Pentamidine is active in a neutropenic murine model of acute invasive pulmonary fusariosis

One population, multiple lifestyles: Commensalism and pathogenesis in the human mycobiome

Candida auris and Candida albicans can result in invasive fungal diseases. And yet, these species can stably and asymptomatically colonize human skin and gastrointestinal tracts. To consider these disparate microbial lifestyles, we first review factors shown to influence the underlying microbiome. Structured by the damage response framework, we then consider the molecular mechanisms deployed by C. albicans to switch between commensal and pathogenic lifestyles. Next, we explore this framework with C. auris to highlight how host physiology, immunity, and/or antibiotic receipt are associated with progression from colonization to infection. While treatment with antibiotics increases the risk that an individual will succumb to invasive candidiasis, the underlying mechanisms remain unclear. Here, we describe several hypotheses that may explain this phenomenon. We conclude by highlighting future directions integrating genomics with immunology to advance our understanding of invasive candidiasis and human fungal disease.

Janus-Faced Molecules against Plant Pathogenic Fungi

The high cytotoxicity of the secondary metabolites of mycotoxins is capable of killing microbes and tumour cells alike, similarly to the genotoxic effect characteristic of Janus-faced molecules. The "double-edged sword" effect of several cytotoxins is known, and these agents have, therefore, been utilized only reluctantly against fungal infections. In this review, consideration was given to (a) toxins that could be used against plant and human pathogens, (b) animal models that measure the effect of antifungal agents, (c) known antifungal agents that have been described and efficiently prevent the growth of fungal cells, and (d) the chemical interactions that are characteristic of antifungal agents. The utilization of apoptotic effects against tumour growth by agents that, at the same time, induce mutations may raise ethical issues. Nevertheless, it deserves consideration despite the mutagenic impact of Janus-faced molecules for those patients who suffer from plant pathogenic fungal infections and are older than their fertility age, in the same way that the short-term cytotoxicity of cancer treatment is favoured over the long-term mutagenic effect.

Review of T-2307, an Investigational Agent That Causes Collapse of Fungal Mitochondrial Membrane Potential

Invasive infections caused by Candida that are resistant to clinically available antifungals are of increasing concern. Increasing rates of fluconazole resistance in non-albicans Candida species have been documented in multiple countries on several continents. This situation has been further exacerbated over the last several years by Candida auris, as isolates of this emerging pathogen that are often resistant to multiple antifungals. T-2307 is an aromatic diamidine currently in development for the treatment of invasive fungal infections. This agent has been shown to selectively cause the collapse of the mitochondrial membrane potential in yeasts when compared to mammalian cells. In vitro activity has been demonstrated against Candida species, including C. albicans, C. glabrata, and C. auris strains, which are resistant to azole and echinocandin antifungals. Activity has also been reported against Cryptococcus species, and this has translated into in vivo efficacy in experimental models of invasive candidiasis and cryptococcosis. However, little is known regarding the clinical efficacy and safety of this agent, as published data from studies involving humans are not currently available.

Therapeutic Challenges of Non-Aspergillus Invasive Mold Infections in Immunosuppressed Patients

While Aspergillus spp. remain the major cause of invasive mold infections in hematologic cancer patients and transplant recipients, other opportunistic molds, such as Mucorales, Fusarium, and Scedosporium spp. are increasingly encountered in an expanding population of patients with severe and prolonged immunosuppression. High potential for tissue invasion and dissemination, resistance to multiple antifungals and high mortality rates are hallmarks of these non-Aspergillus invasive mold infections (NAIMIs). Assessment of drug efficacy is particularly difficult in the complex treatment scenarios of NAIMIs. Specifically, correlation between in vitro susceptibility and in vivo responses to antifungals is hard to assess, in view of the multiple, frequently interrelated factors influencing outcomes, such as pharmacokinetic/pharmacodynamic parameters determining drug availability at the site of infection, the net state of immune suppression, delay in diagnosis, or surgical debulking of infectious foci. Our current therapeutic approach of NAIMIs should evolve toward a better integration of the dynamic interactions between the pathogen, the drug and the host. Innovative concepts of experimental research may consist in manipulating the host immune system to induce a specific antifungal response or targeted drug delivery. In this review, we discuss the challenges in the management of NAIMIs and provide an update about the latest advances in diagnostic and therapeutic approaches.

Effects of intratracheal Fusarium solani inoculation in immunocompetent mice

Fusariosis is an infection that is caused by fungi of the Fusarium genus. It is the second most common fungus that is associated with human fungal infections, usually in immunocompromised individuals. The incidence of such infections has been increasing, including in immunocompetent hosts. Studies of host-pathogen interactions are scarce, and the pathophysiology of the disease is unknown. One limitation of such studies is the lack of adequate techniques for mammalian infection, in which no standardized protocols have been established with fungi with a focus on the respiratory tract. The aim of the present study was to assess the first 24 h of infection after the intratracheal inoculation of F. solani microconidia in immunocompetent mice. Colony-forming units (CFU) were counted, and histopathological analysis was performed. Under conditions of high fungal burden, F. solani caused lethal tissue damage in the lungs. Under conditions of low fungal burden, the infection was not lethal, but several alterations of pulmonary tissue and the presence of the fungus in the lungs were observed. No evidence of fungal dissemination was found in the kidneys, spleen, liver, or heart 24 h after infection. The present intratracheal model effectively established fungal infection and appears to be suitable for studies of Fusarium spp.

Aspergillus tanneri sp. nov., a new pathogen that causes invasive disease refractory to antifungal therapy

The most common cause of invasive aspergillosis (IA) in patients with chronic granulomatous disease (CGD) is Aspergillus fumigatus followed by A. nidulans; other aspergilli rarely cause the disease. Here we review two clinical cases of fatal IA in CGD patients and describe a new etiologic agent of IA refractory to antifungal therapy. Unlike typical IA caused by A. fumigatus, the disease caused by the new species was chronic and spread from the lung to multiple adjacent organs. Mycological characteristics and the phylogenetic relationship with other aspergilli based on the sequence analysis of Mcm7, RPB2, and Tsr1 indicated that the new species, which we named as A. tanneri, belongs to Aspergillus section Circumdati. The species has a higher amphotericin B, voriconazole, and itraconazole MIC and causes more chronic infection in CGD mice than A. fumigatus. This is the first report documenting IA in CGD patients caused by a species belonging to the Aspergillus section Circumdati that is inherently resistant to azoles and amphotericin B. Unlike the results seen with many members of Aspergillus section Circumdati, ochratoxin was not detected in filtrates of cultures grown in various media. Our phenotypic and genetic characterization of the new species and the case reports will assist future diagnosis of infection caused by A. tanneri and lead to more appropriate patient management.

Mouse models for the study of fungal pneumonia: a collection of detailed experimental protocols for the study of Coccidioides, Cryptococcus, Fusarium, Histoplasma and combined infection due to Aspergillus-Rhizopus

Mouse models have facilitated the study of fungal pneumonia. In this report, we present the working protocols of groups that are working on the following pathogens: Aspergillus, Coccidioides, Cryptococcus, Fusarium, Histoplasma and Rhizopus. We describe the experimental procedures and the detailed methods that have been followed in the experienced laboratories to study pulmonary fungal infection; we also discuss the anticipated results and technical notes, and provide the practical advices that will help the users of these models.

Emerging fungal pathogens in pulmonary disease

PURPOSE OF REVIEW

Invasive fungal infections of the lung have been increasing due to the increase of the population most at risk. This review aims to describe some of the emerging fungal pathogens and their complex management.

RECENT FINDINGS

With the increase in immunosuppressed populations, physicians are increasingly encountering uncommon fungal pathogens that historically have been difficult to identify and treat. Many of these fungal infections present with similar clinical features and often show similar histopathological changes. Treatment options are more complex because of an increasing number of antifungals that have become available for clinical use. The correct usage of these antifungals in addressing emerging fungal infections is unclear, however. Drawing from in-vitro and in-vivo susceptibility testing and case reports, some deductions may be made for the best empirical treatment of these deadly diseases. In general, the newer triazoles (voriconazole and posiconazole) and the use of combination therapy have shown promise.

SUMMARY

Invasive fungal infections are on the increase and contribute significantly to overall mortality, particularly among transplant recipients. With the lack of well designed controlled clinical studies, physicians will need to draw from previously described cases and in-vitro susceptibility testing to optimize therapy.