Mechanism of fluconazole resistance of Candida tropicalis in clinical isolates

Objective To investigate fluconazole resistance of C and ida tropica lis and its molecular mechanism.Methods One hundred and forty-two clinical isolates of Candida tropicalis were collected.Fluconazole suscep tibility was tested in vitro wtth broth microdilution method M 27-A2.The CtERG11 genes of Candida tropicalis were am plified and sequenced.Results Of the 142 isolates collected,128(90.1%)were susceptible to fluconaz loe,4(2.8%)we resuscep tible dose-dependent(S-DD)and 10(7.1%)were fluconazo le-resistant.The C tERG11 gene sequences of Candida tropica lisiso lates were compared with that of Candida tropicalis ATCC 750 and the fluconazole-susceptible strains were completely identical with Candida tropicalis ATCC 750.Two silent mutations of G1362A and C1404T were detected in the fluconzaloe S-DD strains;sevennucleo tide substitutions of T225C,A 242C,T243C,G264A,A 395T,C461T and G1362A were found in the four fluconazole-resistant isolates,which resulted in missense mutations of D81A,Y132F and S154F.The nucleotide substitutions of A 242C,T243C,G1362A and C1404T were detected and D81A was a novel aminomutation.Conclusion The fluconazole-resistant rate of Candida tropicalisis 7.1% and the missense mutations of D81A,Y132F,and S154F in CtERG11 geneseem to be associated with the fluconaz loeres is tance of Candida tropic lis.