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Infectious Disease Clinics of North... Jun 2021Histoplasmosis is one of the commonest endemic mycoses in the Americas yet is often underdiagnosed and neglected as a public health priority. This review outlines the... (Review)
Review
Histoplasmosis is one of the commonest endemic mycoses in the Americas yet is often underdiagnosed and neglected as a public health priority. This review outlines the evolving understanding of its epidemiology and the clinical syndromes of histoplasmosis, in addition to up-to-date diagnostic and treatment guidelines. A focus on histoplasmosis in advanced HIV is included. The challenges pertinent to histoplasmosis management in Latin America, with recommendations made through international expert consensus are discussed.
Topics: Endemic Diseases; HIV Infections; Histoplasma; Histoplasmosis; Humans; Immunocompromised Host
PubMed: 34016287
DOI: 10.1016/j.idc.2021.03.011 -
Current Topics in Microbiology and... 2019Histoplasmosis, caused by the dimorphic environmental fungus Histoplasma capsulatum, is a major mycosis on the global stage. Acquisition of the fungus by mammalian hosts... (Review)
Review
Histoplasmosis, caused by the dimorphic environmental fungus Histoplasma capsulatum, is a major mycosis on the global stage. Acquisition of the fungus by mammalian hosts can be clinically silent or it can lead to life-threatening systemic disease, which can occur in immunologically intact or deficient hosts, albeit severe disease is more likely in the setting of compromised cellular immunity. H. capsulatum yeast cells are highly adapted to the mammalian host as they can effectively survive within intracellular niches in select phagocytic cells. Understanding the biological response by both the host and H. capsulatum will facilitate improved approaches to prevent and/or modify disease. This review presents our current understanding of the major pathogenic mechanisms involved in histoplasmosis.
Topics: Animals; Histoplasma; Histoplasmosis; Humans; Virulence
PubMed: 30043340
DOI: 10.1007/82_2018_114 -
Microbiology Spectrum Jun 2016Filamentous mycoses are often associated with significant morbidity and mortality. Prompt diagnosis and aggressive treatment are essential for good clinical outcomes in... (Review)
Review
Filamentous mycoses are often associated with significant morbidity and mortality. Prompt diagnosis and aggressive treatment are essential for good clinical outcomes in immunocompromised patients. The host immune response plays an essential role in determining the course of exposure to potential fungal pathogens. Depending on the effectiveness of immune response and the burden of organism exposure, fungi can either be cleared or infection can occur and progress to a potentially fatal invasive disease. Nonspecific cellular immunity (i.e., neutrophils, natural killer [NK] cells, and macrophages) combined with T-cell responses are the main immunologic mechanisms of protection. The most common potential mold pathogens include certain hyaline hyphomycetes, endemic fungi, the Mucorales, and some dematiaceous fungi. Laboratory diagnostics aimed at detecting and differentiating these organisms are crucial to helping clinicians make informed decisions about treatment. The purpose of this chapter is to provide an overview of the medically important fungal pathogens, as well as to discuss the patient characteristics, antifungal-therapy considerations, and laboratory tests used in current clinical practice for the immunocompromised host.
Topics: Antibodies, Fungal; Antifungal Agents; Aspergillus fumigatus; CD4-Positive T-Lymphocytes; Histoplasma; Humans; Immunocompromised Host; Mucorales; Mycoses
PubMed: 27337469
DOI: 10.1128/microbiolspec.DMIH2-0002-2015 -
Current Opinion in Microbiology Dec 2019Temperature serves as a fundamental signal in biological systems. In some microbial pathogens of humans, mammalian body temperature triggers establishment and... (Review)
Review
Temperature serves as a fundamental signal in biological systems. In some microbial pathogens of humans, mammalian body temperature triggers establishment and maintenance of a developmental program that allows the microbe to survive and thrive in the host. Histoplasma capsulatum is one of a group of fungal pathogens called thermally dimorphic fungi, all of which respond to mammalian body temperature by converting from an environmental mold form that inhabits the soil into a parasitic form that causes disease in the host. It has been known for decades that temperature is a key signal that is sufficient to trigger the switch from the soil to host form (and vice versa) in the laboratory. Recent molecular studies have identified a number of key regulators that are required to specify each of the developmental forms in response to temperature. Here we review the regulatory circuits that govern temperature-dependent dimorphism in Histoplasma.
Topics: Adaptation, Physiological; Fungal Proteins; Gene Expression Regulation, Fungal; Histoplasma; Histoplasmosis; Humans; Respiratory Tract Infections; Soil Microbiology; Temperature; Virulence
PubMed: 31739263
DOI: 10.1016/j.mib.2019.10.011 -
Journal of Microbiology (Seoul, Korea) Mar 2016Human fungal pathogens that cause invasive infections are hidden killers, taking lives of one and a half million people every year. However, research progress in this...
Human fungal pathogens that cause invasive infections are hidden killers, taking lives of one and a half million people every year. However, research progress in this field has not been rapid enough to effectively prevent or treat life-threatening fungal diseases. To update recent research progress and promote more active research in the field of human fungal pathogens, eleven review articles concerning the virulence mechanisms and host interactions of four major human fungal pathogens-Candida albicans, Cryptococcus neoformans, Aspergillus fumigatus, and Histoplasma capsulatum-are presented in this special issue.
Topics: Aspergillosis; Aspergillus fumigatus; Candida albicans; Candidiasis; Cryptococcosis; Cryptococcus neoformans; Fungi; Histoplasma; Histoplasmosis; Host-Pathogen Interactions; Humans; Mycoses; Virulence
PubMed: 26920875
DOI: 10.1007/s12275-016-0647-8 -
Balkan Medical Journal Oct 2019
Topics: Adrenal Glands; Aged, 80 and over; Anorexia; Histoplasma; Histoplasmosis; Humans; Male; Tomography, X-Ray Computed
PubMed: 31397142
DOI: 10.4274/balkanmedj.galenos.2019.2019.4.104 -
Open Biology Mar 2022Exposure to fungal pathogens from the environment is inevitable and with the number of at-risk populations increasing, the prevalence of invasive fungal infection is on... (Review)
Review
Exposure to fungal pathogens from the environment is inevitable and with the number of at-risk populations increasing, the prevalence of invasive fungal infection is on the rise. An interesting group of fungal organisms known as thermally dimorphic fungi predominantly infects immunocompromised individuals. These potential pathogens are intriguing in that they survive in the environment in one form, mycelial phase, but when entering the host, they are triggered by the change in temperature to switch to a new pathogenic form. Considering the growing prevalence of infection and the need for improved diagnostic and treatment approaches, studies identifying key components of fungal recognition and the innate immune response to these pathogens will significantly contribute to our understanding of disease progression. This review focuses on key endemic dimorphic fungal pathogens that significantly contribute to disease, including , and species. We briefly describe their prevalence, route of infection and clinical presentation. Importantly, we have reviewed the major fungal cell wall components of these dimorphic fungi, the host pattern recognition receptors responsible for recognition and important innate immune responses supporting adaptive immunity and fungal clearance or the failure thereof.
Topics: Fungi; Histoplasma; Humans; Immunity, Innate
PubMed: 35259948
DOI: 10.1098/rsob.210219 -
Medical Mycology Mar 2005A fungus isolated in France from the fur of a bat, which produces characterized large tuberculate conidia (aleurioconidia) similar to those produced by the mycelial form...
A fungus isolated in France from the fur of a bat, which produces characterized large tuberculate conidia (aleurioconidia) similar to those produced by the mycelial form of Histoplasma capsulatum (Ajellomyces capsulatus) is described. Colonies are white at first, but then become rosy buff from the centre outwards. Sectoring, resulting in the appearance of patches or areas of dark green mycelium, occurs spontaneously. Single-celled conidia are formed on undifferentiated hyphae, and may be sessile, or borne laterally on short stalks or producing in an intercalary position as it is the case in the genus Chrysosporium. This fungus is clearly distinguishable from any described species and is described as Chrysosporium chiropterorum sp. nov. C. chiropterorum, like H. capsulatum, produces gelatinase, and is non-keratinolytic but strongly ureolytic. Both species are associated with bat dwellings. C. chiropterorum differs from H. capsulatum by faster growth, pink or green colonies, and failure to produce microconidia as well as lack of conversion to a yeast phase in vitro at 37 degrees C.
Topics: Animals; Chiroptera; Chrysosporium; France; Gelatinases; Hair; Histoplasma; Mycelium; Peptide Hydrolases; Urease
PubMed: 15832559
DOI: 10.1080/13693780400006096 -
Trends in Microbiology Mar 2005Histoplasma capsulatum is a significant respiratory and systemic fungal pathogen. Although many molecular tools have been developed, the fulfillment of Koch's postulates... (Review)
Review
Histoplasma capsulatum is a significant respiratory and systemic fungal pathogen. Although many molecular tools have been developed, the fulfillment of Koch's postulates to determine gene function has been hampered by obstacles to homologous gene targeting. Because H. capsulatum displays a considerable array of virulence mechanisms and has a 40-Mb genome that is currently being sequenced, the capability to perform high-throughput molecular manipulations would clearly be beneficial. Recent demonstration and application of experimental RNA interference (RNAi) technology promises a major contribution to advances in this area.
Topics: Gene Targeting; Histoplasma; Nucleic Acid Conformation; RNA Interference; Virulence
PubMed: 15737724
DOI: 10.1016/j.tim.2005.01.001 -
Virulence 2015Fungi are among the most common microbes encountered by humans. More than 100, 000 fungal species have been described in the environment to date, however only a few... (Review)
Review
Fungi are among the most common microbes encountered by humans. More than 100, 000 fungal species have been described in the environment to date, however only a few species cause disease in humans. Fungal infections are of particular importance to immunocompromised hosts in whom disease is often more severe, especially in those with impaired cell-mediated immunity such as individuals with HIV infection, hematologic malignancies, or those receiving TNF-α inhibitors. Nevertheless, environmental disturbances through natural processes or as a consequence of deforestation or construction can expose immunologically competent people to a large number of fungal spores resulting in asymptomatic acquisition to life-threatening disease. In recent decades, the significance of the innate immune system and more importantly the role of dendritic cells (DC) have been found to play a fundamental role in the resolution of fungal infections, such as in dimorphic fungi like Histoplasma and Paracoccidioides. In this review article the general role of DCs will be illustrated as the bridge between the innate and adaptive immune systems, as well as their specific interactions with these 2 dimorphic fungi.
Topics: Animals; Dendritic Cells; Histoplasma; Histoplasmosis; Host-Pathogen Interactions; Humans; Immunity, Cellular; Immunity, Innate; Paracoccidioides; Paracoccidioidomycosis
PubMed: 25933034
DOI: 10.4161/21505594.2014.965586