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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Free Living Amoebae Lecture PDF - King Salman International University

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