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Enlarged nuclei; HPV
Viruses that form multinucleated giant cells (synctyia)
Come in 3's: MMR, & the 3 alpha-Herpesviruses (HSV-1, HSV-2, VZV)
How to diagnose Mycoplasma pneumoniae
Grows on Eaton's agar; no cell wall, so neither positive nor negative Gram staining. Cell membrane does contain cholesterol, though = the only one. "Fried-egg" colonies when grown on cholesterol-rich medium. Walking pneumonia = CXR looks worse than pt. High level of cold agglutinins (IgM Ab's): RBC's clump together when placed on ice.
N.meningitides: sepsis, adrenal insufficiency, DIC, death.
2 bacteria with toxins that inactivate EF-2 (elongation factor -- messes up protein synthesis)
Corynebacterium diphtheriae, Pseudomonas
Only 1 gram-neg. "Nagging Pests Must Breathe": Nocardia, Pseudomonas, Mycobacterium, Bacillus
Detects Ab's against Rickettsia species, except for Q fever (Coxiella burnetti).
Only 1 gram-neg. "Can't Breathe Air": Clostridium, Bacteroides, Actinomyces.
Thrush (HIV/immunocomp, neonates, DM); diaper rash; vulvovaginitis (DM, antibiotics); endocarditis (IV drug users). Yeast w/pseudohyphae, but germ tube at 37C (remember, all the C fungi are yeast at some point).
- 1) Allergic bronchopulmonary aspergillosus. (IgE)
- 2) Fungus ball in lung cavity (mycetoma).
- 3) Invasive lung disease (immunocomp) -- often-asymptomatic pneumonia, but deadly.
- Mold w/septate hyphae.
Yeast w/pseudohyphae. Chronic meningitis & pneumonia. India ink (not very sensitive), latex agglutination.
Mucor & Rhizopus spp.
Molds; mucormycosis. Pts w/diabetic ketoacidosis & leukemia. Frontal lobe abscesses, infarcts of distal tissue.
By Malassezia furfur. Hot, humid weather; some patches don't tan. Spaghetti & meatball = both hyphae & yeast.
Pneumocystis jiroveci (carinii)
Diffuse interstitial pneumonia in AIDS (otherwise, usually asymptomatic). Yeast. Silver stain.
Dimorphic, rose gardener = local pustule w/nodules along lymphatics.
Protozoan cysts in water -- bloating, flatulence, foul-smelling diarrhea (often seen in campers) -- but not bloody (no intestinal wall invasion). Metronidazole.
Protozoans in general
Single-celled eukaryotes. Forms: cyst (protected form that's infective) & trophozoite (active, feeding form)
Usually asympt in men. Women = foul greenish discharge, itching, burning. Can be infected multiple times b/c no immunity ever acquired (non-invasive organism).
- Starts as hard, red area = chagoma. Then, fever + heart (tachycardia) + CNS (meningoencephalitis).
- If progresses to chronic infect (years later), then Chagas' disease: dilated cardiomyopathy, mega-esophagus & -colon.
- Transmission: Reduviid (kissing) bug -- has wild animal reservoirs.
Trypanosoma gambiense & rhodesiense
- Sleeping sickness -- West & East African, respectively. (East is more deadly...so if you have that version, then you're going to the E.R.) Transmitted by Tsetse fly.
- Recurrent fever (b/c of Ag variation), lymphadenopathy, somnolence, coma.
Sandfly. The protozoans (amastigote form) live inside macrophages. 1) Cutaneous form: 1 (or multiple) skin ulcers. 2) Visceral: hepatosplenomegaly, pancytopenia, spiking fevers & weight loss.
- 2nd most common malaria strain (remember FAVE). Cyclic fever, HA, hepatosplenomegaly/anemia.
- Relapse, b/c dormant form (hypnozoite) lies in liver. Chloroquine-sensitive. Use primaquine for prophylaxis (they're protected from chloroquine in liver).
Most infectious (and common?). Induces knob formation on RBC's --> sequestration in microvasculature --> infarcts.
Malaria life cycle & resistance
- Sporozoites infect & grow in liver --> trophozoites --> schizonts --> release lots of merozoites, which infect RBC's. Inside RBC's, whole life cycle repeats... merozoites released again (hemolysis). Some merozoites become gametocytes, which mosquito takes up for mating.
- Resistance develops when ppl have different Duffy antigens (which malaria uses to bind to RBC's & get in).
Babesiosis = fever, hemolytic anemia (b/c the protozoan invades RBC's). Deer tick, northeastern US.
Severe diarrhea in AIDS pts (mild in everyone else -- travel, daycare). The cysts are visible on acid-fast staining. (Other acid-fast stainers: the bacteria Mycobacterium & Nocardia, the great TB mimicker!)
Cat feces & meat contain cysts. Brain: birth defects in fetuses, abscesses in HIV pts (HA, focal neuro signs, retinitis --> blind). A baby might be fine, but then in 20's: reactivation --> retinitis --> blind.
Dysentery. More common in developing countries (cysts in water, fecal-to-oral). Bloody diarrhea (when trophozoites invade intestinal wall), liver abscess/RUQ pain... but most infections actually asymptomatic.
- Foul play: Rapidly fatal meningoencephalitis. Ingest while swimming in fresh water (via cribiform plate).
- Dirty contact lenses: keratitis --> blind
- Tapeworms (mate in GI tract) + flukes.
- Tapeworms: T.solium, D.latum, E.granuilosus
- Flukes: Schistosoma, C.sinensis, P.westsermani
Nematode (roundworm) species where you eat the eggs
Enterobius, Ascaris, Trichinella spiralis, Toxocara canis (eggs in eggs)
Worm species where larvae penetrate your skin
- Roundworms: Strongyloides, Necator americanus (hookworm)
- Flukes: Schistosoma
- If you eat tapeworm larvae, then brain cysts.
Nematode (roundworm) species transmitted by an insect vector
Onchocerca (female blackfly), Loa loa (deer, horse, & mango flies), Wuchereria bancrofti (female mosquito)
Pinworm. Ingest eggs (food, or fecal-to-oral) --> mature in gut --> eggs hatch at perianal opening
Giant roundworm. Ingest eggs --> intestinal infection. Kids can get malnutrition, gut obstruction... but many people infected w/o much disease.
Ingest eggs (raw pork) --> larvae settle in skeletal muscle, periorbital edema (rarely, brain).
Larvae (in soil) enter skin --> intestinal infection: vomiting, diarrhea, & also anemia.
Hookworm. Step on larvae --> intestinal infection can cause anemia, b/c suck blood.
Skin inflammation & ulcers; found in drinking water.
River blindness; larvae (microfilariae) transmitted by female blackfly, & worms die in cornea. Also, "lizard skin" (thick, dry, dark pigment). The microfilariae can cause allergic rxns.
Skin swelling (can see worm crawling in conjunctivae!). Deer, horse, & mango flies.
Elephantiasis when worms die in lymph vessels --> fibrosis; takes 9 months or so. Female mosquito.
Eat eggs in food. Granulomas (cause blindness if in retina) & larvae migrating in organs.
- Pork tapeworm (ingest larvae in undercooked pork) --> intestinal infection.
- If you ingest eggs instead: neurocysticercosis -- mass lesions in brain.
Fish tapeworm. B12 deficiency --> anemia.
Dog tapeworm. Eat eggs --> cysts in liver, lung, brain. If fluid is released from these cysts, then anaphylaxis.
Mature larvae (cercariae) penetrate skin --> fever (Katayama), dermatitis --> Granulomas/fibrosis of liver & spleen (obv, can cause portal HTN). Africa & Asia, snail host.
Fluke (flatworm) in undercooked fish. Pigmented gallstones, cholangiocarcinoma.
Flatworm in undercooked crab meat. Lung inflammation/ 2ndary bacterial infection.
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