Abstract/Summary

Clinical mass spectrometry (MS) has had great success in the last two decades for the identification of microorganisms using matrix‐assisted laser desorption/ionisation (MALDI) MS biotyping. In this thesis, the application of the more recently developed liquid atmospheric pressure (LAP) MALDI has been applied to the analysis of clinically important samples for biotyping and diagnostic purposes. LAP‐MALDI MS allows the detection of ESI‐ like protein ion signals, whilst maintaining the benefits of traditional MALDI such as high tolerance to contamination and providing additional advantages such as stable and homogenous sample droplets and in turn, stable ion flux. Firstly, the exploration of MS profiling will be discussed, with the identification of clinically relevant bacteria performed via unsupervised statistical analysis of unique lipidomic profiles. This also encompasses the first LAP‐MALDI mass spectra of bacteria possessing lipids and proteins in the same spectrum. Following on from this, antimicrobial resistance was investigated via the multiplex detection of antibiotic hydrolysis in the presence of bacteria possessing β‐lactamase resistance genes. In this assay, the lipidomic profiles for bacteria were still present, therefore AMR detection and species identification can be coupled in a single assay. Finally, LAP‐MALDI’s potential use in infectious disease detection was also explored in animals. Bovine tuberculosis poses a high risk to cattle health and UK farming, and therefore efficient diagnostics are vital. The use of LAP‐MALDI MS allows the detection of a key inflammatory protein (S100‐A12), which is correlated to infection in cattle. Linear discriminant analysis (LDA) shows the discrimination between healthy cattle, and two disease states with high sensitivity and specificity. Collectively, this thesis highlights the valuable contribution LAP‐MALDI could present in clinical diagnostics, providing more rapid and more informative diagnostic results, for both humans and animals.