A peptide-based LC-MS/MS method for detection and identification of Salmonella serovars

摘要

We have previously presented a top-down LC-ESI-MS/MS platform for identification of Salmonella serovar differentiating proteins (McFarland et. al., Anal. Chem. 2014, 86, 6879-6886). Here, we extend our method to the peptide level and propose an LC-ESI-MS/MS-based "bottom-up" approach to differentiate Salmonella serovars, with the end goal being increased sensitivity and specificity. Our LC-MS/MS data display that the an average of 99.2% of tryptic peptides in a Salmonella isolate match the corresponding serovar sequence databases, while the peptide matches to other serovar databases within a subspecies level are ～ 96.8%, different subspecies ～ 81.7%, different species ～ 75.8%, and different genus ～ 51.2%. The data suggest that the comparison of peptide matches between LC-MS/MS and reference databases can correctly identify a Salmonella isolate at the subspecies level. Further, to increase assay specificty, a list of Salmonella discriminating peptides were used for cluster analysis to understand the relative relatedness among the serovars and the major discriminatory peptides. Both HCA and PCA show 2 distinct groups where serovars within S. enterica subsp. enterica were clustered into a group while S. Bongori was populated at a separate cluster. Top discriminatory markers were identified for distinguishing Salmonella serovar Typhimurium, Saintpaul, Heidelberg, Paratyphi B, Muenchen and Enteritidis and Bongori.