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Free Living Amoeba Flashcards

1
Q

Where are free-living amebae usually found in the environment?

A

They are commonly found in fresh and saltwater, decaying organic matter, and damp soil.

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2
Q

What are the common habitats of free-living amebae?

A

contaminatedpools, stagnant ponds, freshwater lakes & streams,thermal springs & spas

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3
Q

How do free-living amebae behave when found in humans?

A

In humans, they act as parasites and can cause severe infections.

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4
Q

To which family does Naegleria fowleri belong?

A

It belongs to the family Vahlkampfiidae

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5
Q

To which family does Naegleria fowleri belong?

A

It belongs to the family Vahlkampfiidae

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6
Q
A

It has a third stage in its life cycle, the flagellate stage, which is uncommon among amebae.

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7
Q

What are ameboflagellates, and how do they relate to Naegleria fowleri?

A

Ameboflagellates are organisms that can exist in both ameboid and flagellated forms. Naegleria fowleri exhibits this dual-stage characteristic.

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8
Q

What disease does Naegleria fowleri cause?

A

It causes Primary Amebic Meningoencephalitis (PAM), also known as Naegleriasis.

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9
Q

What is the infective stage of Naegleria fowleri?

A

trophozoite stage

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10
Q

What makes the life cycle of Naegleria fowleri unique?

A

It has three stages:

Cyst stage (dormant form)

Trophozoite stage (active feeding form and infective stage)

Flagellate stage (a temporary form used for movement).

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11
Q

What is the significance of the flagellate stage in Naegleria fowleri?

A

The flagellate stage allows the organism to move quickly in water, facilitating its survival and transition between environments.

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12
Q

Which form of Naegleria fowleri is resistant and found in soil?

A

cyst form is resistant and found in soil.

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13
Q

Where is the amebic trophozoite stage of Naegleria fowleri typically found?

A

water.

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14
Q

What happens to the trophozoite stage under favorable conditions

A

It transforms into the flagellate stage.

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15
Q

What happens to the trophozoite stage under unfavorable conditions?

A

encysts itself, forming a cyst.

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16
Q

How many flagella does the biflagellate form of Naegleria fowleri have?

A

has two flagella.

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17
Q

In what type of environment is the biflagellate form found?

A

It is found in water.

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18
Q

What is the mode of transmission of Naegleria fowleri?

A

inhalation of trophozoites found in water.

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19
Q

Which stage of Naegleria fowleri is responsible for infection in humans?

A

trophozoite stage is the infective form.

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20
Q

How does Naegleria fowleri enter the human body?

A

enters through the nasal passages when contaminated water is inhaled.

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21
Q

What is the size range of the Naegleria fowleri trophozoite?

A

7-20 μm

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22
Q

Describe the cytoplasm of the Naegleria fowleri trophozoite.

A

It is finely granular and contains vacuoles

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23
Q

How many nuclei does the Naegleria fowleri trophozoite have?

A

single nucleus with a large central karyosome.

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24
Q

What is the characteristic feature of the Naegleria fowleri trophozoite nucleus?

A

large central karyosome and no peripheral chromatin.

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25
How does the Naegleria fowleri trophozoite move?
directional manner using large broad pseudopods.
26
What does PAM stand for?
Primary Amebic Meningoencephalitis
27
What type of infection is PAM?
It is an acute, fulminant, purulent infection of the brain and meninges.
28
What type of infection is PAM?
It is an acute, fulminant, purulent infection of the brain and meninges.
29
What type of infection is PAM?
It is an acute, fulminant, purulent infection of the brain and meninges.
30
What does "acute" mean in the context of PAM?
Symptoms appear within one week of infection.
31
What does "fulminant" mean in relation to PAM?
The disease progresses rapidly and severely.
32
What does "fulminant" mean in relation to PAM?
The disease progresses rapidly and severely.
33
What does "purulent" mean in relation to PAM
It involves increased WBC accumulation in the CNS, leading to pus formation
34
When was PAM first identified?
1965
35
How many reported cases of PAM were there as of 1996?
179 cases
36
During which season is PAM most common, and why?
Warm summer months, because more people swim in contaminated water
37
Who is most commonly affected by PAM?
Healthy children and young adults with a history of swimming or diving in fresh or brackish water.
38
Who is most commonly affected by PAM?
Healthy children and young adults with a history of swimming or diving in fresh or brackish water.
39
What are common sources of infection for PAM?
Contaminated pools, stagnant ponds, freshwater lakes, streams, thermal springs, and spas.
40
What are common sources of infection for PAM?
Contaminated pools, stagnant ponds, freshwater lakes, streams, thermal springs, and spas.
41
What does "brackish water" mean?
Water where freshwater and saltwater mix, such as river mouths.
42
What is a recently identified mode of transmission for PAM?
Inhalation of contaminated dust.
43
What is the incubation period for PAM?
3 -7 days
44
What are the early symptoms of PAM?
Headache, fever, nausea, vomiting, and stiff neck (nuchal rigidity), Confusion, coma,
45
How soon does death occur after serious symptoms appear of Naegleriasis?
Within 3-6 days.
46
Why is PAM difficult to treat?
The Blood-Brain Barrier (BBB) prevents medications from effectively reaching the parasite inside the brain.
47
What is the best specimen for diagnosing PAM
Fresh cerebrospinal fluid (CSF).
48
In which samples can Naegleria fowleri trophozoites be found?
CSF, nasal discharges (early infection), and tissue biopsy samples
49
What laboratory method is used to directly observe Naegleria fowleri trophozoites?
Microscopy of saline or wet preparations.
50
How do Naegleria fowleri trophozoites appear under a microscope?
They are motile in fresh preparations.
51
What hematologic finding is common in PAM?
Increased neutrophils and RBCs in the CSF.
52
What are the common CSF abnormalities in PAM?
Increased WBC count and elevated protein levels.
53
Which culture technique is used to isolate Naegleria fowleri?
Nutrient agar with Escherichia coli (trophozoites feed on bacteria, creating a clearing in the agar)
54
What is the best diagnostic test for PAM?
PCR or Indirect Fluorescent Antibody (IFA) tests.
55
What is the best diagnostic test for PAM?
PCR or Indirect Fluorescent Antibody (IFA) tests.
56
What is the most commonly used routine test for diagnosing PAM?
Microscopy
57
What is the primary drug used to treat PAM?
Amphotericin B
58
How is Amphotericin B administered for PAM?
It can be given intravenously (IV) or intrathecally (directly into the spinal canal).
59
Which additional drugs may be used alongside Amphotericin B for PAM treatment?
Miconazole or Rifampicin.
60
Why is treatment for PAM difficult?
The Blood-Brain Barrier (BBB) limits the effectiveness of medications
61
How can water sources like hot tubs and baths be maintained to prevent PAM?
By proper chlorination and disinfection.
62
How can swimming-related PAM infections be prevented?
Avoid swimming in unfamiliar bodies of water, especially warm freshwater lakes, ponds, and hot springs.
63
What type of CNS condition is associated with Acanthamoeba species?
Granulomatous amebic encephalitis (GAE).
64
How does GAE differ from other infections in terms of pus formation?
GAE does not produce pus; instead, it forms granulomas where the parasite is contained by cells and tissues in the CNS.
65
Who is most at risk for Acanthamoeba infections?
Immunocompromised and chronically ill individuals
66
What ocular condition can Acanthamoeba species cause?
Acanthamoeba keratitis.
67
How is Acanthamoeba infection acquired?
Through respiratory inhalation, eye invasion, or skin ulcers with hematogenous spread to the CNS.
68
What is the size range of Acanthamoeba trophozoites?
10-45 μm.
69
What are the key morphological features of Acanthamoeba trophozoites?
Single nucleus with a large, centrally located karyosome, and absence of peripheral chromatin.
70
Why is Acanthamoeba called the "thorny ameba"?
Because "Acantho" means thorns, and the ameba has a spiky appearance.
71
What is the size of Acanthamoeba cysts?
10-20 μm.
72
What is a distinguishing feature of Acanthamoeba cysts?
They are double-walled, with the outer wall having a wrinkled appearance.
73
How does GAE progress in the body?
It has an insidious onset with a long course and spreads hematogenously.
74
Is GAE associated with swimming pools?
No, it is not associated with swimming pools.
75
What symptoms are associated with GAE? HAFFS
Headache, fever, fatigue, stiff neck, and altered mental status.
76
What is Acanthamoeba keratitis?
A chronic infection of the cornea.
77
Who is at risk of Acanthamoeba keratitis?
Contact lens wearers using homemade or non-sterile saline solutions.
78
How can Acanthamoeba be introduced into the eye?
Through corneal trauma.
79
What are the symptoms of Acanthamoeba keratitis?
Painful, gradual loss of vision and refractory corneal ulcers.
80
How is Acanthamoeba resistant in the environment?
It is resistant to desiccation and mild chlorination.
81
How can Acanthamoeba be detected in the lab?
By microscopy, detecting trophozoites in CSF, or cysts and trophozoites in brain biopsy tissue.
82
What staining techniques are used to identify Acanthamoeba?
Giemsa stain, calcofluor stain, and indirect immunofluorescent staining.
83
What culture method is used for Acanthamoeba?
Similar to Naegleria, creating visible tracks in agar.
84
What are the treatment options for GAE?
Sulfamethazine
85
How is Acanthamoeba keratitis treated?
With antifungal and antimicrobial drugs like ketoconazole, miconazole, propamidine, pentamidine, rifampicin, and isothianate.
86
What is the last resort for treating severe Acanthamoeba keratitis?
Corneal replacement (eye transplant).

PARASITOLOGY (6 decks)

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