LESA-MS detects differences in lipid profiles between healthy and footrot-affected tissues

Ovine footrot is a highly contagious polymicrobial infection causing lameness in sheep with an associated UK economic burden upwards of £24m per annum. Changes in gene expression affecting lipid metabolism have been reported in footrot-affected compared to healthy feet, however, the role of lipids in footrot pathogenesis has not been studied. Previously, liquid extraction surface analysis mass spectrometry (LESA-MS) has been used to sample lipids from bacterial colonies and thin tissue sections. Here we present LESA-MS analysis of lipids extracted from both healthy and footrot-affected tissue samples. The samples comprised abundant phospholipids in the region m/z 700-850, that were common to both sample types, two of which were identified as phosphatidylcholines PC 16:0/18:1 and PC 16:0/16:1. Abundant lipids in each sample between m/z 950-1150 were different. A variety of lipids identified by accurate mass and MS/MS as triacylglycerols were higher in abundance in healthy tissue sections than footrot-affected ones, with t-tests confirming statistical significance. Lipids identified by accurate mass as either phosphatidylserines or phosphatidylthreonines were detected in higher abundance in footrot-affected tissue sections; MS/MS did not aid assignment of these. We present a rapid lipidomic analysis approach that could inform on the role of lipids in pathogenesis of footrot and other inflammatory diseases.