Specimen Type

Cerebrospinal fluid (CSF)

Tissue (brain, lung, skin, corneal scraping)

Specimen Required

Collection Instructions:

Submit immediately without delay.

Note: Preferred specimen for Acanthamoeba culture from an ocular source is corneal scraping or biopsy. Swab is suboptimal and may result in a falsely negative result.

Reject Due To

Useful For

Detection and identification of Acanthamoeba species, Balamuthia mandrillaris and Naegleria fowleri in central nervous system or ocular specimens

Clinical Information

Acanthamoebae spp., Naegleria fowleri and Balamuthia mandrillaris are free living amebas that are aerobic, eukaryotic protists. N. fowleri has three life cycle stages: trophozoites, flagellates, and cysts. Both Balamuthia mandrillaris and Acanthamoeba spp. have a trophozoite stage, non-motile and active, respectively; and cyst stage.

Human exposure to Acanthamoeba spp. is widespread given its presence in soil and fresh water in a variety of geographic conditions and areas; illness caused by Acanthamoeba spp. is most commonly found in individuals with compromised immune systems or in contact lens wearers.

Granulomatous amebic encephalitis (GAE) commonly occurs when Acanthamoeba spp. enters the lower respiratory tract or ulcerated or broken skin in individuals with compromised immune systems. Chronic granulomatous lesions or amebic keratitis (AK), of the eye and cornea can also be caused by some Acanthamoeba sp. AK infections can occur in contact lens wearers and may be attributed to poor contact lens hygiene or in individuals who have had corneal trauma. AK infections may result in blindness if left untreated.

Diagnosis can be made through microscopic examination of wet mount preparations of fresh CSF showing motile amoebae and of stained smears or through microscopic examination of scrapings or aspirates of the eye, cornea, or skin lesions.

Interpretation

Organisms seen on stains of the original specimen smear and/or growth on culture media are positive tests.Detection of Amoeba in ocular and sterile specimens constitutes a medical emergency. Positive findings will be telephoned to the ordering physician.

Cautions

The preferred specimens for Acanthamoeba ocular culture are corneal scrapings and/or biopsy. Swabs are suboptimal and may result in a falsely-negative
result.

Reference

Eberhard, M., Gabrielli, A., Savioli, L., and Visvesvara, G. 2008. Naegleriasis, Acanthamediasis, and Balamuthiasis, p. 438-441. In Heymann, D. L., Control of Communicable Diseases Manual, 19^th ed. American Public Health Association, Washington, DC.

Koshy, A. A., Blackburn, B. G., and Singh, U. 2010. Free-Living Amebas, p. 3427-3436. In Mandell, D., Bennett, J. E., and Dolin, R. Principles and practice of infectious diseases, 7^th ed., vol. 2. Churchill Livingstone, Elsevier, Philadelphia, PA.

Ma P, Visvesvara GS, Martinez AJ, et al. 1990. Naegleria and Acanthamoeba infections. Rev. Infect. Dis. 12:490-513.

Visvesvara, G. S. 2007. Pathogenic and Opportunistic Free-Living Amebae, p. 2082-2091. In Murray, P. R., Baron, E. J., Jorgensen, J. H., Landry, M. L., and Pfaller, M. A. Manual of Clinical Microbiology, 9^th ed., vol. 2. ASM Press, American Society for Microbiology, Washington, DC.

Microscopy

Culture

Performing Laboratory Location

Newfoundland & Labrador Public Health Laboratory, St. John’s, NL.