2.2 MALDI-TOF MS identification
A small amount of biomass from each isolate was spotted onto the MALDI target plate, covered with 1μl of formic acid 100% for on-plate protein extraction and allowed to dry. Then, 1μl of organic matrix (α-ciano-3,4-hidroxicinamic acid -HCCA-) was added and allowed to dry again prior to MALDI-TOF MS analysis. Strains were identified with an MBT Smart MALDI Biotyper (Bruker Daltonics, Bremen, Germany) using the updated database containing 9957 reference spectra profiles.