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USMLE Step 1 > Microbiology - Mycology & Parasites > Flashcards

Microbiology - Mycology & Parasites Flashcards

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USMLE® Step 1 flashcards
1
Q

Systemic mycoses

A
  • can cause pneumonia and can desseminate
  • dimorphic fungi
  • cold (20 C) = mold; heat (37C) = yeast
  • Only exception is coccidioidmycosis, which is spherule (not yeast)
  • can mimic TB (granuloma formation) except there is no person to person contact
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2
Q

Treatment for systemic mycoses

A

Fluconazole or Itraconazole for LOCAL infecton

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3
Q

Systemic mycoses (Name them) - Hint 4

A

Histoplasmosis
Blastomycosis
Coccidiomycosis
Paracoccidiomyocosis

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4
Q

Histoplasmosis

A
  • found in MIssissippi and Ohio River Valleys
  • Causes pneumonia
    Macrophage filled with Histoplasma (smaller than RBC)
  • Found in bird or bat droppings
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5
Q

Blastomycosis

A
  • found in states east of MS River or Central America
  • Causes inflammatory lung disease and can disseminate to skin and bone
  • Forms granulomatous nodules
  • Broad-base budding (same size as RBC)
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6
Q

Coccidiomycosis

A
  • found in Southwestern US, California
  • Causes pneumonia and meningitis
  • Can desseminate to bone and skin
  • Case rate increases after earthquakes (spores in dust are thrown up in aire and becomes spherules in lungs)
  • Spherules flled with endospores (much larger than RBC)
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7
Q

Paracoccidiomycosis

A

Latin America

Budding yeat with “captain’s wheel” formation (much larger than RBC)

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8
Q

Tinea versicolor

A
  • caused by Malassezia furfur
  • degradation of lipids that causes acids that damages melanocytes and cause hypopigmented and/or hyperpigmented patches
  • Occurs in hot, humid weather
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9
Q

Treatment for tinea versicolor

A

Topical miconazole, selenium sulfide (Selsun

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10
Q

“Spaghetti and meatball” appearance on KOH prep

A

Tinea versicolor

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11
Q

Other tinae

A 
Tinea pedis (foot)
Tinea cruris (groin)
Tinea corporis (ringworm on body)
Tinea capitis (head, scalp)
Tinea unguium (Onychomycosis, on fingernails)
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12
Q

Appearance of tinea

A

Pruritic lesions with central clearning resembling ring, caused by dermatophytes (Microsporum, Trichophyton, Epidermophyton)

  • See mold hyphae on KOH
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13
Q

Candida albicans

A
  • opportunistic fungal infections
  • systemic or superficial infection
  • oral or esophageal thrush in immunocompromised pts (AIDS, diabetes, steroids, neonates)
  • vulvovaginitis (diabetic patents)
  • endocarditis in IV drug users
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14
Q

Treatment of Candida albicans

A
  • Topical azole for vulvovaginitis
  • fluconazole or caspofungin for oral/esophageal thrush
  • Fluconazole, amphotericine B or caspofungin for systemic disease
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15
Q

Aspergillus fumigatus

A

Invasive aspergillosis, especially in immunocompromised and those with chronic granulomatous disease

  • Aspergillomas found in lung cavities, especially after TB infection
  • Acute Angles in Aspergillus
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16
Q

Aspergillus fumiagtus infection with asthma or CF

A

Allergic bronchopulmonary aspergilosis (APBA)

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17
Q

Discuss Aspergillus and Hepatocellular carcinoma

A
  • some Aspergillus species produce ANAFLATOXINS associated with HCC
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18
Q

Cryptococcus neoformans

A

Opportunistic fungal infection
Cryptococcal meningitis, Cryptococcosis
Heavily encapsulated yeast. Not dimorphic.
- Acquired through inhalation with hematogenous dissemination to meninges
- “Soap bubble” lesions in brain

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19
Q

Diagnosis for Cryptoccocus neoformans

A
  • “Soap bubble” lesions in (HIV patienty?)
  • Culture on Sabouraud’s agar
  • Stains with India ink
  • Latex agglutination test detects polysaccharide capsular antigen (is more specific)
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20
Q

Mucor and Rhizopus spp.

A

Mucormycosis

  • Disease mostly in ketoacidotic diabetic and leukemic patients
  • Fungi proliferate when there is excess ketone and glucose, penetrate cribiform plate, and enter brain
  • Rhinocerebral, frontal lobe abcesse
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21
Q

Sx: Occurs in ketoacidotic diabetic and leukemic patients

Headache, facial pain, black necrotic eschar on face, may have cranial nerve involvement

A

Mucor and Rhizopus spp.

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22
Q

Pneumocystis jirovecci

A

Causes PCP, a diffuse interstitial pneumonia

  • Inhaled. Most infections are assymptomatic
  • Immunosuppression (e.g. AIDS) predisposes to disease.
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23
Q

Diagnosis of Pneuocystis jirovecci

A
  • Diagnosed by lung biopsy or lavage
  • Disc shaped yeat forms on methenamine silver stain of lung tissue
  • Diffuse, bilateral CXR
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24
Q

Tx of pneumocystis jirovecci

A

TMP-SMX, pentamidine, dapsone

- Start prophylaxis when CD4 drops < 200 cells/mm

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25
Q

Sporothrix schenckii

A

Sporotrichosis
Dimorphic, cigar shaped budding yeast that lies on vegetation
- “Rose Gardner’s disease” - when spores are traumatically introduced by skin (e.g. thorn)
- Causes local pustule or ulcer with nodules along draining lymphatics (ascending lymphaginitis)
- Little systemic illness

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26
Q

Treatment of sprothrix schenckii

A

Itracanazole or Potasium iodid

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27
Q

Opportunistic Fungal Infections

A
  • Candida albicans
  • Aspergillus fumagitus
  • Cryptococcus neoformans
  • Pneumocystis jirovecci
  • Sporothrix schenckii
  • Mucor and Rhizopus spp
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28
Q

GI infection protozoas

A

Giardia lamblia
Entamoeba histolytica
Cryptosporidium

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29
Q

Giardia lamblia

A

Giardiasis: bloating, flatulence, foul-smelling, fatty diarrhea (often seen in campers/hikers) -

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30
Q

Giardia lamblia transmission

A

Cysts in water

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31
Q

Diagnosis of Giardia lamblia

A

Trophozoites or cysts in stool

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32
Q

Treatment of Giardia Lamblia

A

Metronidazole

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33
Q

Entamoeba histolytica

A

Amebiasis: bloody diarrhea (dysentery), liver abscess (“anchovy paste” exudate

  • RUQ pain
  • Histology: flash-shaped ulcer is submucosal ulcer in colon ruptures
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34
Q

Transmission of Entamoeba histolytica

A

Cysts in water

35
Q

Treatment of Entamoeba histolytica

A

Metronidazole

Iodoquinol for assymptomatic cyst passers

36
Q

Diagnosis of Entamoeba histolytica

A

Serology and/or
Trophozoites (with RBCs in the cytoplasm)
Cysts (with multiple nuclei) in stool

37
Q

Cryptosporidium

A 
Severe diarrhea in AIDS
Mild disease (watery diarrhea in healthy individuals)
38
Q

Transmission of cryptosporidium

A

Cysts in water

39
Q

Diagnosis of Cryptosporidium

A

Cysts in acid-fast stain

40
Q

Treatment of Cryptosporidium

A

Prevention ( by filtering city water supplies)

Nitazoxamide in immunocompotent host

41
Q

Protoza-CNS infections

A 
Toxoplasma gondaii
Naegleria fowleri
Trypanosomas brucei
T. gambiense
T. rhodesiense
42
Q

Toxoplasma gondii

A

Brain abscess in HIV (seen in ring-ENHANCING lesions on CT/MRI)

43
Q

Triad of Congenital Toxoplasmosis

A

Chorioretinitis
Hydrocephalys
Intracranial calcifications

44
Q

Transmission of toxoplasma gondii

A 
Cysts in meat or cat feces;
Crosses placenta (pregnant women should avoid cats)
45
Q

Diagnosis of Toxoplasma Gondii

A

Serology
Biopsy
“Crescent shaped trophozoite within macrophages)

46
Q

Treatment of Toxoplasma Gondii

A

Sulfadiazine + Pyremethamine

47
Q

Naegleria fowleri

A

Rapidly fatal meningoencephalitis

  • transmitted by swimming FRESHWATER lakes, enters via cribiform plate
  • diagnosed by amoebas in spinal cord

Tx: amphotericin (for the few survivors)

48
Q

Trypanosoma brucei

A

African sleeping sickness

  • enlarged lymph nodes, recurring fever (due to antigenic variation)
  • Somnolence, Coma
  • transmitted by Tsetse fly, a painful bite
  • diagnosed by blood smear
49
Q

Treatment of Trypanosoma brucei (African sleeping sickness)

A

Suramin for blood borne disease
Melarsoprol for CNS penetration
Melatonin helps with sleep

50
Q

Protozoa for Hematologic infections

A

Plasmodium

Babesia

51
Q

Plasmodium
P. vivax/ovale
P. falciparum
P. malariae

A

Malaria: fever, headache, anemia, splenomegaly - seen in Africa, India

  • transmitted by Mosquito (Anopheles)
52
Q

P. vivax/ovale

A

malaria

  • 48 hour cycle (tertian; includes fever on 1st day thus fevers are 48 hours apart)
  • Dormant form (hypnozite) in liver - infects NEW RBCs
53
Q

P. faciparum

A

sever; irregular fever patters
parasitized RBCS - infects ALL RBCs
- occlude capillaries in brain (cerebral malaria), kidneys, lungs

54
Q

P. malariae

A

72 hours cycle

55
Q

Malaria Diagnosed

A

Blood smear
Trophozoite ring form
RBC schizpont with merozoites

56
Q

Treatment of malaria

A

Chlorquine - blocks Plasmodium heme polymerase

  • Mefloquine
  • Life threatening: quinidine (but test for G6PD deficiency
  • Vivax/ovale - add primaquine if hypnozoite (test for G6PD deficiency)
57
Q

Trypanosoma cruzi

A

Chagas disease:

  • dilated cardiomyopathy
  • mega colon, megaesophagus
  • predominantly in South America
  • transmitted by Reduviid bug (“kissing bug”)
  • diagnosed by blood smear
  • treated with Nirfurtimox
58
Q

Leischemasia donovani

A

Visceral leischmaniasis
(kala-azar)- hyperpigmented skin pattches
Sx: Spiking fevers, Hepatosplenomegaly
Pancytopenia
- transmitted by sandfly
- diagnosed with macrophages containing amastigotes)
- treated with Sodium stibogluconate

59
Q

Trichomonas vaginalis

A

Vaginitis: foul-smelling, GREENISH discharge; itching and burning

  • transmitted by sex (can’t exist outside of human)
  • diagnosed by trophozoites (MOTILE) on wet mount
  • treatmetn: metronidazole for patient and partner

** Not be confused with Gardnerella vaginella (bacterium)

60
Q

Enterobious vemicularis (pinworm)

A
  • nematodes (roundworm)
  • get by ingesting food contaminated with eggs
  • intestinal infection causing anal pruritis (diagnosed via Scotch tape tes)
  • treated with benzadoles or pyrantel pamoate
61
Q

Ascaris lumbricoides (giant roundworm)

A
  • nematodes (roundworm)
  • transmitted fecal-orally; eggs visible in feces in microscope
  • intestinal infection
    • treated with benzadoles or pyrantel pamoate
62
Q

Strongyloides stercolaris

A
  • nematodes (roundworm)
  • larvae in soil penetrate the skin
  • intestinal infection causing VOMITING, DIARRHEA, ANEMIA
  • treatment: ivermectin or albendazole
63
Q

Acylostoma duodenale, Nectar americanicus

Hook worms

A
  • nematodes (roundworms)
  • larvae penetrate skin
  • intestinal infection causing anemia by sucking blood from intestinal walls
  • treatment: bendazoles or pyrantel pamoate
64
Q

Dracunulus medinesis (Guinea worm)

A
  • nematodes (roundworms)
  • found in drinking water
  • causes skin inflammation and ulceration
  • treatment: slow extraction of worm
65
Q

Onchocera volvuls

A
  • nematodes (roundworm)
  • transmitted by female blackfly bite
  • causes hyperpigmented skin and river blindness
  • possible allergic reaction to microfilaria
  • treatment: ivermectin
66
Q

Loa Loa

A
  • nematodes
  • roundworm
  • transmitted by deerfly, horsefly, mangofly
  • causes swelling in skin, worm in conjunctiva
  • treatment: diethylcarmabazine
67
Q

Wuchereria bancrofti

A
  • nematodes
  • block lymphatic vessels
  • elephantiasis: takes 9 months - 1 year after bite to become symptomatic
  • treatment: diethylcarbamazine
68
Q

Toxocara canis

A
  • nematodes
  • transmitted by food containing eggs
  • causes visceral larva migrans (moving larvae)
  • treatment albendazole or mebendazole
69
Q

Nematodes routes of infection

A

Ingested (“EAT”) - Enterobius, Ascaris, Toxocara

Cutaneous (“SANd”) - Strongyloides, Ancylostoma, Necator

70
Q

Taenia solium

A
  • tapeworm
  • ingestion of larvae in undercooked pork
  • ingestion of eggs
  • can cause intestinal infection and cystercosis (infect skeletal muscle),
    neurocysticosis
  • treatment: praziquantel (and - bendazole for neurocysticercosis)
71
Q

Diphyllobothrium latum

A
  • tapework
  • tapeworm (cestodes)
  • ingesting of larvae from raw fish
  • can cause Vitamin B12 deficiency (tapeworm competes for Vitamin B12) –> anemia
  • treatment: praziquantel
72
Q

Echinococcus granulosus

A
  • tapeworm
  • cestodes (tapeworm)
  • ingestion from eggs from dog feces
  • cysts in liver, causing anaphylaxis if antigens release (surgeons inject ethanol to kill cysts)
  • treatment: - bendazoles
73
Q

Shistosoma

A
  • trematodes (flukes)
  • transmitted by snailes; cercarie penetrate human skin
  • cause liver and spleen granulomas and inflammation
  • chronic infection with S. haematobium can lead to SCC of bladder
  • treatment: praziquantel
74
Q

Clonorchis sinensis

A
  • trematodes (flukes)
  • found in undercooked fish
  • can cause biliary tract inflammation –> pigmented gallstones
  • associated with cholangiocarcinoma
  • treatment: praziquantel
75
Q

Paragonimus westermani

A
  • trematodes
  • found in undercooked crab meat
  • can cause lung inflammation and secondary bacterial infection, with hemoptysis
  • treatment: praziquantel
76
Q

Parasite : Brain cysts, seizures

A

Taenia solium (cysticercosis)

77
Q

Parasite: liver cysts

A

Echinococcus granulosus

78
Q

Parasite: Vitamin B 12 deficiency

A

D. latum

79
Q

Parasite: Biliary tract disease, cholangiosarcoma

A

Clonorchis sinesis

80
Q

Parasite: Hemoptysis

A

Paragonimus westermani

81
Q

Parasite: Portal hypertension

A

Schistosoma mansoni

82
Q

Parasite: Hematuria, bladder cancer

A

Schistosoma haematobium

83
Q

Parasite: microcytic anemia

A

Ancylostoma, Necator

84
Q

Paraisite: perianal pruritis

A

Enterobius

USMLE Step 1 (34 decks)

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