The fungal cell wall as a target for the development of new antifungal therapies

In the past three decades invasive mycoses have globally emerged as a persistent source of healthcare-associated infections. The cell wall surrounding the fungal cell opposes the turgor pressure that otherwise could produce cell lysis. Thus, the cell wall is essential for maintaining fungal cell shape and integrity. Given that this structure is absent in host mammalian cells, it stands as an important target when developing selective compounds for the treatment of fungal infections. Consequently, treatment with echinocandins, a family of antifungal agents that specifically inhibits the biosynthesis of cell wall (1-3)β-D-glucan, has been established as an alternative and effective antifungal therapy. However, the existence of many pathogenic fungi resistant to single or multiple antifungal families, together with the limited arsenal of available antifungal compounds, critically affects the effectiveness of treatments against these life-threatening infections. Thus, new antifungal therapies are required. Here we review the fungal cell wall and its relevance in biotechnology as a target for the development of new antifungal compounds, disclosing the most promising cell wall inhibitors that are currently in experimental or clinical development for the treatment of some invasive mycoses.     

Aspectos actuales de las enfermedades invasivas por hongos filamentosos

Invasive fungal infections have become a major cause of morbimortality in intensive care patients, persons suffering from cancer or immune deficiencies, and other diseases with impaired immunity. Candida albicans remains the most frequent fungal pathogen, but advances in the diagnosis, prevention and treatment of invasive candidiasis are leading to important etiological changes. Among the emerging invasive mycoses, are those caused by filamentous fungi, such as Aspergillus, Lomentospora/Scedosporium, Fusarium or the Mucorales. Invasive aspergillosis is difficult to diagnose, and although there are diagnostic tools available, their use is not widespread, and their effectiveness vary depending on the group of patients. Clinical suspicion in high-risk patients, radiological diagnosis and the use of biomarkers, such as 1,3-β-D-glucan and galactomannan, can be of great help. However, diagnostic resources are limited in other mycoses, but radiology, pathological studies and the microbiological diagnosis can be useful. The high mortality of these mycoses requires early empirical antifungal treatment in many cases. Voriconazole is the first choice for treatment of the majority of aspergillosis, scedosporiasis, fusariosis and other hyalohyphomycoses. The treatment of mucormycoses, Lomentospora prolificans infections or mycoses by dematiaceous fungi are more complicated. Amphotericin B is active against many mucoralean fungi, but the combination of two or more antifungal agents could be a therapeutic alternative in many amphotericin B-refractory mycoses. Current clinical challenges include improving the diagnosis and the treatment of these mycoses, along with improving the adequate prevention in patients at high risk of suffering from them.     

Update on Amphotericin B Pharmacology and Dosing for Common Systemic Mycoses

Amphotericin B (AMB) has been used for nearly five decades in the treatment of life-threatening mycoses. While triazoles and echinocandins have largely supplanted the routine use of AMB for common Candida and Aspergillus infections, this prototypical broad-spectrum agent or its lipid formulations are still preferred by many clinicians as the initial empiric antifungal therapy for severely immunosuppressed patients, and remain the preferred treatment in combination with 5-fluorocytosine for cryptococcal meningioencephalitis. This article reviews progress over the last decade in understanding the pharmacology and clinical dosing of AMB formulations for common systemic mycoses, including invasive candidiasis, cryptococcosis, aspergillosis and mucormycosis.     

Clinical efficacy of new antifungal agents

Several new options are now available for treating serious fungal infections. All three echinocandin agents currently available have been shown in randomized, blinded clinical trials to be efficacious in treating candidemia and invasive candidiasis. By contrast, the demonstrated efficacy of the echinocandins for the treatment of invasive aspergillosis has been based on historically controlled salvage treatment trials in patients failing or intolerant of other therapies. The new triazole agents, voriconazole and posaconazole, have a broad spectrum of antifungal activity. Voriconazole has become the agent of choice for invasive aspergillosis. On the basis of compassionate treatment data, posaconazole appears to be effective for treatment of zygomycosis. These agents have also been shown to be effective in the treatment of non-Aspergillus mould infections, several of the endemic mycoses and serious Candida infections.     

Epidemiology of Invasive Fungal Infections in Latin America

The pathogenic role of invasive fungal infections (IFIs) has increased during the past two decades in Latin America and worldwide, and the number of patients at risk has risen dramatically. Working habits and leisure activities have also been a focus of attention by public health officials, as endemic mycoses have provoked a number of outbreaks. An extensive search of medical literature from Latin America suggests that the incidence of IFIs from both endemic and opportunistic fungi has increased. The increase in endemic mycoses is probably related to population changes (migration, tourism, and increased population growth), whereas the increase in opportunistic mycoses may be associated with the greater number of people at risk. In both cases, the early and appropriate use of diagnostic procedures has improved diagnosis and outcome.     

抗真菌药物敏感性试验方法的新进展

真菌感染,尤其是免疫低下患者机会性真菌感染发病率的不断上升使真菌病的治疗面临着严峻的挑战,各种新的抗真菌药物纷纷涌现。临床实践中,人们需要规范快速、易于应用的药敏试验来指导用药和判断预后,抗真菌药物敏感性试验在真菌感染的治疗中起着重要作用。     

Pseudomycetoma for microsporum canis: report of a case diagnosed by fine needle aspiration biopsy

BACKGROUND: Fine needle aspiration biopsy (FNAB) of the skin is useful in subcutaneous lesions. Dermatophytes are almost exclusively superficial cutaneous mycoses and constitute 70-80% of all mycoses and 5% of dermatologic consultations. Inflammatory and invasive forms, as well as infections that remain in chronic forms or persist in spite of treatment, are more frequent in immunocompromised individuals. The clinicalpresentations of these invasive cases are dermatopbytic granulomas (granuloma of Wilson-Majocchi and pseudomycetoma) or Hadida's disease. CASE: A 17-year-old male with an 8-year history of tinea capitis and multiple kerion lesions in the occipital region, left foot and right elbow resistant to conventional treatment was diagnosed by KOH tests and cultures as Microsporum canis. Two months before consultation he noticed the slow growth of a subcutaneous nodule in the base of the neck. FNAB of the neck nodule was performed. The diagnosis of pseudomycetoma by Microsporum canis was made. CONCLUSION: We report a case of pseudomycetoma caused by Microsporum canis, with the diagnosis made by FNAB. This case appears to be the first one diagnosed by this method in a human.     

Is there a role for antibody testing in the diagnosis of invasive candidiasis?

During the last decades, the use of antibody tests for the diagnosis of invasive mycoses has declined as a consequence of the general belief that they are insensitive and non-specific. However, there is a clear evidence that antibodies can be detected in highly immunodeficient patients (such as bone marrow transplant recipients), and that those antibodies are useful for the diagnosis. Antibody tests are currently in use as diagnostic tools for some primary mycoses, such as the endemic mycoses, aspergilloma, allergic bronchopulmonary aspergilosis and sporothrichosis. For invasive candidiasis, diagnostic methods must differentiate Candida colonization of mucous membranes or superficial infection from tissue invasion by this microorganism. Substantial progress has been made in diagnosis of invasive candidiasis with the development of a variety of methods for the detection of antibodies and antigens. However, no single test has found widespread clinical use and there is a consensus that diagnosis based on a single specimen lacks sensitivity. It is necessary to test sequential samples taken while the patient is at greatest risk for developing invasive candidiasis to optimize the diagnosis. Results obtained from a panel of diagnostic tests in association with clinical aspects will likely be the most useful strategy for early diagnosis and therapy.     

Augmentation of innate host defenses against opportunistic fungal pathogens

Development of invasive fungal infection is the result of the complex interaction between fungal and host factors. The outcome of infection, once it has developed, depends upon appropriate use of antifungal therapy, surgical debridement as indicated, and improvement of host defenses. Thus, there have been major efforts for development of new strategies for immunomodulation and augmentation of host defenses in prevention and treatment of invasive mycoses. These modalities include granulocyte and granulocyte-macrophage colony-stimulating factors, interferon-γ, granulocyte transfusions, immunotherapy with infusion of dendritic cells and T cells, anti-heat shock protein 90 monoclonal antibodies, long pentraxin 3, mannose-binding lectin, and deferasirox. Although major strides in our understanding of augmentation of host response to invasive fungal infections are opening up novel avenues of therapy to harness patients’ innate immune systems against these frequently lethal pathogens, well-designed clinical trials are needed to demonstrate safety and efficacy of these new approaches.     

Epidemiología de las micosis invasoras: un paisaje en continuo cambio

The landscape of invasive mycoses is in a continuous evolution with important implications for their diagnosis and treatment. The overall burden remains high, particularly in neonates and the elderly, patients admitted to intensive care units, using prostheses, catheters or other intravenous devices, those receiving different immunosuppressant treatments or antineoplastic chemotherapy, or transplant recipients. In addition, opportunistic mycoses can be associated with HIV infection. Many fungal infections are acquired by inhalation, direct contact or ingestion, but fungi can also enter into the bloodstream through needles or catheters.Invasive candidiasis remains the most frequent mycosis, but its aetiology progressively shifts from Candida albicans to other species of Candida, such as Candida parapsilosis, Candida glabrata, or the multiresistant Candida auris. However, aspergillosis can be predominant in specific conditions, such as bone marrow transplant recipients. Moreover, Pneumocystis, Cryptococcus, Fusarium and Rhizopus can cause devastating illnesses. There are significant variations among hospitals and countries that are related to many factors, such as local characteristics of mycoses and patients, or different practices between medical and surgical wards. The attributed mortality remains high, ranging from 30% in invasive candidiasis to 90-100% in some clinical presentations of scedosporiosis and mucormycosis. The extremely complexity of patients and the growing diversity of pathogenic fungi are major challenges for improving diagnosis, creating surveillance networks, and implementing control measures for these invasive infections.     

The role of antifungal susceptibility testing in the management of patients with invasive mycoses

The availability of standardized antifungal susceptibility testing methodologies as well as the definition of interpretative breakpoints have made possible the establishment of useful correlations between in vitro testing data and clinical results with antifungal drugs such as fluconazole and itraconazole in patients with oropharyngeal candidiasis. The results obtained in these studies, however, can not be extrapolated to other organisms or clinical syndromes. Although there has been some recent progress, the interpretations of in vitro and in vivo results obtained in patients suffering cryptococcosis or invasive candidiasis needs to be further defined in order to establish meaningful clinical-laboratory correlations. Furthermore, the method needs to be fully standardized in case of filamentous fungi. It can be anticipated that the development, standardization and validation of in vitro antifungal susceptibility testing will guide clinicians in the management of patients with invasive mycoses.     

Micafungina en el tratamiento de la infección fúngica en modelos animales

BackgroundMicafungin is an echinocandin antifungal drug recently approved for the treatment of candidiasis. The possibility of its clinical use against other invasive mycoses, has aroused the interest of numerous investigators in evaluating its efficacy in different animal models.ObjectivesTo critically review the current data on the use of micafungin in the treatment of invasive mycoses in animal models.MethodsWe searched the PubMed/Medline data base (National Library of Medicine) from 2005 to 2008, both inclusive, on the use of micafungin in the experimental treatment of the fungal infection.Results and conclusionsSeven, of a total of 18 articles reviewed, were done in animal models of candidiasis and six in animal models of pulmonary or SNC aspergillosis. Similarly to the other echinocandins, caspofungin and anidulafungin, micafungin seems to exert a fungicidal activity against Candida albicans and Candida glabrata and a fungistatic activity against Aspergillus fumigatus. The paradoxical effect observed in lung tissue the experimental caspofungin treatment of aspergillosis has not been seen in the case of micafungin. The available data demonstrate a higher efficacy of micafungin versus fluconazole in the experimental treatment of C. albicans infections caused by strains susceptible in vitro to both drugs. To improve the efficacy of micafungin in the treatment of C. glabrata and A. fumigatus infections, several authors have tested different combined therapies, the combination of micafungin with amphotericin B being that showed the best results.     

Advances and limitations in the early diagnosis of invasive yeast infections

In the last years, the main advances in the serological diagnosis of mycoses caused by yeasts have occurred in the area of antibody and (1-3)-beta-D-glucan detection. Commercialization of the Candida albicans IFA IgG test and detection of antibodies against recombinant antigens Hwp1 and enolase are the most important contributions to the first area. Detection of (1-3)-beta-D-glucan confirms its usefulness as a good marker for the diagnosis of invasive candidiasis. The most recent studies suggest that combination of two tests to detect antígen, antibodies, (1-3)-beta-D-glucan and DNA will be needed to optimize the diagnosis of systemic yeast infections.     

IRIS and Fungal Infections: What Have We Learned?

Restoration of pathogen-specific immunity as a result of highly active antiretroviral therapy or reduction of immunosuppression in solid-organ transplant recipients can result in a destructive inflammatory response known as the immune reconstitution inflammatory syndrome (IRIS). Though immune reconstitution disorders can occur in the context of a number of infectious and neoplastic processes, IRIS associated with invasive mycoses, in particular cryptococcosis, is a highly prevalent and morbid entity worldwide. Recent consensus definitions and prospective analyses of cryptococcal IRIS, with particular attention to baseline clinical features, serum and cerebrospinal fluid biomarkers, and the evolution of these over time in individual patients have provided critical insights into pathogenesis. This review focuses on the current understanding of IRIS in the context of opportunistic mycoses, with particular attention to Cryptococcus infection, and discusses the basis for this understanding, including biomarkers as clues to pathogenesis and aids in diagnosis and novel approaches to prevention and management.     

Candidiasis invasora en el paciente crítico quemado

BackgroundThe advances in burn care therapy have extended considerably the survival of seriously burned patients, exposing them to infectious complications, notably fungal infections. Due to the difficulty in the diagnosis of invasive mycoses and their high associated mortality rates, approaches to prophylactic or pre-emptive antifungal therapy in high-risk burned patients have been proposed, although these guidelines remain controversial. On the other hand, the management of these conditions is a serious problem, especially in critically ill patients with multiorgan failure, including severely ill burn patients due to the shortage of available antifungal agents. However, in the last several years, the range of antifungal agents has been significantly extended, which have led to an improvement in the treatment of invasive fungal infection in this population.Clinical caseWe report a case of invasive candidiasis in a severelly ill burns patient successfully treated with an echinocandin. In this case report, current treatment options are discussed, and a review of the literature of previously published cases is made.ConclusionsThere are still significant gaps in our knowledge of the optimal diagnostic and management approach for invasive candidiasis in burn patients. Prospective studies are needed in this population to optimise management and improve outcomes in this state of high morbidity and mortality.     

Opportunistic invasive mycoses in AIDS. An autopsy study of 211 cases.

The opportunistic mycoses are an important cause of morbidity-mortality among patients with severe immunosuppression provoked by HIV. We present a study of 211 serial autopsies of patients with HIV/AIDS infection carried out by our service in a period of 10 years, observing frequency of invasive mycoses of the 44.1%. Pneumocystis carinii infection was the most frequent (32%) with a prevalence of lung affection. Candidiasis follows it in order of frequency with 31.1%, predominantly the oropharyngeal manifestation. Systemic or cerebromeningeal cryptococcosis were serious and common disorder (29%). Diseminated histoplasmosis occurred in 9.6% and in three cases (3.2%) pulmonary aspergillosis was diagnosed as a postmortem discovery in cavity lesions. In our series, other less common HIV-associated were not identified.     

In vitro antifungal activity of voriconazole: New data after the first years of clinical experience

Voriconazole has been developed to meet the increasing need for new and useful antifungal agents for the treatment of invasive mycoses. This review describes the spectrum of voriconazole antifungal activity based on data from in vitro studies published during the last three years. This survey demonstrates that voriconazole has a broad antifungal spectrum against the most common fungal pathogens being its action fungistatic for Candida and fungicidal for Aspergillus and other filamentous fungi. Overall, more than 95% of all Candida isolates tested are susceptible to voriconazole and less than 3% are resistant. Similar or even better activity rates have been described for Aspergillus, Cryptococcus and most of yeasts and moulds of medical importance. We also discuss the limitations related to the azole cross-resistance observed in some Candida glabrata isolates, the poor activity of voriconazole against Scedosporium prolificans, its activity against fungal biofilms and the great potential usefulness of combination of voriconazole with other antifungal drugs.     

医学真菌菌株保藏方法概述

近年来,随着真菌感染的患者急剧增加,真菌病已经成为一个重要的公共卫生问题。对医学真菌流行病学、致病机理、耐药机理以及防治策略的研究尤为重要,而所有研究的基础都建立在对医学真菌的进行有效的保藏。医学真菌的保藏方法很多,包括传代法、蒸馏水法、冷冻干燥保藏法等,保藏方法的选择因实验室条件、菌种和研究要求不同而不同。本文对目前常用的几种医学真菌菌种保藏方法的优缺点及其应用等做了综述。     

植入性真菌病

植入性真菌病或称皮下组织真菌病,常见于热带和亚热带地区。此类感染有许多共同特征,包括相似的流行病学和感染方式等,有些还有明显的地域性。其临床表现形态各异,治疗困难,如不及时治疗常会导致畸形甚至致残,严重影响患者的生活质量。本文旨在对临床上重要的植入性真菌病,如孢子丝菌病、足菌肿、着色芽生菌病、暗色丝孢霉病和接合菌病的流行病学特征、临床表现、诊断和治疗进展做一复习。     

Photodynamic Therapy in the Treatment of Superficial Mycoses: An Evidence-based Evaluation

Photodynamic therapy (PDT) is effective in the destruction of fungi. In order to evaluate the efficacy and safety of PDT for superficial mycoses, we performed an evidence-based review of published literature. Database of MEDLINE, EMBASE, and Cochrane Library was searched until March 2010. English-language articles evaluating the efficacy and safety of PDT for superficial mycoses were included. No randomized clinical trials were found. Seven reports described the antifungal effect of PDT against 63 superficial mycoses patients. Eight of 10 (80%) tinea cruris patients and 6 of 10 (60%) tinea pedis were led to mycological cure after 1–3 treatments. Unfortunately, only 4 (40%) tinea cruris patients and 3 (30%) tinea pedis had a persist healing at the 8-week follow-up. Six of the 9 (66.7%) foot-interdigital mycoses patients recovered clinically and microbiologically after 1 or 4 treatments. Only 2 patients (22.2%) had a persist healing at the 8-week follow-up. Eleven of 30 (36.6%) onychomycosis patients were cure for 18 months after treatment, and 3 onychomycosis patients were all cure in other 2 reports. The therapeutic effect of PDT for one pityriasis versicolor patients was well. Overall tolerability of PDT was good. Therefore, it is unclear what PDT’s place for superficial mycoses will be. Further clinical trials are needed to evaluate the efficacy of PDT to treat superficial mycoses. It is also important to optimize treatment protocols in order to cope with recurrence.