Ann Clin Microbiol.  2024 Jun;27(2):149-153. 10.5145/ACM.2024.27.2.9.

Can Acanthamoeba keratitis be properly diagnosed without culture in the real-world clinical microbiology laboratory?: a case report

• Park B
• Chung HS
• Won EJ
• Sung H
• Kim MN

• KMID: 2557875
• DOI: http://doi.org/10.5145/ACM.2024.27.2.9

Abstract

Acanthamoeba species are ubiquitous, free-living organisms found in the environment. They can cause a sight-threatening cornea disease, termed Acanthamoeba keratitis, and are often misdiagnosed, causing delayed administration of the correct treatment. Herein, we report a case of Acanthamoeba keratitis diagnosed without culture. A 12-year-old girl with a history of wearing contact lenses presented with complaints of pain, irritation, and hyperemia in the left eye. Corneal scraping-smeared slide, and liquids with contact lenses were submitted to the clinical microbiology laboratory. Cultures of Acanthamoeba spp. were not available; thus, they were stained with calcofluor white. The isolation of Acanthamoeba from the corneal scraping allowed the detection of trophozoites and cysts based on their morphological characteristics. PCR targeting the 18s rRNA gene and subsequent sequencing revealed 99% identity with the Acanthamoeba spp. Although it is challenging to find real-world evidence of Acanthamoeba in clinical microbiology without using culture methods, this case underscores the need for clinical microbiology laboratories to maintain their inspection capabilities.

Keyword

Acanthamoeba keratitis; cyst; trophozoite; morphology

Figure

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  Fig. 1. Anterior segment photographs of the patient in this case study. The top two anterior segment images were taken under slit-lamp microscope (A, B) and the bottom two images were under cobalt blue light after fluorescein dye staining (C, D). During the slit-lamp microscopy examination of the patient's left eye, radial keratoneuritis was observed in the central corneal stroma, while vitreous and retina showed no abnormalities.

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  Fig. 2. Morphological analysis of Acanthamoeba spp. using calcofluor-white staining. (A) Acanthamoeba cysts in a group under light microscopy (400×, scale bar = 10 μm). (B) Acanthamoeba trophozoites with a single large nucleus and numerous vacuoles were conspicuous under light microscopy (200×, scale bar = 10 μm). (C) Remarkable Acanthamoeba cysts with double cyst walls under fluorescence microscopy (400×, scale bar = 10 μm). (D) Acanthamoeba trophozoites were relatively unremarkable under fluorescence microscopy (400×, scale bar = 10 μm).

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