CComparison of Candida species identification tests using conventional and molecular-based assays

Abstract

Candida is a clinically important pathogen, as attested by several reports of Candidalinfections. Some strains may cause severe diseases, high mortality rate and are drug resistant. Rapid, specific, and accurate diagnostic methods are needed for effective treatment for infected patients. The objective of this study was to compare identification methods for Candida spp. which are suitable for routine work in various laboratory contexts. The identification methods were CHROM agar, assimilation test, MALDI-TOF MS, and nucleic acid sequencing. Thirty-one Candida isolates were cultured on Sabouraud dextrose agar. Species identification by colony characterization, sugar utilization pattern and mass spectra were determined using CHROM agar, assimilation test and MALDI-TOF MS, respectively. The Candida species were confirmed by nucleotide sequencing of internal transcribed spacer regions as a reference method of this study. C. tropicalis, C. albicans, and C. krusei (Pichia kudriavzevii) strains exhibited 100% consistent test results. Two species of C. glabrata and C. parapsilosis complex showed 87.1% accuracy of CHROM agar, while assimilation test and MALDI-TOF MS showed 100% accuracy compared with the sequencing method. The turnaround time for MALDI-TOF MS was approximately 30 minutes, while the CHROM agar and assimilation test took about 48-72 hours, and the sequencing time was about 2-7 days. Fast and accurate method of Candida species identification is important to the patient treatment process. Traditional and standard methods used may have some limitations for species identification compared to newer techniques like MALDI-TOF MS. However, the new techniques also require operator experience and laboratory readiness. Turnaround time, cost expense on machine maintenance, price of chemical reagents were the important factors considered for selecting the most appropriatemethod for routine laboratory testing.