Fascinella #004

Acanthamoeba

There are around 22 species in the genus Acanthamoeba; a group of free-living protozoa that are widely dispersed in the environment. The Neff strain of Acanthamoeba castellani (recovered from Golden Gate Park in the 1960s) has been a significant contributor to the development of eukaryotic cell biology, since it has similarities to mammalian cells and can be grown easily in the laboratory.

There are several Acanthamoeba species that can cause human infection, including A. castellani, A.polyphaga, A. culbertsoni and A. astronyxis. The commonest infection is amoebic keratitis in contact lens wearers (video). Fortunately much less common is amoebic panencephalitis in which only a small percentage of patients respond to therapy. This generally occurs in patients with underlying co-morbidities such as diabetes, malignant disease, immunodeficiency or malnutrition.

Acanthamoebas can also act as a vehicle or potential vector for intracellular bacterial infections such as Legionnaires’ Disease 2, melioidosis3 and even MRSA infection4. Evidence is lacking to prove their role as the principal means of exposure to infection, but amoebas can evidently provide an environmental reservoir to protect bacteria that are capable of human infection.

Acanthamoeba

Video: Acanthamoeba from contact lens keratitis. Amoebic trophozoites phagocytose bacteria (E.coli) grown on non-nutrient agar.

References

  1. Wikipedia – Acanthamoeba.
  2. Rowbotham TJ. Preliminary report on the pathogenicity of Legionella pneumophila for freshwater and soil amoebae. J Clin Pathol 1980; 33:1179-1183.
  3. Inglis TJ, Rigby P, Robertson TA, Dutton NS, Henderson M, Chang BJ.  Interaction between Burkholderia pseudomallei and Acanthamoeba species results in coiling phagocytosis, endamebic bacterial survival, and escape. Infect Immun. 2000; 68: 1681-1686 [PMID Reference]
  4. Huws SA, Smith AW, Enright MC, Wood PJ, Brown MR. Amoebae promote persistence of epidemic strains of MRSA. Environ Microbiol. 2006; 8: 1130-1133. [PMID Reference]

Author Credit: Dr Tim Inglis

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