The A756T Mutation of the Gene Associated With Resistance to Itraconazole in Isolated From Mycotic Mastitis of Cows.

() has been recently recognized as an important pathogen involved in mycotic mastitis of cows. The phenotypic and molecular characteristics of 15 clinical isolates collected from cows with clinical mastitis in three herds of Yinchuan, Ningxia, were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. In addition to sequencing analysis, the gene that encodes 14α-demethylases, the expression of the gene, and efflux transporters and in itraconazole-susceptible (S), itraconazole-susceptible dose dependent (SDD), and itraconazole-resistant (R) isolates was also quantified by a quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) assay. Sequencing analysis revealed three synonymous codon substitutions of the gene including T939C, A756T, and T642C in these clinical isolates. Among them, T642C and T939C mutations were detected in itraconazole-resistant and -susceptible isolates, but the A756T substitution was found only in itraconazole-resistant isolates. Importantly, the expression of the gene in itraconazole-resistant isolates was significantly higher compared with itraconazole-SDD and itraconazole-susceptible isolates ( = 0.052 and = 0.012, respectively), as determined by the qRT-PCR assay. Interestingly, the expression of the gene was also significantly higher in itraconazole-resistant isolates relative to the itraconazole-SDD and itraconazole-susceptible strains. Notably, the expression of was positively associated with resistance to itraconazole ( = 0.4177 in SDD compared with S, = 0.0107 in SDD with R, and = 0.0035 in S with R, respectively). These data demonstrated that mutations of the gene were involved in drug resistance in . The A756T synonymous codon substitution of the gene was correlated with an increased expression of drug-resistant genes including and in itraconazole-resistant isolates examined in this study.