Polymerase chain reaction diagnosis in fungal keratitis caused by Alternaria alternata

PURPOSE: To contribute toward assessing the effectiveness of polymerase chain reaction as a rapid method in diagnosis of torpid keratitis caused by opportunistic fungi. METHODS: Interventional case report. A 50-year-old man with a corneal abscess in the right eye treated for a period of 6 months with different combinations of broad-spectrum antibiotics and steroids was referred to our center. Corneal scraping was taken for microbiological study, including classic cultures and polymerase chain reaction. Amplified DNA was sequenced to identify the pathogen. RESULTS: Polymerase chain reaction amplification was negative for Acanthamoeba species and positive for fungi. The sequence analysis showed Alternaria alternata as the causal agent in 24 hours. Cultures confirmed the identification in 10 days. CONCLUSION: Polymerase chain reaction amplification with subsequent DNA-typing was revealed to be a useful method for detection of ocular pathogens such as A. alternata involved in cases of torpid keratitis, even in the presence of broad-spectrum antimicrobial therapy.