Tebuconazole Induced Resistance To Triazole Antifungal Agents In Aspergillus Fumigatus

Resistance to medical triazole medicals has been frequently reported in Aspergillus fumigatus isolates,and became a major clinical problem.Triazole fungicides were used widely used in agricultural production all over the world.It has a vital significance to understand the relationship between applications of triazole fungicides and the resistance in A.fumigatus aganist medical triazoles.Four strains of A.fumigatus,which are sensitive to triazole medicals,were isolated from the greenhouses in Zhejiang province.A significant reduction in the susceptibility of these strains to triazole medicals was obsserved with their successive exposure to tebuconazole.High resistance of these reduced strains with MICs of 16 mg/L to voriconazole was found in the experiments.It was found that mutations of TR46/Y121F/T289A in cyp51A occurred in all of the tebuconazole induced strains,suggesting that the use of tebuconazole in agriculture might induce triazole resistance related mutations in cyp51A of A.fumigatus.To analyze the relationship between the mutations of TR46/Y121F/T289A and resistance of A.fumigatus to triazole medicals,recombinant plasmids with and without mutations(TR46/Y121F/T289A)in the cyp51A gene were constructed.Compared to the controls,the resistance to triazole medicals was observed in of mutant transformants,indicating that the mutations of TR46/Y121F/T289A in the cyp51A gene might closely be related the resistance of A.fumigatus.Relative expression quantity of cyp51A gene was measured by qRT-PCR,and the results showed that relative expression quantity of mutant transformants and tebuconazole-induced strain was significantly increased comparing to the wild-type strain.Metabolic resistance and resistance stability of resistance strain were studied.The data indicated that all of the tebuconazole induced strains are not capable of metabolizing the target traizole medicals.It might be concluded that the resistance of tebuconazole induced strains to medical triazole is mainly derived from mutations in cyp51A gene.This genetic mutations based resistance was found to be hereditary stability.The results obtained in this study indicated that resistance of A.fumigatus to triazole medicals could be induced by tebuconazole.This might imply that the widely application of tebuconazole might be a driving force for clinical resistance of A.fumigatus.