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USMLE1 - Microbiology > 3. Fungi and Parasites > Flashcards

3. Fungi and Parasites Flashcards

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1
Q

Fungal spores

A

Most fungal spores are asexual. Both coccidioidomycosis and histoplasmosis are transmitted by inhalation of asexual spores. Conidia = asexual fungal spores (e.g., blastoconidia, athroconidia)

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2
Q

Histoplasmosis. Location, Presentation, Findings

A

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]):

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3
Q

Blastomycosis. Location, presentation, findings

A

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.

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4
Q

Coccidioidomycosis

A

Dimorphic fungi that can cause systemic mycosis, endemic to Southwestern USA, California. case rate increase after earthquakes (spores in dust thrown up in air and become spherules in lungs). Causes pneumonia and meninngitis; can disseminate to bone and skin. Found in San Juoquin Vally or desert (desert bumps) vally fever; spherule filled with endospores (much larger than RBC)

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5
Q

Paracoccidioidomycosis

A

Budding yeast with “captain’s wheel” formation much larger than RBC. Latin America.

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6
Q

What are the Dimorphic fungi. Treatment for local and systemic infections.

A

(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)

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7
Q

Tinea versicolor. Agent, Etiology/Presentation, Treatment, Finding

A

Caused by Malassezia furfur. Degradation of lipids produce acids taht damage melanocytes and cause hypopigmented and hyperpigemented patches. Occurs in hot, humid weather. Tx: topical miconazole, selenium sulfide (Selsun). Spaghetti and meatballs appearance on KOH prep.

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8
Q

Tinea pedis, cruris, corporis, capitis

A

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.

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9
Q

Candida albicans ( alba = white)

A

Systemic or superficial fungal infxn. Yeast w/ pseudohyphae in culture at 20C; germ tube formation at 37C (diagnostic).

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10
Q

Candida albicans Causes what?

A

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

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11
Q

Candida albicans Tx?

A

Nystatin for superficial infxn Amphotericin B for serious systemic infxn

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12
Q

Aspergillus fumigatus Causes what?

A

Causes: Allergic bronchopulmonary aspergillosis Lung cavity aspergilloma (fungus ball) Invasive aspergillosis, especially in immunocompromised indvls and those w/ chronic granulomatous dz

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13
Q

Aspergillus fumigatus

A

Mold w/ septate hyphae that branch at a V-shaped (45 degree) angle Not dimorphic.

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14
Q

Cryptococcus neoformans Causes what?

A

Causes: Crytococcal meningitis Cytococcosis

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15
Q

Cryptococcus neoformans

A

Heavily encapsulated yeast . Not dimorphic. Found in soil, pigeon droppings.

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16
Q

Cryptococcus neoformans Culture? Identification?

A

Culture w/ Sabouraud’s agar. Stains w/ India ink. Latex agglutination test detects pollysaccharide capsular Ag. Soap bubble lesions in brain.

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17
Q

Mucor and Rhizopus species

A

Cause mucormycosis. Mold w/ irregular nonseptate hyphae branching at wide angles (> 90 degrees).

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18
Q

Mucormycosis epidemiology/pathogenesis

A

(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.

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19
Q

Pneumocystis jiroveci (formerly carinii) Causes what? Mode of transmission? In whom?

A

Causes diffuse interstitial pneumonia. Most infxns asymptomatic. Inhaled. Immunosuppression predisposes to dz.

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20
Q

Pneumocystis jiroveci (formerly carinii) (organism)

A

Yeast (originally classified as protozoan). Identified by methenamine silver stain of lung tissue.

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21
Q

Pneumocystis jiroveci (formerly carinii) Dx?

A

Diffuse, bilateral CXR appearance. Dx by lung biopsy or lavage: identified by methenamine silver stain of lung tissue.

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22
Q

Pneumocystis jiroveci (formerly carinii) Tx?

A

TMP-SMX, pentamidine, dapsone. Start prophylaxis when CD4 drops < 200 cells/mL in HIV pts.

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23
Q

Sporothrix schenkii Causes what?

A

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.

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24
Q

Sporothrix schenkii Organism?

A

Dimorphic fungus that lives on vegetation. Cigar-shaped budding yeast visible in pus.

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25
Q

Sporothrix schenkii Tx?

A

Itraconazole or potassium iodide

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26
Q

Protozoa: Giardia lamblia Dz? Transmission? Dx? Tx?

A

Giardiasis: bloating, flatulence, foul-smelling diarrhea (often seen in campers/hikers) Transmitted via cysts in water Dx: trophozoites or cysts in stool Tx: Metronidazole

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27
Q

Protozoa: Trachomonas vaginalis Dz? Transmission? Dx? Tx?

A

Causes vaginitis: foul-smelling, greenish discharge; itching and burning Transmission: sexual Dx: Trophozoites (motile) on wet mount Tx: Metronidazole

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28
Q

Protozoa: Trypanosoma cruzi Dz? Transmission? Dx? Tx?

A

Causes Chagas’ dz (dilated cardiomyopathy, megacolon, megaesophagus); predominantly in South America Transmitted by Reduviid bug (kissing bug) Dx by blood smear Tx w/ Nifurtimox

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29
Q

Protozoa: Trypanosoma: T. gambiense T. rhodesiense Dz? Transmission? Dx? Tx?

A

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)

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30
Q

Protozoa: Leishmania donovani Dz? Transmission? Dx? Tx?

A

Causes visceral leishmaniasis (kala-azar): spiking fevers, hepatosplenomegaly, pancytopenia Transmitted by sandfly Dx via macrophages containing amastigotes Tx w/ sodium stibogluconate

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31
Q

Protozoa: Plasmodium: P. vivax P. ovale P. malariae P. falciparum Dz? Transmission? Dx? Tx?

A

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

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32
Q

Protozoa: Babesia Dz? Transmission? Dx? Tx?

A

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

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33
Q

Protozoa: Crytosporidium Dz? Transmission? Dx? Tx?

A

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 :-(

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34
Q

Protozoa: Toxoplasma gondii Dz? Transmission? Dx? Tx?

A

Causes brain abscess in HIV, birth defects (ring-enhancing brain lesions) Transmitted by cysts in meat or cat feces; crosses placenta (pregnant women should avoid cats!) Dx: serology, biopsy Tx: Sulfadiazine + primethamine

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35
Q

Protozoa: Entamoeba histolytica Dz? Transmission? Dx? Tx?

A

Causes amebiasis: bloody diarrhea, (dysentery), liver abscess, RUQ pain Transmission: cysts in water Dx: Serology and/or trophozoites or cysts in stool; RBCs in cytoplasm of entaoema Tx: Metronidazole and iodoquinol

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36
Q

Protozoa: Naegleria fowleri Dz? Transmission? Dx? Tx?

A

Causes rapidly fatal meningoencephalitis Transmission: swimming in freshwater lakes (enter via cribiform plate) Dx: amoebas in spinal fluid Tx: none :-(

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37
Q

Nematodes (roundworms): Enterobius vermicularis (pinworm) Transmission/dz? Tx?

A

Transmission via food contaminated w/ eggs; intestinal infection; causes anal pruritis (the Scotch tape test) Tx: Mebendazole/pyrantel pamoate

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38
Q

Transmission via food contaminated w/ eggs; intestinal infection; causes anal pruritis (the Scotch tape test) Tx: Mebendazole/pyrantel pamoate

A

Enterobius vermicularis (pinworm)

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39
Q

Nematodes (roundworms): Ascaris lumbricoides (giant round worm) Transmission/dz? Tx?

A

Eggs are visible in feces; intestinal infxn. Tx: Mebendazole/pyrantel pamoate.

40
Q

Eggs are visible in feces; intestinal infxn. Tx: Mebendazole/pyrantel pamoate.

A

Ascaris lumbricoides (giant round worm)

41
Q

Nematodes (roundworms): Trichinella spiralis Transmission/dz? Tx?

A

In undercooked meat, usually pork; Inflammation of muscle (larvae encyst in muscle); periorbital edema. Tx: Thiabendazole.

42
Q

In undercooked meat, usually pork; Inflammation of muscle (larvae encyst in muscle); periorbital edema. Tx: Thiabendazole.

A

Trichinella spiralis

43
Q

Helminths

A

Multicellular organisms. Life cycle involves stages in other organisms.

44
Q

Nematodes (roundworms): Strongyloides stercoralis Transmission/dz? Tx?

A

Larvae in soil penetrate the skin; intestinal infxn; causes vomiting, diarrhea, and anemia. Tx: Ivermectin/thiabendazole.

45
Q

Larvae in soil penetrate the skin; intestinal infxn; causes vomiting, diarrhea, and anemia. Tx: Ivermectin/thiabendazole.

A

Strongyloides stercoralis

46
Q

Nematodes (roundworms): Ancylostoma duodenale, Necator americanus (hookworms) Transmission/dz? Tx?

A

Larvae penetrate skin of feet; intestinal infxn can cause anemia (sucks blood from intestinal walls) Tx: Mebendazole/pyrantel pamoate (worms are BEND y; treat w/ meBEND azole)

47
Q

Larvae penetrate skin of feet; intestinal infxn can cause anemia (sucks blood from intestinal walls) Tx: Mebendazole/pyrantel pamoate (worms are BEND y; treat w/ meBEND azole)

A

Ancylostoma duodenale, Necator americanus (hookworms)

48
Q

Nematodes (roundworms): Dracunculus medinensis Transmission/dz? Tx?

A

In dirnking water; skin inflammation and ulceration Tx: Niridazole

49
Q

In dirnking water; skin inflammation and ulceration Tx: Niridazole

A

Dracunculus medinensis

50
Q

Nematodes (roundworms): Onchocerca volvulus Transmission/dz? Tx?

A

Transmitted by female blackflies; causes river blindness, w/ skin nodules and lizard skin. Can have allergic reaction to microfilaria. Tx: Ivermectin (IVER mectin for rIVER blindness

51
Q

Transmitted by female blackflies; causes river blindness, w/ skin nodules and lizard skin. Can have allergic reaction to microfilaria. Tx: Ivermectin (IVER mectin for rIVER blindness

A

Onchocerca volvulus

52
Q

Nematodes (roundworms): Loa loa Transmission/dz? Tx?

A

Transmitted by deer fly, horse fly, and mango fly; causes swelling in skin (can see worm crawling in conjunctiva) Tx: Diethylcarbamazine

53
Q

Transmitted by deer fly, horse fly, and mango fly; causes swelling in skin (can see worm crawling in conjunctiva) Tx: Diethylcarbamazine

A

Loa loa

54
Q

Nematodes (roundworms): Wucheria bancrofti Transmission/dz? Tx?

A

Female mosquito; Causes blockage of lymphatic vessels (elephantiasis) Takes 9 mos to 1 yr after bite to get elephantiasis syndrome Tx: Diethylcarbamazine

55
Q

Female mosquito; Causes blockage of lymphatic vessels (elephantiasis) Takes 9 mos to 1 yr after bite to get elephantiasis syndrome Tx: Diethylcarbamazine

A

Wucheria bancrofti

56
Q

Nematodes (roundworms): Toxocara canis Transmission/dz? Tx?

A

Food contaminated w/ eggs; Causes granulomas (if in retina –> blindness!) and visceral larva migrans Tx: diethylcarbamazine

57
Q

Food contaminated w/ eggs; Causes granulomas (if in retina –> blindness!) and visceral larva migrans Tx: diethylcarbamazine

A

Toxocara canis

58
Q

Cestodes (tapeworms): Taenia solium Transmission/dz? Tx?

A

Ingestion of larvae envysted in undercooked pork leads to intestinal tapeworms. Ingestion of eggs causes cysticercosis and neurocysticercosis, mass lesions in brain (swiss cheese appearance) Tx: Praziquantel for intestinal worms and cysticercosis; albendazole for neurocysticercosis

59
Q

Ingestion of larvae envysted in undercooked pork leads to intestinal tapeworms. Ingestion of eggs causes cysticercosis and neurocysticercosis, mass lesions in brain (swiss cheese appearance) Tx: Praziquantel for intestinal worms and cysticercosis; albendazole for neurocysticercosis

A

Taenia solium

60
Q

Cestodes (tapeworms): Diphyllobothyrium latum Transmission/dz? Tx?

A

Ingestion of larvae in raw freshwater fish. Causes vitamin B12 deficiency, resulting in anemia. Tx: Praziquantel.

61
Q

Ingestion of larvae in raw freshwater fish. Causes vitamin B12 deficiency, resulting in anemia. Tx: Praziquantel.

A

Diphyllobothyrium latum

62
Q

Cestodes (tapeworms): Echinococcus granuloosus Transmission/dz? Tx?

A

Eggs in dog feces when ingested can cause cysts in liver; Causes anaphylaxis if organism’s Ags are released from cyst. Tx: Albendazole

63
Q

Eggs in dog feces when ingested can cause cysts in liver; Causes anaphylaxis if organism’s Ags are released from cyst. Tx: Albendazole

A

Echinococcus granuloosus

64
Q

Trematodes (flukes): Schistosoma Transmission/dz? Tx?

A

Snails are host; Cercariae penetrate skin of humans, causes granulomas, fibrosis, and inflammation of the spleen and liver. Chronic infxn w/ S. haematobium can lead to squamous cell carcinoma of the bladder. Tx: Praziquantel.

65
Q

Snails are host; Cercariae penetrate skin of humans, causes granulomas, fibrosis, and inflammation of the spleen and liver. Chronic infxn w/ S. haematobium can lead to squamous cell carcinoma of the bladder. Tx: Praziquantel.

A

Schistosoma

66
Q

Trematodes (flukes): Clonorchis sinensis Transmission/dz? Tx?

A

Undercooked fish; Causes inflammation of the biliary tract –> pigmented gallstones. Also associated w/ cholangiocarcinoma. Tx: Praziquantel.

67
Q

Undercooked fish; Causes inflammation of the biliary tract –> pigmented gallstones. Also associated w/ cholangiocarcinoma. Tx: Praziquantel.

A

Clonorchis sinensis

68
Q

Trematodes (flukes): Paragonimus wetermani Transmission/dz? Tx?

A

Undercooked crab meat; causes inflammation and secondary bacterial infxn of the lung. Tx: Praziquantel.

69
Q

Undercooked crab meat; causes inflammation and secondary bacterial infxn of the lung. Tx: Praziquantel.

A

Paragonimus wetermani

70
Q

Nematode routes of infxn –> Ingestion

A

E nterobius A scaris T richinella (You’ll get sick if you EAT these!)

71
Q

Nematode routes of infxn –> Cutaneous

A

S tongyloides A ncyclostoma N ecator (These get into your feet from SAN d)

72
Q

Brain cysts, seizures

A

Taneia solium (cysticercosis)

73
Q

Parasite hints - Finding: Taneia solium (cysticercosis)

A

Parasite hints - organism: Brain cysts, seizures

74
Q

Liver cysts

A

Echinococcus granulosus

75
Q

Parasite hints - Finding: Echinococcus granulosus

A

Parasite hints - organism: Liver cysts

76
Q

B12 deficiency

A

Diphyllobothrium latum

77
Q

Parasite hints - Finding: Diphyllobothrium latum

A

Parasite hints - organism: B12 deficiency

78
Q

Biliary tract dz

A

Clonorchis sinensis

79
Q

Parasite hints - Finding: Clonorchis sinensis

A

Parasite hints - organism: Biliary tract dz

80
Q

Hemoptysis

A

Paragonimus westermani

81
Q

Parasite hints - Finding: Paragonimus westermani

A

Parasite hints - organism: Hemoptysis

82
Q

Portal HTN

A

Shistosoma mansoni

83
Q

Parasite hints - Finding: Shistosoma mansoni

A

Parasite hints - organism: Portal HTN

84
Q

Hematuria, bladder cancer

A

Schistosoma haematobium

85
Q

Parasite hints - Finding: Schistosoma haematobium

A

Parasite hints - organism: Hematuria, bladder cancer

86
Q

Microcytic anemia

A

Ancyclostoma, Necator

87
Q

Parasite hints - Finding: Ancyclostoma, Necator

A

Parasite hints - organism: Microcytic anemia

88
Q

Perianal pruritis

A

Enterobius

89
Q

Parasite hints - Finding: Enterobius

A

Parasite hints - organism: Perianal pruritis

90
Q

Tricky T’s: Typhoid fever

A

caused by bacterium Salmonella typhi.

91
Q

Tricky T’s: Typhus

A

caused by bacteria Rickettsia prowazekii (epidemic), Rickettsia typhi (endemic), and Rickettsia tsutsugamushi (scrub typhus)

92
Q

Tricky T’s: Chlamydia trachomatis

A

Bacteria, STD

93
Q

Tricky T’s: Treponema

A

Spirochete; causes syphilis (T. pallidum) or yaws (T. pertenue)

94
Q

Tricky T’s: Trichomonas vaginalis

A

Protozoan, STD.

95
Q

Tricky T’s: Typanosoma

A

Protozoan, causes Chagas’ dz (T. cruzi) or African sleeping sickness.

96
Q

Tricky T’s: Toxoplasma

A

protozoan, a TORCH infxn.

97
Q

Tricky T’s: Trichinella spiralis

A

Nematode in undercooked meat.

USMLE1 - Microbiology (7 decks)

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