Lesson 3.4

• caused by monomorphic or dimorphic fungi that are ubiquitous and part of normal flora


  Opportunistic mycoses
• -less virulent than endemic mycoses and invade tissues of immunocompromised hosts.

  -(high case fatality ratio)

  -resolution does not confer immunity - reinfection/reactivation may occur when host immunity once again compromised


  Opportunistic mycoses
• • most common species: Candida albicans (yeast form isolated)
  • NF of skin, and mucous membrane of GI tract
  • 3rd most common cause of central-line associated bloodstream infection
  • produce yeast and hyphae in vivo


  Candida spp
• • Usage of broad spectrum antibiotic
  • Prolonged antibiotic usage
  • Pregnancy
  • Diabetes mellitus
  • Malnutrition

  Candida spp (Risk Factor)
• • Cutaneous candidiasis
  • Oropharyngeal candidiasis: white patches, esophagitis, cheilitis
  • Onychomycosis (nail infection)
  • Vulvovaginitis (vaginal thrush)
  • CNS invasive infections
  • Diaper rash 


  Clinical Manifestation: Candidiasis AKA Moniliasis or Thrush
• • Direct microscopic exam: using KOH or Gram-stain
  • C. albicans: formation of pseudohyphae and budding yeast


  Laboratory Diagnosis of Candida spp
• • Culture: Feathering (BA and EMB)
  • CHROMagar Candida: detects mixed species, rapid ID of Candida spp. (C. albicans: green; C. tropicalis: blue)
  • Screening test for C. albicans: germ tube/serum test
  • Addition of organism to serum and incubated at 35'C for 2-4 hours
  • C. albicans: (+) germ tube
  • Confirmatory (C. albicans): chlamydospores (+) on Cornmeal agar (isolated) room temp for 48-72 hours
  • Blastoconidia formation: Sucrose (+)


  Culture on Candida spp
• • Alkaline pH will rule out vaginosis and trichomoniasis
  • pH (4.5 or above) = candidiasis
  • Vaginal discharge + 10% KOH (direct microscopy)
  • Fungal culture


  Differential diagnosis for vaginal infection
• • most frequently isolated mold
  • normal saprophyte in soil
  • transmitted through inhalation
  • Most common agents: A. fumigatus, A. flavus
  • Less common agents: A. niger, A. terreus, A. nidulans, A. versicolor


  Aspergillus spp
• 1. Allergic bronchopulmonary aspergillosis (ABPA)
  2. Allergic Aspergillus sinusitis
  3. Aspegilloma of the lung AKA fungus ball or Farmer's lung disease
  4. Invasive aspergillosis
  5. A flavus - produce aflatoxin, a carcinogenic hepatotoxin, associated with food poisoning


  Clinical manifestation of Aspergillus spp
• • Direct examination: demonstrates dichotomous hyaline septate hyphae
  • Culture: SDA, Czapek - <50% sensitivity and best identified after culture through vesicles (swollen conidiophores)
  • Serology: Galactomannan - best used on serial specimens from high risk patients and serves as an early indication to begin pre-emptive antifungal therapy and aggressive pursuing of definitive diagnosis


  Laboratory Diagnosis of Aspergillus spp
• • geophilic (environmental)
  • AKA Filobasidiella neoformans
  • Normal saprophyte in soil, bird excrements commonly detected in pigeon dropping
  • transmitted through inhalation of infectious form (non-capsulated yeast or basidiospores) from environment

  Cryptococcus neoformans
• • >80% of cases are associated with HIV infection
  • occurs in ~3% of solid organ transplant
  • Sites: pulmonary - dissemination
  • CNS: cryptococcal meningitis or cyptococcemia
  • Others: skin, bone, eyes, prostate

  Clinical Manifestations of Cryptococcosis AKA European blastomycosis
• • Direct Microscopy: *India ink - encapsulated yeast (CSF)
  • 70-90% sensitivity in HIV (+) patients
  • ~50% sensitivity in HIV (-) patients
  • Capsule not produced in vitro
  • *Histopathology/ Biopsy - detection of narrow-based budding yeasts in tissue
  • Culture: (Gold standard)
  • Serology: Immunochromatography/LFA, latex agglutination, ELISA


  Laboratory Diagnosis of Cryptococcus neoformans
• • grows well on standard fungal media: SDA without cycloheximide
  • (+) bird seed/ niger seed agar - black colonies due to (+) phenol oxidase
  • biochemical test: (+) UREASE

  Culture on Cryptococcus neoformans
• • Serology test in Cryptococcus neoformans
  • detects cryptococcal capsular polysaccharide antigen (CrAg) from blood even before the development of symptoms
  • more sensitive and specific compared to previous latex agglutination assays

  Immunochromatography/LFA (lateral flow assay)
• • endemic and opportunist fungi
  • occurs primarily in HIV-infected individuals in Southeast Asia (Thailand) and southern china


  Penicillium marneffei
• • mimics TB, leishmaniasis, histoplasmosis, and cryptococcosis
  • fever, cough, pulmonary infiltrates, lymphadenopathy, organomegaly, anemia, leukopenia, thrombocytopenia
  • skin: molluscum contagiosum-like lesions


  Clinical Manifestations of Penicillium marneffei
• • Specimens: blood, BM, BAL, tissue
  • Culture:
  • 37'C - yeast-like form that divides by fission, does not bud, and more pleomorphic and elongated than Histoplasma
  • 25'C - mold form with brush-like structures, conidiophore and extending conidia resemble a brush/penicillius, and red pigment in agar


  Laboratory Diagnosis of Penicillium marneffei
• • formerly classified as protozoan but molecular analysis showed DNA is similar to fungi
  • unknown reservoir and transmitted via inhalation


  Pneumocystis jiroveci (carinii)
• • AIDS patients: most common cause of pneumonia (PCP) pnemocystis pneumonia and most common opportunistic infection in AIDS patients
  • may also cause extrapulmonary manifestations


  Clinical Manifestations of Pneumocystis jiroveci (carinii)
• • cannot be isolated/cultured; thus, must demonstrate cyst/trophozoites in BAL, other respiratory samples, pleural fluid, lung, and other biopsy samples
  • Giemsa stain for trophic forms
  • Gomori methenamine silver (GMS) - cyst forms
  • Serology: detection of B-D-glucan (not specific for P.jiroveci)


  Laboratory Diagnosis of Pneumocystis jiroveci (carinii)