Abstract
Mass spectrometry (MS) in Selected Reaction Monitoring (SRM) mode is proposed for in-depth characterisation of microorganisms in a multiplexed analysis. Within 60–80 minutes, the SRM method performs microbial identification (I), antibiotic-resistance detection (R), virulence assessment (V) and it provides epidemiological typing information (T). This SRM application is illustrated by the analysis of the human pathogen Staphylococcus aureus, demonstrating its promise for rapid characterisation of bacteria from positive blood cultures of sepsis patients.
Highlights
® ® ® MicroScan (Siemens) or BD Phoenix systems[2]
Proteotypic peptides, i.e. specific peptides that characterise at the level of both species and strains, were selected in order to track the following features: i) I-peptides to confirm S. aureus identification at the species level, ii) R-peptides specific to PBP2a and PBP2c to detect Methicillin-Resistant S. aureus (MRSA), iii) V-peptides characteristic of selected virulence factors (PVL and toxic shock syndrome toxin 1 (TSST-1)) and iv) T-peptides which provide typing information (e.g. Protein A peptides)
Detection of 109 peptides from 27 S. aureus proteins was performed in a single experiment (Supplementary Table 1)
Summary
® ® ® MicroScan (Siemens) or BD Phoenix systems[2]. Initiated by the pioneering work of Fenselau et al.[3], whole cell mass spectrometry (MS) has revolutionised microbial identification using Matrix-Assisted Laser-Desorption/Ionisation—Time-Of-Flight (MALDI-TOF) MS. To overcome the global delay for identification and AST, MALDI-TOF MS identification associated with conventional AST has recently been performed directly on positive blood cultures (Fig. 1), reducing the time to results by two days[7]. Staphylococcus aureus was chosen as a model to demonstrate the feasibility of the MS method we propose here These common, Gram-positive bacteria can be responsible for both community- and hospital-acquired infections. S. aureus produces a variety of virulence factors encoded by either the core genome or the accessory genome[14] Among the latter, the toxic shock syndrome toxin 1 (TSST-1) and Panton-Valentine Leukocidin (PVL) toxin are archetypal and their detection calls for anti-toxin therapy in addition to conventional antimicrobial treatment[15]. The method can be applied either directly to bacterial colonies or to positive blood cultures
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