Rapid bacterial species identification and antibiotic susceptibility testing in positive blood cultures have an important impact on the antibiotic treatment for patients. To identify extended-spectrum beta-lactamases (ESBL) directly in positive blood culture bottles, we developed a workflow of saponin extraction followed by a bottom-up proteomics approach using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The workflow was applied to positive blood cultures with Escherichia coli and Klebsiella pneumoniae collected prospectively in two academic hospitals over a 4-month period. Of 170 positive blood cultures, 22 (12.9%) contained ESBL-positive isolates based on standard susceptibility testing. Proteomic analysis identified CTX-M ESBLs in 95% of these isolates directly in positive blood cultures, whereas no false positives were found in the non-ESBL producing positive blood cultures. The results were confirmed by molecular characterisation of beta-lactamase genes. Based on this proof-of-concept study, we conclude that LC-MS/MS-based protein analysis can directly identify extended-spectrum beta lactamases in E. coli and K. pneumoniae positive blood cultures, and could be further developed for application in routine diagnostics.

Additional Metadata
Keywords Beta-lactamase, Blood cultures, ESBL, Mass spectrometry, Proteomics
Persistent URL dx.doi.org/10.1007/s10096-017-2975-y, hdl.handle.net/1765/99209
Journal European Journal of Clinical Microbiology & Infectious Diseases: an international journal on pathogenesis, diagnosis, epidemiology, therapy, and prevention of infectious diseases
Citation
Fleurbaaij, F, Goessens, W.H.F, van Leeuwen, H.C, Kraakman, M, Bernards, S.T, Hensbergen, P, & Kuijper, E. (2017). Direct detection of extended-spectrum beta-lactamases (CTX-M) from blood cultures by LC-MS/MS bottom-up proteomics. European Journal of Clinical Microbiology & Infectious Diseases: an international journal on pathogenesis, diagnosis, epidemiology, therapy, and prevention of infectious diseases, 1–8. doi:10.1007/s10096-017-2975-y