Liquid Extraction Surface Analysis Mass Spectrometry of ESKAPE Pathogens.

The ESKAPE pathogens (, , , , , and ) represent clinically important bacterial species that are responsible for most hospital-acquired drug-resistant infections; hence, the need for rapid identification is of high importance. Previous work has demonstrated the suitability of liquid extraction surface analysis mass spectrometry (LESA MS) for the direct analysis of colonies of two of the ESKAPE pathogens ( and ) growing on agar. Here, we apply LESA MS to the remaining four ESKAPE species ( E745, KP257, AYE, and S11) as well as V583 (a close relative of ) and a clinical isolate of AC02 using an optimized solvent sampling system. In each case, top-down LESA MS/MS was employed for protein identification. In total, 24 proteins were identified from 37 MS/MS spectra by searching against protein databases for the individual species. The MS/MS spectra for the identified proteins were subsequently searched against multiple databases from multiple species in an automated data analysis workflow with a view to determining the accuracy of identification of unknowns. Out of 24 proteins, 19 were correctly assigned at the protein and species level, corresponding to an identification success rate of 79%.