Quizlet - Protozoa Fungi and Parasites Flashcards
Mycoplasma pneumoniae Causes…? Epidemiology of dz?
Classic cause of atypical walking pneumonia (insidious onset, HA, nonproductive cough, diffuse interstitial infiltrate) Mycoplasmal pneumonia is more common in pts < 30 years of age. Frequent outbreaks in military recruits and prisons.
Mycoplasma pneumoniae Info on bacterium?
No cell wall. Not seen on gram stain. Only bacterial membrane containing cholesterol. Grown on Eaton’s agar.
Mycoplasmal pneumonia Dx and labs? Tx?
X-ray looks worse than pt (walking pneumonia w/ diffuse interstitial infiltrate) High titer cold agglutinins (IgM) Tx: TCN or erythromycin (bugs are naturally PCN-resistant b/c they have no cell wall)
Fungal spores
Most fungal spores are asexual. Both coccidioidomycosis and histoplasmosis are transmitted by inhalation of asexual spores. Conidia = asexual fungal spores (e.g., blastoconidia, athroconidia)
Histoplasmosis
Dimorphic fungi that can cause systemic mycosis, endemic to Mississippi and Ohio river valleys. Causes pneumonia. In bird or bat droppings. Intracellular (tiny yeast inside macrophages [below]):
Blastomycosis
Dimorphic fungi that can cause systemic mycosis, endemic to states east of Mississippi River and Central America Causes inflammatory lung dz and can disseminate to skin and bone. Forms granulomatous nodules. Big, Broad-Based Budding: Culture on Sabouraud’s agar.
Coccidioidomycosis
Dimorphic fungi that can cause systemic mycosis, endemic to Southwestern USA, California. Causes pneumonia and meninngitis; can disseminate to bone and skin. Found in San Juaquin Vally or desert (desert bumps) vally fever
Paracoccidioidomycosis
Dimorphic fungi that can cause systemic mycosis, endemic to rural Latin America Captain’s wheel appearance (budding yeast below):
Dimorphic fungi
(Histoplasmosis, Blastomycosis, Coccidioidomycosis, and Paracoccidioidomycosis) Mold in soil (@ lower temps) and yeast in tissue (@higher/body temp: 37C), except coccidioidomycosis, which is a spherule in tissue. Cold = Mold, Heat = Yeast All can cause pneumonia and can disseminate. Tx: fluconazole or ketoconazole for local infxn, amphotericin B for systemic infxn. Systemic mycoses can mimic TB (granuloma formation)
Geography of systemic mycoses/dimorphic fungi
Tinea versicolor
Caused by Malassezia furfur. Occurs in hot, humid weather. Tx: topical miconazole, selenium sulfide (Selsun). Spaghetti and meatballs appearance on KOH prep.
Tinea pedis, cruris, corporis, capitis
Pruritic lesions w/ central celaring resembling a ring, caused by dermatophytes (Microsporum, Trichophyton, and Epidermophyton). See mold hyphae on KOH prep, not dimorphic. Pets are a reservoir for Microsporum and can be treated w/ topical azoles.
Candida albicans ( alba = white)
Systemic or superficial fungal infxn. Yeast w/ pseudohyphae in culture at 20C; germ tube formation at 37C (diagnostic).
Candida albicans Causes what?
Causes: Oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS) Vulvovaginitis (high pH, diabetes, use of ABX) Diaper rash Endocarditis in IV drug users Disseminated candidiasis (to any organ) Chronic mucocutaneous candidiasis
Candida albicans Tx?
Nystatin for superficial infxn Amphotericin B for serious systemic infxn
Aspergillus fumigatus Causes what?
Causes: Allergic bronchopulmonary aspergillosis Lung cavity aspergilloma (fungus ball) Invasive aspergillosis, especially in immunocompromised indvls and those w/ chronic granulomatous dz
Aspergillus fumigatus
Mold w/ septate hyphae that branch at a V-shaped (45 degree) angle Not dimorphic.
Cryptococcus neoformans Causes what?
Causes: Crytococcal meningitis Cytococcosis
Cryptococcus neoformans
Heavily encapsulated yeast . Not dimorphic. Found in soil, pigeon droppings.
Cryptococcus neoformans Culture? Identification?
Culture w/ Sabouraud’s agar. Stains w/ India ink. Latex agglutination test detects pollysaccharide capsular Ag. Soap bubble lesions in brain.
Mucor and Rhizopus species
Cause mucormycosis. Mold w/ irregular nonseptate hyphae branching at wide angles (> 90 degrees).
Mucormycosis epidemiology/pathogenesis
(caused by Muro and Rhizopus spp.) Dz most likely in ketoacidotic diabetic and leukemic pts. Fungi also proliferate in the walls of blood vessels and cause infarction and necrosis of distal tissue. Rhinocerebral, frontal lobe abscesses.
Pneumocystis jiroveci (formerly carinii) Causes what? Mode of transmission? In whom?
Causes diffuse interstitial pneumonia. Most infxns asymptomatic. Inhaled. Immunosuppression predisposes to dz.
Pneumocystis jiroveci (formerly carinii) (organism)
Yeast (originally classified as protozoan). Identified by methenamine silver stain of lung tissue.
Pneumocystis jiroveci (formerly carinii) Dx?
Diffuse, bilateral CXR appearance. Dx by lung biopsy or lavage: identified by methenamine silver stain of lung tissue.
Pneumocystis jiroveci (formerly carinii) Tx?
TMP-SMX, pentamidine, dapsone. Start prophylaxis when CD4 drops < 200 cells/mL in HIV pts.
Sporothrix schenkii Causes what?
Sporotrichosis. When traumatically introduced into the skin, typically by a thorn (rose gardener’s dz), causes local pustule or ulcer w/ nodules along draining lymphatics (ascending lymphangitis). Little systemic illness.
Sporothrix schenkii Organism?
Dimorphic fungus that lives on vegetation. Cigar-shaped budding yeast visible in pus.
Sporothrix schenkii Tx?
Itraconazole or potassium iodide
Protozoa: Giardia lamblia Dz? Transmission? Dx? Tx?
Giardiasis: bloating, flatulence, foul-smelling diarrhea (often seen in campers/hikers) Transmitted via cysts in water Dx: trophozoites or cysts in stool Tx: Metronidazole
Protozoa: Trachomonas vaginalis Dz? Transmission? Dx? Tx?
Causes vaginitis: foul-smelling, greenish discharge; itching and burning Transmission: sexual Dx: Trophozoites (motile) on wet mount Tx: Metronidazole
Protozoa: Trypanosoma cruzi Dz? Transmission? Dx? Tx?
Causes Chagas’ dz (dilated cardiomyopathy, megacolon, megaesophagus); predominantly in South America Transmitted by Reduviid bug (kissing bug) Dx by blood smear Tx w/ Nifurtimox
Protozoa: Trypanosoma: T. gambiense T. rhodesiense Dz? Transmission? Dx? Tx?
Cause African sleeping sickness: enlarged LNs, recurring fever (due to antigenic variation), somnolence, coma Transmitted by Tsetse fly Dx via blood smear Tx w/ SUR amin for blood-borne dz, or MELA rsoprol for CNS penetration (it SUR e is nice to sleep; MELA tonin helps w/ sleep)
Protozoa: Leishmania donovani Dz? Transmission? Dx? Tx?
Causes visceral leishmaniasis (kala-azar): spiking fevers, hepatosplenomegaly, pancytopenia Transmitted by sandfly Dx via macrophages containing amastigotes Tx w/ sodium stibogluconate
Protozoa: Plasmodium: P. vivax P. ovale P. malariae P. falciparum Dz? Transmission? Dx? Tx?
Cause malaria: cyclic fever, HA, anemia, splenomegaly. Severe (cerebral) malaria w/ P. falciparum. P. vivax and P. ovale have dormant forms in liver (hypnozoites) –> relapsing malaria Transmitted by mosquito (Anopheles) Dx via blood smear Tx w/ Chloroquine (primaquine to prevent relapse caused by P. vivax, P. ovale), sulfadoxine + pyrimethamine, mefloquine, quinine
Protozoa: Babesia Dz? Transmission? Dx? Tx?
Cause babesiosis: fever and hemolytic anemia; predominantly in northeastern USA. Transmitted by Ixodes tick. Dx: blood smear, no RBC pigment, appears as a Maltese cross Tx: Quinine, clindamycin
Protozoa: Crytosporidium Dz? Transmission? Dx? Tx?
Causes severe diarrhea in AIDS Mild dz (watery diarrhea) in non-immunocompromised Transmitted by cysts in water Dx: cysts on acid-fast stain Tx: None :-(