Case report

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Case report

• Reporter I2 ???

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• A 45-year-old man who had been feeling unwell for
  several months visited his internist complaining
  of headache, dizziness, nausea, vomiting, extreme
  tiredness, and fever. The patient had been taking
  prednisone for a relapse of chronic ulcerative
  colitis.

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• On examination, the physician noted that the
  patient had nuchal rigidity and appeared
  confused. He performed a lumbar puncture. CSF was
  sent to the laboratory for bacterial and viral
  cultures. The Gram stain showed many neutrophils
  but no bacteria.

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• To rule out amebic encephalitis, the physician
  asked that a wet mount be prepared from the
  patients CSF. Microscopic examination of this
  preparation revealed motile amebic trophozoites.
  Cultures were negative for bacteria and viruses.

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• A biopsy specimen containing the parasite causing
  this patients infection is shown in Fig. 29.1.

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QUESTIONS

• 1. Which ameba would you expect to be causing
  this patients infection? What is the name of
  this infection?

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Answer

• Acanthamoeba spp.
• granulomatous amebic encephalitis (GAE)
• Once infected, a person may suffer with
  headaches, stiff neck, nausea and vomiting,
  tiredness, confusion, lack of attention to people
  and surroundings, loss of balance and bodily
  control, seizures, and hallucinations. Signs and
  symptoms progresses over several weeks and death
  usually occurs.

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QUESTIONS

• 2. Which ameba may cause a more serious and acute
  CNS infection and may be confused with this
  parasite?

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Answer

• Naegleria fowleri
• Infection with Naegleria causes the disease
  primary amebic meningoencephalitis (PAM), a brain
  inflammation, which leads to the destruction of
  brain tissue.
• Initial signs and symptoms of PAM include
  headache, fever, nausea, vomiting, and stiff
  neck. As the ameba causes more extensive
  destruction of brain tissue this leads to
  confusion, lack of attention to people and
  surroundings, loss of balance and bodily control,
  seizures, hallucinations. The disease progresses
  rapidly and infection usually results in death
  within 3 to 7 days.

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QUESTIONS

• 3. How can you distinguish between these amebae?

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QUESTIONS

• 4. How do the infections caused by these two
  parasites differ?

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Answer

• PAM occurs in persons who are generally healthy
  prior to infection. Central nervous system
  involvement arises from organisms that penetrate
  the nasal passages and enter the brain through
  the cribriform plate. The organisms can multiply
  in the tissues of the central nervous system and
  may be isolated from spinal fluid. In untreated
  cases death occurs within 1 week of the onset of
  symptoms.

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Answer

• GAE occurs in persons who are immunodeficient in
  some way the organisms cause a granulomatous
  encephalitis that leads to death in several weeks
  to a year after the appearance of symptoms. The
  primary infection site is thought to be the
  lungs, and the organisms in the brain are
  generally associated with blood vessels,
  suggesting vascular dissemination. Prior to 1985
  amoebae had been reported isolated from diseased
  eyes only rarely cases were associated with
  trauma to the eye. In 1985-1986, 24 eye cases
  were reported to CDC and most of these occurred
  in wearers of contact lenses. It has been
  demonstrated that many of these infections
  resulted from the use of home-made saline
  solutions with the contact lenses.

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QUESTIONS

• 5. How is the laboratory diagnosis of this
  infection made?

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Answer

• In Naegleria infections, the diagnosis can be
  made by microscopic examination of cerebrospinal
  fluid (CSF). A wet mount may detect motile
  trophozoites, and a Giemsa-stained smear will
  show trophozoites with typical morphology.

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Answer

• In Acanthamoeba infections, the diagnosis can be
  made from microscopic examination of stained
  smears of biopsy specimens (brain tissue, skin,
  cornea) or of corneal scrapings, which may detect
  trophozoites and cysts. Cultivation of the causal
  organism, and its identification by direct
  immunofluorescent antibody, may also prove
  useful.

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QUESTIONS

• 6. Does the ameba causing CNS infection in this
  patient cause other types of infections?

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Answer

• Acanthamoeba can enter the skin through a cut,
  wound, or through the nostrils. Once inside the
  body, amebas can travel to the lungs and through
  the bloodstream to other parts of the body,
  especially the central nervous system (brain and
  spinal cord).

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Answer

• Through improper storage, handling, and
  disinfection of contact lenses, Acanthamoeba can
  enter the eye and cause keratitis resulting
  superficial corneal abrasions.

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QUESTIONS

• 7. Which other free-living ameba, recently placed
  in the same genus as this parasite, causes a CNS
  infection in humans?

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Answer

• Acanthamoeba culbertsoni
• Acanthamoeba polyphaga ?eyes infection
• Acanthamoeba castellanii
• Acanthamoeba palestinensis ?CNS infection
• Acanthamoeba astronyxis ?CNS infection
• Acanthamoeba hatchetti ?eyes infection
• Acanthamoeba rhysodes

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QUESTIONS

• 8. Why is there no satisfactory treatment
  available to treat this infection?

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Answer

• Treatment with sulfamethazine may be effective in
  controling Acanthamoeba spp.
• The following agents have been used to
  successfully eliminate the amoebic infection in
  the eye ketoconazole, microconazole, and
  propamidine isothionate however, penetrating
  keratoplasty has been necessary to restore useful
  vision.

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Thanks for your attention