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Performance of lipid fingerprint-based MALDI-ToF for the diagnosis of mycobacterial infections

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Title: Performance of lipid fingerprint-based MALDI-ToF for the diagnosis of mycobacterial infections
Authors: Gonzalo, X
Broda, A
Drobniewski, F
Larrouy-Maumus, G
Item Type: Journal Article
Abstract: Objectives Bacterial diagnosis of mycobacteria is often challenging because of the variability of the sensitivity and specificity of the assay used, and it can be expensive to perform accurately. Although matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) has become the workhorse of clinical laboratories, the current MALDI methodology (which is based on cytosolic protein profiling) for mycobacteria is still challenging due to the number of steps involved (up to seven) and potential biosafety concerns. Knowing that mycobacteria produce surface-exposed species-specific lipids, we here hypothesized that the detection of those molecules could offer a rapid, reproducible and robust method for mycobacterial identification. Methods We evaluated the performance of an alternative methodology based on characterized species-specific lipid profiling of intact bacteria, without any sample preparation, by MALDI MS; it uses MALDI-time-of-flight (ToF) MS combined with a specific matrix (super-2,5-dihydroxybenzoic acid solubilized in an apolar solvent system) to analyse lipids of intact heat-inactivated mycobacteria. Cultured mycobacteria are heat-inactivated and loaded directly onto the MALDI target followed by addition of the matrix. Acquisition of the data is done in both positive and negative ion modes. Blinded studies were performed using 273 mycobacterial strains comprising both the Mycobacterium tuberculosis (Mtb) complex and non-tuberculous mycobacteria (NTMs) subcultured in Middlebrook 7H9 media supplemented with 10% OADC (oleic acid/dextrose/catalase) growth supplement and incubated for up to 2 weeks at 37°C. Results The method we have developed is fast (<10 mins) and highly sensitive (<1000 bacteria required); 96.7% of the Mtb complex strains (204/211) were correctly assigned as MTB complex and 91.7% (22/24) NTM species were correctly assigned based only on intact bacteria species-specific lipid profiling by MALDI-ToF MS. Conclusions Intact bacterial lipid profiling provides a biosafe and unique route for rapid and accurate mycobacterial identification.
Issue Date: 27-Aug-2020
Date of Acceptance: 21-Aug-2020
URI: http://hdl.handle.net/10044/1/82651
DOI: 10.1016/j.cmi.2020.08.027
ISSN: 1198-743X
Publisher: Elsevier
Journal / Book Title: Clinical Microbiology and Infection
Copyright Statement: © 2020 The Author(s). Published by Elsevier Ltd on behalf of European Society of Clinical Microbiologyand Infectious Diseases. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Sponsor/Funder: Wellcome Trust
Funder's Grant Number: 105603/Z/14/Z
Keywords: MALDI
1103 Clinical Sciences
1117 Public Health and Health Services
Publication Status: Published online
Online Publication Date: 2020-08-27
Appears in Collections:Department of Infectious Diseases
Faculty of Natural Sciences

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