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Journal of Clinical Microbiology, August 2005, p. 4026-4036, Vol. 43, No. 8
0095-1137/05/$08.00+0     doi:10.1128/JCM.43.8.4026-4036.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Novel 5-Flucytosine-Resistant Clade of Candida dubliniensis from Saudi Arabia and Egypt Identified by Cd25 Fingerprinting

Microbiology Research Division, Dublin Dental School and Hospital, Trinity College, University of Dublin, Dublin 2, Republic of Ireland,¹ Department of Clinical Microbiology and Infectious Diseases, The Hebrew University-Hadassah Medical Center, Jerusalem, Israel,² Jeddah Kidney Center, King Fahad Hospital, Jeddah, Saudi Arabia,³ National Cancer Institute, Cairo, Egypt,⁴ Medical Mycology Unit, Department of Pathology, College of Medicine, King Khalid University Hospital, Riyadh, Saudi Arabia,⁵ Microbiology Laboratory, Department of Pathology & Laboratory Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia⁶

Received 10 March 2005/ Returned for modification 25 April 2005/ Accepted 28 April 2005

DNA fingerprinting of Candida dubliniensis isolates using the species-specific probe Cd25 previously showed that this species consists of two distinct groups, termed Cd25 group I and Cd25 group II. The present study investigated the population structure of 30 C. dubliniensis oral isolates from Saudi Arabia and Egypt using Cd25 fingerprinting and rRNA gene internal transcribed spacer region-based genotyping. Cd25 fingerprinting analysis of these isolates revealed two distinct populations, the first of which consisted of 10 closely related genotype 1 isolates (average similarity coefficient [S_AB] value, 0.86). The second population of 20 isolates was much more heterogeneous (average S_AB value, 0.35) and consisted of two distinct subpopulations, one of which consisted of genotype 3 isolates (n = 13) and the other of genotype 4 isolates (n = 7). A mixed dendrogram generated from the fingerprint data from the 30 Saudi Arabian and Egyptian isolates, 5 Israeli isolates, and 51 previously characterized international isolates (32 of Cd25 group I and 19 of Cd25 group II) revealed the presence of three distinct main clades. The first corresponded to the previously described Cd25 group I and contained all the Saudi Arabian, Egyptian, and Israeli genotype 1 isolates mixed with international isolates. The second clade corresponded to the previously described Cd25 group II and contained three Israeli isolates, one genotype 2 isolate, one genotype 3 isolate, and a genotype 4 variant isolate, which were mixed with international isolates. The third clade has not been described before and consisted solely of the 20 Saudi Arabian and Egyptian genotype 3 and 4 isolates identified in this study and a previously described genotype 4 Israeli isolate. All 20 Cd25 group III isolates exhibited high-level resistance to 5-flucytosine (MIC 128 µg/ml), whereas all Cd25 group I and Cd25 group II isolates tested (10 Saudi Arabian and Egyptian, 16 Israeli, and 24 international) were susceptible to 5-flucytosine (MIC 0.125 µg/ml). The results of this study show for the first time the presence of a novel 5-flucytosine-resistant clade of C. dubliniensis (Cd25 group III) that is predominant among isolates from Saudi Arabia and Egypt and absent from a previously characterized international collection of 98 isolates from 15 countries.

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