Opportunistic Flashcards
Where is candida albicans normally found?
Skin, mouth, and GI tract. NEVER should be in blood!
What does candida albicans look like histologically?
pseudohypahe and budding yeasts at 20degrees, germ tubes at 37
What disease manifestations can candida albicans cause?
- Oral/esophageal thrush in immunocompromised (neonates, steroids, DM, AIDS)
- Vulvovaginitis (DM, abx use)
- Diaper rash, rash in skin folds of obese individuals
- Disseminated disease, endocarditis in IV drug users
What is the treatment for vaginal candidiasis?
Topical -azole
What is the treatment for oral/esophageal candidiasis?
Nystatin swish&swallow, fluconazole or caspofungin
What is the treatment for systemic candidiasis?
Fluconazole, caspofungin, or amphotericin B.
Where is aspergillus normally found?
Everywhere, frequent lab contaminant.
What does aspergillus look like histologically?
1) Branching septated hyphae - acute angles, 45 degrees.
2) Conidiophore w/ radiating chains: broom-like
What disease manifestations does aspergillus cause?
- Allergic bronchopulmonary pneumonia - IgE mediated, associated with cystic fibrosis and asthma. May cause bronchiectasis and EOSinophilia.
- Aspergilloma = fungas ball in lung cavity, esp after TB infxn
- Aspergillus flavus can produce aflatoxins, associated with hepatocellular carcinoma
- Invasive aspergillus (hematogenous spread) can cause necrotizing pneumonia and disseminate to other organs.
In what patient population is invasive aspergillus more common?
immunocompromised and those with CGD.
How is allergic bronchopulmonary aspergillosus treated?
Corticosteroids
How is aspergilloma treated?
Removal via surg
How is invasive aspergillosis treated?
treat w/ voriconazole, amphotericin B or caspo.
Where is cryptococcus neoformans found?
Pigeon droppings, soil, respiratory transmission
What does cryptococcus look like histologically?
Heavily encapsulated (polysaccharide) yeast. Not dimorphic! Culture on Sabourad agar, stain w/ India Ink and is mucicarmine.
What test of cryptococcus is most specific?
Latex agglutination test - detects polysaccaride antigen.
What are the disease manifestations of cryptococcus?
- Subacute or chronic meningitis. (hematogenous spread)
- Pneumonia
- skin lesions that look like acne
“soap bubble” lesions in brain.
How do mucor and rhizopus spp grow?
saphrophytic molds. Broad, non-septated, branching hyphae (90 degrees)
In what patient population does mucor/rhizopus cause disease?
Ketoacidotic pts or neutropenic pts.
What is mucor/rhizopus mode of entry?
Fungi proliferate in blood vessel walls, penetrate cribiform plate, enter brain
How does mucor/rhizopus present?
Rhinocerebral, frontal lobe abscess, cavernous sinus thrombosis, black necrotic eschar on face, headache/facial pain/cranial nerve involvement
Treatment/prognosis for mucor/rhizopus?
Aggressive surgical debridement, amphotericin B. Rapidly fatal.
Where is pneumocystis carinii/jirovecii located?
Acquired at early age by respiratory route.
What does pneumocystis jirovecii look like histologically?
Flying-saucer/disc-shaped appearing yeast-like fungus on methenamine silver stain
In what patient population does pneumocystis jirovecii cause disease?
AIDS patients w/ CD4 counts <200. Most common opportunistic infxn in AIDS. 15% chance of infxn/yr, 80% lifetime risk w/out ppx.
What is the presentation of pneumocystis jirovecii ?
PCP pneumonia; diffuse interstitial pneumonia with diffuse, ground-glass opacities on CXR/CT.
What is the ppx for pneumocystis jirovecci?
TMP-SMX, pentamindine
Dapsone/atovaquone (ppx only)
PPs when CD4 count<200.
Where does sporothrix schenckii live?
On vegetation
What does sporothrix schenckii look like histologically?
Dimorphic, cigar-shaped budding yeast.
How does sporothrix schenckii cause disease?
Spores introduced into skin by thorn (rose gardener’s disaese), causing local pustule/ulcer with nodules along draining lymphatics (Ascending lymphangitis).
Disseminated dx in immunocompromised host.
What is the treatment for sporothrix schenckii?
Itraconazole or potassium iodide.
