Development, Optimization, and Validation of a Multiplex Real-Time PCR Assay on the BD MAX Platform for Routine Diagnosis of Acanthamoeba Keratitis

The reported number of cases of Acanthamoeba amebic keratitis (AK) is continually increasing. Molecular diagnosis has become the first choice of ophthalmologists for identifying and confirming this clinically problematic diagnosis. However, in-house molecular diagnostic procedures are time-consuming and may not be compatible with the urgency of the situation. In this study, a previous in-house AK-PCR technique was adapted for use on BD MAX (Becton Dickinson, Heidelberg, Germany), a fully integrated, automated platform for molecular biology, for the rapid routine diagnosis of AK. Different protocols were compared to optimize DNA extraction from Acanthamoeba cysts. The analytical parameters of the AK-BD MAX PCR were evaluated. Thirty-two samples were simultaneously tested with AK-BD MAX PCR and the original AK-PCR from which it was developed. A thermal-shock pretreatment protocol was validated. The analytical parameters obtained with BD MAX were similar to those obtained with the previous in-house AK-PCR method. The performance of AK-BD MAX PCR was then assessed for routine testing on 40 clinical samples, mostly corneal scrapings. Frozen, ready-to-use, in-house PCR premixes were stable over 8 months. Overall, 34 of the 40 clinical samples (85%) were considered to be true negatives; 4 (10%), probable AK; and 2 (5%), possible AK. This newly developed AK-BD MAX PCR is reliable, rapid, and efficient, and should facilitate Acanthamoeba keratitis diagnosis.