• Clinical science

Candidiasis

Abstract

Candida albicans is the most common cause of candidiasis and appears almost universally in low numbers on healthy skin, in the oropharyngeal cavity, and in the gastrointestinal and genitourinary tracts. In immunocompetent individuals, C. albicans usually causes minor localized infections, including thrush (affecting the oral cavity), vaginal yeast infections (if there is an underlying pH imbalance), and infections of the intertriginous areas of skin (e.g., the axillae or gluteal folds). More widespread and systemic infections may occur in immunocompromised individuals (e.g., neonates, diabetics, and HIV patients), with the esophagus most commonly affected (candida esophagitis). Localized cutaneous candidiasis infections may be treated with topical antifungal agents (e.g., clotrimazole). More widespread and systemic infections require systemic therapy with fluconazole or caspofungin.

Etiology

Pathogen

Risk factors

Candida albicans appears almost universally in low numbers on healthy adults but can cause disease in certain high-risk patients, especially those that are immunocompromised!

References:[1][2][3][4]

Pathophysiology

  • Local infection: imbalance in local flora (e.g., triggered by antibiotic use) → local overgrowth of C. albicans → local mucocutaneous infection (e.g., oropharyngeal infection, vaginitis)
  • Systemic infection: local mucocutaneous infection → breach of skin/mucosal barrier or translocation (IV catheterisation, ascending infection in pyelonephritis, or resorption via GIT) → direct invasion of bloodstream (candidemia) → spread to visceral tissues → disseminated organ infection (e.g., pyelonephritis, endocarditis)

References:[1][5][6][7]

Clinical features

Local mucocutaneous

Systemic candidiasis

  • Candidemia: symptoms may vary from fever to sepsis (hard to distinguish from bacterial sepsis)
  • Infiltration of organs may occur either directly (e.g., ventriculoperitoneal shunt in meningitis) or hematogenous
  • Infiltration of any organ
    • Chorioretinitis
    • Muscle abscesses
    • Pneumonia Pneumonia caused by candida is extremely rare, but usually very severe and often fatal.
    • Meningitis
    • Endocarditis
    • Possible signs of multiorgan system failure
  • Chronic disseminated candidiasis
    • Also known as hepatosplenic candidiasis
    • Mostly in patients with hematologic malignancies
    • High persistent fever
    • Right upper quadrant pain, vomiting, nausea

References:[1][8][5][9][10][11]

Diagnostics

A suspected diagnosis based on clinical appearance requires confirmation with additional tests.

  • KOH test (potassium hydroxide smear) on a wet mount preparation of scrapings or smears (best initial test): budding yeasts, hyphae, and pseudohyphae
  • Blood or tissue culture (best confirmatory test)
    • Candida spp. form yeast cells and pseudohyphae at 20–25°C
    • Candida albicans forms germ tubes at 37°C
  • Candida antigen detection
  • Endoscopy (with or without biopsy)
    • Indications
      • Immunocompetent individuals with odynophagia
      • Candida infection not responsive to oral fluconazole therapy
    • Findings: white mucosal plaque-like lesions
  • Additional tests in suspected candidemia with visceral involvement

References:[12][13][14]

Treatment

Local mucocutaneous

Systemic treatment

  • Indications
  • Drug of choice: IV caspofungin; or micafungin (echinocandins) for 2 weeks after resolution of symptoms and documented clearance of C.albicans
  • Alternatives
    • Fluconazole: in patients not critically ill and if a resistance is unlikely
      • MOA: inhibition of yeast cytochrome p450 enzyme 14-alpha demethylase, which inhibits cell membrane formation
    • Lipid formulation amphotericin B: because of toxicity, only indicated if there is intolerance, limited availability, or resistance to alternatives

References:[1][11][13][14][15][16]