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Volume 31, Number 7—July 2025

Research

Emergence of Flucytosine-Resistant Candida tropicalis Clade, the Netherlands

Fatima Zohra Delma1, Bram Spruijtenburg1, Jacques F. Meis, Auke W. de Jong, James Groot, Johanna Rhodes, Willem J.G. Melchers, Paul E. Verweij, Theun de Groot, Eelco F.J. Meijer2, and Jochem B. Buil2Comments to Author 
Author affiliation: Radboud University Medical Center, Nijmegen, the Netherlands (F.Z. Delma, B. Spruijtenburg, J.F. Meis, J. Rhodes, W.J.G. Melchers, P.E. Verweij, T. de Groot, E.F.J. Meijer, J.B. Buil); Canisius-Wilhelmina Hospital (CWZ)/Dicoon, Nijmegen (B. Spruijtenburg, T. de Groot, E.F.J. Meijer); University of Cologne, Cologne, Germany (J.F. Meis); National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands (A.W. de Jong, J. Groot, P.E. Verweij)

Main Article

Table

Reported 5-FC resistance rates in different published reports in study of non–wild-type Candida tropicalis clade, the Netherlands*

Total no. isolates Year collected Body site of isolation Methods used† Country MIC criteria,‡ mg/L No. (%) isolates with elevated 5-FC MICs Reference
70
 NA
 NA
 NA
 France
 NA
 NA (80)
 (26)
60
 NA
 Different sites
 Disc diffusion test, macrodilution with YNBG broth
 United Kingdom
 I, 2–8 6 (10) (27)
R, >8
17 (28)
30
 NA
 NA
 NCCLS
 Italy
 I, 8–16; R, >32
0
 (28)
117
 1998–2000
 Different sites
 NCCLS
 Spain
 I, 8–16 6 (5.1) (29)
R, >32
 0
759
 1992–2001
 Different sites
 NCCLS
 Worldwide collection§
 I, 8–16 60 (1) (16)
R, >32
 NA (7)
33
 2000–2001
 Blood
 CLSI M27-A2
 United States
 I, 8–16 0 (30)
R, >32
 1 (3)
34
 NA
 NA
 ATB Fungus
 Spain
 R, >32
3 (8.8)
 (31)
62
 2001–2002
 Blood
 NCCLS M27-A2
 Japan
 R, >32
NA (8.1)
 (32)
60
 2004–2006
 Different sites
 CLSI M27-A2, Etest
 Germany
 R, >32
NA (58.3)
 (33)
130
 2002–2006
 Blood
 EUCAST
 France
 R, >8
45 (35)
 (18)
97
 2006
 NA
 Etest
 Taiwan
 I, 8–16 1 (1) (34)
R, >32
 NA
303
 NA
 Blood
 CLSI M27-A3
 United States
 I, 8–16 5 (1.65) (35)
R, >32
 4 (1.32)
149
 2007–2008
 Blood
 VITEK-2
 South Korea
 I, 8–16; R, >32
0
 (36)
126
 NA
 Blood
 CLSI M27-A3
 Worldwide collection¶
 NA
 NA (10.3)
 (37)
359 2008–2024 Different sites EUCAST The Netherlands >16 106 (29.5) (17)

*CLSI, Clinical and Laboratory Standards Institute; EUCAST, European Committee on Antimicrobial Susceptibility Testing; 5-FC, flucytosine; I, intermediate resistance; NA, not applicable; NCCLS, National Committee for Clinical Laboratory Standards; R, resistant; YNBG, yeast nitrogen base glucose. †CLSI was formerly known as NCCLS. CLSI M27 broth dilution method for yeast (38). ATB Fungus test, Etest, and VITEK-2 were purchased from bioMérieux (https://www.biomerieux.com). ‡Resistance status and MICs used to interpret level of resistance to 5-FC in each study. §North America, Latin America, Europe, and Asia-Pacific. ¶United States, Europe, Latin America, and the Asia-Pacific region.

Main Article

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Main Article

1These first authors contributed equally to this article.

2These senior authors contributed equally to this article.

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