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Medical Microbiology > Chapter 48 - Blood and Tissue Protozoa > Flashcards

Chapter 48 - Blood and Tissue Protozoa Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Plasmodium spp.

  • what disease are they responsible for?
  • what are the 5 species?
A

Malaria

  • P. vivax (80% of infections)
  • P. falciparum
  • P. malariae
  • P. ovale
  • P. knowlesi
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2
Q

Plasmodium spp.

- what is the vector?

A
  • female anopheline mosquito
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3
Q

Life Cycle of Plasmodium

  • First 2 steps
    • how does the illness enter the host?
    • what organ is affected?
A
  • Vector bites you, releasing sporozites into the puncture wound.
  • Within an hour carried to the liver.
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4
Q

Life Cycle of Plasmodium

  • What step is the Preerythrocye?
    • describe the steps in this cycle.
A

Preerythrocye or primary exoerythrocytic cycle

  • Divide (Schizogony)
    • Schizont—Is a trophozoite with dividing nuclei
    • Mature schizont—Contains merozoites that invade RBCs.
  • Exoerythrocytic merozoites
  • Merozoite—Is the young trophozoite
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5
Q

Life Cycle of Plasmodium: Erythrocytic Cycle

  • Describe the two steps to this cycle.
  • What part of the Plasmodium life cycle does this make up?
A
  • Merozoites leave the liver and invade RBC and feed on hemoglobin
  • mosquito then takes a blood meal of infected RBCs
  • Last two steps
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6
Q

Life Cycle of Plasmodium:

  • define schizont
  • what is a mature schizont?
  • what are gametocytes?
A
  • Schizont—Is a trophozoite with dividing nuclei.
  • Mature schizont—Contains merozoites that invade RBCs.
  • Gametocytes—Includes mature male or female merozoites
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7
Q

Plasmodium vivax

  • primary disease?
  • where is the most common geographic location(s) for this disease?
A
  • Causes benign tertian malaria.

- Is widely distributed in the tropics, subtropics, and temperate zones.

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8
Q

Plasmodium vivax

- what are the main morphologic characteristics of this disease organism?

A
  • Infection of young cells
  • Enlargement of RBCs (one to two times the normal size)
  • Schüffner dots
  • Delicate ring
  • Very amoeboid trophozoites
  • Schizont containing 12 to 24 merozoites
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9
Q

Plasmodium vivax

  • can a patient relapse?
  • what are paroxysms and how often to they occur?
  • define hypnozoites.
A
  • Relapses occur.
  • Paroxysms are when the clinical signs manifest themselves in a patient.
  • Paroxysms may cycle every 48 hours.
  • Resting stages are called hypnozoites
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10
Q

Plasmodium vivax

- what triggers the paroxysms?

A
  • Occur when the schizont releases the merozoites
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11
Q

Plasmodium vivax

  • how often does the pathogen cycle through?
    • what does that correspond with?
A
  • Cycle 44-48 hrs.

- Corresponds with cycles of paroxysms

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12
Q

Plasmodium vivax

- what are the cell stages of the life cycle?

A
  • Early trophozite – ring form
  • Schuffner dots-in all except very early.
  • Trophozoite ameboid
  • Schizont with TWELVE -
    TWENTY-FOUR merozoites
  • Macro and microgametes
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13
Q

Plasmodium ovale

- geographic range?

A

Geographic range is confined to central West Africa and some South Pacific islands

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14
Q

Plasmodium ovale

- how does this change the morphology of the cells it infects/what does it look like under a microscope?

A
  • Infection of young cells
  • Enlargement of RBCs with fimbriated edges (oval)
  • Early appearance of Schüffner dots
    Smaller ring than P. vivax
  • Schizont containing EIGHT merozoites
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15
Q

Plasmodium ovale

  • relapses?
  • paroxysm cycles?
A
  • Relapses are possible but with spontaneous recovery.

- Paroxysms cycle every 48 hours

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16
Q

Plasmodium ovale

  • describe the morphology of the infected erythrocytes
    • size
    • edges
    • shape
A
  • 1.25x enlarged
  • fimbriated
  • oval
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17
Q

Plasmodium ovale

  • what do the trophs look like?
  • describe the schizonts
    • how many merozoites?
    • color of pigment?
    • pattern of schizonts?
  • what shape are the gametocytes?
A

Trophs: compact

Schizonts:

  • 6-14 merozoites
  • dark pigment
  • rosettes
  • gametocytes are round-oval
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18
Q

Plasmodium malariae

  • type of malaria caused?
  • geographic distribution?
A
  • Causes quartan malaria
  • associated with nephrotic syndrome
  • Is sporadically distributed
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19
Q

Plasmodium malariae

- infected RBC characteristics?

A
  • Infection of older cells
  • Normal-size RBCs
  • No stippling
  • Thick ring, large nucleus
  • TROPHS that form “BANDS” across the cell
  • Schizont containing 6 to 12 merozoites
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20
Q

Plasmodium malariae

  • relapses?
  • define recrudescence
  • how frequent are the paroxysm cycles?
A
  • No relapses occur, but recrudescence is recognized.
  • a new outbreak after a period of abatement or inactivity
  • every 72 hours
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21
Q

Plasmodium falciparum

  • type of malaria caused?
  • geographic distribution?
A
  • Causes malignant tertian malaria.

- Is confined to tropical areas

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22
Q

Plasmodium falciparum

- characteristics of infected cells?

A
  • Invasion of all stages of RBCs (heavy parasitemia)
  • Comma-like red dots (Maurer dots)
  • Multiple ring forms, some appliqué forms
  • Crescent-shaped gametocytes
23
Q

Plasmodium falciparum

  • how often do fever cycles occur?
  • relapses?
A
  • Fever cycles every 36 to 48 hours.

- No relapses occur.

24
Q

Plasmodium falciparum

  • where does schizogony occur?
  • what happens to the organs infected?
A
  • Schizogony occurs in spleen, liver, and bone marrow.

- Vessels of organs become plugged, causing fatal complications (e.g., black water fever).

25
Q

Plasmodium falciparum

  • describe the rings in the infected RBCs
  • trophs - how often seen in peripheral smears
A
  • rings are double chromatin dots, accole then forms, which allows for multiple infections in the same cell
  • trophs are compact and rarely seen in peripheral blood
26
Q

Plasmodium falciparum

  • Gametocytes
    • two different forms?
  • which is seen in peripheral blood?
  • how many merozoites in a schizont?
  • how often seen in peripheral blood?
A
  • Gametocytes: mature form and immature form
  • immature form rarely seen in peripheral blood
  • 8-24 merozoites in a schizont
    • rarely seen in peripheral blood
27
Q

Plasmodium knowlesi

  • geographic location?
  • what is the best way to detect?
A
  • Is associated with forested areas of Southeast Asia.

- Higher detection rate with PCR

28
Q

Plasmodium knowlesi

  • characteristics?
    • what do the early stages resemble?
    • what do the later stages resemble?
  • stippling?
  • chromatin?
  • unique characteristic of the trophs?
  • how many merozoites
A
  • Early stages resemble P. falciparum and
  • later/mature stages resemble P. malariae
  • RBC’s are all sizes, no true stippling
  • Multiple rings, with 2 to dots of chromatin
  • Band forms with trophozytes
  • Schizonts with 16 merozoites
29
Q

Plasmodium knowlesi

  • what is the gold standard for diagnosis?
  • what type of specimen is preferred?
  • how is it diagnosed in the field?
A
  • Thick and thin blood films
    • 200 and 300 oil immersion fields are examined
  • Giemsa or Wright stain is acceptable.
  • EDTA
  • Rapid malaria tests are now available (dipstick, cartridge).
30
Q

Plasmodium knowlesi

  • why is it hard to detect with automated instruments?
  • what non-smear test is used?
A
  • Automated instruments are not designed to detect intracellular parasites.
  • Polymerase chain reaction (PCR) with specific deoxyribonucleic acid (DNA) probes is used
31
Q

Plasmodium knowlesi

  • treatment
    • drugs
    • what phase is being treated?
  • why is it so hard to treat?
A
  • Schizonticides, gametocytocides, and sporonticides are directed against relapses.
  • Chloroquine-resistant P. falciparum is present in most endemic areas.
32
Q

Babesia spp.

  • mode of transmission
  • what other protozoa life cycle does it mimic?
  • what is the main difference?
A
  • Is transmitted by ticks. Genus Ixodes.
  • Has a life cycle similar to Plasmodium
  • no exoerythrocytic stage
33
Q

Babesia spp.

  • how do trophs reproduce?
  • what makes the ring forms unique?
  • what makes the chromatin unique?
A
  • Trophs reproduce by binary fission.
  • Ring forms are pleomorphic. Can be outside erythrocytes.
  • Maltese cross tetrads may be present
34
Q

Babesia spp.

  • what disease does it mimic?
  • how is it diagnosed?
A
  • Similar clinically to malaria

- Diagnosis with thick and thin blood smears

35
Q

Babesia vs. Plasmodium

  • transmission
  • hosts
  • geographic locations
A

Babesia

  • Is transmitted by ticks. Genus Ixodes.
  • Infect wild and domestic animals
  • Worldwide, US outbreaks around Cape Cod, LI, east coast Islands

Plasmodium

  • Is transmitted by Anopheles mosquito
  • Infects humans
  • Tropics and subtropics, some temperate
36
Q

Babesia vs. Plasmodium

  • life cycle stages
  • troph reproduction
  • troph size
A

Babesia

  • Has a lifecycle similar to Plasmodium spp., but no exoerythrocytic stage.
  • Trophs reproduce by binary fission.
  • Trophozoites are smaller than P. falciparum

Plasmodium

  • Has an exo and endoerythrocytic stage.
  • Troph reproduce by schizogony
37
Q

Babesia vs. Plasmodium

  • ring forms
  • ring form location
  • # of species
A

Babesia

  • Ring forms are pleomorphic.
  • Can be outside erythrocytes.
  • Maltese cross tetrads may be present
  • About 100 species

Plasmodium

  • Inside the cell.
  • Ringforms are uniform.
  • 5 species
38
Q

Babesia vs. Plasmodium

  • symptoms
  • diagnosis
A

Babesia & Plasmodium (same for both)

  • Fever, chills, malaise, anemia, hepatosplenomegaly.
  • Diagnosis with thick and thin blood smears
39
Q

Trypanosoma spp.

  • what type of protozoa are they?
  • what is the common name for the diseases it causes?
    • how many types/what names are the subgroups of the diseases?
A

Hemoflagellate protozoa

Trypanosomiasis

  • African sleeping sickness
    • East African
    • West African
  • Chagas’ disease
    • American
    • Trypanosoma cruzi
40
Q

Trypanosoma spp.

- what are the three main features in an amastigote?

A
  • nucmeus
  • basal body
  • kinetoplast
41
Q

Trypanosoma spp.

- what are the two additional features that a mature trypomastigote possesses?

A
  • an undulating membrane

- a flagellum

42
Q

African sickness - East vs West:

  • organism
  • vector
  • reservoir
A

East

  • Trypanosoma brucei rhodesiense
  • tsetse fly (morsitans)
  • animals

West

  • Trypanosoma brucei gambiense
  • tsetse fly (palpalis)
  • humans
43
Q

African sickness - East vs West:

  • illness time frame
  • lymphadenopathy
A

East

  • acute w/early CNS invasion, less than 9 months
  • minimal

West

  • chronic w/late CNS invasion, months to years
  • prominent
44
Q

African sickness - East vs West:

  • parasitemia
  • epidemiology
A

East

  • high
  • anthropozoonosis, game park

West

  • low
  • anthropozoonosis, rural populations
45
Q

African sickness - East vs West:

  • diagnostic stage
  • recommended specimens
A

East and West (same for both)

  • Trypomastigote
  • chancre aspirate, lymph node aspirate, blood, CSF
46
Q

African Trypanosomiasis

- what is a unique feature that makes this challenging to treat?

A
  • Unique feature is that they can change the antigenic surface coat of the outer membrane.
47
Q

American Trypanosomiasis (Chagas’ Disease): T. cruzi vs T. rangell

  • vector
  • reservoir
A

T. cruzi

  • reduviid bug
  • opossums, dogs, cats, wild rodents

T. rangell

  • reduviid bug
  • wild rodents
48
Q

American Trypanosomiasis (Chagas’ Disease): T. cruzi vs T. rangell

  • symptomatic?
  • recommended specimens?
A

T. cruzi

  • symptomatic, can be acute or chronic
  • blood, lymph node, aspirate, chagoma

T. rangell

  • asymptomatic
  • blood
49
Q 
American Trypanosomiasis (Chagas’ Disease): T. cruzi vs T. rangell
- diagnostic stage
A

T. cruzi

  • blood:
    • Trypomastigote
  • tissue:
    • amastigote

T. rangell

  • blood:
    • Trypomastigote
  • tissue:
    • none
50
Q

Trypanosomiasis

- what are the three stages?

A
  • Amastigotes
  • Trypomastigotes
  • Epimastigotes
51
Q

Leishmania spp.

- Disease spectrum:

A
  • Cutaneous lesions (flattened plaque or ulcer)
  • Mucocutaneous infections
  • Visceral involvement
52
Q

Leishmania spp.

Two phases:

A
  • Amastigote—Intracellular parasite in humans

- Promastigote—Form found in vector

53
Q

Leishmania spp.

- what are some common hospital and in-the-field diagnostic tests?

A
  • Exudate from the lesion is smeared and stained.

- A rapid dipstick test is also available for the detection of anti-Leishmania antibodies.

Medical Microbiology (6 decks)

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