Diagnostic par PCR des kératites à Acanthamoeba spp

Aim: Evaluation of a PCR assay as a diagnostic tool for detection of Acanthamoeba slop. in patients presenting infectious keratitis. Methods: Between August 2001 and November 2002, 342 clinical specimens consisting in corneal scrapings from 334 patients were tested for Acanthamoeba using direct microscopy, culture, and PCR. A fragment of Acanthamoeba 18S rRNA gene was amplified using a set of primers referred to as Nelson's primers. Results: A diagnosis of Acanthamoeba keratitis was considered for nine patients. Amoeba growth in culture was unfruitful for all of these cases. Eight patients had corneal scrapings that tested positive with PCR; in two cases direct microscopy observations confirmed PCR results. For one patient, a negative PCR result was obtained; however, a second corneal sample and cysts staining on May-Grunwald-Giemsa were positive. A false-positive PCR result was noted related to another amebic genus. A risk factor was found in all Acanthamoeba keratitis cases (contact lenses, trauma). Topical treatment was successful, and keratoplasty was necessary afterwards for optical rehabilitation in five patients. Conclusion: This study suggests that PCR is a sensitive diagnostic tool, superior to conventional techniques for detecting Acanthamoeba in corneal lesions.