Evaluation of MALDI-TOF MS for Identification of Species in the Candida parapsilosis Complex from Candidiasis Cases.

BACKGROUND

Phenotypically identified Candida parapsilosis is actually a complex of 3 member species named Candida parapsilosis sensu stricto (CPSS), Candida orthopsilosis (CO), and Candida metapsilosis (CM), which can be identified only by molecular methods and automated methods such as MALDI-TOF mass spectrometry (MS). This study was undertaken to evaluate the VITEK MS, which uses the principle of MALDI-TOF MS for the identification of member species of C. parapsilosis complex (CPC).

METHODS

In this cross-sectional study, 126 presumptively identified and stocked isolates of CPC were included. Definite identification to species level was done by VITEK MS and PCR as the gold standard method. Clinico-demographic characters and risk factors were analyzed. Antifungal susceptibility testing was performed for fluconazole and voriconazole.

RESULTS

Twelve isolates were not identified as CPC either by VITEK MS or PCR and hence were excluded from the analysis. Out of 114 CPC isolates, 89 (78.1%), 18 (15.8%), and 7 (6.1%) isolates were identified as CPSS, CO, and CM, respectively, by VITEK MS. PCR identified 84 (79.2%), 15 (14.2%), and 7 (6.6%) isolates as CPSS, CO, and CM, respectively. However, PCR did not detect 8 isolates of CPSS detected by VITEK MS. VITEK MS showed 95.3% agreement in species identification and showed a kappa coefficient of 0.87, which is almost perfect agreement. Predominant isolations of all 3 species were from blood. Resistance was observed more in CPSS for both the azoles.

CONCLUSION

MALDI-TOF MS can be used as a rapid, reliable, cost-effective method to identify the species of CPC.