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Medical Microbiology > Chapter 49 - Other Protozoa > Flashcards

Chapter 49 - Other Protozoa Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Free-Living Amebae

- what are the three most common encountered genera?

A
  • Naegleria
  • Acanthamoeba
  • Balamuthia
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2
Q

Free-Living Amebae

  • What part of the body do they target?
  • What are some examples of diseases?
A

Tend to cause infections of the central nervous system (CNS).

  • Primary amebic meningoencephalitis (PAM)
  • Granulomatous amebic encephalitis (GAE)
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3
Q

Naegleria fowleri

  • What well-known name does this go by?
  • What is its path of entry?
  • what disease is it responsible for?
A
  • The brain eating amoeba
  • Amebae enter the nasal cavity and migrate to the brain.
  • Rapidly causes fatal PAM
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4
Q

Naegleria fowleri

- the two trophozoite forms are?

A
  • Amoeboid

- Flagellate

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5
Q

Naegleria fowleri

- describe the shape and cell wall of the cysts.

A
  • Cysts are round with a thick double wall.
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6
Q

Acanthamoeba spp.

- what are the stages and where can they be observed?

A
  • No flagellate stage is known.

- Cysts and trophozoites can be observed in samples.

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7
Q

Acanthamoeba spp.

  • What are the two main infections caused by this species?
  • what is the main difference between the two?
A

Granulomatous amebic encephalitis

  • Is associated with underlying disease (no freshwater contact).
  • May take several weeks or months to establish disease.

Amebic keratitis

  • Is associated with direct exposure to contaminated material or solutions.
  • Wearing contacts is the leading risk factor.
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8
Q

Acanthamoeba spp.

- what are the 4 main ways to diagnose?

A
  • Culture with nonnutrient plates overlaid with Escherichia coli
  • Cerebrospinal fluid (CSF) examination
  • Cytospin slides preparations using bronchoalveolar lavage (BAL)
  • Tissue biopsy
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9
Q

Naegleria fowleri

vs. Acanthamoeba spp.
- how many forms?
- what are those forms?
- what diseases does each cause?
- water/not water related?

A

N. fowleri

  • 3 forms
    • Trophozoite forms are:
  • – Amoeboid
  • – Flagellate
    • Cysts are round with a thick double wall
  • Rapidly causes fatal PAM.
  • Water related

Acanthamoeba

  • 2 forms
    • No flagellate stage is known.
    • Cysts and trophozoites.
  • Granulomatous amebic encephalitis and amebic keratitis
  • Not water related
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10
Q

Balamuthia mandrillaris

  • what disease does it cause?
  • what is the prognosis for the host?
A
  • Is a rare cause of human amebic encephalitis.

- Death may occur 1 week to several months after symptoms

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11
Q

Balamuthia mandrillaris

  • what other amoeba is this similar to?
  • how is it differentiated?
A
  • Balamuthia is differentiated from Acanthamoeba on the basis of nuclear morphologic characteristics (multiple nucleoli compared with only one).
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12
Q

Balamuthia mandrillaris

- how is it cultured?

A
  • Can be cultured using monkey kidney cells and mucosal replicating cells (MRC), human epidermoid carcinoma (HEp-2), and macrophages.
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13
Q

Balamuthia mandrillaris

- what are the layers of the cyst?

A
  • appear to have 3 layers
    • Outer wrinkled ectocyst
    • Middle structure-less mesocyst
    • Inner thin edocyst
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14
Q

Trichomonas vaginalis

  • describe the shape and size
  • describe the membrane,
A
  • pear-shaped
  • 7-23um length
  • 5-15um length
  • undulating membrane that extends half the length of the body
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15
Q

Trichomonas vaginalis

  • what are the number of nuclei?
  • what is the visibility under a microscope?
A
  • 1 nuclei

- not seen in unstained mounts

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16
Q

Trichomonas vaginalis

  • describe its motility
  • how many flagella do they have and where are they located?
A
  • jerky and rapid
  • 3-5 anterior flagella, 1 posterior
  • no free posterior flagellum
17
Q

Trichomonas vaginalis

  • what samples are they seen in?
  • what is their infective stage?
A
  • seen in urine, urethral discharge, and vaginal smears

- infective stage the troph

18
Q

Trichomonas vaginalis

  • where is it usually found?
  • what are the clinical findings?
  • at what stage is it seen in clinical findings?
A
  • vagina in females, urethra and prostate in males
  • leukorrhea, pruritus vulvae (white urethral discharge in males)
  • seen in clinical settings only as a troph
19
Q

Trichomonas vaginalis

  • how is it acquired?
  • how long can it live?
A
  • Acquired primarily through sexual intercourse

- Capable of survival for extended periods

20
Q

Toxoplasma gondii

  • what is the broad range of hosts it infects?
  • what is its definitive host?
A
  • Infects most warm blooded animals

- Cats are definitive host

21
Q

Toxoplasma gondii

- what are the 6 steps to its life cycle?

A
  • Cats ingest oocysts
  • Organisms released and invade epithelial cells of small intestine.
  • Asexual cycle
  • Sexual cycle with formation of oocysts
  • Oocysts excreted (Uninfective)
  • One to five days become infective
22
Q

Toxoplasma gondii

- what are the three different stages to its life cycle?

A 
Tachyzoites
- Cresent shaped 
- One end more rounded than the other
- Geimsa is the stain of choice
Bradyzoides
- Found within tissue cysts 
- PAS positive
Oocysts
- Contain sporozoites
23
Q

Toxoplasma gondii

- diagnosis?

A
  • Serologic method (most common):
    • Identifies Toxoplasma gondii antibodies.
  • Polymerase chain reaction (PCR)
  • Examination of biopsy specimens, buffy coats, or CSF
  • Isolation in tissue culture or laboratory animals
24
Q

Toxoplasmosis

- symptoms for the immunocompetent?

A
  • No clinical symptoms are observed in most patients.

- Some will have an acute infection (e.g., lymphadenopathy).

25
Q

Toxoplasmosis

- symptoms for the immunocompromised?

A
  • CNS is primarily involved.
  • Myocarditis can develop.
  • Pneumonitis is prevalent.
26
Q

Toxoplasmosis, congenital

  • when is the fetus at the highest?
  • what are the symptoms?
A
  • Is severe if the mother acquires the organism during the first or second trimester.
  • Symptoms include retinochoroiditis, cerebral calcification, and hydrocephaly.
27
Q

Toxoplasmosis, ocular

- what type of infection develops?

A
  • Congenital or acquired chorioretinitis infection develops.

Medical Microbiology (6 decks)

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