not yet approved for invasive candidiasis. As infections caused by non-albicans Candida spp. with growing resistance to fluconazole increase, antifungal susceptibility testing may be important to guide therapy. Unfortunately, few studies exist describing the impact of real-time antifungal susceptibility testing on the treatment of invasive fungal infections.

SUMMARY

Newer antifungal agents with broader anti-Candida activity, fewer adverse events and minimal resistance are currently available. The challenge clinicians face is choosing when to use these agents appropriately, while considering the changing Candida epidemiology and susceptibility trends without over-treating fluconazole-sensitive pathogens. Unfortunately, the correlation of antifungal susceptibility testing results by any method and clinical outcome is mostly lacking. We suggest that a concerted examination of the utility of real-time antifungal susceptibility testing and its effect on clinical outcomes by guiding appropriate antifungal therapy for high-risk patients with invasive candidiasis is warranted.

Anidulafungin: review of a new echinocandin antifungal agent

Anidulafungin (Vicuron Pharmaceuticals) is a new echinocandin antifungal with potent activity against Aspergillus and Candida spp. Anidulafungin is a noncompetitive inhibitor of (1,3)-beta-D-glucan synthase within fungal cells. The drug is rapidly distributed and steady-state concentrations are achieved after the first dose, when a loading dose of twice the daily maintenance dose is given on day 1. Drug biotransformation occurs via chemical degradation, with no hepatic metabolism or renal elimination. A favorable pharmacokinetic profile and lack of significant drug interactions suggest that patients can receive anidulafungin without dosage adjustments. These characteristics, in addition to comparable efficacy to fluconazole (Diflucan, Pfizer Ltd) in the treatment of esophageal candidiasis, support further investigation of its use in the treatment of systemic fungal infections caused by Candida and Aspergillus spp.

Guidelines for the antibiotic treatment of endocarditis in adults: report of the Working Party of the British Society for Antimicrobial Chemotherapy

The BSAC Guidelines on Endocarditis were last published in 1998. The Guidelines presented here have been updated and extended to reflect changes in both the antibiotic resistance characteristics of causative organisms and the availability of new antibiotics. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking, and therefore a consensus approach has again been adopted. The Guidelines cover diagnosis and laboratory testing, suitable antibiotic regimens and causative organisms. Special emphasis is placed on common causes of endocarditis, such as streptococci and staphylococci, however, other bacterial causes (such as enterococci, HACEK organisms, Coxiella and Bartonella) and fungi are considered. The special circumstances of prosthetic endocarditis are discussed.

Utility of real-time antifungal susceptibility testing for fluconazole in the treatment of candidemia

Our study prospectively examined the use of real-time antifungal susceptibility testing among 119 patients with candidemia at a large tertiary university medical center over a 1-year period. Susceptibility results to fluconazole were reported to physicians a mean of 5.1 days after the initial positive blood culture for Candida. Physicians believed that receiving antifungal susceptibility testing results was helpful and not infrequently altered therapy on the basis of results. Outcomes, including mortality and resolution of infection, among 20 (17%) patients with fluconazole-resistant and fluconazole-susceptible dose-dependent isolates were relatively poor compared to those among patients with fluconazole-susceptible isolates, but probably reflect severity of illness. Routine susceptibility testing as an adjunct to the treatment of candidemia has significant potential and warrants further study.

Native valve endocarditis due to Candida glabrata treated without valvular replacement: a potential role for caspofungin in the induction and maintenance treatment

Conventional antifungal therapy for fungal endocarditis has been associated with a poor cure rate. Therefore, combined medical and surgical therapy has been recommended. However, new potent antifungal agents, such as echinocandins, could increase the medical options and, in some cases, avoid the need for surgery. We report a case of Candida endocarditis treated successfully without valve replacement with intravenous liposomal amphotericin B (total dose, 4 g) and intravenous caspofungin (a 100-mg loading dose followed by 50 mg per day for 8 weeks) as induction therapy and intravenous caspofungin (100 mg 3 times per week for 12 weeks) as maintenance therapy.

Development and characterization of an in vivo central venous catheter Candida albicans biofilm model

Biofilms represent a niche for microorganisms where they are protected from both the host immune system and antimicrobial therapies. Biofilm growth serves as an increasing source of clinical infections. Candida infections are difficult to manage due to their persistent nature and associated drug resistance. Observations made in biofilm research have generally been limited to in vitro models. Using a rat central venous catheter model, we characterized in vivo Candida albicans biofilm development. Time-course quantitative culture demonstrated a progressive increase in the burden of viable cells for the first 24 h of development. Fluorescence and scanning electron microscopy revealed a bilayered architecture. Adjacent to the catheter surface, yeast cells were densely embedded in an extracellular matrix. The layer adjacent to the catheter lumen was less dense. The outermost surface of the biofilm contained both yeast and hyphal forms, and the extracellular material in which they were embedded appeared fibrous. These architectural features were similar in many respects to those described for in vitro models. However, scanning electron microscopy also revealed host cells embedded within the biofilm matrix. Drug susceptibility was determined by using two assays and demonstrated a biofilm-associated drug resistance phenotype. The first assay demonstrated continued growth of cells in the presence of supra-MIC antifungal drug concentrations. The second assay demonstrated reduced susceptibility of biofilm-grown cells following removal from the biofilm structure. Lastly, the model provided sufficient nucleic material for study of differential gene expression associated with in vivo biofilm growth. Two fluconazole efflux pumps, CDR1 and CDR2, were upregulated in the in vivo biofilm-associated cells. Most importantly, the studies described provide a model for further investigation into the molecular mechanisms of C. albicans biofilm biology and drug resistance. In addition, the model provides a means to study novel drug therapies and device technologies targeted to the control of biofilm-associated infections.

A new era of antifungal therapy

Invasive fungal infections pose major management problems for clinicians caring for hematopoietic cell transplant patients. Two major fungal genera, Candida and Aspergillus, account for most fungal infections. Rates of systemic Candida infection range from 15% to 25%, mostly in the pre-engraftment period. Prophylaxis by fluconazole has dramatically reduced the frequency of early Candida infections. Caspofungin has recently been shown to offer an excellent alternative to amphotericin B (with less toxicity) or fluconazole (with a broader spectrum) for therapy of systemic Candida infections. Aspergillus infections occur in 15% to 20% of allogeneic hematopoietic cell transplant patients, most frequently in the post-engraftment period; they are associated with a severe diminution of cell-mediated immune responses by graft-versus-host disease and prolonged corticosteroid use. Voriconazole, a recently introduced broad-spectrum azole, has excellent activity against Aspergillus and is generally well tolerated. Voriconazole currently offers the best prospect for success and tolerance as a first-line treatment for aspergillosis. Second-line therapies include lipid formulations of amphotericin B, caspofungin, or intravenous itraconazole. Unfortunately, early initiation of therapy for aspergillosis is frequently not possible because of inaccurate diagnostics. One new diagnostic, the galactomannan assay, has recently been approved, and others are in development; these offer promise for earlier diagnosis without the need for invasive procedures. It is hoped that these new therapies and new diagnostics will usher in a new era of antifungal therapy.

Prophylaxis and treatment of invasive candidiasis in the intensive care setting

The term "invasive candidiasis" encompasses a group of infections of increasing relevance in the intensive care setting. Prophylaxis is an attractive strategy when dealing with diseases of high prevalence, morbidity, and mortality. The success of prophylaxis is determined by the selection of a population at high risk and the use of the safest and most effective drug. Although risk factors for this disease are known, risk assessment strategies need to be developed to predict a high likelihood of disease so that targeted prophylaxis can be offered. Recent advances in antifungal therapy, such as development of the azoles and echinocandins, have resulted in excellent prophylactic and therapeutic choices for the management of this problem.

A Randomized, Double-Blind, Parallel-Group, Dose-Response Study of Micafungin Compared with Fluconazole for the Treatment of Esophageal Candidiasis in HIV-Positive Patients

BACKGROUND

Severely immunocompromised individuals are highly susceptible to Candida infection of the esophagus. This randomized, double-blind study assessed the dose-response relationship of the new echinocandin antifungal, micafungin, compared with that of standard fluconazole treatment.

METHODS

A total of 245 patients (age, > or =18 years) with a prior diagnosis of acquired immunodeficiency syndrome/human immunodeficiency virus (HIV) infection and esophageal candidiasis, confirmed by endoscopy and culture, were randomized to receive micafungin (50, 100, or 150 mg per day) or fluconazole (200 mg per day). Both agents were administered once per day by a 1-h intravenous infusion for 14-21 days. The primary efficacy end point was endoscopic cure rate, defined as endoscopy grade of 0 at the end of therapy.

RESULTS

The endoscopic cure rate (grade 0) was dose-dependent with 50, 100, and 150 mg of micafungin per day at 68.8%, 77.4%, and 89.8%, respectively. Symptoms improved or resolved rapidly (3-7 days of treatment in the majority of patients). The endoscopic cure rate for 100 and 150 mg of micafungin per day (83.5%) was comparable to that for 200 mg of fluconazole per day (86.7%; 95% confidence interval for the difference in endoscopic cure rate, -14.0% to 7.7%). The overall safety and tolerability was acceptable, with no important differences between micafungin (all doses) and fluconazole.

CONCLUSIONS

The dose-response findings demonstrate a greater efficacy with micafungin at 100 and 150 mg per day than at 50 mg per day. This study also indicates that the efficacy of micafungin (at dosages of 100 and 150 mg per day) was comparable to that of fluconazole, suggesting that micafungin represents a valuable new treatment option for esophageal candidiasis in HIV-positive patients.

Fungal endocarditis

Recent advances in medicine have caused fungal endocarditis (FE) to be a more common disease entity. Many fungi are potential pathogens in FE, although Candida species and Aspergillus species are the most common. Valvular heart disease is the necessary underlying condition for FE, with intravenous devices and antibiotic use being the predisposing factors for yeast endocarditis, whereas immunosuppression in patients with valvulopathy predisposes for mold endocarditis. Better prognosis of FE depends on fast and accurate diagnosis and subsequent treatment. Echocardiography was the most valuable recent technique in the past two decades that allowed early diagnosis of FE and is probably responsible for the improved prognosis of patients with FE. In the future, development of nonculture-based diagnostic tests may further improve the sensitivity, specificity, and rapidity of microbiologic diagnosis of FE. Novel approaches in treatment, such as new antifungal drugs, also may assist in achieving cure and further improving the prognosis of this disease entity.

Supportive care

To optimize treatment outcomes for hematologic malignancies, minimizing the consequences of treatment complications requires as much skill as the choice of the treatment itself. Myelosuppression and immunosuppression are frequent complications and have potentially serious infectious consequences. Invasive fungal infections and infections from respiratory viruses are increasing in frequency and have life-threatening potential. Damage to vital organs, especially the liver, is another important concern. In this chapter, the scope of invasive fungal and respiratory viral infections, recent insights into the pathogenesis of hepatic sinusoidal injury, and recent developments that impact prevention and treatment approaches for these complications are described. In Section I, Dr. John Wingard describes the advantages and disadvantages of various treatment options for invasive infections by the two chief fungal pathogens, Candida and Aspergillus. Adjunctive therapies and practical considerations that clinicians should weigh in choosing one or another of the various agents are discussed. The studies that have evaluated antifungal prophylaxis and empirical treatment strategies are reviewed. Finally, new approaches such as combination therapy, new diagnostics, and efforts to bolster host immunity are considered. In Section II, Dr. W. Garrett Nichols describes the epidemiology of community-acquired respiratory viruses (CRV) in patients with hematologic malignancies. Risk factors, clinical syndromes, and possible indirect effects of CRV infections are discussed. Treatment and prevention options are reviewed. In Section III, Dr. George McDonald describes sinusoidal obstruction syndrome (once known as hepatic veno-occlusive disease). Recent insights into pathogenesis are described. Diagnostic criteria and the advantages and disadvantages of various diagnostic methods are reviewed and prognosis is considered. Prevention and treatment options are discussed.