Opportunistic Mycoses

Snapshot

• A 40-year-old woman presents to the emergency room with a week of fever, cough, and hemoptysis. She has a history of HIV and has been noncompliant with her medications and has a history of tuberculosis that was adequately treated. She reports feeling increasing fatigue. A chest CT shows nodules with a halo sign. A bronchoalveolar lavage with biopsy eventually reveals fungus with septate hyphae branching at acute angles invading into lung tissue. (Invasive aspergillosis)

Candida albicans

• Classification
  • yeast with budding and pseudohyphae
  • germ tube formation at 37°C (diagnostic)
  • can be part of normal flora
• Risk factors
  • immunocompromised status
  • hospital admission, especially in the ICU
• Clinical syndrome
  • immunocompetent hosts present with skin and mucous membrane infections
    • oral thrush
      • white plaque on the tongue that can be scraped off
      • associated with use of inhaled corticosteroids
    • candidal intertrigo
      • well-demarcated, erythematous, and itchy plaques in the skin folds
  • vulvovaginitis
    • • thick “cottage cheese” white discharge
      • itchiness
  • immunocompromised hosts usually present with systemic disease
    • local infection is due to T-cell deficiency while systemic infection is due to neutropenia
    • esophagiti 
      • dysphagia and throat pain
      • endoscopy shows white plaques along the esophagus
    • endocarditis
      • associated with IV drug users
      • fevers and a new murmur
    • disseminated/invasive candidiasis
      • fever and septic shock
• Studies
  • definitive diagnosis requires blood or other tissue culture
  • wet mount with potassium hydroxide prep of vaginal fluid shows yeast with pseudohyphae
  • germ tube formation at 37°C 
• Treatment
  • nystatin
    • local infections
  • azoles
    • local and systemic infections
    • first-line if the fungus is not resistant
  • echinocandins
    • systemic infections
    • first-line due to increased resistance to azoles
  • amphotericin B
    • systemic infections
• second-line or for pregnant women

Cryptococcus neoformans

• Classification
  • urease-positive monomorphic encapsulated yeast with 5-10 μm narrow budding
  • transmitted via inhalation and found in soil and pigeon droppings
• Risk factors
  • immunocompromised status
  • HIV/AIDS patients
• Clinical syndrome
  • pulmonary cryptococcosis
    • most common site of infection 
  • cryptococcal meningitis
  • cryptococcal encephalitis
  • presents with fevers, headaches, and generalized malaise
• Studies and imaging
  • head imaging with computed tomography (CT) or magnetic resonance imaging (MRI)
    • soap bubble lesions 
    • variable enhancing lesions
    • hydrocephalus
  • detection of capsular antigen in serum or cerebrospinal fluid (CSF)
    • latex agglutination test 
  • CSF studies
    • culture on Sabouraud agar
    • India ink stain shows yeast with clear halos  
    • mucicarmine shows yeast with red inner capsules 
• Treatment
  • amphotericin B + flucytosine
    • for 10-14 days
  • fluconazole
    • after treatment with amphotericin B and flucytosine
• maintenance and suppressive therapy

Aspergillus spp.

• Classification 
  • most commonly Aspergillus fumigatus
  • monomorphic fungus with septate hyphae branching at acute angles (45 degrees)
  • found in soil and decomposed material
  • transmission via inhalation of spores called conidia 
• Risk factors
  • immunocompromised status
  • hematologic malignancy
  • asthma
  • pre-existing lung disease
• Clinical syndrome
  • invasive aspergillosis
    • invasive infection of the lung
    • causes persistent fever and cough with hemoptysis
  • aspergilloma 
    • mycetoma (“fungal ball”) in pre-existing cavity (i.e., tuberculosis)
    • causes cough with hemoptysis or asymptomatic
  • allergic bronchopulmonary aspergillosis (ABPA)
    • hypersensitivity reaction in patients with cystic fibrosis or asthma
    • causes bronchiectasis and eosinophilia
    • causes cough with hemoptysis, brownish black mucus plugs in expectorate, and wheezing
• Studies and imaging
  • invasive aspergillosis
    • nodules with halo sign and cavitary lesions on computed tomography (CT)
    • pathologic examination showing invasive hyphae into tissue 
    • positive cultures or serology
  • aspergilloma
    • mobile round or ovoid mass on chest CT 
    • positive cultures or serology
  • ABPA
    • bronchiectasis on CT  
    • elevated eosinophils or IgE in ABPA
• Treatment
  • invasive aspergilloma
    • voriconazole + amphotericin B
      • first-line
    • caspofungin
      • second-line
  • aspergilloma
    • surgical resection
  • ABPA
    • steroids
• first-line

Mucormycosis

• Classification
  • Mucor and Rhizopus spp. 
    • fungi with irregular, broad, and nonseptate hyphae branching at wide or right angles 
    • found in soil and decomposed material 
    • transmission via inhalation of spores or direct inoculation through trauma
• Risk factors
  • diabetic ketoacidosis
  • immunocompromised status
  • trauma or burns
• Clinical syndrome
  • mucormycosis (rhinocerebral infection) 
    • headache
    • congestion
    • sinus pressure and pain 
    • black necrotic eschar on face, particular nares or palate
• Studies and imaging
  • computed tomography (CT) shows air-fluid levels in the sinuses and bony destruction 
  • biopsy of affected tissue shows nonseptate hyphae with wide-angle branching 
• Treatment 
  • amphotericin B
    • first-line
  • isavuconazole
    • second-line
  • surgical debridement
• for patients who need it, in addition to antifungals
   

Pneumocystis jiroveci

• Classification
  • a yeast-like fungus
  • transmission via airborne
• Risk factors
  • immunocompromised status (e.g., hyper IgM syndrome)
  • HIV
  • smoking
• Clinical syndrome
  • interstitial pneumonia 
    • progressive exertional dyspnea
    • chest pain
    • nonproductive cough
    • fever and chills
    • hemoptysis is rare
• Imaging
  • chest radiograph will show bilateral infiltrates 
  • computed tomography will show patchy ground-glass opacities sand pneumatoceles
• Studies
  • histology with methenamine silver, Diff-Quik, or Wright stain of lung tissue 
    • disc-shaped yeast
• Treatment 
  • trimethoprim-sulfamethoxazole (TMP-SMX)
    • prophylaxis (CD4+ count < 200 cells/mm³) and first-line therapy
  • corticosteroids
    • severe cases
  • pentamidine, atovaquone, or dapsone
  • second-line therapy if resistant to TMP-SMX or allergic