Candida species is a topic covered in the Johns Hopkins Antibiotic (ABX) Guide.

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MICROBIOLOGY

  • Fungal organism with multiple different morphologies (depending upon species and environmental conditions)
    • Yeast: spherical single cells with ability to bud. Usually about 3-6µm in diameter.
      • Likely important in facilitating dissemination through fluids (e.g. saliva, urine, water, bloodstream) to distant sites.
      • The yeast forms of C. glabrata tend to be smaller at about 2-5 µm
    • Pseudohyphae: filamentous structures composed of elongated yeast cells in chains and have constrictions at septal junctions (rather than true septa).
      • Pseudohyphae are NOT seen with C. glabrata
    • True hyphae: filamentous structures composed of cells with uniform in width. Have true septa.
      • Typically seen with C. albicans, C. dubliniensis and C. tropicalis. Facilitate invasion of tissues
      • Germ tube: when incubated in serum, C. albicans and C. dubliniensis form an early hyphal structure called the germ tube. This can be used for rapid and preliminary identification of these species.
    • Chlamydospores: rounded, thick walled structures, several times the size of the yeast, typically found at ends of hyphae: Seen with C. albicans and C. dubliniensis.
  • Diagnostic tests:
    • Stains: organisms may be visualized via KOH, Gram stain, calcofluor white, Grocott-Gomori’s methanamine silver (GMS) and periodic-acid-Schiff (PAS)
    • Culture: grows aerobically in a range of media including blood culture broth, blood agar, Sabouraud agar and Mueller Hinton agar.
      • For blood cultures, continuous monitoring systems are as good as the lysis centrifugation ("fungal isolator") method.
      • False negatives are common in candidemia with any blood culture technique.
    • Identification of individual species facilitated microscopic morphology, biochemical tests, chormatogenic agar and PNA FISH techniques.
    • Serum beta D glucan (BDG): Levels >60-80 pg/ml suggest invasive disease. Causes of false positives include severe burns, extensive gauze packing, other fungal infections.
  • Most important species is C. albicans, which causes nearly all mucosal candidiasis and is generally the most common cause of invasive disease. However, epidemiology varies by geographical region, extent of antifungal (esp. azole class) exposure and local hospital epidemiology.
    • Other species of importance are C. glabrata, C. parapsilosis (especially in association with implanted devices), C. tropicalis, C. krusei, C. guilliermondii, C. kefyrand C. lusitaniae (this module).
    • See separate module for Candida albicans.

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Last updated: May 28, 2016