Microsatellite Length Polymorphism for DNA-Based Typing of Candida albicans Isolated from HIV Positive Patients in Tehran, Iran

The importance of Candida albicans as the most common cause of fungal infections in humans is undeniable. Genotyping methods have been developed as useful tools to differentiate between fungal strains isolated from various infections. Several molecular typing methods have been described for C. albicans, and fragment length analysis of microsatellites called microsatellite fragment length polymorphism (MLP) is one of the most accurate genotyping methods.
The present study aimed at evaluating the genetic diversity and genetic relationships among C. albicans isolates recovered from HIV-positive patients with oral candidiasis in Iran using MLP.
We analyzed 30 isolates of C. albicans obtained from HIV-positive patients in Tehran. Genotypes of C. albicans isolates associated with oropharyngeal candidiasis were determined using microsatellite length polymorphism analysis. Three loci including EF3, CDC3, and HIS3 were amplified using multiplex PCR. After amplification, the product was run on an automated single-capillary genetic analyzer, and band sizes (known as alleles) were calculated with gene scan mapper.
PCR MLP typing of the 30 isolates under study yielded 27 different profiles, and the discriminatory power index was obtained as 0.993. Ten alleles and 18 different combinations were detected for the EF3 gene, 7 alleles and 18 combinations for the EF3 gene, and 10 alleles and 14 combinations for the HIS3 gene. Only 2 isolates were homozygous in all the 3 loci. To identify the origin of superficial infections in 6 patients, C. albicans isolates from the superficial as well as oral samples were simultaneously genotyped. Results showed the identity of genotypes in 4 of these patients. For 1 patient, the C. albicans genotype of the nails was different from the genotype observed in the oral cavity, which raised the possibility of an exogenous source for the superficial infection. Also, there were changes at only 1 or 2 alleles, which represented microevolution in some isolates.
The high variation of genotypes throughout the population of C. albicans suggested that the microsatellite fragment length polymorphism using multiplex PCR-based system provided high-speed genotyping, indicating its usefulness in molecular epidemiological evaluation.