Expanding the applications of Rapid Evaporative Ionisation Mass Spectrometry (REIMS): microbial detection, diagnostics and metabolic profiling
File(s)
Author(s)
Burke, Adam
Type
Thesis
Abstract
The swift diagnosis of infection and identification of the causative microorganism is imperative to improving patient outcomes. Traditional identification techniques rely on microbial culturing, which is time consuming, labour intensive and subject to interpretation. Molecular methods are expensive and require extensive sample preparation. Commercial MALDI-ToF systems have become integrated into clinical microbiology laboratory workflows due to their ease of use, low per-sample cost, and ability to reduce sample turnaround times by one day. Although these systems have revolutionised clinical labs, they still largely rely on isolation and pre-culture of microorganisms prior to analysis. Some attempts have been made to develop “direct from sample analysis”, however protocols include extensive sample preparation steps and provide unreliable results in the case of poly-microbial samples.
The ambient Rapid Evaporative Ionisation Mass Spectrometry (REIMS) phospholipid based profiling technique has been previously shown to accurately classify isolated clinical microorganisms from agar media. REIMS offers an advantage over existing methods in that real time analysis can be conducted on intact cells with no sample preparation required. This project expands on previous work through the development of a methodology allowing liquid sample analysis, and its direct application to clinical specimens without the requirement of pre-culture.
In the analysis of clinical urine samples, culture negative and culture positive specimens were discriminated successfully, and species-specific biomarkers were identified. Species-specific biomarkers were also detected in synthetic mixed cultures, indicating the potential for REIMS in poly-microbial sample analysis. Additionally, the technique was applied to bovine milk in the investigation of mastitis, and was able to discern mastitis positive and negative milk samples. REIMS was shown to be a versatile culture free microbial identification system with applications outside of the human clinical laboratory, and offers an alternative to existing methods in the veterinary field, which also rely on microbial culture for non-ambiguous species identification.
The ambient Rapid Evaporative Ionisation Mass Spectrometry (REIMS) phospholipid based profiling technique has been previously shown to accurately classify isolated clinical microorganisms from agar media. REIMS offers an advantage over existing methods in that real time analysis can be conducted on intact cells with no sample preparation required. This project expands on previous work through the development of a methodology allowing liquid sample analysis, and its direct application to clinical specimens without the requirement of pre-culture.
In the analysis of clinical urine samples, culture negative and culture positive specimens were discriminated successfully, and species-specific biomarkers were identified. Species-specific biomarkers were also detected in synthetic mixed cultures, indicating the potential for REIMS in poly-microbial sample analysis. Additionally, the technique was applied to bovine milk in the investigation of mastitis, and was able to discern mastitis positive and negative milk samples. REIMS was shown to be a versatile culture free microbial identification system with applications outside of the human clinical laboratory, and offers an alternative to existing methods in the veterinary field, which also rely on microbial culture for non-ambiguous species identification.
Version
Open Access
Date Issued
2019-05
Date Awarded
2019-11
Copyright Statement
Creative Commons Attribution NonCommercial NoDerivatives Licence
Advisor
Takats, Zoltan
Marchesi, Julian
Sponsor
Waters Corporation
Publisher Department
Department of Surgery & Cancer
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)