Inactivation of sterol Delta5,6-desaturase attenuates virulence in Candida albicans.
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.
Chau
Andrew S
AS
Schering Plough Research Institute, K15-4-4700, 2015 Galloping Hill Road, Kenilworth, NJ 07033. paul.mcnicholas@spcorp.com.
Gurnani
Maya
M
Hawkinson
Robyn
R
Laverdiere
Michel
M
Cacciapuoti
Anthony
A
McNicholas
Paul M
PM
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
D000935:Antifungal Agents; D001393:Azoles; D004271:DNA, Fungal; D004791:Enzyme Inhibitors; D010088:Oxidoreductases; C039306:sterol delta-5 desaturase