Notes on Fungal Infections Lecture

Learning Objectives

• Describe the general features of fungal infections.
• Identify risk factors for developing a fungal infection.
• Describe the clinical manifestations of common fungal infections.

General Features of Fungal Infections

• Common in immunocompromised patients.
• Exceptions: infections from dimorphic fungi and dermatophytes.
• Typical presentation: Subacute to chronic.
  • Exceptions: candidemia and mucormycosis.
• Person-to-person transmission is rare, with some exceptions in dermatophytes and mucocutaneous candidiasis.
• No specific symptoms to distinguish fungal from bacterial infections.
• Typical antibiotics ineffective; exception is pneumocystis.

Risk Factors for Fungal Infections

Major Risk Factors:

• Hematopoietic stem cell transplant (1st 30 days).
• Induction chemotherapy for hematologic malignancies (e.g., acute leukemia).
• Solid organ transplantation.

Minor Risk Factors:

• Other chemotherapy.
• Critical illness.
• Mechanical ventilation.
• Indwelling lines.
• Hemodialysis.
• Total parenteral nutrition (TPN).
• Malnutrition.
• AIDS.
• Mucositis.
• Recent use of broad-spectrum antibiotics.
• Diabetes.
• Recent intra-abdominal surgery.

Classification of Fungal Infections

1. Superficial Infections

   • Caused by dermatophytes.
   • Common infections include:
     • Tinea capitis (scalp).
     • Tinea barbae (beard).
     • Tinea corporis (ringworm).
     • Tinea cruris (jock itch).
     • Tinea pedis (athlete's foot).
   • Candidal infections:
     • Candidal intertrigo (skin folds).
     • Onychomycosis (nail infection).
     • Tinea versicolor (caused by Malassezia, presents as skin patches).

2. Mucocutaneous Infections

   • Caused by Candida.
   • Common infections include:
     • Oral thrush (pseudomembranes on tongue).
     • Esophageal candidiasis.
     • Vulvovaginitis (yeast infection).

3. Cutaneous Infections

   • Example: Sporotrichosis (caused by Sporothrix shenckii).
   • Contracted through soil/organic material inoculation.

4. Deep Primary Infections

   • Caused by dimorphic fungi.
   • Rare CNS infections from histoplasmosis/blastomycosis.
   • Pulmonary diseases from:
     • Histoplasmosis (cave disease).
     • Blastomycosis.
     • Coccidioidomycosis (Valley fever).
   • Symptoms: fever, cough, chest pain, constitutional symptoms.
   • Diagnosed based on geography:
     • Histoplasmosis: Midwest, Appalachian Mountains.
     • Blastomycosis: Ohio River Valley, parts of Canada.
     • Coccidioidomycosis: American Southwest.

5. Deep Opportunistic Infections

   • Occur mostly in immunocompromised individuals.
   • High mortality rates.
   • Examples:
     • Cryptococcus meningitis.
     • Candidemia.
     • Rhinocerebral mucormycosis (fast-spreading; requires immediate treatment).
     • Invasive pulmonary aspergillosis (associated with neutropenia).

Diagnosis of Fungal Infections

• Microscopy on fluid/tissue samples

  • Identification through specific morphology.
  • Helpful stains: potassium hydroxide, calcofluor white, India ink.

• Cultures

  • Routine blood cultures for candidemia.
  • Specific fungal cultures for systemic infections (may take weeks).

• Serological Tests

  • Antigen and antibody tests (e.g., cryptococcal antigen).
  • Galactomannan test for Aspergillus infection (sensitivity and specificity issues).

Conclusion

• Next video will cover medically problems indirectly caused by fungi and pseudoscience related to fungal infections.