Longitudinal Genotyping of Candida dubliniensis Isolates Reveals Strain Maintenance, Microevolution, and the Emergence of Itraconazole Resistance

Abstract

We investigated the population structure of 208 Candida dubliniensis isolates obtained from 29 patients (25 human immunodeficiency virus [HIV] positive and 4 HIV negative) as part of a longitudinal study. The isolates were identified as C. dubliniensis by arbitrarily primed PCR (AP-PCR) and then genotyped using the Cd25 probe specific for C. dubliniensis. The majority of the isolates (55 of 58) were unique to individual patients, and more than one genotype was recovered from 15 of 29 patients. A total of 21 HIV-positive patients were sampled on more than one occasion (2 to 36 times). Sequential isolates recovered from these patients were all closely related, as demonstrated by hybridization with Cd25 and genotyping by PCR. Six patients were colonized by the same genotype of C. dubliniensis on repeated sampling, while strains exhibiting altered genotypes were recovered from 15 of 21 patients. The majority of these isolates demonstrated minor genetic alterations, i.e., microevolution, while one patient acquired an unrelated strain. The C. dubliniensis strains could not be separated into genetically distinct groups based on patient viral load, CD4 cell count, or oropharyngeal candidosis. However, C. dubliniensis isolates obtained from HIV-positive patients were more closely related than those recovered from HIV-negative patients. Approximately 8% (16 of 194) of isolates exhibited itraconazole resistance. Cross-resistance to fluconazole was only observed in one of these patients. Two patients harboring itraconazole-resistant isolates had not received any previous azole therapy. In conclusion, longitudinal genotyping of C. dubliniensis isolates from HIV-infected patients reveals that isolates from the same patient are generally closely related and may undergo microevolution. In addition, isolates may acquire itraconazole resistance, even in the absence of prior azole therapy.

Impact of Brief Exposure to Drugs with Antifungal Properties on the Susceptibility of Oral <b><i>Candida dubliniensis</i></b> Isolates to Lysozyme and Lactoferrin

“…However, our data indicate that exposure to drugs such as polyenes, echinocandins, azoles as well as chlorhexidine gluconate may enhance the susceptibility of Candida to lysozyme and lactoferrin, thereby increasing the defense capability of these salivary constituents towards this yeast. Interestingly, resistance of C. dubliniensis to fluconazole, voriconazole, and itraconazole has been documented previously [8][9][10]. Furthermore, resistance of C. dubliniensis to 5-fluorocytosine in isolates obtained from Kuwait and the Middle East region has also been documented [11,12].…”

“…Likewise, a breakthrough in C. dubliniensis fungemia was made in a patient during sustained exposure to voriconazole [9]. Longitudinal genotyping of C. dubliniensis isolates from patients with HIV infection has shown resistance to itraconazole, even in the absence of prior azole therapy [10]. C. dubliniensis strains resistant to 5-fluorocytosine have also been isolated in Kuwait and in the Middle East region [11,12].…”

Sucesso terapêutico da terbinafina em um caso de esporotricose

“…Microevolution is an important factor during host colonization. 15 These mutations may have occurred during the treatments, since 22 months elapsed between the first and second collection. In order to elucidate this question it would be necessary to do the RAPD with several other primers or to sequence hypervariable regions in the DNA of the isolates.…”

Rapid Differentiation of <b><i>Candida dubliniensis</i></b> from <b><i>Candida albicans</i></b> by Early <i>D</i>-Xylose Assimilation

“…Although neither C. albicans nor C. dubliniensis has high rates of antifungal drug resistance among isolates derived from blood or other body sites, the rate of azole resistance among oral isolates of C. dubliniensis from HIV-infected patients is much greater [5,6,7,8]. Easy to use, rapid assimilation methods have been developed for the differentiation of Candida glabrata from other Candida species, for instance, the GLABRATA RTT test [25] (Fumouze Diagnostics, France) and the rapid-assimilation-of-trehalose test [26].…”

“…Resistance as well as diminished susceptibility to fluconazole has also been observed in C. dubliniensis isolates obtained from HIV-infected patients [5,6]. Recently a breakthrough in C. dubliniensis fungemia occurred in a patient during prolonged exposure to voriconazole [7], and it was revealed that C. dubliniensis isolates from HIV-infected patients may acquire itraconazole resistance, even in the absence of prior azole therapy [8]. Development of such resistance may have important implications for antifungal therapy and indicate a need for a method to distinguish C. dubliniensis from Candida albicans as well as from other Candida species.…”