title: Inactivation of sterol Delta5,6-desaturase attenuates virulence in Candida albicans.
abstract: Two clinical Candida albicans isolates that exhibited high-level resistance to azoles and modest decreases in susceptibility to amphotericin B were cultured from unrelated patients. Both isolates harbored homozygous nonsense mutations in ERG3, which encodes an enzyme, sterol Delta5,6-desaturase, involved in ergosterol synthesis. Extraction and analysis of the sterols from both isolates confirmed the absence of sterol Delta5,6-desaturase activity. Although the loss of sterol Delta5,6-desaturase activity is known to confer resistance to azoles, this mechanism of resistance has rarely been seen in clinical isolates, suggesting that such mutants are at a competitive disadvantage. To test this hypothesis, the virulence of the erg3 mutants was assayed by using a mouse systemic infection model. The mutants were significantly less virulent than the wild-type comparator strains. However, the kidney fungal burdens in mice infected with the erg3 mutants were similar to those in mice infected with the wild-type strains. Similar results were obtained by using a laboratory-generated homozygous erg3 deletion mutant (D. Sanglard et al., Antimicrob. Agents Chemother. 47:2404-2412, 2003). Reintroduction of a wild-type ERG3 allele into the homozygous deletion mutant restored virulence, ergosterol synthesis, and susceptibility to azoles, confirming that these phenotypic changes were solely due to the inactivation of Erg3p.
authors.affiliation: Schering Plough Research Institute, K15-4-4700, 2015 Galloping Hill Road, Kenilworth, NJ 07033. paul.mcnicholas@spcorp.com.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Chau
authors.forename: Maya
authors.initials: M
authors.lastname: Gurnani
authors.forename: Robyn
authors.initials: R
authors.lastname: Hawkinson
authors.forename: Michel
authors.initials: M
authors.lastname: Laverdiere
authors.forename: Anthony
authors.initials: A
authors.lastname: Cacciapuoti
authors.forename: Paul M
authors.initials: PM
authors.lastname: McNicholas
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D001393:Azoles / Q000494:pharmacology; D002176:Candida albicans / Q000187:drug effects* / Q000201:enzymology / Q000472:pathogenicity*; D002177:Candidiasis / Q000382:microbiology; D004271:DNA, Fungal / Q000096:biosynthesis; D025141:Drug Resistance, Fungal; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005838:Genotype; D007668:Kidney / Q000382:microbiology; D051379:Mice; D008826:Microbial Sensitivity Tests; D009154:Mutation / Q000502:physiology; D010088:Oxidoreductases / Q000037:antagonists & inhibitors* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000935:Antifungal Agents; D001393:Azoles; D004271:DNA, Fungal; D004791:Enzyme Inhibitors; D010088:Oxidoreductases; C039306:sterol delta-5 desaturase