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Naegleria fowleri Infection (cont.)

How is a Naegleria fowleri infection diagnosed?

Naegleria fowleri should be suspected in people, especially children, with exposure to freshwater who have symptoms of meningitis or meningoencephalitis listed above. The characteristics of the presentation may be nonspecific at first, leading clinicians to suspect more common diseases such as bacterial or viral meningitis. Routine tests may show a high blood white cell count and images of the brain may show inflammation, but neither of these are specific to PAM. A spinal tap will be done and the spinal fluid often shows elevated levels or white cells and red cells. Routine staining (Gram staining) does not detect the amoeba. Thus, it is important to do a wet mount to look for the motile amoeba under the microscope.

Definitive tests for N. fowleri infection are done in only a few labs in the country. They use one of the following three methods:

  1. N. fowleri nucleic acid tests in CSF or biopsy tissue using PCR
  2. N. fowleri antigen tests in CSF or biopsy tissue using immunohistochemistry (IHC)
  3. It is also possible to culture N. fowleri, but this must be done in the presence of bacteria and at higher temperatures, which is not routinely done in most laboratories.

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