Molecular heterogeneity of fluconazole‐resistant and ‐susceptible oral Candida albicans isolates within a single geographic locale

The emergence of drug‐resistant Candida albicans in immunocompromised patients is common. A disconcerting aspect of this phenomenon is the rapid emergence of C. albicans strains that are resistant to a widely used azole drug, fluconazole (FLZ). To understand the origin of FLZ‐resistant yeast isolates, we investigated molecular profiles of 20 geographically related oral C. albicans isolates using three genotyping methods: randomly amplified polymorphic DNA‐PCR, with six different primers (OBU1, OBU2, OBU3 RSD6, RSD11 and RSD12); electrophoretic karyotyping by pulsed‐field gel electrophoresis; and Hinf I restriction fragment analysis. Of the 20 isolates studied, 10 were FLZ‐ resistant and originated from patients with oral candidosis with a history of FLZ therapy, and the remainder were FLZ susceptible from individuals with oral candidosis, but without a history of FLZ therapy. A composite genotype was generated for each strain by combining molecular types derived from the three independent molecular methods. The composite profiles indicated genetic diversity amongst both the FLZ‐resistant as well as ‐sensitive isolates, and no specific features emerged distinguishing the drug‐resistant and ‐sensitive groups. These observations cast doubt on the theory of a clonal origin of FLZ‐resistant C. albicans isolates.