CNS Module: Free Living Amoebae
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Questions and Answers

What is the primary mode of transmission for Naegleria fowleri?

  • Entry through the nasal mucosa (correct)
  • Contaminated food
  • Contact with infected soil
  • Inhalation of spores

    • Which of the following is NOT a clinical manifestation of primary amoebic meningoencephalitis (PAM)?

  • Severe abdominal pain (correct)
  • Fever
  • Sore throat
  • Nausea and vomiting

    • What are the three known morphologic forms of Naegleria fowleri?

  • Trophozoites, cysts, and flagellates (correct)
  • Amoeboid forms, spores, and hyphae
  • Cysts, trophozoites, and flagellates
  • Flagellate forms, cysts, and spores

    • Which of the following infections is caused by Acanthamoeba?

    <p>Granulomatous amoebic encephalitis (A)</p> Signup and view all the answers

    Which statement about Naegleria fowleri prevalence is correct?

    <p>It exhibits higher prevalence during the summer. (B)</p> Signup and view all the answers

    What is a common neurological symptom associated with primary amoebic meningoencephalitis?

    <p>Severe headaches (C)</p> Signup and view all the answers

    What does Kernig’s sign indicate in the context of meningitis?

    <p>Nuchal rigidity (D)</p> Signup and view all the answers

    What type of infections can be prevented by understanding the transmission of free living amoebae?

    <p>Infections caused by free living amoebae (C)</p> Signup and view all the answers

    What is a diagnostic sign of meningitis observed in patients?

    <p>Inability to fully straighten the leg when the hip is flexed (B)</p> Signup and view all the answers

    What is the preferred method for diagnosing Naegleria fowleri infection?

    <p>Microscopic examination of cerebrospinal fluid (C)</p> Signup and view all the answers

    Which combination of medications has shown effectiveness against Naegleria fowleri infections?

    <p>Amphotericin B and rifampin (A)</p> Signup and view all the answers

    What is one recommended preventive measure for Naegleria fowleri infections in swimming pools?

    <p>Adequate chlorination of pools (D)</p> Signup and view all the answers

    Which group of individuals is at increased risk for direct eye invasion by Acanthamoeba species?

    <p>Contact lens wearers (A)</p> Signup and view all the answers

    What is a common symptom of granulomatous amebic encephalitis caused by Acanthamoeba?

    <p>Slowly developing headaches (D)</p> Signup and view all the answers

    How do Acanthamoeba species typically enter the body to cause infection?

    <p>Via nasal inhalation or aspiration (B)</p> Signup and view all the answers

    Which of the following factors is a predisposing condition for CNS infections caused by Acanthamoeba?

    <p>Being immunocompromised (A)</p> Signup and view all the answers

    Flashcards

    Kernig's Sign

    A diagnostic sign for meningitis where the patient cannot fully straighten their leg when their hip is flexed at 90 degrees due to tightness in the hamstring muscles.

    Free-living amoebae

    Free-living amoebae are single-celled organisms that can live independently in various environments like water and soil.

    Naegleria Infection (Brain-Eating Amoeba)

    A rare but serious brain infection caused by a single-celled amoeba called Naegleria fowleri, often found in warm freshwater.

    Pathogenic free-living amoebae

    These amoebae are capable of causing infections in humans. Examples include Naegleria fowleri and Acanthamoeba sp.

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    Non-pathogenic free-living amoebae (Coprozoic)

    These amoebae live in the environment but are not known to cause harm in humans.

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    Diagnosis of Naegleria Infection

    The primary method for diagnosing Naegleria infection involves microscopic examination of cerebrospinal fluid (CSF) to identify the amoeba's trophozoite stage.

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    Mode of transmission of free-living amoebae

    The infective stage (amoebic trophozoite) enters the body through the nose, often during swimming in contaminated water.

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    Treatment of Naegleria Infection

    Naegleria infection is typically treated with amphotericin B, a potent antifungal drug that may be effective in some cases.

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    Acanthamoeba sp. infections

    Acanthamoeba keratitis is an infection of the cornea (the clear outer layer of the eye) and can cause vision problems. Granulomatous amoebic encephalitis (GAE) is a rare, brain infection that affects the central nervous system (CNS).

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    Acanthamoeba Species

    A group of amoebas that can cause various infections, including granulomatous amebic encephalitis (GAE) and Acanthamoeba keratitis.

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    Acanthamoeba Trophozoite

    The active, feeding stage of Acanthamoeba, capable of multiplying and causing infections.

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    Naegleria fowleri infection

    Primary amoebic meningoencephalitis (PAM) is a severe and rapidly progressing brain infection typically caused by Naegleria fowleri.

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    Naegleria fowleri morphologic forms

    Naegleria fowleri exists in three forms: amoeboid trophozoite, flagellate form, and cyst. The amoeboid form is the infective stage.

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    Acanthamoeba Cyst

    The dormant, hardy stage of Acanthamoeba, resistant to harsh conditions, and able to survive outside the host.

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    Kernig’s sign

    A sign of meningitis characterized by stiffening of the hamstrings, causing resistance to extending the leg at the knee.

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    Mode of Transmission of Acanthamoeba

    Acanthamoeba infections can be acquired through aspiration or nasal inhalation of the amoeba, or by direct invasion of the eye.

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    Study Notes

    Faculty of Medicine Level 3 CNS Module: Free Living Amoebae

    • Lecture: Free living amoebae
    • Professor: Gehan Salah Sadek
    • Date: 15/11/2022

    Intended Learning Outcomes

    • Students will identify the transmission methods of free-living amoebae.
    • Students will distinguish between Naegleria fowleri and Acanthamoeba species.
    • Students will describe the clinical characteristics of primary amoebic meningoencephalitis (PAM), granulomatous amoebic encephalitis (GAE), and Acanthamoeba keratitis.
    • Students will support preventive measures for infections caused by free-living amoebae.

    Free Living Amoebae

    • Categorized into pathogenic and non-pathogenic types.
    • Pathogenic free-living amoebae include Naegleria fowleri and Acanthamoeba species.
    • Non-pathogenic free-living amoebae (Coprozoic) are not associated with disease.

    Naegleria fowleri

    • Exclusive ameba with three forms: ameboid trophozoites, flagellate forms, and cysts.
    • Characteristics of ameboid trophozoites include large karyosome and pseudopods.
    • Flagellate forms have flagella and characteristic size ranges.
    • Cysts display a double cell wall structure

    Epidemiology of Naegleria fowleri

    • Predominantly found in warm bodies of water, including lakes, streams, and swimming pools.
    • Prevalence is higher in summer months.
    • Infection occurs through nasal inhalation of ameboid trophozoites.

    Clinical Picture: Naegleria fowleri

    • Asymptomatic: Nasal colonization is common but asymptomatic.
    • Primary amoebic meningoencephalitis (PAM): Characterized by rapid tissue destruction in the brain. Initial manifestations include fever, headache, sore throat, nausea, and vomiting, followed by meningitis symptoms like stiff neck and seizures.

    Acanthamoeba species

    • Common disease: granulomatous amebic encephalitis (GAE), Acanthamoeba keratitis
    • Common associated characteristics: pseudopods and large karyosome. Trophozoites and cysts.

    Mode of Transmission: Acanthamoeba species

    • CNS infection: Aspiration/inhalation via lower respiratory tract.
    • Eye infection (keratitis): Direct invasion, common in contact lens wearers and those with corneal trauma.

    Clinical Picture: Acanthamoeba species

    • CNS infection: Symptoms develop slowly, including headaches, seizures, neck stiffness, nausea, and vomiting. Lesions of the brain often contain trophozoites and cysts.
    • Infections may spread to other parts of the body like kidneys, pancreas, prostate, and uterus.

    Diagnosis

    • **Naegleria fowleri: Cerebrospinal fluid (CSF) examination, saline and iodine wet mounts.
    • Acanthamoeba: CSF examination.

    Treatment

    • Naegleria fowleri: Prompt, aggressive treatment with amphotericin B, sometimes combined with rifampin or miconazole, is crucial. Survival is rare without swift intervention.
    • Acanthamoeba: Sulfamethazine has shown potential; however, treatment challenges exist due to delayed recognition of the infection.

    Prevention and Control

    • Health education regarding water safety, particularly for warm bodies of water.
    • Adequate chlorination of swimming pools and hot tubs.
    • Prompt repair of cracks in pools, tubs, and baths to eliminate potential contamination sources.

    Kernig's Sign

    • A diagnostic sign for meningitis.
    • Inability to fully straighten the leg when the hip is flexed and 90 degrees, due to hamstring stiffness.

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    Related Documents

    Free Living Amoebae Lecture PDF - King Salman International University

    Description

    This quiz focuses on the CNS module related to free living amoebae, particularly identifying transmission methods and differentiating between Naegleria fowleri and Acanthamoeba. It also covers clinical characteristics of infections caused by these amoebae and preventive measures. Perfect for Level 3 Faculty of Medicine students.

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