Title: Genetic relatedness of Candida albicans clinical isolates from Candida bloodstream infections in a Malaysian population
Abstract: Background: Candida is an opportunistic eukaryotic diploid fungus, which can cause bloodstream infections (BSIs) in immunocompromised or immunodeficient persons. With candidemia representing the most common BSI, its frequency is increasing drastically worldwide, even with antifungal treatment, resulting in high mortality and morbidity rates. The aim of this study was to investigate the genetic relatedness of the most prevalent Candida species in Candida BSIs in a Malaysian population via Randomly Amplified Polymorphic DNA (RAPD)-PCR fingerprinting. Methods: Forty-four Candida BSI blood cultures were originally obtained from University Malaya Medical Centre (UMMC). The blood cultures were then cultured and maintained on Sabouraud's Dextrose agar (SDA), after which genomic DNA was extractd from single colonies. Polymerase chain reaction (PCR) and gel electrophoresis was then carried out on the isolated DNA using ITS1 and ITS4 pan-fungal primers to amplify the fungal internal spacer conserved regions. CHROMagar™ Candida was used culture clinical isolates to confirm their identity.These two methods were combined to conclude the predominant causative species of Candida in these BSIs. Clinical isolates of the predominant Candida species were then genotyped via RAPD-PCR fingerprinting using PST, an arbitrary oligonucleotide primer. Computer-assisted clustering analysis and construction of the phylogenetic tree was carried out to analyze the genetic relatedness of these clinical isolates. Results: The consolidated results of the molecular and biochemical methods of Candida spp identification showed that C. albicans is the most prevalent species (31.81%), with fourteen clinical isolates out of forty-four. RAPD-PCR fingerprinting resulted in eight distinctive polymorphic bands. The average SAB value of the fourteen C. albicans clinical isolates was 0.733 ± 0.172, hence describing the overall non-relatedness of these isolates. When analyzing the results individually, only five of the fourteen were observed to be similar, with SAB values of 1.00 each. Four isolates had SAB values of 0.80-0.99, which suggests that microevolution might have occurred and that these clinical isolates possibly belong to different strains. The remaining five isolates were unrelated (SAB of <0.80). Conclusion: The observations from this study may provide useful insights into the Candida albicans population structure and epidemiology in Malaysian Candida BSIs, as well as its mode of propagation.