MALDI-TOF Mass Spectrometry as a Rapid Screening Alternative for Non-tuberculous Mycobacterial Species Identification in the Veterinary Laboratory

Abstract

Non-tuberculous mycobacteria (NTM) are difficult to identify by biochemical and genetic methods due to their microbiological properties and complex taxonomy. The development of more efficient and rapid methods for species identification in the veterinary microbiological laboratory is, therefore, of great importance. Although MALDI-TOF Mass Spectrometry (MS) has become a promising tool for the identification of NTM species in human clinical practise, information regarding its performance on veterinary isolates is scarce. This study assesses the capacity of MALDI-TOF MS to identify NTM isolates (n = 75) obtained from different animal species. MALDI-TOF MS identified 76.0% (n = 57) and 4% (n = 3) of the isolates with high and low confidence, respectively, in agreement with the identification achieved by Sanger sequencing of housekeeping genes (16S rRNA, hsp65, and rpoB). Thirteen isolates (17.3%) were identified by Sanger sequencing to the complex level, indicating that these may belong to uncharacterised species. MALDI-TOF MS approximated low confidence identifications toward closely related mycobacterial groups, such as the M. avium or M. terrae complexes. Two isolates were misidentified due to a high similarity between species or due to the lack of spectra in the database. Our results suggest that MALDI-TOF MS can be used as an effective alternative for rapid screening of mycobacterial isolates in the veterinary laboratory and potentially for the detection of new NTM species. In turn, Sanger sequencing could be implemented as an additional method to improve identifications in species for which MALDI-TOF MS identification is limited or for further characterisation of NTM species.

Rifampicin resistant Mycobacterium tuberculosis and associated factors among presumptive pulmonary tuberculosis patients in Mogadishu, Somalia

“…Furthermore, Sanger sequencing could be used as an additional method to improve identifications in species for which MALDI-TOF MS identification is limited. 12 …”

Recent progress in the genotyping of bovine tuberculosis and its rapid diagnosis via nanoparticle-based electrochemical biosensors

“…61 This method has the benet of being able to use DNA isolated from infected tissue samples without the need for bacterial isolation. 62 Further automatization and development of this method has been directed to employ recognition systems based on microbeads, like Luminex platforms, 63 multiplexed primer extension depending on spoligotyping assay using matrixassisted laser desorption ionization time of ight mass spectrometry (MALDI-TOF MS), 64 microarray, 65,66 melting curve analysis and ligation based amplication. 58 One of the most important advantages of spoligotyping is its ability to be used directly in clinical samples without the requirement for preparatory culture due to its true sensitivity estimated at 10 fg of chromosomal DNA, or the DNA of 2-3 bacterial cells.…”

Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry in veterinary medicine: Recent advances (2019–present)

“…While the authors report finding antimicrobial-resistant strains, no direct link proving owner-pet transmission was reported. Lorente-Leal et al [50] investigated MALDI-TOF to identify non-tuberculosis mycobacteria. The MS method successfully identified over ¾ of isolates with high confidence.…”