Implementating a methodology for identification of Sporothrix complex isolates by MALDI-TOF ICMS

Abstract

Sporotrichosis is a subcutaneous mycosis worldwide distributed. However, Latin America, South Africa, India and Japan are areas of high endemicity. Recently, the combination of phenotypic and genotypic features suggested that Sporothrix schenckii should not be considered as a single taxon causing sporotrichosis once the 3 new species S. brasiliensis, S. globosa and S. mexicana have recently been described for the Science. Sporothrix mexicana was related with environmental samples and apparently restricted to Mexico. However, our Research Group has recently described the first case of human sporotrichosis caused by S. mexicana in Portugal [1]. A key identification for the Sporothrix complex species has now been proposed. It includes macro- and micro-morphology and auxonogram analyses using raffinose and sucrose as carbon sources. Nevertheless, identification based on this methodology could be inconclusive due to phenotypic variability within these species. In addition, conclusive species identification is reached only after partial calmodulin gene (CAL) sequence analysis. In order to show the potentiality of Matrix-Assisted Laser Desorption⁄Ionisation Time-Of-Flight Intact Cell Mass Spectrometry (MALDI-TOF ICMS) technique on the identification of Sporothrix complex species the aim of this study was to optimise the MALDI-TOF ICMS methodology for the 4 available Sporothrix isolates related with human sporotrichosis. For that proposal the type strain S. brasiliensis IPEC16490 (CBS 120339) and the reference strains S. globosa IPEC27135, S. schenckii IPEC27722 and S. mexicana MUM11.02 were used. Data obtained from the MALDI-TOF ICMS analyses show that the best spectral profiles and statistic clustering were obtained when the microbial cell were analysed on the yeast phase.