The relationship between the genotype and clinical factors of filamentous fungus causing-keratitis

Background The study on the classification of fungi is very important for the diagnosis and treatment of fungal keratitis.Identifying the different species of filamentous fungi is a critical factor for the application of anti-fungal drug in treating keratitis.ObjectiveThis report studies the relationship between the genotype of filamentous fungi and the clinical factors.MethodsFifty-two patients with filamentous fungal keratitis determined by clinical and laboratory examination were recruited in Tongren Hospital from January 2006-December 2006.The lesions were graded on the severity of the corneal ulcer and the presence of hypopyon.The filamentous fungal keratitis was treated with topical and systemic administration of anti-fungal drugs or corneal transplantation.The isolates were cultured in potato culture and identified by morphological characteristics based on the Nelson criterion and genotyped by the rDNA ITS method.The clinical data was retrospectively analyzed.ResultsForty-eight species (eubacteria are bacteria,not fungi)of fungus were identified by morphological characteristics,and the filamentous fungi were divided into 4 types based on the phylogenetic relationships within the rDNA ITS of the 52 filamentous fungi.The morphological characteristics and genotype were confirmed in 48 strains of eubacteria and 31 strains of 52 filamentous fungi (90.3%).The 4 groups of fungi were classified by genotype as follows:group 1 represents 22 strains including 20 strains of Fusarium solani and 2 strains of Fusarium oxysporum;group 2 represents 12 strains including 8 strains of Fusarium moniliformis,3 strains of Fusarium proliferatum and 1 strain of Fusarium incarnatum;group 3 represents 5 strains including 1 strain of Fusarium moniliformis and 4 unknown strains;group 4 represents 13 strains including 10 strains of Aspergillus spp.and 3 strains of Alternaria spp.Significant differences were found in the disease duration (P=0.00),inducing cause (P=0.03),ulcer grade (P=0.01)and outcome of the anti-fungal treatment (P=0.035)when compared between group 1 and 2 with group 3 and 4.Conclusion Filamentous fungi that cause keratitis could be correctly identified by sequencing the internal tanscribed spacer of rDNA.There are significant clinical differences among the groups classified by genotype. Key words: filamentous fungus; keratitis; genotype