User:Biobartram/Balamuthia mandrillaris

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Balamuthia mandrillaris is a free-living amoeba that is known to cause the rare but deadly neurological condition known as granulomatous amoebic encephalitis (GAE).^[1] B. mandrillaris is a soil dwelling amoeba and was first discovered in 1986 in the brain of a mandrill that died in the San Diego Wild Animal Park.^[2][3]

B. mandrillaris can infect the body through open wounds or by inhalation.^[4] Balamuthia has been isolated in nature.^[5][6]It is believed to be distributed throughout the temperate regions of the world. This is supported somewhat by the detection of antibodies to the protist in healthy individuals.

The generic name Balamuthia was given by Govinda Visvesvara (b. September 28, 1931), in honor of his late mentor, parasitologist William Balamuth (1914–1981), for his contributions to the study of amoebae.^[7] It was in 1993 when Visvesvara isolated and studied the pathogen for the first time.^[7][8]

Article body

Pathology

B. mandrillaris is larger than human leukocytes, thus making phagocytosis impossible. Instead, the immune system attempts to contain them at the portal of entry (usually an open wound) by mounting a type IV hypersensitivity reaction.^[9] Upon introduction, the amoeba may form a skin lesion, or in some cases, may migrate to the brain, causing a condition known as granulomatous amoebic encephalitis,^[10] (GAE), which is usually fatal. This granulomatous feature is mostly seen in immunocompetent patients; immunocompromised individuals exhibit a "perivascular cuffing".^[11] Balamuthia-induced GAE can cause focal paralysis, seizures, and brainstem symptoms such as facial paralysis, difficulty swallowing, and double vision.^[12]

Balamuthia may also cause a variety of non-neurological symptoms, including skin lesions, which can progress to GAE. Patients experiencing this particular syndrome may report a skin lesion (often similar to those caused by MRSA), which does not respond well to antibiotics. The lesion is usually localized and very slow to heal, or fails to heal altogether. In some presentations, this infection may be mistaken for certain forms of skin cancer or cutaneous leishmaniasis. Balamuthia lesions are most often painless.^[12]

Culturing and Identification

Balamuthia is most easily identifiable in a brain biopsy performed on an individual suffering from GAE. The amoeba cannot be cultured on an agar plate coated with E. coli because (referred to as a xenic culture), unlike Naegleria or Acanthamoeba, Balamuthia mandrillaris does not feed on bacteria (at least in laboratory conditions). Instead, Balamuthia must be cultured on primate hepatocytes or human brain microvascular endothelial cells (the cells that constitute the blood–brain barrier) (referred to as an axenic culture).^[13]

Vero cells have been suggested as a possible cheaper and faster alternative to culture the organism.^[14] Several types of animal cells have been used in B. Mandrillaris culturing including rat glioma cells, human lung cells, and human brain microvascular endothelial cells.^[12] These animal cells are added to a specified axenic growth medium for culturing. At the same time, and xenic culture is also performed to help differentiate between Balamuthia and other amebae.^[12]

References