Mucous Membrane and Deep Organ Fungal Infections

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Mucous Membrane and Deep Organ Fungal Infections

• Dr. John R. Warren
• Department of Pathology
• Northwestern University
• Feinberg School of Medicine
• June 2007

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Fungal Diseases

• Yeast and Pseudohyphae in Tissue (37oC) and
  Culture (30oC)
• Yeast Without Hyphae or Pseudohyphae in Tissue
  (37oC) and Culture (30oC)
• Yeast in Tissue (37oC) and Hyphae in Culture
  (30oC)1
• Hyphae in Tissue (37oC) and Culture (30oC)
• 1Dimorphic fungi

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Yeast and Pseudohyphae in Tissue and Culture

• Candida albicans1
• Candida tropicalis
• Candida glabrata2
• Candida parapsilosis
• Candida krusei
• 1Predominant species in clinical specimens
• 2C. glabrata (formerly Torulopsis glabrata) does
  not form hyphae or pseudohyphae

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Yeast Without Hyphae or Pseudohyphae in Tissue
and Culture

• Cryptococcus neoformans

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Yeast in Tissue and Hyphae in Culture1

• Histoplasma capsulatum
• Blastomyces dermatitidis
• Coccidioides immitis
• 1Dimorphic fungi

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Hyphae in Tissue and Culture

• Aspergillus species1
• Zygomycetes genera2
• 1A. fumigatus, A. flavus, A. niger, A. terreus
• 2Rhizopus, Mucor, Absidia

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Candidiasis

• Candida albicans most common species
• Yeast and pseudohyphae present in tissue (37oC)
  and culture (30oC)
• Oral candidiasis (thrush), esophageal
  candidiasis, invasive candidiasis (necrotizing
  esophagitis, colonic mucosal necrosis in
  neutropenic patients intravascular catheter),
  candidal endocarditis

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Candidiasis

• Colonization of mucosal surfaces, impairment of
  host defenses (neutropenia, decreased T cells),
  dissemination from mucosal sites of colonization
  (especially the esophagus)

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Laboratory Diagnosis of Candidasis

• Tissue visualization of yeast and pseudohyphal
  forms by methenamine silver and PAS stain
• Germ-tube formation (filamentous extensions from
  yeast cells in a serum suspension of yeast)
  presumptive identification of Candida albicans
• Pseudohyphae with sporulation on deficient agar
  medium (corn meal) presumptive identification of
  yeast as Candida1
• Carbohydrate assimilation patterns (growth/no
  growth with single carbohydrate substrates)
• 1Presence of large and brightly refractile
  chlamydospores diagnostic of Candida albicans

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Cryptococcosis

• Cryptococcus neoformans pathogenic, other species
  saprophytic
• Yeast forms in tissue (37oC) and culture (30oC)
• CNS cryptococcosis Insidious with mild headache,
  memory lapses, personality change, no or mild
  fever, occasionally signs of meningeal irritation
  (nuchal ridigity)

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Cryptococcosis

• Disseminated cryptococcosis-skin, bone, prostate
• Natural habitat Soil, especially soil mixed with
  excretion of birds (pigeons)
• Organisms inhaled with lung portal of entry
• Primary infection usually clinically inapparent

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Cryptococcosis

• Cryptococcus neoformans neurotropic with
  dissemination to the brain causing
  meningoencephalitis
• Cryptococcal disease occurs primarily in
  immunocompromised conditions including AIDS,
  lymphoreticular malignancies, and corticosteroid
  therapy

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Laboratory Diagnosis of Cryptococcosis

• Tissue visualization of variably sized (4- 10
  ?m) narrow-based budding yeast forms by
  methenamine silver and PAS stain
• Tissue visualization of yeast capsule by
  mucicarmine stain
• Microscopic visualization of encapsulated
  variably sized yeast forms in India ink
  preparation of cerebrospinal fluid

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Laboratory Diagnosis of Cryptococcosis

• Urease production
• Inability to reduce nitrate
• Growth of variably sized yeast forms without
  hyphae or pseudohyphae on deficient agar medium
  (corn meal)
• Production of melanin from caffeic acid
  (3,4-dihydrocinnamic acid) on niger seed agar
• Carbohydrate assimilation patterns

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Histoplasma capsulatum

• A dimorphic fungus Mold at cool environmental
  temperatures (25o-30oC) and yeast at internal
  body temperature (37oC)
• Endemic to the drainage basins of the Ohio,
  Missouri, and Mississippi River valleys
• Key virulence factor?Inhibition of phagolysosome
  acidification

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Histoplasmosis

• Inhalation of spores released by environmental
  mold form initiates pulmonary infection
• Inhaled spores transform into yeast cells within
  alveolar spaces with infection of alveolar
  macrophages
• Primary infection asymptomatic or mild, and
  infection with H. capsulatum becomes latent

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Histoplasmosis

• Decrement in CD4 T cell function (AIDS, age
  especially older men with chronic obstructive
  pulmonary disease and/or diabetes mellitus)
  induces reactivation of latent infection with
  chronic cavitary histoplasmosis of the lung
  causing hemoptysis, or disseminated
  histoplasmosis with fever, weight loss,
  hepatosplenomegaly, adrenal insufficiency, and/or
  meningitis

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Laboratory Diagnosis of Histoplasmosis

• Presence of small (2-4 ?m) intracellular yeast
  cells surrounded by a clear halo in macrophages
  (Giemsa stain)
• Growth of mold in culture at 30oC with presence
  of large tuberculate macroconidia
  (conidiaspores) and numerous microconidia
• Conversion of mold to small yeast cells at 37oC

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Blastomycosis

• Blastomyces dermatitidis a dimorphic fungus
  (yeast form in tissue at 37oC and mold form in
  culture at 30oC)
• Disease produced primarily by extrapulmonary
  dissemination, especially to the skin but also to
  the genitourinary tract (prostate, epididymis),
  and bone

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Blastomycosis

• Natural habitat Soil containing decayed
  vegetation or decomposed wood along waterways or
  next to lakes
• Regions adjacent to the Mississippi and Ohio
  River valleys endemic
• Air-born spores released by environmental mold
  form inhaled into the lungs with clinically
  inapparent (generally) pulmonary infection
• Blastomycosis usually not opportunistic infection
  and occurs in normal host

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Laboratory Diagnosis of Blastomycosis

• Tissue visualization of uniformly large (10-15
  ?m) broad-based budding yeast forms with thick
  double-contured cell walls by methenamine silver
  and PAS stain
• Growth of mold in culture at 30oC with oval or
  pyriform microconidia at the tips of
  conidiophores (lollipops)
• Conversion to yeast forms at 37oC

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Coccidioidomycosis

• Coccidioides immitis a dimorphic fungus (growth
  as a mold at 30oC and as spherules in tissue at
  37oC)
• Endemic regions Hot desert sands of the San
  Joaquin Valley of California and southern Arizona
  
• Most primary pulmonary infections clinically
  inapparent, or present with mild flulike symptoms
  (fever, arthralgia) and varying degrees of cough
  and sputum production

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Coccidioidomycosis

• Chronic cavitary pulmonary disease mimicking
  bronchogenic carcinoma or tuberculosis in 2 of
  infected individuals (especially in diabetics)
• Disseminated coccidioidomycosis involving skin,
  bone, and muscle (AIDS)
• Air-born spores (arthroconidia) from
  environmental mold forms inhaled causing initial
  pulmonary infection

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Laboratory Diagnosis of Coccidioidomycosis

• Tissue visualization of thick-walled spherules of
  variable size (10-60 ?m) by methenamine silver
  and PAS stain
• Spherules partially or completely filled by
  endospores, intact or ruptured, or collapsed with
  no endospores
• Growth of mold at 30oC with hyphae forming
  alternately light-staining cells and
  dense-staining arthrospores

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Coccidioidomycosis

• Conversion of Coccidioides immitis to spherule
  form in 37oC culture difficult and requires
  special conditions
• DNA probe assay or HS exoantigen detection
  utilized instead of spherule conversion to
  confirm culture identification of Coccidioides
  immitis

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Zygomycosis (Mucormycosis)

• Class Zygomycetes
• Most common genus Rhizopus
• Less common genera Mucor, Absidia
• Hyphae present in tissue (37oC) and culture
  (30oC)
• Laboratory diagnosis by morphology of sporangia,
  sporangiophores, and vegetative hyphae

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Zygomycosis (Mucormycosis)

• Rhinocerebral zygomycosis with rapidly developing
  necrosis of tissue in the paranasal and frontal
  sinuses extending into the periorbital tissue,
  and invasion through the cribriform plate into
  the base of the brain
• Disseminated zygomycosis

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Zygomycosis (Mucormycosis)

• Inhalation of air-born spores from the
  environment and implantation of spores on the
  nasal mucosa and sinuses
• Opportunistic infection occurring in debilitated
  patients, especially diabetics with ketoacidosis,
  and leukemic patients neutropenic secondary to
  cytotoxic therapy

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Aspergillosis

• Most common species A. fumigatus
• Less common species A. flavus, A. niger, A.
  terreus
• Laboratory diagnosis by morphology of the
  fruiting body born on the termini of specialized
  spore-forming hyphal cells (conidiophores)

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Aspergillosis

• Primary diseases Allergic bronchopulmonary
  aspergillosis, aspergilloma (fungus ball),
  invasive infection
• Aspergillus angiocentric with a strong
  predisposition for blood vessel invasion causing
  occlusive thrombosis and tissue infarction

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Aspergillosis

• Inhalation of environmental spores and
  implantation in the lungs
• Contamination of hospital ventilation systems by
  spores, dispersal of soil spores at construction
  sites
• Immunocompromised patients (leukemia, lymphoma,
  high-dose steroids, AIDS), patients with cystic
  spaces in the lungs (TB cavity, bronchiectasis)

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Recommended Reading

• Winn, W., Jr., Allen, S., Janda, W., Koneman,
• E., Procop, G., Schreckenberger, P., Woods,
• G.
• Konemans Color Atlas and Textbook of
• Diagnostic Microbiology, Sixth Edition,
• Lippincott Williams Wilkins, 2006
• Chapter 21. Mycology.

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Recommended Reading

• Murray, P., Baron, E., Jorgensen, J., Landry, M.,
  Pfaller, M.
• Manual of Clinical Microbiology, 9th Edition, ASM
  Press, 2007
• Shean, Y.R. Chapter 118. Algorithms for
  Detection and Identification of Fungi.
• Hazen, K.C., and Howell, S.A. Chapter 119.
  Candida, Cryptococcus, and Other Yeasts of
  Medical Importance.
• Verweij, P.E., and Brandt, M.E. Chapter 121.
  Aspergillus, Fusarium, and Other Opportunistic
  Moniliaceous Fungi.
• Richardson, M.D., and Koukila-Kaehkoelae, P.
  Chapter 122. Rhizopus, Rhizomucor, Absidia, and
  Other Agents of Systemic and Subcutaneous
  Zygomycoses.
• Brandt, ME., and Warnock, D.W. Chapter 123.
  Histoplasma, Blastomyces, Coccidioides, and Other
  Dimorphic Fungi Causing Systemic Mycoses.