Two cases of acanthamoeba keratitis diagnosed only by real-time polymerase chain reaction.

PURPOSE: To report 2 cases of Acanthamoeba keratitis whose causative pathogen was detected only by real-time polymerase chain reaction (PCR). METHODS: Histological examinations of corneal scrapings were stained with Fungiflora Y. Corneal scrapings were also cultured on nonnutrient agar. Real-time PCR analyses of corneal scrapings were also performed. RESULTS: Both cases had clinical signs and risk factors of Acanthamoeba infection. Histological examinations of corneal scrapings with Fungiflora Y staining were negative, and the cultures did not grow any pathogens. Real-time PCR analysis was positive for Acanthamoeba DNA from 2 corneal scrapings. Antiamoebic treatments led to excellent clinical improvements. CONCLUSIONS: These results indicate that PCR analyses can detect the DNA of Acanthamoeba in corneal scrapings and may be a valuable supplemental examination. This method is especially helpful when clinical signs and risk factors of Acanthamoeba infection are present but histological examinations with Fungiflora Y staining and cultures are negative.