Fluconazole treatment is effective against a Candida albicans erg3/erg3 mutant in vivo despite in vitro resistance

Taiga Miyazaki, Yoshitsugu Miyazaki, Koichi Izumikawa, Hiroshi Kakeya, Shunichi Miyakoshi, John E. Bennett, Shigeru Kohno

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Candida albicans ERG3 encodes a sterol C5,6-desaturase which is essential for synthesis of ergosterol. Defective sterol C5,6 desaturation has been considered to be one of the azole resistance mechanisms in this species. However, the clinical relevance of this resistance mechanism is still unclear. In this study, we created a C. albicans erg3/erg3 mutant by the "Ura-blaster" method and confirmed the expected azole resistance using standard in vitro testing and the presence of ergosta-7,22-dien-3β-ol instead of ergosterol. For in vivo studies, a wild-type URA3 was placed back into its native locus in the erg3 homozygote to avoid positional effects on URA3 expression. Defective hyphal formation of the erg3 homozygote was observed not only in vitro but in kidney tissues. A marked attenuation of virulence was shown by the longer survival and the lower kidney burdens of mice inoculated with the reconstituted Ura+ erg3 homozygote relative to the control. To assess fluconazole efficacy in a murine model of disseminated candidiasis, inoculum sizes of the control and the erg3 homozygote were chosen which provided a similar organ burden. Under these conditions, fluconazole was highly effective in reducing the organ burden in both groups. This study demonstrates that an ERG3 mutation causing inactivation of sterol C5,6-desaturase cannot confer fluconazole resistance in vivo by itself regardless of resistance measured by standard in vitro testing. The finding questions the clinical significance of this resistance mechanism.

Original languageEnglish (US)
Pages (from-to)580-586
Number of pages7
JournalAntimicrobial agents and chemotherapy
Issue number2
StatePublished - Feb 2006
Externally publishedYes

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases


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