Volume 31, Number 5—May 2025
Research
Exponential Clonal Expansion of 5-Fluorocytosine–Resistant Candida tropicalis and New Insights into Underlying Molecular Mechanisms
Nissrine Abou-Chakra, Karen Marie Thyssen Astvad, Jan Martinussen, Amalie Sofie Eilsø Munksgaard, and Maiken Cavling Arendrup
Table 3
Overview of target gene mutations found in Candida tropicalis isolates in study of clonal expansion of 5-fluorocytosine–resistant C. tropicalis, Denmark
| Amino acid alteration | Mutation type | No. strains | Total strains, N = 104 | Expected effect on protein | Modal MIC, mg/L (range)† |
|---|---|---|---|---|---|
| FCY2 | |||||
| E49X | Nonsense (homozygous) | 30 (R) | 32 (R) | Premature termination, loss of function | >16, non–wild-type |
| Q7X | Nonsense (homozygous) | 1 (R) | 32 (R) | Premature termination, loss of function | >16, non–wild-type |
| K6NfsX10 | Single-nucleotide deletion (homozygous) | 1 (R) | 32 (R) | Frameshift leading to premature termination, loss of function | >16, non–wild-type |
| E49X & M162I | Heterozygous | 12 (S) | 72 (S) | No significant impact on transporter function | 0.125 (0.06–0.5) |
| H201I | Heterozygous | 1 (S) | 72 (S) | No significant impact on transporter function | 0.125 |
| I473L | Heterozygous | 2 (S) | 72 (S) | No significant impact on transporter function | (0.06–0.125) |
| M130T | Heterozygous | 1 (S) | 72 (S) | No significant impact on transporter function | 0.25 |
| M162I | Heterozygous | 1 (S) | 72 (S) | No significant impact on transporter function | 0.125 |
| S108F | Heterozygous | 1 (S) | 72 (S) | No significant impact on transporter function | 0.06 |
| W67X | Heterozygous | 1 (S) | 72 (S) | Discrete impact on transporter function | 0.5 |
| S258X |
Heterozygous |
1 (S) |
72 (S) |
No significant impact on transporter function |
0.25 |
| FUR1 | |||||
| K5Q & A157S |
Homozygous |
1 (S) |
72 (S) |
No impact on 5-FC conversion |
0.125 (0.06–0.5) |
| URA3 | |||||
| K177E | Homozygous | 30 (R) + 2 (S) | 32 (R) + 72 (S) | No impact on protein function | 0.125 (0.06–0.5) |
*Strains were wild-type except as indicated. FCY2, purine-cytosine permease; FUR1, uracil phosphoribosyltransferase; R, resistant (non–wild-type); S, susceptible (wild-type); URA3, orotidine-5'-phosphate decarboxylase †Modal MIC value presented for alterations represented by >10 isolates, MIC range in parentheses for alterations represented by <10 isolates, and MIC value for alterations found in a single isolate. For comparison, modal MIC for wild-type population is 0.125 mg/L.
Page created: April 14, 2025
Page updated: April 25, 2025
Page reviewed: April 25, 2025
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