In vitro antifungal activity of a novel lipopeptide antifungal agent, FK463, against various fungal pathogens

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.

An Optimized Lock Solution Containing Micafungin, Ethanol and Doxycycline Inhibits Candida albicans and Mixed C. albicans - Staphyloccoccus aureus Biofilms

Candida albicans is a major cause of catheter-related bloodstream infections and is associated with high morbidity and mortality. Due to the propensity of C. albicans to form drug-resistant biofilms, the current standard of care includes catheter removal; however, reinsertion may be technically challenging or risky. Prolonged exposure of an antifungal lock solution within the catheter in conjunction with systemic therapy has been experimentally attempted for catheter salvage. Previously, we demonstrated excellent in vitro activity of micafungin, ethanol, and high-dose doxycycline as single agents for prevention and treatment of C. albicans biofilms. Thus, we sought to investigate optimal combinations of micafungin, ethanol, and/or doxycycline as a lock solution. We performed two- and three-drug checkerboard assays to determine the in vitro activity of pairwise or three agents in combination for prevention or treatment of C. albicans biofilms. Optimal lock solutions were tested for activity against C. albicans clinical isolates, reference strains and polymicrobial C. albicans-S. aureus biofilms. A solution containing 20% (v/v) ethanol, 0.01565 μg/mL micafungin, and 800 μg/mL doxycycline demonstrated a reduction of 98% metabolic activity and no fungal regrowth when used to prevent fungal biofilm formation; however there was no advantage over 20% ethanol alone. This solution was also successful in inhibiting the regrowth of C. albicans from mature polymicrobial biofilms, although it was not fully bactericidal. Solutions containing 5% ethanol with low concentrations of micafungin and doxycycline demonstrated synergistic activity when used to prevent monomicrobial C. albicans biofilm formation. A combined solution of micafungin, ethanol and doxycycline is highly effective for the prevention of C. albicans biofilm formation but did not demonstrate an advantage over 20% ethanol alone in these studies.

Echinocandin antifungals: review and update

The echinocandins are a new and unique class of antifungal agents that act on the fungal cell wall by way of noncompetitive inhibition of the synthesis of 1,3-beta-glucans. All agents of this class are of parenteral formulation, with no oral preparations available. Caspofungin (Cancidas) was the first approved echinocandin, followed recently by micafungin (Mycamine) and anidulafungin (Eraxis). The precise role of the echinocandins in the antifungal armamentarium is still unfolding. Caspofungin is approved for the treatment of candidal esophagitis and candidemia, salvage therapy of Aspergillus infections and for empirical therapy of febrile neutropenia. Micafungin is likewise approved for candidal esophagitis, in addition to antifungal prophylaxis for hematopoietic stem cell transplant recipients. Anidulafungin is also approved for treatment of candidal esophagitis, as well as therapy of candidemia. There has been anecdotal use of these agents to treat less common fungal pathogens, as well as limited use as a component of combination antifungal therapy. The echinocandins are an important addition to the antifungal armamentarium in the treatment of fungal infections in both immunocompromised patients and those with normal immunity.

ScedosporiumSpecies Infections and Treatments

Scedosporium species are now increasingly isolated from immunocompromised and immunocompetent patients. Unfortunately, Scedosporium species infections are generally resistant to amphotericin B, and S. prolificans strains are particularly resistant to presently-available antifungal agents. Here we review the microbiology, expanding epidemiology, numerous clinical presentations, and diagnostic tools available for Scedosporium species infections. Finally, we detail the available in vitro, animal model, and clinical data on the treatment of Scedosporium species infections with special emphasis on the role of newer antifungal therapies for these recalcitrant infections.

KB425796-A, a novel antifungal antibiotic produced by Paenibacillus sp. 530603

The novel antifungal macrocyclic lipopeptidolactone, KB425796-A (1), was isolated from the fermentation broth of bacterial strain 530603, which was identified as a new Paenibacillus species based on morphological and physiological characteristics, and 16S rRNA sequences. KB425796-A (1) was isolated as white powder by solvent extraction, HP-20 and ODS-B column chromatography, and lyophilization, and was determined to have the molecular formula C79H115N19O18. KB425796-A (1) showed antifungal activities against Aspergillus fumigatus and the micafungin-resistant infectious fungi Trichosporon asahii, Rhizopus oryzae, Pseudallescheria boydii and Cryptococcus neoformans.

Purpureocillium lilacinum as a cause of cavitary pulmonary disease: a new clinical presentation and observations on atypical morphologic characteristics of the isolate

The first case of cavitary pulmonary disease caused by Purpureocillium lilacinum is described. The isolate showed atypical microscopic characteristics similar to Acremonium and Fusarium spp., which necessitated molecular identification by sequencing of multiple conserved loci. The patient responded to voriconazole, reinforcing its therapeutic efficacy for P. lilacinum infections.

Overview of treatment options for invasive fungal infections

The introduction of several new antifungals has significantly expanded both prophylaxis and treatment options for invasive fungal infections (IFIs). Relative to amphotericin B deoxycholate, lipid-based formulations of amphotericin B have significantly reduced the incidence of nephrotoxicity, but at a significant increase in drug acquisition cost. Newer, broad-spectrum triazoles (notably voriconazole and posaconazole) have added significantly to both the prevention and treatment of IFIs, most notably Aspergillus spp. (with voriconazole) and the treatment of some emerging fungal pathogens. Finally, a new class of parenteral antifungals, the echinocandins, is employed most frequently against invasive candidal infections. While the role of these newer agents continues to evolve, this review summarizes the activity, safety and clinical applications of agents most commonly employed in the treatment of IFIs.

Review of the pharmacology and clinical studies of micafungin

Micafungin, like other members of the echinocandin class, has a unique mechanism of action that inhibits the synthesis of 1,3-β-D glucans in the fungal cell wall. It has been approved for treatment of esophageal candidiasis, invasive candidiasis including candidemia, and for prophylaxis of Candida infections in patients undergoing hematopoietic stem cell transplantation. Although efficacy and safety have also been demonstrated in pediatric populations, micafungin is approved for this indication in Europe and Japan, but not in the United States. It has demonstrated activity against Candida spp. including those that are azole-resistant as well as Aspergillus and a few other clinically important molds. It is administered intravenously as a once daily infusion and does not require dose adjustments for renal or moderate hepatic dysfunction. Its safety record, favorable tolerability profile, and few drug interactions make it an important agent for the treatment of invasive fungal infections.

Zygomycetes infections in pediatric hematology oncology patients: a case series and review of the literature

Fungi from the Zygomycetes class are increasingly recognized causes of infection in immunosuppressed children, but no comprehensive literature review and few case series have been published on the topic. A case series of 6 pediatric oncology patients with Zygomycetes infections cared for at our institution was constructed, and a concurrent search of the English language literature for Zygomycetes infections in children with oncologic disorders was undertaken. Our case series described 6 patients (5 male) between the ages of 2.5 and 19.5 years. One patient was diagnosed with rhinocerebral disease, 2 with rhinosinusitis, 2 with pulmonary involvement, and 1 with a gastrointestinal presentation. Five patients survived. Our literature review identified 82 cases from 61 studies. The mean subject age was 10.8 years (1.4 to 21.0 y). About 92.7% of all patients suffered from some form of leukemia, with 70.7% suffering from acute lymphoblastic leukemia. Overall, 58.5% of reported patients survived, with individuals with disseminated disease showing the worst prognosis (68.2% mortality) and those with cutaneous disease the best (14.3% mortality). Survival is increasingly reported in the literature, perhaps as a result of improved diagnostic capabilities, increased physician awareness and increased reliance on adjunctive surgical therapy.

Bloodstream infections due to Trichosporon spp.: species distribution, Trichosporon asahii genotypes determined on the basis of ribosomal DNA intergenic spacer 1 sequencing, and antifungal susceptibility testing

The reevaluation of the genus Trichosporon has led to the replacement of the old taxon Trichosporon beigelii by six new species. Sequencing of the ribosomal DNA (rDNA) intergenic spacer 1 (IGS1) is currently mandatory for accurate Trichosporon identification, but it is not usually performed in routine laboratories. Here we describe Trichosporon species distribution and prevalence of Trichosporon asahii genotypes based on rDNA IGS1 sequencing as well as antifungal susceptibility profiles of 22 isolates recovered from blood cultures. The clinical isolates were identified as follows: 15 T. asahii isolates, five Trichosporon asteroides isolates, one Trichosporon coremiiforme isolate, and one Trichosporon dermatis isolate. We found a great diversity of different species causing trichosporonemia, including a high frequency of isolation of T. asteroides from blood cultures that is lower than that of T. asahii only. Regarding T. asahii genotyping, we found that the majority of our isolates belonged to genotype 1 (86.7%). We report the first T. asahii isolate belonging to genotype 4 in South America. Almost 50% of all T. asahii isolates exhibited amphotericin B MICs of >or=2 microg/ml. Caspofungin MICs obtained for all the Trichosporon sp. isolates tested were consistently high (MICs >or= 2 microg/ml). Most isolates (87%) had high MICs for 5-flucytosine, but all of them were susceptible to triazoles, markedly to voriconazole (all MICs <or= 0.06 microg/ml).

Micafungin: a sulfated echinocandin

Micafungin is the second approved antifungal agent in the echinocandin series and is now used worldwide in chemotherapy for life-threatening fungal infections. It is water-soluble and is semi-synthesized from the acylated cyclic hexapeptide FR901379, a natural product from the fungus Coleophoma empetri F-11899, through enzymatic deacylation of FR901379, followed by chemical reacylation with the optimized N-acyl side chain. The water solubility of micafungin is ascribed to a sulfate moiety in the molecule. This feature differentiates micafungin from other echinocandin members. Micafungin is a potent inhibitor of 1,3-beta-glucan synthase, an enzyme necessary for cell-wall synthesis of several fungal pathogens.

Genetic diversity and antifungal susceptibility testing of Trichosporon asahii isolated of Intensive Care Units patients

Trichosporon asahii is an opportunistic pathogen, associated with a high mortality rate in immunocompromised patients. In this study, ten isolates, recovered from oral cavity and urine of patients in Intensive Care Units (ICU) over six months, were identified by classical and molecular methods, typed by RAPD and tested in vitro for susceptibility to fluconazole, itraconazole, 5-flucytosine and amphotericin B. A total agreement between the identification of Trichosporon sp by PCR based on sequences of the Internal Transcribed Spacer Regions (ITS) and on the sequences of small-subunit (SSU) ribosomal DNA (rDNA) was found. Randomly amplified of polymorphic DNA (RAPD), with primers P6 and M13, was used to determine the genomic profiles. The dendogram analysis indicated that almost all strains showed similarity >0.9 among them and all strains were multidrug-resistant. This study brings new results on the identification and genotyping of T. asahii isolated from Brazilian ICU patients and information about their antifungal drugs susceptibility.

Management of fungal infections following allogeneic stem cell transplantation

Fungal infection remains an important complication in allogeneic stem cell transplantation (allo-SCT). Since the prognosis of fungal infection is poor, prophylaxis is critical for its management; owing to recent progression in allo-SCT management and widespread use of reduced-intensity regimens, the strategy of infectious prophylaxis has also changed. Various antifungals have recently been developed and applied to clinical use. A major change in antifungal management will probably occur in the next few years.

Susceptibility testing and molecular classification of Paecilomyces spp

In vitro susceptibility profiles of 58 Paecilomyces clinical isolates are reported. Amphotericin B, itraconazole, and echinocandins showed poor activity against Paecilomyces lilacinus, while the new triazoles were active against it. Paecilomyces variotii exhibited a different susceptibility pattern, being susceptible to most antifungal agents apart from voriconazole and ravuconazole.

[Investigation of susceptibility testing methods for micafungin: comparison of two microdilution methods]

As there is not yet a standardized in vitro susceptibility test of micafungin (MCFG), we evaluated the methods of such testing, focusing on the judgment method of MIC, based on the National Committee for Clinical Laboratory Standards (NCCLS) M27-A2, M38-A, the proposed standards of The Japanese Society for Medical Mycology (JSMM) for yeast (JSMM-Y) and for filamentous fungi (JSMM-F) against Candida spp. and Aspergillus spp. The judgment of MIC value was performed spectrophotometrically and visually in both (NCCLS and JSMM) assays. Only the spectrophotometric MIC judgment against Aspergillus spp. in the NCCLS assay used two end points: 80% inhibitory concentration (IC80) of the growth control and 50% inhibitory concentration (IC50). The end point for the visual judgment against Aspergillus spp. in the NCCLS assay was determined to be no growth from the small clumps of altered hyphae in the microtiter plate. The other MIC judgments used an IC80 end point. The MICs of MCFG for Candida spp. were </= 0.0039-1mug/ml in both judgments by the two assays. In contrast, there was a large difference of the MIC values against Aspergillus spp. between the NCCLS assay results using the IC80 end point and the visual judgment (> 4mug/ml and 0.0078-0.0313mug/ml). However, the MICs using the IC50 end point and those by JSMM assay agreed with the result of the visual assessment. Therefore, we recommend the JSMM assay, the NCCLS assay using the IC50 end point or the novel visual judgment for the susceptibility testing of MCFG against Aspergillus spp.

Micafungin sodium, the second of the echinocandin class of antifungals: theory and practice

Micafungin is a new drug in the echinocandin class and is currently being investigated in Phase III clinical trials. Like other echinocandins, it inhibits 1,3-beta-D-glucan synthesis, thus achieving fungicidal activity against virtually all Candida spp., including those resistant to fluconazole, and fungistatic activity against Aspergillus spp. Micafungin sodium is available for intravenous administration only. It has a favorable safety and drug-drug interaction profile. Micafungin has been approved by the US FDA for treatment of esophageal candidiasis and for antifungal prophylaxis during the pre-engraftment phase in patients undergoing hematopoietic stem cell transplantation. Considering the competitive pricing as well as the good tolerability and efficacy, at present micafungin seems to be another choice for both of these indications. Current research has proven micafungin sodium to add a rational and effective option to the antifungal armamentarium, especially in esophageal candidiasis refractory to fluconazole treatment, in those intolerant to triazoles or in patients needing concomitant therapy interacting with triazoles. In addition to the current indications, recent uncontrolled clinical trials have demonstrated a marked success in the treatment of candidemia and invasive candidiasis. Results from in vitro studies, animal models, small clinical trials, as well as the obvious comparison with the more established caspofungin, hint at possible future indications such as invasive aspergillosis and empirical antifungal therapy. However, preclinical data on micafungin is inconsistent and published well-designed clinical studies are scarce. More controlled and sufficiently scaled trials are imperative in order to establish micafungin as a reliable and safe option in clinical practice.

The Echinocandins

The changing pattern in fungal infections has driven the need to expand the targets of antifungal activity. The echinocandins are the newest addition to the arsenal against fungal infections. Three echinocandins have been approved by the United States Food and Drug Administration: caspofungin, micafungin, and anidulafungin. These agents have a broad spectrum of activity and are similar to each other with respect to in vitro activity against Candida sp, with micafungin and anidulafungin having similar minimum inhibitory concentrations (MICs) that are generally lower than the MIC of capsofungin. The MICs of the echinocandins are highest against Candida parapsilosis; however, whether this will affect clinical outcomes is unknown. Several case reports have identified clinical failure due to elevated MICs with caspofungin or micafungin against Candida albicans, Candida krusei, and C. parapsilosis. Resistance to the echinocandin class was present in some but not all of the isolates. Empiric therapy with one of the echinocandins for candidemia or invasive candidiasis in patients with neutropenia and those without neutropenia appears to be appropriate when one factors in mortality rate, the increasing frequency of non-albicans Candida infections, and the broad spectrum, safety, and fungicidal effect of the echinocandins. After speciation of the organism, continued therapy with an echinocandin can and should be reevaluated. The echinocandins demonstrate similar in vitro and in vivo activity against Aspergillus sp, but only caspofungin is approved for treatment in patients who are intolerant of or refractory to other therapies. Voriconazole and amphotericin B have demonstrated synergy with the echinocandins. The clinical response to combination therapy has been variable; however, the mortality rate appears to be lower with combination therapy than monotherapy. Large controlled trials are needed to determine the role of combination therapy for invasive aspergillosis. Micafungin and anidulafungin generally have a lower frequency of adverse reactions compared with caspofungin. Phlebitis (3.5-25% of patients) and elevated liver enzyme levels (1-15%) occur more often with caspofungin compared with micafungin and anidulafungin (< 8%). Overall, the three echinocandins are relatively safe and effective agents for the treatment of Candida infections.

Antifungal prophylaxis following reduced-intensity stem cell transplantation

Reduced-intensity stem cell transplantation (RIST) has been developed to be a novel curative option for advanced hematologic diseases. Its minimal toxicity allows for transplantation in patients with advanced age or with organ dysfunction. Young patients without comorbidity can undergo RIST as outpatients. However, fungal infection remains an important complication in RIST. Given the poor prognosis of fungal infection, prophylaxis is critical in its management. The prophylactic strategy is recently changing with the development of RIST. Hospital equipment is important for fungal prophylaxis; however, the median day for the development of fungal infection is day 100, when most RIST patients are followed as outpatients. The focus of fungal management after RIST needs to shift from in-hospital equipment to oral antifungals. Various antifungals have recently been developed and introduced for clinical use. A major change in antifungal management will probably occur within several years.

Determination of MICs of aminocandin for Candida spp. and filamentous fungi

Candida and Aspergillus spp., as well as other filamentous molds, have increasingly been reported as the causes of severe invasive fungal infections. We evaluated the new echinocandin aminocandin (AMN) for its antifungal activities against a range of fungal pathogens by determination of the MICs for the organisms. The MICs of the comparator drugs amphotericin B, caspofungin, micafungin, and voriconazole were also determined. The MICs of AMN for 25 strains each of non-Candida albicans Candida spp. (including Candida parapsilosis, Candida krusei, Candida guilliermondii, and Candida tropicalis), Aspergillus fumigatus, Scedosporium spp., Fusarium spp., and zygomycetes (including Absidia, Mucor, and Rhizopus spp.) were determined by using the Clinical and Laboratory Standards Institute M27-A2 and M38-A methodologies for yeasts and filamentous molds, respectively. The MIC ranges of AMN for all yeasts were similar (0.03 to 4.0 microg/ml), while the MIC ranges of AMN for filamentous fungi were species specific. AMN demonstrated potent antifungal activity against A. fumigatus, limited activity against Scedosporium spp., and no activity against zygomycetes or Fusarium spp. Our data showed that AMN demonstrated potent antifungal activities against all of the yeasts and Aspergillus isolates tested, suggesting that AMN could be an important addition to our arsenal of antifungals for the treatment of invasive fungal disease.

Clinical manifestations, treatment and outcome of Paecilomyces lilacinus infections

The fungus Paecilomyces lilacinus is an emerging pathogen that causes severe human infections, including devastating oculomycosis. Usually, it shows low susceptibility to conventional antifungal drugs in vitro, and variable susceptibility to novel triazoles. A review of the published literature identified 119 reported cases of human infection by P. lilacinus between 1964 and 2004. Most were cases of oculomycosis (51.3%), followed by cutaneous and sub-cutaneous infections (35.3%), and a smaller group of miscellaneous infections (13.4%). Lens implantation is the most frequent predisposing factor for oculomycosis. Cutaneous and sub-cutaneous infections occur mainly in solid organ and bone marrow transplant recipients, although surgery and primary or acquired immunodeficiency are also relevant predisposing factors. Infections in apparently immunocompetent patients have also been reported. Surgical debridement combined with antifungal drug therapy, or the correction of predisposing factors, such as neutropenia, are usually required to obtain improvement. Treatment with traditional antifungal drugs often fails. Voriconazole has demonstrated good activity in both cutaneous and ocular infections in the few cases in which this drug has been used. The new triazoles ravuconazole and posaconazole show good in-vitro activity against P. lilacinus and could be promising therapeutic alternatives.

[Fungal infection following reduced-intensity stem cell transplantation (RIST)]

Hematopoietic stem cell transplantation has been established as a curative treatment for advanced hematologic malignancies. Transplantation with a reduced-intensity conditioning regimen has been developed, and the minimal toxicity of reduced-intensity stem cell transplantation (RIST) has made this procedure available for patients of advanced age or with organ dysfunction. The response of malignant lymphoma and some solid tumors to RIST has been observed. RIST with unrelated donors and umbilical cord blood has been studied. Fungal infection is an important complication of RIST. Since the prognosis of fungal infection is poor, the management has been focused on its prophylaxis. Given recent progression in RIST management, the strategy of infectious prophylaxis has also changed. Equipment in the hospital is important for fungal infection; however, the median day of the development of fungal infection is day 100, when most patients are followed as outpatients. The focus of fungal management after RIST is oral antifungal agents rather than in-hospital equipment. Various antifungal agents have recently been developed and applied for clinical use, and many of these have been developed simultaneously for the first time. A major change in antifungal management will probably occur in the next several years.

Emerging echinocandins for treatment of invasive fungal infections

The echinocandins are a new class of antifungals, developed in response to the need for safe and effective antifungals for the treatment of invasive fungal infections. These agents work by inhibiting 1,3-beta-d-glucan synthase, an enzyme essential for production of cell walls in select fungi. Echinocandins appear to demonstrate favourable activity in vitro against a variety of yeasts (including both Candida albicans and non-albicans Candida) as well as select moulds (including Aspergillus spp.) In general, all echninocandins demonstrate a favourable safety profile and require once-daily parenteral administration. Caspofungin is the first of these agents to be available in the US, and is approved for empirical antifungal therapy in febrile neutropenic patients, candidaemia and select forms of invasive candidiasis, and for management of invasive aspergillosis in patients refractory to or intolerant of other therapies. Micafungin was recently approved by the FDA for treatment of oesophageal candidiasis, and for the prophylaxis of fungal infections in haematopoietic stem cell transplant recipients. Emerging data indicate micafungin may have an important role in the treatment of invasive forms of candidiasis. Anidulafungin is an echinocandin approved in the US for treatment of candidaemia and oesophageal candidiasis. Aminocandin (HMR-3702, IP-960) is an investigational agent, with published experience limited to in vitro studies and animal models of infection.

Overexpression of Candida albicans CDR1, CDR2, or MDR1 does not produce significant changes in echinocandin susceptibility

The micafungin and caspofungin susceptibilities of Candida albicans laboratory and clinical isolates and of Saccharomyces cerevisiae strains stably hyperexpressing fungal ATP-binding cassette (ABC) or major facilitator superfamily (MFS) transporters involved in azole resistance were determined using three separate methods. Yeast strains hyperexpressing individual alleles of ABC transporters or an MFS transporter from C. albicans gave the expected resistance profiles for the azoles fluconazole, itraconazole, and voriconazole. The strains hyperexpressing CDR2 showed slightly decreased susceptibility to caspofungin in agar plate drug resistance assays, as previously reported, but increased susceptibility to micafungin compared with either the strains hyperexpressing CDR1 or the null parent deleted of seven ABC transporters. The strains hyperexpressing CDR1 showed slightly decreased susceptibility to micafungin in these assays. A C. albicans clinical isolate overexpressing both Cdr1p and Cdr2p relative to its azole-sensitive isogenic progenitor acquired resistance to azole drugs and showed reduced susceptibility to caspofungin and slightly increased susceptibility to micafungin in agar plate drug resistance assays. None of the strains showed significant resistance to micafungin or caspofungin in liquid microdilution susceptibility assays. The antifungal activities of micafungin and caspofungin were similar in agarose diffusion assays, although the shape and size of the caspofungin inhibitory zones were affected by medium composition. The assessment of micafungin and caspofungin potency is therefore assay dependent; the differences seen with agar plate drug resistance assays occur over narrow ranges of echinocandin concentrations and are not of clinical significance.

Newer triazole antifungal agents: pharmacology, spectrum, clinical efficacy and limitations

New triazole antifungals (voriconazole, posaconazole, ravuconazole and albaconazole) have been developed to meet the increasing need for new antifungals, and address the rising incidence of invasive fungal infections and the emergence of fungal resistance. This report describes the spectrum of activity of the newer-generation triazoles based on data from in vitro, animal and clinical studies. The authors discuss the use of these agents in combination with other antifungals, the extent of cross-resistance, their toxicity profile and pharmacokinetic properties. A total of two agents are currently available: voriconazole (which is becoming a primary treatment for the management of invasive aspergillosis) and posaconazole (which demonstrates a broad antifungal spectrum). A further two agents, albaconazole and ravuconazole, are undergoing early clinical evaluation and their future is uncertain. For all newer triazoles, concerns about emerging drug-resistant fungi and the incidence and management of breakthrough infections will dictate their role in antifungal prophylaxis and treatment.

Micafungin: a new echinocandin

Micafungin, a potent inhibitor of 1,3-beta-D-glucan synthase, has become the second available agent in the echinocandins class that is approved for use in clinical practice. This agent shares with caspofungin an identical spectrum of in vitro activity against Candida albicans, non-albicans species of Candida, and Aspergillus species, as well as several but not all pathogenic molds. If anything, its in vitro activity appears to be superior to that of caspofungin, although the clinical relevance of this observation is unclear. The clinical role of micafungin appears to be similar to that of caspofungin, although clinical data are still lacking at this stage, with initial approval only for treatment of esophageal candidiasis and prophylaxis in subjects with neutropenia. Pharmacokinetic and pharmacodynamic studies and reports of adverse effects and safety have reported similar but not identical results to those of other agents in the echinocandin class. Factors such as acquisition costs and the potential for resistance development may be more relevant to its widespread use than in vitro and in vivo data comparisons with caspofungin.

Scedosporium apiospermum: changing clinical spectrum of a therapy-refractory opportunist*

Current knowledge on the opportunist Scedosporium apiospermum (teleomorph: Pseudallescheria boydii), generated over a period of more than 120 years, is reviewed. The natural environmental habitat of the fungus is unknown; nutrient-rich, brackish waters like river estuaria have been suggested. The fungus is strongly promoted by agricultural and particularly by industrial pollution.

Efficacy of micafungin alone or in combination against experimental pulmonary aspergillosis

Mortality from invasive pulmonary aspergillosis approaches 80% with few useful therapeutic options available. In these studies, we examined the efficacy of micafungin (MICA) alone or in combination with other antifungals in a model of pulmonary aspergillosis in immunosuppressed DBA/2 mice infected intranasally with conidia of Aspergillus fumigatus 10AF. In the initial study, groups of mice were given saline, or 1, 3 or 10 mg kg(-1) of MICA b.i.d., s.c. All saline controls, and 90% of untreated mice succumbed to infection. The efficacy of MICA was difficult to assess because of an apparent toxicity at 10 mg kg(-1). MICA given at 1 mg/kg significantly prolonged survival over the saline controls (P = 0.008). MICA at 3 or 10 mg kg(-1) versus the saline controls approached significance. No treatment regimen differed in efficacy. The efficacy of combination therapy was assessed, with mice given either no treatment, MICA at 1 mg/kg/dose, 0.8 mg kg(-1) of intravenous amphotericin B (AMB), 100 mg kg(-1) of oral itraconazole (ICZ), or 100 mg/kg/dose of twice-daily subcutaneous nikkomycin Z (NIK). AMB alone and MICA + AMB or MICA +NIK significantly prolonged survival (P < 0.05 - 0.02) over that of the controls. ICZ alone, ICZ+MICA and NIK alone did not significantly prolong survival. MICA alone at 1 mg/kg approached significance in prolonging survival. The combination of MICA and ICZ appeared to be potentially antagonistic. Although AMB+MICA was efficacious, no synergistic activity was noted for any of the regimens. Overall, these results indicate that MICA has moderate activity against pulmonary aspergillosis and might be useful in combination with conventional AMB.

Microbiological Characteristics of Medically Important Trichosporon Species

Trichosporon species are opportunistic pathogens associated with a high mortality rate in immunocompromised patients. Disseminated trichosporonosis is uncommon but reports are increasing. In this study, using 16 stock clinical isolates of suspected Trichosporon species and 4 known Trichosporon strains, we investigated the morphology, physio-biochemistry, molecular biology and antifungal susceptibility characteristics of these Trichosporon spp. and discovered that ITS sequence-based identification is a rapid and accurate identification alternative to most phenotypic or physio- biochemical methods. In vitro antifungal susceptibility tests showed high amphotericin B, itraconazole and terbinafine MIC value in these Trichosporon strains.

Successful Topical Application of a New Antifungal Agent, Micafungin, in the Treatment of Refractory Fungal Corneal Ulcers

PURPOSE

To report the efficacy of topical application of a new antifungal agent, micafungin (MCFG), in the treatment of yeast-related corneal ulcers.

DESIGN

Noncomparative interventional case reports.

PARTICIPANTS

Three patients with yeast-related corneal ulcer after keratoplasty recalcitrant to conventional antifungal treatment for 4 weeks were recruited in this study.

METHODS

Topical 0.1% antifungal MCFG eye drops were applied in 3 patients with yeast-related corneal ulcer every hour while awake until epithelialization. After epithelialization, the frequency of eye drops was reduced to 5 times a day. MCFG eye drops were discontinued 1 month after the disappearance of stromal infiltration in each case. The patients underwent best corrected visual acuity (BCVA) measurements, slit-lamp examination, fluorescein-dye staining, and anterior segment photography. Corneal scrapings and cultures of surgical materials were also performed.

MAIN OUTCOME MEASURES

Changes in ulcer size, stromal infiltration, fluorescein dye staining, and BCVA were looked for.

RESULTS

All corneal ulcers epithelialized within 14 days after commencement of application of 0.1% MCFG eye drops. Yeasts were detected from corneal smears in all eyes. Two cases revealed positive culture isolates for Candida albicans and Candida parapsilosis. No recurrence of fungal keratitis was observed in any of the cases throughout the follow-up periods.

CONCLUSION

Topical 0.1% MCFG eye drops seem to be an effective and a promising option in the treatment of refractory yeast-related corneal ulcers.

Micafungin: pharmacology, experimental therapeutics and clinical applications

Invasive fungal infections are important causes of morbidity and mortality in hospitalised patients. Current therapy with amphotericin B and antifungal triazoles has overlapping targets and is limited by toxicity and resistance. Echinocandins are a new class of antifungal drugs, which inhibit the synthesis of 1,3-beta-D-glucan. This homopolysaccharide is an important component of the cell wall of many pathogenic fungi, providing osmotic stability and functioning in cell growth and cell division. Micafungin, which is a member of the echinocandin class, exhibits in vitro fungicidal or fungistatic activity against a variety of fungal pathogens which include Candida and Aspergillus species but not Cryptococcus, Fusarium or Zygomycetes. Micafungin demonstrates linear pharmacokinetics, which are not altered by drugs metabolised through the P450 enzyme system. The preclinical and clinical data strongly support the development of micafungin for treatment of proven or suspected mucosal and invasive Candida infections in immunocompetent and immunocompromised patients. This paper reviews the preclinical and clinical pharmacology of micafungin and its potential role for treatment of fungal invasive infections in patients.

A randomized, double blind, comparative trial of micafungin (FK463) vs. fluconazole for the treatment of oesophageal candidiasis

AIM

To determine efficacy and safety of intravenous micafungin vs. intravenous fluconazole in the treatment of oesophageal candidiasis.

METHODS

A total of 523 patients > or =16 years with documented oesophageal candidiasis were randomized (1:1) in this controlled, non-inferiority study to receive either micafungin (150 mg/day) or fluconazole (200 mg/day). Response was evaluated clinically and endoscopically. Post-treatment assessments were performed at 2 and 4 weeks after discontinuation of therapy.

RESULTS

Median duration of therapy was 14 days. For the primary end-point of endoscopic cure, treatment difference was -0.3% (micafungin 87.7%, fluconazole 88.0%). Documented persistent invasive disease at the end of therapy was reported in 2.7% and 3.9% of patients, respectively. Both 84.8% of micafungin and 88.7% of fluconazole patients remained recurrence free at 4-weeks post-treatment. The overall therapeutic response rate was 87.3% for micafungin and 87.2% for fluconazole. The incidence of drug-related adverse events was 27.7% for micafungin and 21.3% for fluconazole. Six (2.3%) micafungin- and two (0.8%) fluconazole-treated patients discontinued therapy; rash was the most common event leading to discontinuation.

CONCLUSION

Intravenous micafungin (150 mg daily) is well tolerated and as efficacious as intravenous fluconazole (200 mg daily) in the primary treatment of oesophageal candidiasis, achieving high rates of clinical and endoscopic cure.

Potential use of (1,3)-beta-D-glucan as target of diagnosis and treatment of keratomycosis

PURPOSE

Major problems in the management of keratomycosis stem from the difficulty of its diagnosis and limited choice of antifungal agents. In the present paper we propose a new method of detecting (1,3)-beta-D-glucan, one of the major components of fungal cell wall, in tears from an animal model of keratomycosis. In addition, we investigated the efficacy of topical application of micafungin, a new antifungal agent that inhibits the activity of (1,3)-beta-D-glucan synthase in this animal model.

METHOD

Candida albicans (5 x 10(5) organisms) was inoculated into the corneal stroma of 20 New Zealand White rabbits. The animals were randomly assigned to two groups and treated with subconjunctival injection of 0.5 mL of saline or 0.1% micafungin every day for 3 weeks. The clinical course of keratomycosis in both groups was compared. Before and 3 weeks after the injection of saline or micafungin, 5 microL of tears in each eye were collected by capillary tube. The concentration of (1,3)-beta-D-glucan was quantitatively measured by modified Limulus test.

RESULTS

The concentration of (1,3)-beta-D-glucan was significantly higher in keratomycosis model animals than in controls (mean +/- SD, 17.4 +/- 9.4 pg/mL and 2.8 +/- 1.8 pg/mL, respectively) at 21 days after treatment. Subconjunctival injection of micafungin had no significant effect on ocular lesions of keratomycosis until 9 days, after which ocular lesions significantly improved. Subconjunctival application of micafungin decreased the concentration of (1,3)-beta-D-glucan in tears to 4.9 +/- 3.0 pg/mL at 21 days after treatment.

CONCLUSIONS

Increased levels of (1,3)-beta-D-glucan in tears were detected in this model of keratomycosis. Measuring the concentration of (1,3)-beta-D-glucan in tears may be a reliable noninvasive method for the diagnosis of keratomycosis. Topical application of micafungin was effective in the treatment of keratomycosis.

In vitro antifungal activity of luliconazole (NND-502), a novel imidazole antifungal agent

The in vitro activity of luliconazole (NND-502), a novel imidazole antifungal agent, against dermatophytes and several other groups of medically important fungi including the rare causative agents of dermatomycoses, was studied. The luliconazole susceptibility tests were performed with a total of 58 fungal strains of 23 species of fungi grouped into dermatophytes, dematiaceous fungi, hyaline hyphomycetes, yeastlike fungi, and zygomycetes using a broth microdilution method with RPMI 1640 medium. The minimum inhibitory concentration (MIC) values for luliconazole were compared with those of three reference drugs, lanoconazole (LCZ), bifonazole (BFZ), and terbinafine (TBF), all of which have been popular for the topical treatment of dermatophytosis, cutaneous candidiasis, and other superficial fungal infections in Japan. Luliconazole inhibited growth of all filamentous fungi except zygomycetes at low concentrations (MIC, < or =0.004-0.125 microg/ml), with dermatophytes being most susceptible (MIC, < or =0.004-0.008 microg/ml). The susceptibility of these filamentous fungi to luliconazole was almost equal to that to LCZ, and surpassed TBF and BFZ, although to a lesser extent; yeastlike fungi were also susceptible to luliconazole (MIC, 0.125-4 microg/ml). Again the anti-yeastlike fungi activity of luliconazole was at the same level as LCZ and was greater than that of BFZ and TBF. In contrast to BFZ and TBF, however, luliconazole and LCZ were virtually inactive against zygomycetes.

Micafungin

OBJECTIVE

To review the pharmacology, mycology, chemistry, in vitro susceptibility, pharmacokinetics, clinical efficacy, safety, tolerability, dosage, and administration of micafungin, an echinocandin antifungal agent.

DATA SOURCES

A MEDLINE search, restricted to English language, was conducted from 1978 to November 2003. Supplementary sources included program abstracts from the Interscience Conference on Antimicrobial Agents and Chemotherapy and the Infectious Diseases Society of America from 1996 to 2003 and information available through the manufacturer's Web site.

STUDY SELECTION AND DATA EXTRACTION

In vitro and preclinical studies, as well as Phase II and III clinical trials, were evaluated to summarize the clinical efficacy and safety of micafungin. All published and unpublished trials and abstracts citing micafungin were selected.

DATA SYNTHESIS

Micafungin has shown in vitro activity against many yeasts and a variety of molds. Micafungin can be administered only parenterally. Efficacy has been illustrated in open noncomparative studies of esophageal candidiasis in HIV-infected patients and in comparative trials as antifungal prophylaxis in patients undergoing hematopoietic stem-cell transplantation. Adverse events appear mild and limited; the most commonly reported adverse events include hyperbilirubinemia, nausea, and diarrhea.

CONCLUSIONS

Micafungin has activity against Aspergillus spp. and a variety of Candida spp., including azole-resistant strains. Micafungin demonstrates efficacy in the treatment of esophageal candidiasis in HIV-infected patients and appears superior to fluconazole as antifungal prophylaxis in patients undergoing hematopoietic stem-cell transplantation. Based on case reports and in vitro efficacy, micafungin may prove to be a clinically useful agent in the treatment of other fungal diseases; however, these indications await the results of clinical trials.

Successful treatment of oesophageal candidiasis by micafungin: a novel systemic antifungal agent

AIM

To determine the minimum effective dose and safety of micafungin in the treatment of HIV-related oesophageal candidiasis.

METHOD

A total of 120 patients were enrolled in this open label study of the effects of daily 1 h infusions of micafungin on endoscopically proven fungal oesophagitis. Patients were randomly assigned to receive 12.5, 25, 50, 75 and 100 mg of micafungin daily. Response was evaluated clinically and endoscopically.

RESULTS

The protocol defined minimum effective dose of micafungin was 12.5 mg. The percentage of patients experiencing clearing of physical signs and symptoms showed a dose-response relationship and reached 94.7% in the 100 mg dose group. All patients in the 50, 75 and 100 mg dose groups achieved an endoscopically verified improvement in oesophagitis. Adverse effects of micafungin were generally mild and not dose-related. No serious renal, hepatic or drug-related infusion reactions were encountered.

CONCLUSION

Micafungin was found to be effective, well-tolerated and safe. The minimum effective dose was found to be 12.5 mg and a significant linear trend in the successful treatment of oesophageal candidiasis was observed across the doses used with 75 and 100 mg dose levels achieving high rates of clinical and endoscopic cure.

Micafungin

Micafungin, an echinocandin antifungal agent with a novel mechanism of action, inhibits beta-(1,3)-D-glucan synthase interfering with fungal cell wall synthesis. It shows excellent antifungal activity against a broad range of Candida spp., including azole-resistant strains, and Aspergillus spp. in in vitro and animal studies. In HIV-positive patients, intravenous micafungin 50-150 mg/day dose-dependently eradicated endoscopically confirmed oesophageal candidiasis, with micafungin 100 and 150 mg/day being more effective than micafungin 50 mg/day and as effective as fluconazole 200 mg/day in a double-blind trial. In nonblind trials, micafungin (monotherapy or combination therapy) was effective against invasive aspergillosis, candidiasis and candidaemia in paediatric and adult patients with newly diagnosed or refractory infections. Micafungin 50 mg/day provided significantly better antifungal prophylaxis than fluconazole 400 mg/day in 882 haematopoietic stem cell transplant recipients in a randomised, double-blind trial. Respective overall success rates were 80% and 73.5%. Micafungin is generally well tolerated. Adverse events were not dose- or infusion-related with micafungin 12.5-900 mg/day; no histamine-like reactions occurred. Micafungin was as well tolerated as fluconazole, with numerically fewer micafungin recipients discontinuing treatment (4.2% vs 7.2%).

Successful Micafungin (FK463) Treatment of Invasive Pulmonary Aspergillosis in a Patient with Acute Lymphoblastic Leukemia in a Phase II Study

We treated a 52-year-old woman with acute lymphoblastic leukemia (ALL) who developed invasive pulmonary aspergillosis (IPA) as a result of neutropenia following remission-induction chemotherapy. Although serological test results, such as those for platelia and pastrex, were all negative and the serum level of beta-D-glucan was low, Aspergillus DNA was detected in blood by the polymerase chain reaction method. A clinically documented diagnosis of IPA was made on the basis of chest x-rays, computed tomography scan findings, and the detection of Aspergillus DNA. Micafungin (FK463), a candin class antifungal agent, was administered at a dose of 75 to 150 mg/day, because other antifungal agents were not effective. The increase in serum concentration of micafungin was dose-dependent and was accompanied by improvement of symptoms and objective findings. Micafungin was effective for the treatment of IPA in this patient with ALL.

Efficacy of micafungin alone or in combination against systemic murine aspergillosis

We tested the efficacy of micafungin (FK) alone or in combination with other antifungals against systemic murine aspergillosis. FK alone at 10 mg/kg of body weight/dose prolonged survival (P = 0.01) and reduced CFU in the brain and kidney. Combination therapy that used suboptimal FK with amphotericin B or itraconazole prolonged survival. Although no survivors were free of infection, no antagonism was seen. Nikkomycin Z with FK showed significantly greater potency (P < 0.01) than either alone.

Systemic mycoses in the immunocompromised host: an update in antifungal therapy

Despite significant advances in the management of immunosuppressed patients, invasive fungal infections remain an important life-threatening complication. In the last decade several new antifungal agents, including compounds in pre-existing classes (new generation of triazoles, polyenes in lipid formulations) and novel classes of antifungals with a unique mechanism of action (echinocandins), have been introduced in clinical practice. Ongoing and future studies will determine their exact role in the management of different mycoses. The acceleration of antifungal drug discovery offers promise for the management of these difficult to treat opportunistic infections.

Newer antifungal therapy for emerging fungal pathogens

As the number of immunocompromised patients increases, there is a concomitant increase in the number and diversity of fungal infections. Fungi that were once considered harmless or contaminants are now pathogenic in the immunocompromised host. Often these emerging pathogens are indistinguishable from the more familiar fungal infections; however, they are generally more recalcitrant to conventional antifungal therapies. With the antifungal armamentarium now expanding, the clinician now has many more options for these difficult-to-treat mycoses. We review many of the newer antifungal agents (second-generation triazoles, echinocandins, etc.) as therapeutic options for the recently emerging fungal pathogens.

Antifungal pharmacotherapy for invasive mould infections

The incidence of invasive mould infections is increasing and is associated with significant morbidity and mortality. Among the most prevalent of these infections are those caused by Aspergillus and Fusarium species. Invasive disease caused by moulds frequently presents as a pulmonary infection, but haematogenous infection can occur. Some moulds cause cutaneous disease through either direct inoculation of the skin or secondary spread to the skin after dissemination from another body site. Early diagnosis can often be difficult and, unfortunately, diagnosis occurs late in the course of illness in many cases. Treatment options have historically been limited by the need for intravenous administration (amphotericin B), significant toxicities (amphotericin B), lack of reliable in vitro activity (e.g., amphotericin B in Fusarium and Scedosporium apiospermum infections) and relative lack of clinical experience with newer agents. The recent approval of voriconazole (Vfend, Pfizer) introduces a treatment option that demonstrates both in vitro and in vivo activity against a variety of moulds. With the recent development of the new echinocandin class of antifungal agents and newer broad-spectrum azole antifungal agents with in vitro mould activity, there is a renewed emphasis on fungal treatment strategies. Antimould therapy presents challenges in adverse effect avoidance and management, drug interactions and pharmacoeconomic considerations. Furthermore, combination therapy is being explored with these various new antifungal agents. The administration of an optimal fungicidal therapy early in the course of the illness and control of the underlying disease are vital to prevent complications and mortality from these tenacious mycoses.