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Cold Spring Harbor Perspectives in... Nov 2014Fungi are adept at changing their cell shape and developmental program in response to signals in their surroundings. Here we focus on a group of evolutionarily related... (Review)
Review
Fungi are adept at changing their cell shape and developmental program in response to signals in their surroundings. Here we focus on a group of evolutionarily related fungal pathogens of humans known as the thermally dimorphic fungi. These organisms grow in a hyphal form in the environment but shift their morphology drastically within a mammalian host. Temperature is one of the main host signals that initiates their conversion to the "host" form and is sufficient in the laboratory to trigger establishment of this host-adapted developmental program. Here we discuss the major human pathogens in this group, which are Blastomyces dermatiditis, Coccidioides immitis/posadasii, Histoplasma capsulatum, Paracoccidioides brasiliensis/lutzii, Sporothrix schenckii, and Talaromyces marneffei (formerly known as Penicillium marneffei). The majority of these organisms are primary pathogens, with the ability to cause disease in healthy humans who encounter them in endemic areas.
Topics: Adaptation, Physiological; Blastomyces; Coccidioides; Female; Fungi; Histoplasma; Host-Pathogen Interactions; Humans; Male; Mycoses; Risk Assessment; Temperature; Virulence Factors
PubMed: 25384771
DOI: 10.1101/cshperspect.a019794 -
JAMA Oct 1971
Topics: Chronic Disease; Culture Techniques; Histoplasma; Histoplasmosis; Humans; Skin Tests
PubMed: 5109876
DOI: 10.1001/jama.1971.03190160096034 -
Revista Iberoamericana de Micologia 2014Advances in the classification of the human pathogen Histoplasma capsulatum (H. capsulatum) (ascomycete) are sustained by the results of several genetic analyses that... (Review)
Review
Advances in the classification of the human pathogen Histoplasma capsulatum (H. capsulatum) (ascomycete) are sustained by the results of several genetic analyses that support the high diversity of this dimorphic fungus. The present mini-review highlights the great genetic plasticity of H. capsulatum. Important records with different molecular tools, mainly single- or multi-locus sequence analyses developed with this fungus, are discussed. Recent phylogenetic data with a multi-locus sequence analysis using 5 polymorphic loci support a new clade and/or phylogenetic species of H. capsulatum for the Americas, which was associated with fungal isolates obtained from the migratory bat Tadarida brasiliensis. This manuscript is part of the series of works presented at the "V International Workshop: Molecular genetic approaches to the study of human pathogenic fungi" (Oaxaca, Mexico, 2012).
Topics: Animals; Chiroptera; DNA, Fungal; Genetic Variation; Genotyping Techniques; Histoplasma; Histoplasmosis; Humans; Mexico; Molecular Diagnostic Techniques; Mycology; Phylogeny; Reproduction; Sequence Analysis, DNA; Species Specificity
PubMed: 24252830
DOI: 10.1016/j.riam.2013.09.013 -
Journal of Veterinary Diagnostic... Mar 2013A 12-year-old intact male Miniature Schnauzer dog with chronic diarrhea that was unresponsive to empirical treatment was presented to a referring veterinarian. A...
A 12-year-old intact male Miniature Schnauzer dog with chronic diarrhea that was unresponsive to empirical treatment was presented to a referring veterinarian. A laparotomy was performed, and formalin-fixed biopsies of duodenum, jejunum, and colon were sent to Oklahoma Animal Disease Diagnostic Laboratory for evaluation. Histologic examination revealed a severe, diffuse, granulomatous enteritis and colitis with intralesional yeast and hyphal forms. Grocott methenamine silver stains revealed short, aseptate hyphae co-mingled with 2-8 µm, oval to round yeast organisms consistent with Histoplasma capsulatum. The atypical presentation of both yeast and hyphal forms prompted identification of the organism. Direct sequencing of a polymerase chain reaction product from paraffin-embedded intestinal samples confirmed the presence of Ajellomyces capsulatus with a homology over 99% to several sequences in GenBank. Ajellomyces capsulatus is the holomorphic name for H. capsulatum. Therefore, the mycelial form of a dimorphic fungus such as H. capsulatum can coexist with yeast cells within lesions of histoplasmosis. Following diagnosis, the dog was treated with itraconazole for 6 months and has improved.
Topics: Animals; Dog Diseases; Dogs; Histoplasma; Histoplasmosis; Hyphae; Intestinal Diseases; Intestines; Male; Phylogeny
PubMed: 23512926
DOI: 10.1177/1040638713479604 -
Microbes and Infection Aug 1999Histoplasma capsulatum, the causative agent of the most common systemic fungal infection, histoplasmosis, has become subject to increasing study in parallel with rising... (Review)
Review
Histoplasma capsulatum, the causative agent of the most common systemic fungal infection, histoplasmosis, has become subject to increasing study in parallel with rising prevalence of human immunodeficiency. This review presents a summary of the advances made in the investigation of H. capsulatum genomics, molecular epidemiology, pathogenesis, and molecular genetics.
Topics: AIDS-Related Opportunistic Infections; HIV Infections; Histoplasma; Histoplasmosis; Humans; Midwestern United States; Molecular Epidemiology; Virulence
PubMed: 10816087
DOI: 10.1016/s1286-4579(99)80084-7 -
MSphere Dec 2023is a primary fungal pathogen with the ability to infect otherwise healthy mammalian hosts, causing systemic and sometimes life-threatening disease. Thus far, molecular...
is a primary fungal pathogen with the ability to infect otherwise healthy mammalian hosts, causing systemic and sometimes life-threatening disease. Thus far, molecular genetic manipulation of this organism has utilized RNA interference, random insertional mutagenesis, and a homologous recombination protocol that is highly variable and often inefficient. Targeted gene manipulations have been challenging due to poor rates of homologous recombination events in . Interrogation of the virulence strategies of this organism would be highly accelerated by a means of efficiently generating targeted mutations. We have developed a recyclable CRISPR/Cas9 system that can be used to introduce gene disruptions in with high efficiency, thereby allowing disruption of multiple genes.
Topics: Animals; CRISPR-Cas Systems; Histoplasma; Homologous Recombination; Mutagenesis, Site-Directed; Mutagenesis, Insertional; Mammals
PubMed: 37819140
DOI: 10.1128/msphere.00370-23 -
Microbiological Reviews Jun 1989Several fungi can assume either a filamentous or a unicellular morphology in response to changes in environmental conditions. This process, known as dimorphism, is a... (Review)
Review
Several fungi can assume either a filamentous or a unicellular morphology in response to changes in environmental conditions. This process, known as dimorphism, is a characteristic of several pathogenic fungi, e.g., Histoplasma capsulatum, Blastomyces dermatitidis, and Paracoccidioides brasiliensis, and appears to be directly related to adaptation from a saprobic to a parasitic existence. H. capsulatum is the most extensively studied of the dimorphic fungi, with a parasitic phase consisting of yeast cells and a saprobic mycelial phase. In culture, the transition of H. capsulatum from one phase to the other can be triggered reversibly by shifting the temperature of incubation between 25 degrees C (mycelia) and 37 degrees C (yeast phase). Mycelia are found in soil and never in infected tissue, in contrast to the yeast phase, which is the only form present in patients. The temperature-induced phase transition and the events in establishment of the disease state are very likely to be intimately related. Furthermore, the temperature-induced phase transition implies that each growth phase is an adaptation to two critically different environments. A fundamental question concerning dimorphism is the nature of the signal(s) that responds to temperature shifts. So far, both the responding cell component(s) and the mechanism(s) remain unclear. This review describes the work done in the last several years at the biochemical and molecular levels on the mechanisms involved in the mycelium to yeast phase transition and speculates on possible models of regulation of morphogenesis in dimorphic pathogenic fungi.
Topics: Cell Wall; Histoplasma; Histoplasmosis; Humans; Virulence
PubMed: 2666842
DOI: 10.1128/mr.53.2.186-209.1989 -
Revista Iberoamericana de Micologia 2014High sensitivity and specificity of molecular biology techniques have proven usefulness for the detection, identification and typing of different pathogens. The ITS... (Review)
Review
High sensitivity and specificity of molecular biology techniques have proven usefulness for the detection, identification and typing of different pathogens. The ITS (Internal Transcribed Spacer) regions of the ribosomal DNA are highly conserved non-coding regions, and have been widely used in different studies including the determination of the genetic diversity of human fungal pathogens. This article wants to contribute to the understanding of the intra- and interspecific genetic diversity of isolates of the Histoplasma capsulatum and Sporothrix schenckii species complexes by an analysis of the available sequences of the ITS regions from different sequence databases. ITS1-5.8S-ITS2 sequences of each fungus, either deposited in GenBank, or from our research groups (registered in the Fungi Barcode of Life Database), were analyzed using the maximum likelihood (ML) method. ML analysis of the ITS sequences discriminated isolates from distant geographic origins and particular wild hosts, depending on the fungal species analyzed. This manuscript is part of the series of works presented at the "V International Workshop: Molecular genetic approaches to the study of human pathogenic fungi" (Oaxaca, Mexico, 2012).
Topics: DNA, Fungal; DNA, Ribosomal; DNA, Ribosomal Spacer; Databases, Genetic; Genetic Variation; Histoplasma; Histoplasmosis; Humans; Molecular Diagnostic Techniques; Mycological Typing Techniques; Sporothrix; Sporotrichosis
PubMed: 24270072
DOI: 10.1016/j.riam.2013.10.003 -
European Journal of Clinical... May 1989Histoplasmosis occurs throughout the world but is more common within the endemic areas of North America, particularly in fertile river valleys. Disease manifestations... (Review)
Review
Histoplasmosis occurs throughout the world but is more common within the endemic areas of North America, particularly in fertile river valleys. Disease manifestations range from asymptomatic infection in the normal host with low-inoculum exposure to rapidly fatal, disseminated infection in the severely immunocompromised host, emphasizing the importance of cellular immunity in defense against Histoplasma capsulatum. Diagnosis depends on a high index of suspicion, knowledge of the clinical and epidemiologic features of the infection, and a thorough understanding of the uses and limitations of fungal cultural and serological laboratory procedures. Recently, a method has been developed for rapid diagnosis based on detection of a polysaccharide antigen in body fluids of patients with histoplasmosis. Amphotericin B remains the preferred treatment for more severe forms of histoplasmosis, particularly in the immunocompromised host, but oral treatment with ketoconazole or newer imidozoles appears to be effective in less severe infections in non-immunocompromised individuals.
Topics: Amphotericin B; Histoplasma; Histoplasmosis; Humans; Immune Tolerance; Ketoconazole; Time Factors; United States
PubMed: 2502413
DOI: 10.1007/BF01964063 -
Infection and Immunity Dec 2002
Review
Topics: Animals; Bacteria; Bacterial Infections; Bacterial Proteins; Fungal Proteins; Gene Expression; Genetic Techniques; Histoplasma; Histoplasmosis; Mice; Rabbits; Rats; Virulence
PubMed: 12438320
DOI: 10.1128/IAI.70.12.6518-6523.2002