Dermatophytes are filamentous fungi, which in the majority of cases cause superficial infections of the skin, hair and nails. In clinical laboratory, they are routinely identified with the combined use of cultivation, microscopy of the morphological characteristics and MALDI-TOF MS. However, because dermatophytes are slow growing fungi it is necessary to wait from one to four weeks for a reliable identification.
The purpose of this master’s dissertation was firstly to compare two methods, MALDI-TOF MS and multiplex qPCR, and secondly to evaluate whether these two methods provide good enough dermatophyte identification. Moreover, we wanted to establish a better identification protocol for the most clinically common dermatophytes and introduce it into the standard operating procedures in the clinical laboratory as an addition to morphological identification. In this way we would be able to shorten the time needed for diagnosis and lower the chance of subjective errors. Finally, we wished to attain a better identification with MALDI-TOF MS, and henceforth compared two different solid growing media for dermatophyte cultivation.
Keeping this in mind, we cultivated 103 dermatophyte positive samples, which were sent to the Laboratory for Diagnostics of Fungal Infections at the Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana as clinical samples for diagnostic testing, on two solid growth media i.e., SCA and ID-Fungi Plates, as well as in a liquid growing medium TIO. After 3-5 days we identified the cultures with MALDI-TOF MS. From the liquid medium TIO we isolated the dermatophyte DNA with MagnaCycler and kept it frozen at -20 ␃ until we processed the samples with the DermaGenius® 2.0 kit which uses the multiplex qPCR method as an identification technique.
The results of our study indicate that the analytical specificity of MALDI-TOF MS is improved when the dermatophytes are cultured on ID-Fungi Plates instead of SCA. Secondly the results indicate that multiplex qPCR has a greater analytical specificity compared to MALDI-TOF MS. Therefore, the study points to the conclusion that with additional verification, multiplex qPCR is a promising method with which we could improve the classical identification method that is used in the routine laboratory today.