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Acanthamoeba by PCR

Acanthamoeba

Test Codes

EPIC: LAB7149, Beaker: XACAP, Mayo: ACARP

Department

Send Outs

Instructions

Although verification experiments did not detect Acanthamoeba species DNA in contact lenses from asymptomatic adults, it is possible that PCR may detect asymptomatic colonization/contamination and, therefore, testing should not be performed on asymptomatic individuals

Specimen Collection Criteria

Note:  The preferred specimen for Acanthamoeba by PCR is corneal scraping or biopsy

Collect: Aseptically obtain one of the following specimens.

• Corneal scrapings in a sterile collection container with 1 mL of sterile saline or viral transport media, 1 mL (minimum 0.5 mL)
• Ocular biopsy in a sterile collection container with 1 mL of sterile saline or viral transport media, 5-10 mm (minimum 5 mm)
• Contact lenses in a sterile collection container with 1 mL of sterile saline or viral transport media.
• Contact lens solution in a sterile collection container, minimum 1 mL
• Lens case: Either 1 mL of solution or the entire case

Transport specimens to the Laboratory immediately after collection.

Physician Office/Draw Specimen Preparation

Maintain specimens refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Transport: All specimen types in an appropriate container, refrigerated(2-8°C or 36-46°F).

Rejection Criteria

• Swabs collected with wooden handle.
• Specimens in expired media.
• Specimens containing scalpel blades.
• Specimens not collected and processed as indicated.

Inpatient Specimen Preparation

Transport specimens immediately to the Laboratory after collection.

In-Lab Processing

Transport: All specimen types in an appropriate container, refrigerated (2-8°C or 36-46°F)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 7 days

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Sent to Mayo Medical Laboratories, Rochester, MN

Performed

Monday – Saturday.
Results available 4-6 days.

Reference Range

Negative.

Test Methodology

Real-Time Polymerase Chain Reaction (PCR)/TaqMan DNA Probe Hybridization.

Interpretation

False negative results may occur if the specimen is improperly collected or stored.

Clinical Utility

This test aids in the diagnosis of granulomatous amoebic encephalitis and conjunctivitis (caused by Acanthamoeba).

Clinical Disease

Acanthamoeba causes conjunctivitis and keratoconjunctivitis, painful vision-threatening diseases of the cornea. (1,2) If not promptly treated, it may lead to corneal ulceration and eventually blindness. There may be secondary invasion of the central nervous system. Epidemiologic studies indicate wearing contact lenses is a major risk factor, with significant risk to those persons using homemade saline solutions to clean contact lenses. N. fowleri, a small free-living amoeba found in fresh and brackish water, is the causative agent of primary amoebic meningoencephalitis (PAM). PAM occurs generally in patients who had contact with freshwater (i.e. swimming in lakes) 7-10 days before the onset of symptoms. Organisms enter through the nasal mucosa and migrate through the olfactory nerves to the brain. Untreated, death occurs 3-10 days after the onset of symptoms.

Incubation Period

Acanthamoeba: Unknown, but longer than one week.

Transmission

Transmission occurs by direct contact with contaminated water, saline, or soil. The primary focus of infection is the cornea.

Reference

1. Visvesvara, G., 2015. Pathogenic and Opportunistic Free-Living Amebae. In: Jorgensen, J.H., et. al. (eds.). Manual of Clinical Microbiology. 11^th edition. ASM Press. Washington, D.C.
2. Roy, S., J. Yoder, M. Beach, and G. Visvesvara, Amebic Infections/Infections with Free-Living Ameba (naegleriasis, acanthamoebiasis, balamuthiasis), 2000. Naegleriasis and Acanthamebiasis, In: Heymann, D.L., ed. Control of Communicable Diseases Manual. 20^th ed. Washington D.C., American Public Health Assoc. APHA Press.

CPT Codes

87798

Contacts

Last Updated

10/16/2023