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Boards - Step 1 > Sketchy Micro: Parasites and Fungi > Flashcards

Sketchy Micro: Parasites and Fungi Flashcards

1
Q

Foul smelling dio after drinking fresh water on a camping trip

A

Giardia

  • travelers or campers, found in river/fresh/poorly purified drinking water
  • foul smelling diarrhea 2/2 steatorrhea, no bloddy dio b/c giardia doesn’t invade the enterocytes
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2
Q

Giardia

(a) How to dx
(b) Tx

A

Giardia = parasite of the intestinal tract => foul smelling dio from fresh water

(a) Dx from Stool O&P showing trophozoites, or ELISA stool antigen
(b) Tx w/ metronidazole

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3
Q

Buzzword

(a) Anchovy paste
(b) Diarrhea in HIV pt

A

(a) Anchovy paste = buzzword for the consistently of material inside liver abscess of entamoeba histolytica
(b) Diarrhea in an HIV pt, esp if partially acid fast = cryptosporidium (parasite)

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4
Q

MC site of amoebic abscess

(a) Clinical presentation of intestinal amebiasis
(b) Endoscopic finding of intestinal amebiasis

A

Amoebic abscess from Entamoeba histolytica MC location = R lobe of liver (‘anchovy paste’ pus, nasty)

(a) R. lobe abscess => RUQ pain, intestinal amebiasis is invasive => bloody dio
(b) Causes ulcerations in colon and characteristic ‘flask shaped’ ulcers on endoscopy

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5
Q

Entamoeba Histolytica

(a) Dx
(b) Tx

A

Entamoeba histolytica

(a) Make dx by O&P showing RBC w/ endocytosed trophozoites
-or ELISA antigen
(b) Tx w/ Metronidazole and a luminal agent to elimiate cysts in the intestinal lumen
Luminal agents = paramycin and Iodoquinol

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6
Q

Name a liver abscess that you would treat medically instead of draining

A

Entamoeba Histolytica abscess (usually R liver lobe): tx medically w/ metronidazole and a luminal agent (paromomycin or iodoquinol) instead of draining

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7
Q

Parasite

(a) Stains partially acid fast
(b) Stool O&P shows trophozoites w/ endocytosed RBCs

A

Parasite

(a) Partially acid fast staining = cryptosporidium (causes dio in immunocompromised)
(b) RBCs inside trophozoites = Entamoeba Histolytica

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8
Q

Parasite transmitted by

(a) Cat feces
(b) Water sports, contact solution
(c) Kissing bug

A

(a) Cat feces = toxoplasmosis gondii
(b) Water sports or infected contact solution = Naegleria fowleri (rapidly fatal meningoencephalitis)
(c) Kissing bug = Trypanosoma Cruzi (Chagas)

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9
Q

Why should pregger ladies not scoop kitty litter

A

Risk of toxoplasmosis that congenitally causes: intracranial calcifications, hydrocephalus (seizures), chorioretinitis

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10
Q

How to differentiate toxoplasmosis from CNS lymphoma?

A

Toxo: multiple ring enhancing lesions

vs.

CNS lymphoma: singular lesion, associated w/ EBV

But need biopsy to truly differentiate

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11
Q

Tx for toxo

A

Sulfadiazine and Pyrimethamine (both of which inhibit folate synthesis)

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12
Q

Who gets ppx for toxo?

A

HIV pts w/ CD4 under 100 who test positive for IgG positive for toxo!

Ppx w/ TMP-SMX

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13
Q

Cause of African sleeping sickness

(a) Vector

A

African sleeping sickness (comw, lymphadnopathy, recurrent fevers) = Trypanosoma Brucei (parasite)

(a) Vector = tsetse fly

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14
Q

Clinical features of trypanoseoma brucei

A

Trypanosoma brucei (parasite) => African sleeping sickness

-coma, lymphadnopathy (infects LN), recurrent fever

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15
Q

Tx of trypanosoma brucei w/

Melarsoprol vs. Suramin

A

Trypanosoma brucei = parasite causing African sleeping sickness

Melarsoprol for CNS infection (how it causes coma)

Suramin for the peripheral blood infection)

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16
Q

How to Naegleria fowleri enter the CNS

(a) Clinical presentation

A

Naegleria fowleri = parasite from freshwater lakes that enters the CNS thru the cribiform plate

(a) Presents w/ rapidly fatal meningoencephalitis
Meningitis => nuchal rigidity and fever
Encephalitis => altered mental status

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17
Q

Primary ameobic encephalitis

(a) Bug
(b) How to dx
(c) Tx

A

Primary ameobic encephalitis

(a) Naegleria fowleri
(b) Dx by visualization of ameoba in CSF
- pt will present w/ meningoencephalitis so you’ll do spinal tap
(c) Tx = amphotericin

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18
Q

What causes Chagas disease

(a) Endemic area
(b) Transmission

A

Chagas disease 2/2 Trypanosoma cruzi

(a) Endemic to S. America
(b) Transmitted by kissing bug (Reduviid bug) that deposits its feces on skin, then pt itches it and introduces feces under skin

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19
Q

Clinical features of T. Cruzi disease

A

T. Cruzi (Chagas) think everything dilated

  1. Megacolon- constipation, risk of intestinal perf
  2. Dilated cardiomyopathy- often what they die from
  3. Mega-esophagus
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20
Q

Clinical features of Babesiosis

A

Babesiosis = parasitic infection by babesia

Mostly blood related: hemolytic anemia => jaundice, also irregularly cycling fever

Dx Maltese cross of peripheral thick blood smear

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21
Q

Tx for babesiosis

A

Babesiosis (hemolytic anemia, irregular fever) tx = atorvaquone and macrolide (specifically azithromycin)

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22
Q

Endemic area for

(a) T. cruzi
(b) Babesia

A

Endemic area for

(a) T. cruzi (chagasd siease) = S. America
(b) Babesia = NE US

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23
Q

How to clinically distinguish the species of plasmodium

A

Plasmodium species present w/ different fever cycles

P. malariae: q72 hrs (day 1, day 4)
P. vivax and ovale: tertian fever cycle day 1 and 3 (q48h)
P. falciparum: irregular fever pattern

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24
Q

Malaria species w/ the most severe clinical course

(a) Fever pattern
(b) How does it cause cerebral/renal/pulm issues?

A

P. falciparum has most severe clinical course

(a) Irregular fever pattern
(b) Can present w/ CNS features/pulm/kidney as parasitized RBCs occlude vessels leading to vital organs

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25
Q

2 indications for atovaquone

A
  1. Tx of babesiosis (in combo w/ Azithromycin)

2. Used in combo w/ Proquanil for malaria ppx in travelers

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26
Q

First line tx for malaria

a) Change in tx for resistant (most African species

A

Malaria tx = chloroqine (blacks plasmodium heme polymerase) and primaquine (destroy hypnozoites in liver)

(a) But lots of African species are resistant to chloroquine => use mefloquine

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27
Q

Sickle cell risk for

(a) Babesia
(b) Plasmodium falciparum

A

SCD

(a) Increase risk of severe disease 2/2 babesia => severe anemia
(b) Protective against malaria

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28
Q

Differentiate Leishmaniasis Donovi and Baziliensis

A

Leishmaniasis donovi => visceral leishmaniasis = black fever

vs. cutaneous Leishmaniasis from Baziliensis

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29
Q

Tx for

(a) Cutaneous (Baziliensis) Leishmaniasis
(b) Visceral Leishmaniasis

A

Tx for

(a) Cutaneous leishmaniasis = stibugluconate
(b) Visceral leishmaniasis needs amphotericin

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30
Q

Cause of strawberry cervix

A

Strawberry cervix = trichomoniasis vaginalis (parasite)

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31
Q

Clinical features of trichomoniasis vaginalis

A

Trich => vaginitis w/ green/yellow malodorous discharge

  • vaginal burning/itching (vaginitis)
  • strawberry cervicitis
32
Q

Differentiate the wet mount findings of

(a) Trichomoniasis
(b) Gardnerella
(c) Candida

A

Wet mount

(a) Trichomonas (parasite) = motile trophozoites
(b) Gardnerella (gram variable bacteria) = clue cells
(c) Candida (fungi) = pseudohyphae w/ budding yeast

33
Q

Vaginitis at

(a) pH over 4.5
(b) pH under 4.5

A

Vaginitis

(a) pH above 4.5: vaginitis by trich and Gardnerella
(b) While only candida vaginitis seen at pH under 4.5

34
Q

Tx for trichomoniasis vaginalis

A

Metronidazole for both partners!

Males will be asymptomatic but just will pass it back to their female partner…

35
Q

Main drug for tx w/ helminths

A

Helminths generall tx w/ Albendazole

36
Q

What is the scotch tape test used to diagnose?

A

Scotch tape test used to diagnose pinworm (intestinal nematode)- Enterobius Vermicularis

Scotch tape over anus in the morning, then visualize eggs under the microscope

37
Q

Helmnith dx by larvae (not eggs) in stool

A

Strongyloides stercoralis

Eggs laid in the intestines, only larvae found in stool

38
Q

Buzzword for parasites

(a) Swiss cheese appearance on MRI
(b) Hydatid cysts w/ egg-shell calcifications

A

Parasites

(a) Swiss cheese appearance on MRI = neurocysticercosis from infection of Taenia eggs (not cysts or larvae, just eggs)
(b) Cestode: Echinococcus granulosus causes hydatid liver cysts w/ egg shell caclifications

39
Q

Drug of choice for all trematodes

A

Treat all tresmatodes (schisto) w/ Praziquantel

40
Q

37 yo from E. Europe p/w ride-sided abdominal discomfort and large liver mass w/ cystic lesions, precaution while undergoing surgery

A

MC cause of hydatid cyst = Echinococcus granulosus
-associated w/ eggshell calcifications histologically

Manipulation of cyst can release contents causing anphylactic shock

41
Q

What does it mean to be dimorphic?

A

Dimorphic = form of fungi depends on the temp

-all systemic fungi are dimorphic, most are “yeast in the heat, mold in the cold” but exceptions

Exception:

  • candida is yeast in cold while mold in heat
  • coccidioidomycosis is mold in cold but spherule containing endospores in heat
42
Q

Which disseminated fungal infxn can mimic Tb in chronic form?

A

In chronic form histoplasma can cause calcified nodules and granulomas which mimic Tb

43
Q

If not clinically silent, describe presentation of Histoplasma capsulatum infxn in immunocompetent individual

A

Histo in immunocompetent = usually subclinical, can cause pneumonia and erythema nodosum

Erythema nodosum = painful red nodules on shins

44
Q

Tx of histo vs blasto

A

Both histo, blasto, and while were at it coccidio (3 systemic fungal infxns) tx:

  • azoles for local/mild disease
  • amphotericin B for disseminated/serious/systemic disease
45
Q

Differentiate clinically systemic infxn in immuncompromised pt infected w/ Histo vs. Blasto

A

Clinical presentation: both have lung involvement, then more when disseminates

Histo: hepatosplenomegaly (b/c histo infects macrophages and there’s a shitton of macrophages in the liver and spleen): get calcifications of liver and spleen

Blasto: skin and bones, can even be osteomyelitis

46
Q

2 fungi associated w/ erythema nodosum

A

Erythema nodosum = red painful nodules on shins, only seen in immuncompetent b/c indicates very robust immune response

Associated w/ both

  • histoplasmosis
  • coccidiodomycosis (even more so than histo!)
47
Q

Differentiate infxn of blastomycosis in immunocompetent vs. immunocompromised

A

Blasto (S and E US, Great Lakes and Ohio River Valley)

Immunocompetent: patchy alveolar infiltrate, ‘hazziness’ w/ possibly cavitary lesions on CXR, stays in lungs

Immunocompromised: spreads to skin and bone
-osteomyelitis

48
Q

Differentiate the systemic mycoses by size

A

Smallest (hundreds fit in one macrophage that’s just slightly bigger than an RBC) = Histoplasma

Then blasto is about the size of an RBC

Then coccidio is just about the same or a bit bigger than blasto

Then paracoccidioidomycosis is the largest! huge!

49
Q

Mycosis buzzwords

(a) Dust storm/earth quake
(b) Captain’s wheel

A

(a) Dust storm/earth quake in California or SW US = coccidioidomycosis from inhaled dust spores
(b) Captain’s wheel = yeast form of paracoccidioidomycosis = multiple buds radiating out from a central capsule (S. America => mucocutaneous lesions w/ lymphadenopathy)

50
Q

2 fungi that go against “yeast in the heat, mold in the cold”

A

Coccidioidomycosis: mold in the cold, thick-walled spherule containing endospores in heat (in the body)

Candida: mold in heat, yeast in cold

51
Q

Differentiate coccidiodomycosis in immunocompetent vs. immunocompromised

A

Coccidioidomycosis

Immunocompetent: subclinical or fever cough arthralgia, erythema nodosum

Immunocompromised: disseminate to bone and meninges => meningitis

52
Q

Location of coccidio vs. paracoccidioidomycosis

A

Coccidio in SW US and California

Paracoccidio in S. America

53
Q

MC mode of transmission of systemic mycosis

A

Air/respiratory droplets = mode of transmission for histo/blasto/coccidio/paracoccidio

Coccidio also by dust spores

54
Q

Clinical presentation of paracoccidiodomycosis

A

Mucocutaneous lesions (mucosal ulcers, esp in oral cavity) and lymphadenopathy

55
Q

Tx for malassezia furfur

A

Malassezia furfur = cutaneous mycosis (fungi) that causes pityriasis versicolor = hypo and hyperpigmented skin lesions by production of melanocyte-damaging acids

Confined to the stratum corneum => treat w/ Selsun blue (selenium sulfide) that promotes shedding of stratum corneum)

56
Q

What are dermatophytes?

(a) Tx

A

Dermatophytes = cutaneous fungi that cause tinea infection named by location = ringworm

tinea capitus
tinea corpus
tinea cruris (jock itch)
tinea pedis (athlete’s foot)

(a) Tx = topical azole

57
Q

How to diagnose tinea infection?

A

Dx tinea clinically or w/ KOH stain of stain scraping

58
Q

What is onychomycosis?

(a) Tx

A

Onychomycosis = dermatophytosis (cutaneous fungal infection)

(a) Tx requires oral therapy (not topical): Terbinafine

59
Q

Griseofulvin indications

A

Griseofulvin for Tx refractory or serious dermatophyte (tinea = ringworm) infections that don’t resolve w/ topical azoles

Tinea capitus, tinea corpus, tinea cruris (jock itch), tinea pedis (athlete’s foot)

60
Q

Mycoses buzzword

(a) Cigar shaped yeast
(b) Diaper rash
(c) Heavily encapsulated

A

(a) Cigar shaped yeast = sporothrix schenckii causing ascending lymphadenitis from rose thorn prick
(b) Diaper rash = candida
(c) Heavily encapsulated = cryptococcus neoformans

61
Q

Ascending lymphadenitis caused by what fungi?

A

Sporothrix schenckii- cutaneous fungal infection that spreads as red bumps along the lymphatics

Rose Gardener’s disease b/c get it from the thorn of a rosebush

62
Q

At what CD4 count to worry about susceptibility to

(a) Candida esophagitis
(b) PCP

A

(a) Worry about candida w/ CD4 under 100

(b) Start bactrim ppx for PCP pneumonia at CD4 under 200

63
Q

2 causes of left-sided infective endocarditis in IVDU

A
  1. S. aureus

2. Candida

64
Q

Candida tx

(a) Diaper rash
(b) Candida esophagitis
(c) Oral thrush
(d) Resistant strains

A

Candida

(a) Topical azoles for diaper rash
(b) Amphotericin B for candida esophagitis or other disseminated infection
(c) Nystatin swish and rinse for oral thrush
(d) Resistant strains get caspofungin

65
Q

CGD deficiency increases risk for what 2 fungal infections

A

2 fungi that are catalase positive:

  1. Candida
  2. Aspergillus
66
Q

Differentiate aspergilloma and angioinvasive aspergillosis

A

Aspergillus fumigas can cause

Aspergillomas = fungus balls in the lungs, increased risk when cavities already present (Tb, Klebsiella)

Angioinvasive aspergillosis = invades BVs and quickly spreads through body to kidneys, heart (endocarditis), CNS => ring-enhancing lesions

67
Q

Necrosis of paranasal sinuses: how to differentiate the two mycoses that can cause this

A

2 fungi that can cause necrosis of paranasal sinuses:

  1. Aspergillus fumigas that has septated hyphae w/ acute angle (under 45 degrees)
  2. Mucor has r. angle (90 degree) branching and is not septated
68
Q

Tx for aspergilloma vs. angioinvasive aspergillosis

A

Asperilloma- surgical debridement w/

69
Q

MC cause of fungal meningitis

A

MC fungal meningitis = cryptococcus neoformans

Also can cause meningitis = coccidiomycosis (Cali and SW US)

70
Q

India ink

A

India ink stain of CSF to visualize cryptococcus neoformans (meningitis in immunocompromised)

71
Q

Mycoses buzzwords

(a) Soap bubble CNS lesions
(b) Bread mold
(c) BAL sample stained w/ silver stain

A

(a) Soap bubble in grey matter of the brain = Cryptococcus neoformans meningitis
(b) Bread mold = rhizopus
(c) Bronchoalveolar lavage w/ silver stain- helpful for fungi, can dx PCP or crypto

72
Q

3 ways to diagnose cryptococcus neoformans

(a) BAL
(b) CSF stain
(c) Detect repeating polysacc capsular antigen

A

Diagnose crypto w/ these bc culture takes forever

(a) BAL: stain w/ mucicarmine (red) or methanamine (silver) stain
(b) CSF stain w/ India ink
(c) Latex agglutination test causes agglutination w/ the repeating polysacc capsular antigen

73
Q

Main virulence factor of cryptococcus neoformans

A

Cypto has capsule w/ repeating polysaccharide antigens that prevents phagocytosis

74
Q

Opportunistic fungal infxn that requires certain azole

A

Asperigllus specifically use Voriconazole

75
Q

DKA predisposes pt to what fungal infxn?

A

Mucormycosis b/c mucor and rhizopus (fungi that cause it) proliferate in BV walls especially if high glucose and ketones are present

76
Q

Mucormycosis- clinical presentation

(a) Tx

A

Mucormycosis- invades BVs, then penetrates cribiform plate to enter skull => rhinocerebral mucormycosis and frontal lobe abscess

(a) Need to surgically debride necrotic tissue/drain abscess, and give amphotericin

77
Q

PCP ppx in pt w/ sulfa allergy

A

CD4 under 200 want to protect against PCP, first line is bactrim

If pt has sulfa allergy, use pentamidine

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