The ESKAPE pathogens (
Enterococcus faecium
,
Staphylococcus aureus
,
Klebsiella pneumoniae
,
Acinetobacter baumannii
,
Pseudomonas aeruginosa
, and
Enterobacter cloacae
) 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
(
Staphylococcus aureus
and
Pseudomonas aeruginosa
) growing on agar. Here, we apply LESA MS to the remaining four ESKAPE
species (
E. faecium
E745,
K. pneumoniae
KP257,
A. baumannii
AYE, and
E. cloacae
S11) as well as
E. faecalis
V583 (a close relative
of
E. faecium
) and a clinical isolate of
A. baumannii
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%.