Mi-Kyung Lee1, Laura E Williams, David W Warnock, Beth A Arthington-Skaggs. 1. Mycotic Diseases Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, N.E., Mailstop G-11, Atlanta, Georgia 30333, USA.
Abstract
OBJECTIVES: To investigate possible molecular mechanisms of azole resistance among fluconazole-susceptible bloodstream isolates of Candida albicans that displayed the trailing growth phenomenon, and to compare these isolates with bloodstream and mucosal isolates that showed reduced susceptibilities to fluconazole. METHODS: Twelve C. albicans isolates-seven trailing and five susceptible dose dependent (SDD) or resistant (R)-were screened for ERG11 mutations by DNA sequencing and quantification of ERG11, CDR1 and MDR1 expression by RT-PCR using the LightCycler high-speed PCR system. RESULTS: SDD and R isolates possessed more homozygous ERG11 mutations than did the trailing isolates. Two of these, V404I and V509M, have not been described previously and were found exclusively in fluconazole SDD and R isolates. Quantification of ERG11 expression revealed that both trailing and SDD and R isolates were capable of ERG11 up-regulation in response to fluconazole, although the SDD and R isolates showed maximal up-regulation at higher fluconazole concentrations. Quantification of CDR1 and MDR1 revealed that all isolates, regardless of in vitro fluconazole response, were capable of CDR1 and MDR1 up-regulation following fluconazole exposure. Furthermore, the SDD and R isolates expressed higher constitutive levels of CDR1 and MDR1 or CDR1, respectively, in the absence of drug compared with trailing isolates. CONCLUSIONS: Trailing isolates, although susceptible to fluconazole, express the same molecular mechanisms as SDD and R isolates following fluconazole exposure but regulate them differently.
OBJECTIVES: To investigate possible molecular mechanisms of azole resistance among fluconazole-susceptible bloodstream isolates of Candida albicans that displayed the trailing growth phenomenon, and to compare these isolates with bloodstream and mucosal isolates that showed reduced susceptibilities to fluconazole. METHODS: Twelve C. albicans isolates-seven trailing and five susceptible dose dependent (SDD) or resistant (R)-were screened for ERG11 mutations by DNA sequencing and quantification of ERG11, CDR1 and MDR1 expression by RT-PCR using the LightCycler high-speed PCR system. RESULTS: SDD and R isolates possessed more homozygous ERG11 mutations than did the trailing isolates. Two of these, V404I and V509M, have not been described previously and were found exclusively in fluconazole SDD and R isolates. Quantification of ERG11 expression revealed that both trailing and SDD and R isolates were capable of ERG11 up-regulation in response to fluconazole, although the SDD and R isolates showed maximal up-regulation at higher fluconazole concentrations. Quantification of CDR1 and MDR1 revealed that all isolates, regardless of in vitro fluconazole response, were capable of CDR1 and MDR1 up-regulation following fluconazole exposure. Furthermore, the SDD and R isolates expressed higher constitutive levels of CDR1 and MDR1 or CDR1, respectively, in the absence of drug compared with trailing isolates. CONCLUSIONS: Trailing isolates, although susceptible to fluconazole, express the same molecular mechanisms as SDD and R isolates following fluconazole exposure but regulate them differently.
Authors: M J Espy; J R Uhl; L M Sloan; S P Buckwalter; M F Jones; E A Vetter; J D C Yao; N L Wengenack; J E Rosenblatt; F R Cockerill; T F Smith Journal: Clin Microbiol Rev Date: 2006-01 Impact factor: 26.132
Authors: K Niimi; K Maki; F Ikeda; A R Holmes; E Lamping; M Niimi; B C Monk; R D Cannon Journal: Antimicrob Agents Chemother Date: 2006-04 Impact factor: 5.191