Objectives: The aim of this study was to determine the mating type of oral Candida glabrata isolates taken from two patients over several weeks. Our goal was to determine whether there may be any correlation between the expressed mating type gene and the development of resistance to fluconazole in serial isolates. Methods: Six C. glabrata isolates from two patients who developed resistance during fluconazole treatment for oral candidiasis were collected and maintained on SAB agar plates. The strains were grown in YPD liquid medium for 5-6hrs at 37?C prior to RNA extraction. Total RNA from all isolates was resolved through a formaldehyde agarose gel before transfer onto a nylon membrane. Fragments of the Mata1 and Mata1 open reading frames were PCR amplified from C. glabrata genomic DNA using standard techniques: these were subsequently used as probes following labeling with 32P through random priming, using the Ready-To-Go DNA labeling beads(-dCTP) according to the manufacturer's instructions. Northern blot hybridization was performed following the Church and Gilbert procedure. After high stringency washing, the membrane was exposed to film with intensifying screens at -80?C for 1-5 days before photographic development. The membrane was stripped prior to hybridization with a different probe. Results: Northern blot analysis showed that the isolates were of the MTLa “mating” type. The band seen near 400 bp was consistent with the transcript previously identified for this gene. Conclusions: A previous study indicated that the MTLa1 locus is more commonly expressed in Candida glabrata isolates. However, our two strains were of the MTLa mating type and remained so at each isolation. s28 Candida glabrata strains expressing the MTLa1 gene developed resistance to azole drugs. Resistance to azoles does not appear to be directly related to the MTL locus expressed in these isolates. Supported by NIH/NIDCR Grant #DE11381-05, Dental Oncology Education Program

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