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Candida albicans
  • Diseases
    • in normal hosts
      • oral thrush 
      • candida intertrigo (skin folds)
      • vaginitis
      • diaper rash
      • perleche (angular cheilitis)
        • cracks at the corner of the mouth
        • seen in malnutrition
    • in immunocompromised (especially AIDS or neutropenic)
      • esophagitis
        • thrush spreads down GI tract
      • endocarditis
        • in IV drug users
      • septicemia
        • due to indwelling catheters (e.g. subclavian catheter)
      • disseminated candidiasis
      • chronic mucocutaneous candidiasis
      • local infection is due to T-cell deficiency while systemic infection is due to neutropenia 
  • Candida can be a normal inhabitant of mucocutaneous surfaces and does not necessarily signal the presence of disease 
  • Pathogenesis
    • normal flora → opportunistic infection
  • Laboratory
    • yeast with pseudohyphae and budding at 20°C
    • germ tube formation at 37°C (diagnostic) 
      • true hyphae sprout from yeast and are seen on light microscopy
  • Treatment
    • nystatin for superficial infection
    • amphotericin B for systemic infection
Cryptococcus neoformans
  • Diseases
    • meningitis
      • in AIDS (most common meningitis)
      • in Hodgkins disease (most common meningitis)
      • "soap bubble" lesions in brain 
      • can also cause encephalitis
    • pneumonia
      • seen in pigeon breeders
    • skin and bone infections
  • Pathogenesis
    • transmitted via PIGEON DROPPINGS
    • yeast spreads hematogenously to brain
    • 75% of cases in immunocompromised
  • Laboratory
    • polysaccharide capsule
      • wide capsular halo can be seen
      • the only pathogenic fungus with a polysaccharide capsule
    • unequal budding with narrow base
    • monomorphic
    • culture on Sabouraud's agar
      • urease positive yeast
    • stains with India ink 
    • mucicarmine stains red
    • methenamine silver (GMS) is also used
    • latex agglutination test 
      • detect polysaccharide capsular antigen in CSF
  • Treatment
    • amphotericin B + flucytosine 10 weeks
    • followed by fluconazole
Aspergillus
  • Diseases, pathogenesis, and treatment
    • inhalation of ubiquitous Apergillus spores causes 3 diseases
    • allergic bronchopulmonary aspergillosis 
      • asthma-like allergic reaction in airways
        • proximal bronchiectasis
      • type I and type IV hypersensitivity reactions
      • mucus plugs form but do not penetrate tissue
      • treatment
        • systemic corticosteroids and oral itraconazole
    • aspergilloma 
      • seen in TB patients (or other granulomatous disease)
      • "fungus ball" forms in pre-existing lung cavities
      • treatment
        • surgery
    • invasive aspergillosis
      • invasive infection of the lung
      • usually in immunocompromised
      • pleuritic pain, hemoptysis
      • infiltrate seen on radiograph and CT
      • treat with strongest antifungals including
        • voriconazole, amphotericin B, or caspofungin
  • Toxins
    • Aspergillus produces aflatoxin
      • causes liver damage and liver cancer
        • aflatoxin B1 causes G:C -> T:A mutation in codon 249 of p53 
        • increased risk of hepatocellular carcinoma
  • Laboratory
    • monomorphic
    • septate hyphae branch at acute angles 
      • "ASpergillus is Acute and Septate"
    • fruiting bodies are rare
    • a recycler (found in compost piles)
    • catalase-positive
Mucor, Rhizopus
  • Diseases
    • rhinocerebral infection (mucormycosis) 
      • frontal lobe abscesses
      • paranasal swelling
      • hemorrhage from nose and eyes
    • fungi also penetrate blood vessel walls
      • results in infarction and necrosis
  • Pathogenesis
    • spores found in soil
    • fungus penetrates through sinuses into brain
    • seen in acidotic patients
      • diabetic ketoacidosis
      • leukemia
  • Laboratory
    • irregular non-septate hyphae branch at wide angles
    • filamentous
  • Treatment
    • amphotericin B (must act quickly)
    • surgical debridement
Pneumocystis jiroveci
  • Formerly called P. carinii
  • Diseases
    • "PCP" ("P. carinii" pneumonia)
      • diffuse interstitial pneumonia
        • fever
        • cough and shortness of breath
      • patchy infiltrate with "ground glass" appearance bilaterally on chest radiograph
      • seen in immunosuppressed
        • especially AIDS
          • especially CD4 < 200
        • malnourished or premature babies
  • Pathogenesis
    • inhaled
    • kills type I pneumocytes
    • type II pneumocytes overreplicate and damage alveolar epithelium
    • fluid leaks into alveoli producing an exudate
      • seen as honeycomb appearance on H&E
  • Laboratory
    • a yeast (originally classified as protozoan)
    • obligate extracellular parasite
    • diagnose with
      • lung biopsy or lavage
      • methenamine silver stained cysts seen in tissues
  • Treatment 
    • TMP-SMX
    • if sulfa allergy
      • atovaquone
      • pentamidine
      • dapsone
  • Prophylaxis
    • treated prophylactically in HIV patients with CD4 < 200
 

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