Microbiology - Fungi and Parasites Flashcards
Anaplasma phagocytophilum
Gram -
Obligate intracellular in granulocytes (vs. monocytes for erhliciosis)
Deer tick (Ixodes)
Granulocytic ehrlichiosis
Granulocytes with morulae in cytoplasm
Ancylostoma duodenale
Necator americanus
Intestinal nematode (hookworm) parasite
Larvae penetrate skin → lungs → GI tract
Drinks blood and digests hemoglobin → microcytic anemia
More likely to infect adults; pregnancy complications
Rx: mebendazole, albendazole, pyrantel pamoate
Angiostrongylus cantonesis
Ingestion of snails, slugs Rat lungworm disease –> peripheral and CSF eosinophilia
Anisakis simplex
Ingestion of raw or undercooked seafood Inhabits stomach Kill larvae by freezing
Ascaris lumbricoides
Intestinal nematode (roundworm) parasite
Eggs ingested –> lungs (Loeffler’s syndrome) –> bowel
Causes intestinal, biliary, or pancreatic obstruction
Tx: mebendazole, albendazole, pyrantel pamoate
Aspergillus fumigatus
Mold fungus (not dimorphic)
Catalase +
Septate hyphae branch at acute angles (see picture)
Types:
- Invasive aspergillus in immunosuppressed, neutropenic
- Allergic bronchopulmonary aspergillosis (Type 1 hypersensitivity a/w asthma, CF; high IgE, eosinophilia, proximal bronchiectasis)
- Aspergillomas - colonization of old lung cavities (esp. after TB)
a/w hepatocellular carcinoma (via aflatoxins)
Babesia
Protozoa parasite causes babesiosis (fever, myalgias, headache, hemolytic anemia, thrombocytopenia, increased LFTs); asplenia increases risk of severe disease
Deer tick (Ixodes)
Dx: blood smear may show Maltese cross (see picture), PCR
Tx: atovaquone + azithromycin
Blastomyces dermatiditis
Dimorphic fungus that causes blasomycosis
Yeast have “double-contoured” wall, broad-based budding (see picture)
Causes pneumonia → granuloma formation, cutaneous warts, genitourinary tract infections, osteomyelitis
Endemic in states east of the Mississippi and Central America
Tx (local): itroconazole
Tx (systemic): amphotericin B
Candida albicans
Dimorphic fungus
Pseudohyphae with blastoconidia, true hyphae, germ tubes, and budding yeasts
Catalase +
Can cause candidiasis (oral, esophageal) in immunocompromised patients and candidemia in patients receiving parenteral nutrition through a central venous catheter
Can cause vaginal yeast infections in women –> thick white discharge; diagnose by pseudohyphae on wet prep and normal pH; treat with OTC azole-based ointments or oral fluconazole
Treat disseminated candida with fluconazole, amphotericin B, or caspofungin
Clonorchis sinsensis
Intestinal trematode parasite
Chinese liver fluke
Transmitted from ingestion of metacercarie in undercooked fish
Fluke lives in bile ducts and causes biliary tract inflammation → pigmented stones, and cholangiocarcinoma
Rx: prazinquantel
Coccidioides immitis
Dimorphic fungus that causes coccidioidomycosis (San Joaquin Valley Fever)
Infection by inhalation of arthroconidia → spherules filled with endospores (see picture)
Endemic in southwest U.S.
May have eosinophilia
Causes pneumonia and disseminated disease (meningitis, rash, symmetric arthralgia)
Tx (local): fluconazole, itroconazole
Tx (systemic): amphotericin B
Cryptococcus neoformans
Yeast (not dimorphic)
Budding yeast with a thick capsule → stains with india ink and mucicarmine
Found in soil, pigeon droppings
Urease +
Can cause meningitis in AIDS, pneumonia
Cryptosporidium parvum
Intestinal protozoa parasite
Transmitted from ingestion of oocysts from contaminated water (chlorine resistant)
Causes mild to severe diarrhea (esp. in immunocompromised)
Dx: acid fast stain for oocysts
Tx: filtering water supply, nitazoxanide in immunocompromised hosts
Diphyllobothrium latum
Intestinal cestode (tapeworm) parasite
Ingestion of larvae in raw freshwater fish
Causes B12 deficiency → macrocytic anemia
Tx: Praziquantel
Echinococcus granulosus
Intestinal cestode (tapeworm) parasite
Ingestion of eggs from dog feces
Causes hydatid cysts in the liver causing antiphylaxis if antigens released (surgeon preinjects with ethanol to kill cysts before removal)
Tx: albendazole
Echinococcus granulosus
Intestinal cestode (tapeworm) parasite Ingestion of eggs from dog feces Causes liver cysts with internal daughter cysts Rx: albendazole
Entamoeba histolytica
Intestinal protozoa parasite
Transmitted from ingestion of cysts from contaminated food or water
Causes dysentery, liver abscess (anchovy-paste), flask-shaped ulcers
Dx: serology, trophozoites containing RBCs, cysts (with up to 4 nuclei) in stool
Rx: metronidazole
Enterobius vermicularis
Intestinal nematode (pinworm) parasite
Fecal-oral transmission
Causes peri-anal itching
Diagnose with “scotch tape test”
Rx: mebendazole, pyrantel pamoate
Giardia lamblia
Intestinal protozoa parasite
Transmitted from ingestion of cysts from contaminated water (chlorine resistant)
Causes bloating, flatulence, steatorrhea
Dx: trophozoites or cysts in stool
Tx: metronidazole
Histoplasma capsulatum
Dimorphic fungus that causes histoplasmosis
Endemic in the Ohio and Mississippi River Valleys
Risk factors: exposure to bird or bat droppings, cave diving
Histoplasma hides in macrophages (see picture)
Causes pneumonia but can become systemic
Tx (local): fluconazole, itroconazole
Tx (systemic): amphotericin B
Leishmania
Protozoal parasite with kinetoplast, live in WBCs
Transmitted from bite of female sand fly
Cutaneous, mucosal, or visceral forms
Dx: macrophages containing amastigotes (see picture)
Tx: amphotericin B, sodium stibogluconate
Loa loa
Tissue invasive nematode
Larvae enter wound from Chrysops fly
Adults: subcutaneous nodules (swelling of the skin), worms in conjunctiva
Microfilaria: blood during DAY
Causes calabar swelling, can be in eye
Tx: diethylcarbamazine unless high microfilaria load
Malassezia furfur
Cutaneous mycoses that causes tinea versicolor
Degradation of lipids produces acids that damage melanocytes → hypo or hyperpigmented patches
Occurs in hot, humid weather
Tx: topical miconazole, selenium sulfide
Spaghetti and meatballs appearance (see picture)
Mucor and Rhizopus
Mold
Large non-septate hyphae branch at obtuse angles (see picture)
Causes mucormycosis (facial and paranasal pain and ischemia, headache) in diabetics and leukemic patients –> fungi proliferate in blood vessels when glucose and ketones are high
Can penetrate brain
Tx: surgical debridement of necrotic tissue, amphotericin B, poscanazole
Naegleria fowleri
Protozoa parasite
Transmitted by swimming in freshwater lakes → amoebas enter cribriform plate
Causes rapidly fatal meningoencephalitis
Dx: amoebas in spinal fluid
Tx: amphotericin B
Onchocerca volvulus
Larva enter wound of female black fly bite
Adults and microfilaria live in subcutaneous nodules
Causes river blindness (hyperpigmented skin, blindness) → “black flies, black skin nodules, black sight”
Tx: ivermectin + doxycycline to kill Wolbachia bacteria
Paracoccidoides brasiliensis
Dimophic fungus that causes paracoccidioidomycosis
Budding yeast with “captain’s wheel” formation
Endemic in tropical and subtropical central and south America
Causes pneumonia, chronic mucocutaneous ulcers
Pneumocystis jirovecii
Yeast that can’t be cultured
Can cause pneumocystic pnemonia (PCP) in immunosuppressed patients
Ground-glass appearance on CXR
Treatment and prophylaxis (CD4 count < 200) with TMP-SMX
Disc-shaped yeast form on methenamine silver stain
Schistosoma
Intestinal trematode parasite
Blood fluke
NOT hermaphroditic
Snails release cercariae into water that can penetrate skin
Can cause liver and spleen granulomas, fibrosis → portal HTN (S. mansoni, S. japonicum)
S. haematobium can lead to squamous cell carcinoma of the bladder (painless hematuria)
Tx: praziquantel
Sporothrix schenckii
Dimorphic, cigar-shaped budding yeast
Lives on vegetation and introduced to the skin (rose thorn)
Causes sporotrichosis (local pustule or ulcer with ascending lymphangitis)
Biopsy shows granulomas surrounded by plasma cells
Tx: itraconazole or potassium iodide
Strongyloides stercoralis
Intestinal nematode (roundworm) parasite
Larvae from soil penetrate skin → lungs → GI tract (vomiting, diarrhea, epigastric pain)
Larvae in stool, not eggs
Autoinfection possible
Hyperinfection syndrome in immunocompromised states → test before starting steroids
Rx: ivermectin, albendazole
Taenia solium
Intestinal cestode (tapeworm) parasite
Ingestion of encysted larvae in undercooked pork → intestinal disease
Ingestion of eggs from infected human stool → cystericosis, neurocysticercosis
Rx: prazinquantel, albendazole for neurocystericosis
Tinea infections
Tinea versicolor → malassezia furfur
Tinea pedis (foot), cruris (groin), corporis (body), capitis (head/scalp), unguium (fingernails) → dermatophytes Mirosporum, Trichophyton, Epidermophyton
Toxocara canis and toxocara catis
Ingestion of eggs in dog or cat feces
Visceral larva migrans
Tx: albendazole or mebendazole
Toxoplasma gondii
Obligate intracellular protozoan parasite
Trasmitted from cysts in meat or oocysts in cat feces
May cause TORCH congenital infection (hydrocephalus, scattered intracranial calcifications, chorioretinitis), brain abscess in HIV (multiple ring-enhancing lesions on imaging)
Dx: culture, serology
Tx: pyrimethamine + sulfadiazine
Trichinella spiralis
Tissue invasive nematode Ingestion of cysts in raw or undercooked meat Encysts in striated muscle
Trypanosoma brucei gambiense
Protozoal parasite with kinetoplast
Bite of Tsetse fly Found in W. Africa (rivers)
African trypanosomiasis (sleeping sickness): enlarged lymph nodes, recurring fever, somnolence, coma
More common among endemic population
Chronic presentation
Mott cells (unsecreted IgM)
Dx: blood smear (see picture)
Tx: suramin (for blood-borne disease) or melarsoprol (for CNS penetration)
Trypanosoma brucei rhodesiense
Protozoal parasite with kinetoplast
Bite of Tsetse fly Found in E. Africa (savannah)
African trypanosomiasis (sleeping sickness): enlarged lymph nodes, recurring fever, somonolence, coma
More common among travelers
Acute presentation
Mott cells (unsecreted IgM)
Dx: blood smear (see picture)
Tx: suramin (for blood-borne disease) or melarsoprol (for CNS penetration)
Trypanosoma cruzi
Protozoal parasite that enters the host from the feces of the kissing bug (Reduviid bug)
Causes Chagas disease/American trypaosomiasis
Acute: Romana’s sig (unilateral, painless, periorbital edema)
Chronic: dilated cardiomyopathy, GI disease (megacolon, megaesophagus)
Dx: blood smear
Tx: benznidazole or nifurtimox
Wuchereria bancrofti
Larvae enter skin through female mosquito bite
Adults: lymphatics
Microfilaria: lymph and blood at NIGHT
Lymphatic filariasis, elephantitis, tropical pulmonary eosinophilia
Tx: diethylcarbamazine
What CSF findings are consistent with fungal/TB meningitis?
↑ opening pressure
↑ lymphocytes
↑ protein
↓ glucose
