Etiological identification of 50 isolates from fungal corneal ulceration by semi-nested PCR amplification of ITS2 region

Abstract

Objective To identify the pathogens of 50 cases of fungal corneal ulceration by using semi-nested PCR amplification of ITS2 region. Methods Fifty isolates of fungal corneal ulceration and 3 standard fungal strains cultures were collected and their DNAs were extracted.Their ITS2 regions were amplified by semi-nested PCR and sequenced.The results were compared with the nucleotide sequences in the NCBI GenBank.The pathogens of the fungi were identified and their distribution were analysed. Results The sequences results of the 3 standard fungal strains were consistent with the information in the GenBank.The pathological microorganisms of 50 cases of fungal corneal ulceration were:24 Fusarium (48%)，including 17 Fusarium solani，6 Fusarium oxysporum and 1 Fusarium verticillioide； 10 Aspergillius (20%)，including 5 Aspergillius flavus，3 Aspergillius sydowii and 2 Aspergillius nidulans；6 Penicillium (12%)，including 2 Penicillium citreo-viride, 2 Penicillium multicolor and 2 Penicillium oxalicum；5 Candida (10%), including 3 Candida albicans and 2 Candida parapsilosis；3 Cladosporium (6%), including 2 Cladosporium herbarum and 1 case of Cladosporium cladosporioides；1 case of Neurospora crassa(2%)；1 Alternaria alternata(2%). Conclusion Semi-nested PCR amplification of ITS2 region was proved to be a fast, simple and accurate method to identify pathogens of fungal corneal ulceration, and may be useful for personalized treatment and epidemiological investigation of local fungi.（Chin J Lab Med,2012,35:1163-1166） Key words: Corneal ulcer; Eye infections，fungal; Polymerase chain reaction; DNA，intergenic