%0 Generic %D 2016 %T MALDI-TOF for the identification of Mycobacteria and their drug resistance profiles %A An Van den Bossche %A Pieter-Jan Ceyssens %A Marijke Hendrickx %A Vanessa Mathys %K drug susceptibility testing %K identification %K MALDI-TOF %K Mycobacterium tuberculosis %X

In the last years, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been increasingly introduced as a valuable method for the identification of bacteria and yeast1. This technique, which generates mass spectra that are compared to reference spectra in databases, is accurate, fast and cost-effective compared to traditional biochemical and molecular techniques.

For the identification of Mycobacteria, this method is more challenging due to the special need for inactivation and protein extraction. Although several studies have been published, there is no clear consensus on the processing of Mycobacteria for MALDI-TOF MS and outcomes vary from 55% correct identifications to 97%2-4. In this study, we optimized an extraction protocol and evaluated its efficiency using the Brüker Biotyper system v3.0 for 194 cultures. In total 88.6% (172/194) of the samples were correctly identified on the species-level using a cut-off score of 1.8 and 91.75% (178/194) using a cut-off of 1.65. All samples of the Mycobacterium tuberculosis complex were correctly classified (52/52), while 126 of the 142 Non-tuberculosis Mycobacteria were accurately identified at a 1.65 cut-off.

Recently, it was described that MALDI-TOF MS can also be used for drug-susceptibility testing (DST) in bacteria. The MS-ASTRA technology is based on the parallel incubation of a culture in presence or absence of an antibiotic. By adding an internal standard during the protein extraction, semi-quantitative measurements of the bacterial biomass can be derived from the MALDI-TOF spectra7.

In this study, we show that this technology can be applied on Mycobacteria. 34 clinical M. tuberculosis isolates were investigated for their resistance profile to four different drugs (rifampicin, isoniazid, ethambutol and linezolid), yielding a 100% concordance to the BACTEC MGIT results. Moreover, incubation with serial dilutions allowed a correct determination of the Minimal Inhibitory Concentrations of isoniazid and rifampicin. Therefore, this method has the potential to provide a cost-effective and fast alternative for classical phenotypic DST, independent of the mechanism of drug resistance. However, a current lack of automation hinders implementation in diagnostic laboratories.

%B 37th Annual Congress of the European Society of Mycobacteriology %I ESM %C Catania, Sicily, Italy %8 06/2017 %G eng