Utility of Real-Time Polymerase Chain Reaction in Diagnosing and Treating Acanthamoeba Keratitis

Purpose: Using real-time polymerase chain reaction (PCR), we detected Acanthamoeba and monitored the changes in Acanthamoeba DNA copy number over the treatment course in patients suspected of Acanthamoeba keratitis (AK). Methods: Subjects were 6 patients (average age, 26.2 years) suspected of AK at the Kinki University Outpatient Clinic. For detection of Acanthamoeba, patients' corneal scrapings were collected for smear analysis, culture, and real-time PCR. After the diagnosis of AK was confirmed, treatment was initiated based on the quantitative result of the real-time PCR. Results: Both the smear and culture were positive for Acanthamoeba in 4 cases and negative in 2 cases (agreement in 3 cases and disagreement in 2 cases). By real-time PCR, all 6 cases were positive for Acanthamoeba with an average DNA copy number of 4.8 ± 9.1 × 103 copies per sample. We further monitored the variation in the Acanthamoeba DNA copy number over the treatment course and successfully treated all the patients. DNA copy number provided a parallel with other clinical features of AK. Conclusions: Real-time PCR can be a useful method for a rapid and precise diagnosis of AK. Moreover, utility of the Acanthamoeba DNA copy number obtained by real-time PCR can help ophthalmologists in making the best treatment decision.