A total of 30
C. albicans isolates were collected from patients with HIV and OPC in Tehran, Iran. Moreover,
C. albicans was isolated from 8 out of 30 patients with recurrent OPC in 2 different episodes. To identify the origin of cutaneous and nail infections in six patients,
C. albicans isolates, as well as isolates related to OPC were analyzed.
C. albicans isolates were collected from CHROMagar Candida and Sabouraud dextrose agar media after incubation for 72 hours at 35°C. Phenotypic identification was confirmed using different tests including chlamydospore production, colony morphology on CHROM agar, and carbohydrate assimilation using rapid yeast identification system (Remel Inc., USA) (
14,
15).
For DNA extraction, a physicochemical method was applied. A portion of the yeast colony was washed with phosphorous-buffered saline containing 50 mM EDTA and 0.5% SDS. Afterwards, the freeze-thawing method with glass beads was applied to disrupt the yeasts. After centrifugation for 2 minutes at 12,000 g, lysis buffer (500 mL) was added to the precipitate, followed by incubation for 10 minutes. Potassium acetate buffer (150 µL, pH = 4.8; 28.5 mL of distilled water; 60 mL of 5 M potassium acetate; 11.5 mL of glacial acetic acid) was then added to the tube and vortexed for a short period.
Centrifugation (2 minutes at 12,000 g) was used to remove the precipitated proteins and cell debris. The supernatant was transferred to a microtube and centrifuged for 2 minutes at 12,000 g. After decanting the supernatant to a new microtube (1.5 mL), isopropyl alcohol was added with an equal volume. The tube was briefly mixed via inversion and centrifuged for 2 minutes at 12,000 g. After removing the supernatant, the DNA pellet was washed 3 times in 70% ethanol (300 µL). The supernatant was discarded after centrifugation for 1 minute at 12,000 g. Then, DNA was dried and dissolved in distilled water (50 µL).
To determine DNA concentration and its purification, optical density (OD) was read and run on agarose gel. To amplify the 3 loci, multiplex PCR was performed in a reaction volume of 50 µL, containing 5 mM of MgCl
2, 1X PCR buffer, 0.2 mM of each dNTP, 1.25 U of Taq gold polymerase (Applied Biosystems), 5 pmol of EF3 (Chromosome 5) primers, and 2 pmol of CDC3 (Chromosome 1), and HIS3 (chromosome 2) primers. The microsatellite markers were amplified with the primers (
Table 1), and different dyes were used to label a primer from each set. The EF3 antisense primer was stained using fluorescein amidite (FAM), CDC3 sense primer was labeled with hexachlorofluorescein (HEX), and HIS3 sense primer was labeled with NED (
16). The PCR included initial denaturation at 95°C for 10 minutes, followed by 30 cycles at 95°C for 30 seconds, at 55°C for 30 seconds, and at 72°C for 60 seconds, followed by a final extension at 72°C for 30 minutes. After amplification, 2 µL of the PCR product was added to formamide (20 µL) and 6-TAMRA Genescan 500 size standard (0.5 µL, Applied Biosystems). The samples were run on an ABI XL 370 genetic analyzer after denaturation at 95°C for 120 seconds and were placed in an ice bath. Moreover, the GeneMapper Version 5 (Applied Biosystems) was used to determine the band size (allelic number) (
13,
16,
17).