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Medical Microbiology > Chapter 47 - Intestinal Protozoa > Flashcards

Chapter 47 - Intestinal Protozoa Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Intestinal Protozoa:

  • Uni/multicellular?
  • Pro/eukaryotic?
  • How do they multiply?
A
  • Are unicellular eukaryotic organisms.

- Multiply by binary fission.

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2
Q

Amoebae (Sarcodina)

  • What do they use for movement?
  • (Non)pathogenic?
A
  • Contain pseudopodia (cytoplasmic protrusions).

- Are free living, pathogenic or nonpathogenic

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3
Q

Entamoeba histolytica

  • What diseases is this responsible for?
  • How is it transmitted?
  • Describe the movement.
A
  • Agent of amebic colitis and amebic liver abscess
  • Fecal oral route
  • Rapid and unidirectional movement
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4
Q

Entamoeba histolytica

  • Describe the chromatin arrangement.
  • Describe the karyosome.
  • Describe the cytoplasm.
A
  • Evenly arranged chromatin on nuclear membrane.
    • chromatiodal body/bar in cysts
  • Small compact karyosome
    • multiple in cysts
  • Cytoplasm finely granular
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5
Q

Entamoeba histolytica

- What does it like to eat?

A
  • Red blood cells (RBCs) in cytoplasm

- - *no longer a diagnostic feature of E. histolytica

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6
Q

Entamoeba dispar

- How many of these samples contain ingested RBCs?

A
  • 16% of E. dispar clinical samples contain ingested red blood cells
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7
Q

Entamoeba histolytica

  • What stages must be reported?
  • How big are members of each stage?
A
  • Must report cysts and/ or trophs
  • Size
    • Trophs 12-60µm (usual 15-20µm)
    • Cysts 10-20µm
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8
Q

Entamoeba histolytica

  • What ailments is it responsible for?
  • What does it do to the cells/tissues?
A
  • Amebic colitis
  • Liver involvement
  • Amebic lesions, cell lysis and tissue necrosis.
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9
Q

Entamoeba histolytica

- What is the process by which trophs cause pathogenesis?

A
  • Trophs interact through a series of steps:
    • Adhesion to the target cell
    • Phagocytosis
    • Cytopathic effects
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10
Q

Entamoeba histolytica

- Where does cyst formation occur?

A
  • Cysts formation only occurs in the intestinal tract, infective stage and mode of transmission
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11
Q

Entamoeba histolytica

- What type of immune response does it induce?

A
  • Induces both humoral and cell mediated immune responses
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12
Q

Entamoeba histolytica

- What two classes of drugs are used for treatment?

A
  • Luminal amebicides

- Tissue amebicides

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13
Q

Entamoeba histolytica

- What are four different methods for detection?

A
  • Antigen detection
  • Histology
  • Nucleic acid–based tests
    • Real-time PCR
    • Multiplex assays
  • Serologic detection
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14
Q

Entamoeba dispar

  • what parasite is this morphologically identical to?
  • (non)pathogenic?
A
  • E. histolytica and E. dispar are morphologically identical species.
  • E. histolytica/E. dispar cysts are spherical and usually measure 12 to 15 μm (range may be 10 to 20 μm).
  • nonpathogenic
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15
Q

What are four main features that distinguish E. dispar from Entamoeba coli?
- E. coli (non)pathogenic?

A
  • Entamoeba coli
    • Cysts ingested, produce trophs in intestinal tract to excreted infective cysts.
    • Trophs larger.
    • Chromatoidal bars-splintered
    • Mature cyst 8 nuclei
    • nonpathogenic
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16
Q

Endolimax nana

  • (non)pathogenic?
  • Cyst shape?
A
  • nonpathogenic

- cyst is spherical/ovoid in shape

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17
Q

Endolimax nana mature cyst

  • size?
  • how many nuclei?
  • describe the cyst wall.
  • Chromatoidal bodies?
A
  • Diameter: 5-15um
  • 4 nuclei when mature
  • refractile cyst wall
  • c. bodies not usually found
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18
Q

Endolimax nana

  • size?
  • describe the cytoplasm.
  • how many nuclei?
    • describe the nuclei.
  • chromatin?
  • describe the pseudopodia.
  • motility?
A
  • 6-15um
  • cytoplasm is granular and vacuolated
  • nucleus (1) has a large, irregularly shaped karyosome that may appear “blot-like”
  • no peripheral chromatin on the nuclear membrane
  • pseudopodia are blunt and hyaline
  • sluggish, non-progressive motility
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19
Q 
Iodamoeba butschilii
- pathogenic?
Trophs:
- size?
- motility?
- describe size and location of karyosome.
- describe the cytoplasm.
- what is the distinguishing characteristic of the nucleus?
Cysts:
- size and shape?
- how many nuclei?
A 
- nonpathogenic
Trophs:
- 8-20µm
- fairly active motility
- Large karyosome, central or eccentric
- Vacuolated cytoplasm
-- Large glycogen vacuole
- Nucleus may appear to have a halo
Cysts:
- round to oval
- 5-20µm
- Single nucleus
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20
Q

Blastocystis hominis

- what are the four major forms?

A
  • Cyst (thick- and thin-walled)
  • Central vacuole (central body)
  • Amoeboid (rare)
  • Granular (in culture)
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21
Q

Blastocystis hominis

- What are the symptoms?

A
  • Causes diarrhea, cramps, nausea, fever, and vomiting
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22
Q

Blastocystis hominis

- what are the three most common ways to make a diagnosis?

A
  • Routine stool examination. Quantitate
  • Antigen detection using enzyme-linked immunosorbent assays (ELISAs)
  • Antibody detection using ELISA and fluorescent antibody tests
23
Q

Flagellates

  • where in the body can they be found?
  • What are the four most common and what are their distinguishing characteristics?
  • which of those four are considered pathogenic?
A
  • Genera may live in the gastrointestinal tract, bloodstream, or tissues.
  • Common species (with characteristics) include:
    • Giardia lamblia (sucking disk and axonomes)
    • Dientamoeba fragilis
    • Chilomastix mesnili (cytostome and spiral groove)
    • Pentatrichomonas hominis (undulating membrane)
  • G. lamblia and D. fragilis are considered pathogenic
24
Q

Giardia lamblia (duodenenalis)

  • mode of transmission?
  • symptoms?
A
  • Is acquired from contaminated food or drink.

- Giardiasis causes diarrhea with no blood, mucus, or exudate.

25
Q 
Giardia lamblia (duodenenalis)
Trophs:
- shape?
- how do they reproduce?
- what do they use to attach to their host?
A
  • tear-drop shaped.
  • Divide by longitudinal binary fission producing 2 daughter trophozites
  • Attach to intestinal epithelium by ventral disk
26
Q

Giardia lamblia (duodenenalis)
Cysts:
- where in the body to these form?
- what structures to these have that the trophs do not?

A
  • Cysts form as it moves through the jejunum
  • median bodies
  • axonomes
27
Q

Giardia lamblia (duodenenalis)

  • how common is it?
  • what are the subgenotypes and how do they differ?
A
  • Most common cause of intestinal infection worldwide
  • Subgenotypes A-B
    • Subgenotype B is only isolated from humans
    • Subgenotype A is in both animal and humans
28
Q

Giardia lamblia (duodenenalis)

  • what kind of diseases does it cause?
  • what is its antigenic variation?
A 
Spectrum of disease
- Asymptomatic infection
- Intestinal disease
- Chronic disease
Antigenic variation
- Variant-specific surface proteins (VSPs)
29
Q 
Giardia lamblia (duodenenalis)
- what are the four most common ways to make a diagnosis?
A
  • Because of attachment may take 5-6 stool specimens
  • Antigen detection by:
    • ELISA
    • Fluorescent methods with monoclonal antibodies
    • Immunochromatographic strips
  • Histologically
  • Nucleic acid–based tests
    • Multiplex assays
    • xTAG Gastrointestinal Panel
30
Q 
Giardia lamblia (duodenenalis)
- what is the treatment?
A
  • Self-limiting
  • Metronidazole
  • nitrazoxanide
  • tinidazole
31
Q

Dientamoeba fragilis

  • How many nuclei in the troph?
  • Describe the appearance of the chromatin?
  • Vacuoles?
  • What is the outstanding feature that sets this apart from other parasites?
A
  • One to two nuclei in trophozoite
  • nuclear chromatin is fragmented into 3-5 granules.
  • Vacuolated cytoplasm
  • NO KNOWN CYST STAGE
32
Q

Dientamoeba fragilis

  • Collection methods?
  • Viability/stability?
A

Collection

  • 3 samples
  • 24 to 48 hours of viability of trophs
  • Have been recovered in formed stool.
33
Q

Dientamoeba fragilis

- Symptoms?

A
  • Diarrhea
  • Abdominal pain
  • Nausea
  • Poor weight gain
  • Eosinophilia
34
Q 
Flagellates:
Chilomastix mesnili
- pathogenic?
- shape of troph?
- # of nuclei?
- define cytostome.
A
  • Nonpathogenic
  • Pear shaped trophozoite
  • Single nucleus
  • Distinct oral groove(cytostome)
35
Q

Flagellates:
Chilomastix mesnili
- cyst shape?
what is a feature/demarcation unique to the cyst?

A
  • Cysts pear or lemon shaped

- typical cytostomal fibril (shepherd’s crook)

36
Q

Ciliates

  • What are the types of nuclei seen in this class?
  • What is the one pathogen seen in this class?
A 
Two types of nuclei
- Macronucleus
- Micronucleus- one or more
Only one pathogen
- Balantidium coli
37
Q

Balantidium coli

  • what animal, aside from humans, is this associated with?
  • where does it invade in humans? what does it do?
A
  • pig

- Organism can invade tissues and form ulcers

38
Q

Balantidium coli

  • Morphologic characteristics (troph)
    • nuclei
    • cytosome
  • Morphologic characteristics (cyst)
    • nuclei
A 
Troph
- Two nuclei 
-- Macronucleus
-- Micronucleus
- A cytosome on the anterior pointed end
Cyst
- two nuclei
39
Q

Balantidium coli

  • cytoplasm?
  • diagnosis?
  • treatment?
A
  • Cytoplasm with many vacuoles
  • Best by direct smear
  • Tetracycline
40
Q

Sporozoa (Apicomplexa)

  • multi/unicellular?
  • where in the body does it invade?
  • 3 classes?
A
  • Unicellular with apical complex
  • In the gastrointestinal tract of vertebrates throughout life
    Classes
  • Cyclospora
  • Cryptosporidium
  • Cystoisospora belli
41
Q

Cryptosporidium spp. (parvum)

  • method of transmission?
  • where does it infect?
A
  • Are acquired from contaminated water or infected persons.

- Infect epithelial cells of gastrointestinal tract

42
Q

Cryptosporidium spp. (parvum)

- life cycle?

A
  • Ingestion of oocysts
  • Trophozoite development
  • Merogony (asexual amplification)
  • Gametogony (sexual differentiation)
  • Formation of new oocytes (sporogony)
43
Q

Life Cycle of Cryptosporidium

  • how many sporozoites?
  • where do they invade?
  • what is the next stage of development?
  • cycles of mergonoy?
  • next stage of development?
  • how many meroizoites?
  • next stage of development?
  • final stage of development?
A
  • Oocysts releases 4 sporozoites
  • Invade epithelial cells
  • Develop into Trophs
  • 2-3 cycles asexual amplification (Mergonoy)
  • Different meronts
  • Contain 4-8 merozoites
  • Merozoites develop by gametogony
  • New sporozoites by sporogony
44
Q

Cryptosporidium spp

  • Extracelular stage?
  • Typical age of patient?
A
  • The only extracellular stage is the oocyst.

- Infection of children <5yo.

45
Q

Cryptosporidium spp

  • diagnosis?
  • treatment?
A 
Diagnosis
- Special (modified acid-fast) stains 
- Antigen detection (e.g., direct fluorescent antigen)
- Polymerase chain reaction (PCR)
- Histologic examination 
Treatment
- Nitazoxanide is drug of choice
46
Q

Cyclospora cayetanensis

  • mode of transmission?
  • typical hosts?
A
  • Transmission is fecal, oral, or linked to fresh produce.

- Involves only humans as hosts

47
Q

Cyclospora cayetanensis

- pathogenesis?

A
  • Exhibits an influenza-like illness with nausea, vomiting, and explosive diarrhea.
  • Can be associated with biliary disease.
48
Q

Cyclospora cayetanensis

- prevention?

A
  • Wear gloves while gardening in endemic areas.
  • Wash produce.
  • Reportable to Public Health Dept and CDC
49
Q

Cyclospora cayetanensis

- diagnosis?

A
  • difficult to see on wet mounts
  • Special (acid-fast) stains—Oocysts appearing
    pink to red
    – Don’t stain well with trichrome
  • Ultraviolet (UV) epifluorescence
  • Flow cytometry
50
Q

Isospora (Cystoisospora) belli

  • common name of disease?
  • mode of transmission?
A
  • Is implicated in traveler’s diarrhea

- passed in stool

51
Q

Isospora (Cystoisospora) belli

  • shape of oocysts?
  • size of oocysts?
A
  • Oocysts are long and oval

- 20-33µm long

52
Q

Isospora (Cystoisospora) belli

  • life cycle
    • # of sporonts
    • # of sporocysts
    • # of sporozoites
A
  • One immature sporont internally, may develop into two sporocysts, each with 4 sporozoites.
53
Q

Isospora (Cystoisospora) belli

- Diagnosis?

A
  • Examination of fresh material
    • By wet mount.
  • Auramine-rhodamine stain may be helpful
  • Histologic examination
  • No PCR

Medical Microbiology (6 decks)

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