TABLE 1.

Susceptibilities to 5FC, 5FU, and FLC of C. lusitaniae wild-type strain 6936, null mutants, and the revertant strains constructed for this studya

Strain or genotypeMIC (μg/ml)Growth in RPMI containing 5FC-FLCd
5FC5FUFLC
6936≤0.5≤0.52.0
fcy2Δ::REP-URA3-REPb64.0≤0.52.0+ (4-16)
fcy1Δ::REP-URA3-REPb128.0≤0.52.0+ (8-32)
fur1Δ::REP-URA3-REPb≥512.0≥512.02.0
fcy2Δ::[FCY2-URA3]::REPc≤0.5≤0.52.0
fcy1Δ::[FCY1-URA3]::REPc≤0.5≤0.52.0
  • a Susceptibility testing was performed by microdilution assays with RPMI medium according to CLSI (formerly NCCLS) standards (7) and as described previously (3, 8) by routinely using the quality control strain Candida krusei ATCC 6258.

  • b Null mutants were derived from auxotrophic strain 6936 ura3[D95V].

  • c Engineered revertants were derived from complementation experiments.

  • d Testing for the occurrence of 5FC-FLC cross-resistance was performed by using a 5FC concentration gradient from 256 to 0.5 μg/ml in association with a constant concentration of 16 μg/ml FLC. Values in parentheses correspond to the ranges of 5FC concentrations (in μg/ml) that allowed the growth of the strains (+); −, no growth.