Fourier Transform Infrared Spectroscopy Application for Outbreak Typing in a Referral Intensive Care Unit: Phylogenetic Analysis and Clustering Cut-Off Definition.

Recently has emerged as a multi-resistant fungal pathogen, with a significant clinical impact, and is able to persist for a long time on human skin and hospital environments. It is a critical issue on the WHO fungal priority list and therefore it is fundamental to reinforce hospital surveillance protocols to limit nosocomial outbreaks. The purpose of this study was to apply Fourier transform infrared spectroscopy (FT-IR) to investigate the phylogenetic relationships among isolated strains from a outbreak at the University Intensive Care Unit of a Tertiary University hospital in Turin (Italy). To calculate a clustering cut-off, intra- and inter-isolate, distance values were analysed. The data showed the presence of a major Alfa cluster and a minor Beta cluster with a defined clustering cut-off. The results were validated by an external strain and Principal Component and Linear Discriminant Analyses. The application of FT-IR technology allowed to obtain important information about the phylogenetic relationships between the analysed strains, defining for the first time a "not WGS-based" clustering cut-off with a statistical-mathematical approach. FT-IR could represent a valid alternative to molecular methods for the rapid and cost-saving typing of strains with important clinical implications.