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The Journal of Molecular Diagnostics :... Jun 2021Laboratory diagnosis of histoplasmosis is based on various methods, including microscopy, culture, antigen, and DNA detection of Histoplasma capsulatum var. capsulatum...
Laboratory diagnosis of histoplasmosis is based on various methods, including microscopy, culture, antigen, and DNA detection of Histoplasma capsulatum var. capsulatum or Histoplasma capsulatum var. duboisii. To improve sensitivity of existing real-time quantitative PCR (qPCR) assays, we developed a new RT-qPCR assay that allows amplification of whole nucleic acids of Histoplasma spp. validated on suspected cases. The limit of detection was 20 copies, and the specificity against 114 fungal isolates/species was restricted to Histoplasma spp. Whole nucleic acids of 1319 prospectively collected consecutive samples from 907 patients suspected of having histoplasmosis were tested routinely between May 2015 and May 2019 in parallel with standard diagnostic procedures performed in parallel. Forty-four had proven histoplasmosis attributable to H. capsulatum var. capsulatum (n = 40) or H. capsulatum var. duboisii (n = 4) infections. The results of RT-qPCR were positive in 43 of 44 patients (97.7% sensitivity) in at least one specimen. Nine of 863 cases (99% specificity) were RT-qPCR positive and therefore classified as possible cases. RT-qPCR was positive in 13 of 30 (43.3%) blood samples tested in proven cases. A positive RT-qPCR result in blood was significantly associated with H. capsulatum var. capsulatum progressively disseminated histoplasmosis with a positive RT-qPCR result in 92.3% of the immunocompromised patients with disseminated disease. This new Histoplasma RT-qPCR assay enabling amplification of H. capsulatum var. capsulatum and H. capsulatum var. duboisii is highly sensitive and allows the diagnosis of histoplasmosis advantageously from blood and bronchoalveolar lavage fluid.
Topics: DNA, Fungal; Genes, Fungal; Histoplasma; Humans; Limit of Detection; Prospective Studies; Real-Time Polymerase Chain Reaction; Reproducibility of Results; Reverse Transcriptase Polymerase Chain Reaction
PubMed: 33706012
DOI: 10.1016/j.jmoldx.2021.02.007 -
PLoS Pathogens May 2020
Review
Topics: AIDS-Related Opportunistic Infections; HIV Infections; Histoplasma; Histoplasmosis; Humans; Latin America
PubMed: 32407383
DOI: 10.1371/journal.ppat.1008449 -
PloS One 2018Although early and rapid detection of histoplasmosis is essential to prevent morbidity and mortality, few diagnostic tools are available in resource-limited areas,... (Comparative Study)
Comparative Study
BACKGROUND
Although early and rapid detection of histoplasmosis is essential to prevent morbidity and mortality, few diagnostic tools are available in resource-limited areas, especially where it is endemic and HIV/AIDS is also epidemic. Thus, we compared conventional and molecular methods to detect Histoplasma capsulatum in sera and blood from HIV/AIDS patients.
METHODOLOGY
We collected a total of 40 samples from control volunteers and patients suspected of histoplasmosis, some of whom were also infected with other pathogens. Samples were then analyzed by mycological, serological, and molecular methods, and stratified as histoplasmostic with (group I) or without AIDS (group II), uninfected (group III), and infected with HIV and other pathogens only (group IV). All patients were receiving treatment for histoplasmosis and other infections at the time of sample collection.
RESULTS
Comparison of conventional methods with nested PCR using primers against H. capsulatum 18S rRNA (HC18S), 5.8S rRNA ITS (HC5.8S-ITS), and a 100 kDa protein (HC100) revealed that sensitivity against sera was highest for PCR with HC5.8S-ITS, followed by immunoblotting, double immunodiffusion, PCR with HC18S, and PCR with HC100. Specificity was equally high for double immunodiffusion, immunoblotting and PCR with HC100, followed for PCR with HC18S and HC5.8-ITS. Against blood, sensitivity was highest for PCR with HC5.8S-ITS, followed by PCR with HC18S, Giemsa staining, and PCR with HC100. Specificity was highest for Giemsa staining and PCR with HC100, followed by PCR with HC18S and HC5.8S-ITS. PCR was less efficient in patients with immunodeficiency due to HIV/AIDS and/or related diseases.
CONCLUSION
Molecular techniques may detect histoplasmosis even in cases with negative serology and mycology, potentially enabling early diagnosis.
Topics: Adult; Female; HIV Infections; Histoplasma; Humans; Male; Middle Aged
PubMed: 29342162
DOI: 10.1371/journal.pone.0190408 -
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 -
PLoS Pathogens Sep 2022The fungal pathogen Histoplasma capsulatum (Hc) invades, replicates within, and destroys macrophages. To interrogate the molecular mechanisms underlying this...
The fungal pathogen Histoplasma capsulatum (Hc) invades, replicates within, and destroys macrophages. To interrogate the molecular mechanisms underlying this interaction, we conducted a host-directed CRISPR-Cas9 screen and identified 361 genes that modify macrophage susceptibility to Hc infection, greatly expanding our understanding of host gene networks targeted by Hc. We identified pathways that have not been previously implicated in Hc interaction with macrophages, including the ragulator complex (involved in nutrient stress sensing), glycosylation enzymes, protein degradation machinery, mitochondrial respiration genes, solute transporters, and the ER membrane complex (EMC). The highest scoring protective hits included the complement C3a receptor (C3aR), a G-protein coupled receptor (GPCR) that recognizes the complement fragment C3a. Although it is known that complement components react with the fungal surface, leading to opsonization and release of small peptide fragments such as C3a, a role for C3aR in macrophage interactions with fungi has not been elucidated. We demonstrated that whereas C3aR is dispensable for macrophage phagocytosis of bacteria and latex beads, it is critical for optimal macrophage capture of pathogenic fungi, including Hc, the ubiquitous fungal pathogen Candida albicans, and the causative agent of Valley Fever Coccidioides posadasii. We showed that C3aR localizes to the early phagosome during Hc infection where it coordinates the formation of actin-rich membrane protrusions that promote Hc capture. We also showed that the EMC promotes surface expression of C3aR, likely explaining its identification in our screen. Taken together, our results provide new insight into host processes that affect Hc-macrophage interactions and uncover a novel and specific role for C3aR in macrophage recognition of fungi.
Topics: Actins; Receptors, Complement; Macrophages; Histoplasma; Receptors, G-Protein-Coupled; Histoplasmosis; Peptide Fragments
PubMed: 36174103
DOI: 10.1371/journal.ppat.1010237 -
Clinical Microbiology Reviews Oct 1991This review summarizes the biology of Histoplasma capsulatum in relation to a wide variety of corresponding pathologies in histoplasmosis. Features of these disease... (Review)
Review
This review summarizes the biology of Histoplasma capsulatum in relation to a wide variety of corresponding pathologies in histoplasmosis. Features of these disease syndromes can be explained in part by natural variations within the fungal population and adaptations made by individual organisms to specific environments. H. capsulatum grows as mycelia and conidia in the soil; once inhaled, the organism undergoes a dramatic morphological and physiological conversion to a yeast form. The yeasts proliferate within the phagolysosomes of macrophages, using a variety of specific strategies for intracellular survival. Even avirulent strains or variants are able to avoid being killed by macrophages and instead establish inapparent or persistent infections. The ingested avirulent organisms assume enlarged shapes similar in appearance to those seen in histological sections of tissues from patients with histoplasmosis. Respiratory tract epithelial cells also appear to play a role in persistence: within them yeasts undergo phenotypic switching akin to the phase variation observed in other pathogens. This particular change involves the loss or modification of cell wall alpha-(1,3)-glucan, which is also correlated with the spontaneous appearance of avirulent variants. The repertoire of adaptive responses and natural variations within this species probably evolved from the need to adjust to a wide range of dynamic environments. In combination with the immune status of the host, these characteristics of H. capsulatum appear to influence the epidemiology, extent, and persistence of histoplasmosis.
Topics: Animals; Histoplasma; Histoplasmosis; Host-Parasite Interactions; Humans
PubMed: 1747859
DOI: 10.1128/CMR.4.4.411 -
Journal of Clinical Microbiology Nov 1986
Topics: Antibodies, Fungal; Cross Reactions; Histoplasma; Histoplasmosis; Humans; Serologic Tests
PubMed: 3771780
DOI: 10.1128/jcm.24.5.905-.1986 -
BMJ Case Reports Jun 2020A 50-year-old woman with a history of kidney transplant presented with 2 days of abdominal pain after 6 months of recurrent streptococcal pharyngitis, fevers, weight...
A 50-year-old woman with a history of kidney transplant presented with 2 days of abdominal pain after 6 months of recurrent streptococcal pharyngitis, fevers, weight loss and a new rash on her chest and back. Her examination was notable for a unilateral tonsillar exudate and 2-3 mm pink papules with a fine scale over her chest and back. CT of the abdomen and chest demonstrated several large lymph nodes, and laboratory investigation revealed new cytopenias and elevated transaminases. Urine antigen testing for was negative, but a fungal complement fixation panel was reactive for antibodies. Skin biopsy revealed intracellular organisms consistent with She underwent treatment with liposomal amphotericin B but due to nephrotoxicity, drug interactions and worsening transaminitis, therapy was changed to itraconazole. The diagnosis and management of disseminated histoplasmosis presents multiple challenges, which are of particular importance in patients with a history of renal transplantation.
Topics: Antibodies, Fungal; Antifungal Agents; Antigens, Fungal; Diagnosis, Differential; Female; Histoplasma; Histoplasmosis; Humans; Immunocompromised Host; Itraconazole; Kidney Transplantation; Lymphadenopathy; Lymphoproliferative Disorders; Middle Aged; Postoperative Complications; Radiography, Abdominal; Radiography, Thoracic; Tomography, X-Ray Computed; Treatment Outcome
PubMed: 32532906
DOI: 10.1136/bcr-2019-233976 -
Cellular Microbiology Mar 2019Recognition and internalisation of intracellular pathogens by host cells is a multifactorial process, involving both stable and transient interactions. The plasticity of...
Recognition and internalisation of intracellular pathogens by host cells is a multifactorial process, involving both stable and transient interactions. The plasticity of the host cell plasma membrane is fundamental in this infectious process. Here, the participation of macrophage lipid microdomains during adhesion and internalisation of the fungal pathogen Histoplasma capsulatum (Hc) was investigated. An increase in membrane lateral organisation, which is a characteristic of lipid microdomains, was observed during the first steps of Hc-macrophage interaction. Cholesterol enrichment in macrophage membranes around Hc contact regions and reduced levels of Hc-macrophage association after cholesterol removal also suggested the participation of lipid microdomains during Hc-macrophage interaction. Using optical tweezers to study cell-to-cell interactions, we showed that cholesterol depletion increased the time required for Hc adhesion. Additionally, fungal internalisation was significantly reduced under these conditions. Moreover, macrophages treated with the ceramide-glucosyltransferase inhibitor (P4r) and macrophages with altered ganglioside synthesis (from B4galnt1 mice) showed a deficient ability to interact with Hc. Coincubation of oligo-GM1 and treatment with Cholera toxin Subunit B, which recognises the ganglioside GM1, also reduced Hc association. Although purified GM1 did not alter Hc binding, treatment with P4 significantly increased the time required for Hc binding to macrophages. The content of CD18 was displaced from lipid microdomains in B4galnt1 macrophages. In addition, macrophages with reduced CD18 expression (CD18 ) were associated with Hc at levels similar to wild-type cells. Finally, CD11b and CD18 colocalised with GM1 during Hc-macrophage interaction. Our results indicate that lipid rafts and particularly complex gangliosides that reside in lipid rafts stabilise Hc-macrophage adhesion and mediate efficient internalisation during histoplasmosis.
Topics: Animals; Cell Adhesion; Cell Line; Endocytosis; Histoplasma; Host-Pathogen Interactions; Macrophages; Membrane Microdomains; Mice, Inbred C57BL; Mice, Knockout
PubMed: 30427108
DOI: 10.1111/cmi.12976 -
PLoS Neglected Tropical Diseases Jun 2016Histoplasma capsulatum comprises a worldwide complex of saprobiotic fungi mainly found in nitrogen/phosphate (often bird guano) enriched soils. The microconidia of...
BACKGROUND
Histoplasma capsulatum comprises a worldwide complex of saprobiotic fungi mainly found in nitrogen/phosphate (often bird guano) enriched soils. The microconidia of Histoplasma species may be inhaled by mammalian hosts, and is followed by a rapid conversion to yeast that can persist in host tissues causing histoplasmosis, a deep pulmonary/systemic mycosis. Histoplasma capsulatum sensu lato is a complex of at least eight clades geographically distributed as follows: Australia, Netherlands, Eurasia, North American classes 1 and 2 (NAm 1 and NAm 2), Latin American groups A and B (LAm A and LAm B) and Africa. With the exception of the Eurasian cluster, those clades are considered phylogenetic species.
METHODOLOGY/PRINCIPAL FINDINGS
Increased Histoplasma sampling (n = 234) resulted in the revision of the phylogenetic distribution and population structure using 1,563 aligned nucleotides from four protein-coding regions. The LAm B clade appears to be divided into at least two highly supported clades, which are geographically restricted to either Colombia/Argentina or Brazil respectively. Moreover, a complex population genetic structure was identified within LAm A clade supporting multiple monophylogenetic species, which could be driven by rapid host or environmental adaptation (~0.5 MYA). We found two divergent clades, which include Latin American isolates (newly named as LAm A1 and LAm A2), harboring a cryptic cluster in association with bats.
CONCLUSIONS/SIGNIFICANCE
At least six new phylogenetic species are proposed in the Histoplasma species complex supported by different phylogenetic and population genetics methods, comprising LAm A1, LAm A2, LAm B1, LAm B2, RJ and BAC-1 phylogenetic species. The genetic isolation of Histoplasma could be a result of differential dispersion potential of naturally infected bats and other mammals. In addition, the present study guides isolate selection for future population genomics and genome wide association studies in this important pathogen complex.
Topics: Animals; Genetic Variation; Global Health; Haplotypes; Histoplasma; Histoplasmosis; Humans; Phylogeny; Phylogeography
PubMed: 27248851
DOI: 10.1371/journal.pntd.0004732