Biological Consulting Services of North Central Florida, Inc.

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Naegleria fowleri Amoeba Detection and Analysis in Water

Naegleria fowleri (commonly referred to as the "brain-eating amoeba"), is a free-living microscopic ameba (single-celled living organism). It can cause a rare and devastating infection of the brain called primary amebic meningoencephalitis (PAM). The ameba is commonly found in warm freshwater (e.g. lakes, rivers, and hot springs) and soil. Naegleria fowleri usually infects people when contaminated water enters the body through the nose. Once in the nose, the amoeba travels to the brain where it causes PAM which is usually fatal. Infection typically occurs when people go swimming or diving in warm freshwater places like lakes and rivers. In very rare instances, Naegleria infections may also occur when contaminated water from other sources (such as inadequately chlorinated swimming pool water or heated and contaminated tap water) enters the nose.

Naegleria fowleri is normally found in the natural environment and is well adapted to surviving in various habitats, particularly warm-water environments. Although the trophozoite stage is relatively sensitive to environmental changes, the cysts are more environmentally hardy. There are no means yet known that would control natural Naegleria fowleri levels in lakes and rivers. Naegleria fowleri does not survive in sea water nor has it been detected in sea water.

In general, the CDC does not recommend testing untreated rivers and lakes for Naegleria fowleri as the ameba is naturally occurring and there is no established relationship between detection or concentration of Naegleria fowleri and risk of infection. Environmental testing may be warranted for investigations in which Naegleria fowleri detection may be useful for establishing geographical distribution in new environments, survival in disinfected water bodies, or in household water systems.

Naegleria fowleri trophozoites and the more resistant cysts are sensitive to chlorination and monochloramine used for disinfection of drinking water and swimming pools if adequate levels are maintained and monitored. The chlorine sensitivity is moderate and in the same range as the cysts from Giardia intestinalis, another waterborne pathogen.

Recent events and reported cases of infection have caused much public fear and speculation.  The CDC website has many useful facts and recomendations for the public and utilities on the treatment of water systems and disinfection of the pathogen.

 

Naegleria fowleri test methods

BCS provides multiple analytical services for the detection of Naegleria fowleri. The methodology utilized depends on the clients needs and level of sensitivity required. Sampling kits for the analysis of water and/or sediment are provided to the client. Sample size can range between 1-500 liters depending on the water source. Up to 10 liters of  water can be shipped directly to the lab for analysis. For larger volumes, water filtration through specially provided filters is conducted by the client and the filters are sent back to the lab for analysis.

Analysis methods include:

Direct visualization: The motile amoeba can often be seen moving under a microscope when looking at a fresh sample of cerebral spinal fluid (CSF) from an infected individual. The amoeba can also be stained with a variety of stains, such as Giemsa-Wright or a modified trichrome stain for identification.

Immunohistochemistry (IHC): An antibody specific to Naegleria fowleri can be used in conjunction with another antibody that deposits a chemical or glows under specific types of light (indirect fluorescent antibody [IFA]) to directly stain the amoeba in tissue.

Polymerase Chain Reaction (PCR): Specific molecular tools can amplify DNA from the amoeba in CSF or tissue to specifically identify its presence. Looking at strains or subtypes of Naegleria fowleri can be done, but little is known about the natural populations in the environment which makes it difficult to interpret what the findings mean.

Ameba culture: The sample is added to a growth plate covered in bacteria that serves as a food source for Naegleria fowleri. Incubating at a higher temperature selects for Naegleria fowleri growth, which can be visualized as tracks made by the ameba as it moves across the plate eating the bacteria. Growing Naegleria fowleri in mammalian cell culture and looking for toxic cell effects is also possible.

Environmental Detection: Water samples can be collected, concentrated and put into culture to grow and select for Naegleria fowleri. Samples can be tested using the serologic or molecular methods described above.


Pricing: please contact BCS for pricing and appropriate methodology.

 

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