timone.univ-mrs.fr/MST_YPestis/mst. We observed no growth over 7 days for any of the Y. pestis isolates being studied after ethanol inactivation. MALDI-TOF protein profiles for the three main biotypes following 70% ethanol inactivation, including Y. pestis Antiqua (Y. pestis Nairobi-rattus), Medievalis (Y. pestis 14-47), and Orientalis (Y. pestis 6/69M) are shown in Figure 1. Figure 2 contains a pseudo-gel representing the protein profile for the three Y. pestis biotypes. Figure 1 Protein profile of the major Y. pestis biotypes generated by MALDI-TOF-MS. a.i., arbitrary intensity given by the software. Figure 2 Pseudo-gel representing the protein profile obtained after
MALDI-TOF-MS analysis of Y. pestis organisms representative of the Antiqua, Medievalis and Orientalis biotypes. arb.u., arbitrary unit – transcription for arbitrary intensity https://www.selleckchem.com/products/defactinib.html in the Bruker software; selleck inhibitor sp# is the numbers of the spectrum. MALDI-TOF-MS identification of check details Yersinia organisms For the Y. pestis
isolates, default identification against the Bruker database resulted in a false result of Y. pseudotuberculosis with an identification score > 2 in two of two cases. When the identification was performed using our local updated database, the isolates were correctly matched as Y. pestis in two of two cases with an identification score > 2.7, effectively identifying the isolates at the species level. The 11 Y. enterocolitica isolates were correctly identified as Y. enterocolitica with an identification score Org 27569 > 2. Further analysis of the Y. pestis isolates using ClinPro Tools software allowed us to assign them to a biotype, with the exception of the Y. pestis JHUPRI strain for which the unique MALDI-TOF profile did not match any of the three biotypes. Reproducibility of MALDI-TOF-MS identification We obtained a unique MALDI-TOF profile for each
of the 39 Yersinia isolates being studied: for each isolate, the 12 MALDI-TOF profiles derived from triplicate analysis were similar and yielded identical, accurate identification. A list of m/z values characteristic for Y. pestis is given in additional file 1. Discussion Given that the MALDI BioTyper™ database contained 42 Yersinia profiles derived from 11 species but lacked the major pathogen Y. pestis, as well as the recently described species Y. massiliensis , we aimed to complete this database by deriving a MALDI-TOF profile for 12 species currently included in the Yersinia genus . We obtained a unique MALDI-TOF profile for each of the Yersinia species used in this study. In each case, the species-specific profile did not match any of the 3,000 non-Yersinia profiles deposited in the MALDI BioTyper™ database, including those for closely-related enteric bacteria.