Optimized MALDI TOF Mass Spectrometry Identification of Francisella tularensis Subsp. holarctica

Abstract

Francisella tularensis is a tier 1 agent causing the zoonosis tularemia. This highly infectious Gram-negative bacterium is occasionally isolated from human samples (especially blood samples) in routine clinical microbiology laboratories. A rapid and accurate method for identifying this pathogen is needed in order to optimize the infected patient’s healthcare management and prevent contamination of the laboratory personnel. MALDI TOF mass spectrometry has become the gold standard for the rapid identification of most human pathogens. However, F. tularensis identification using such technology and commercially available databases is currently considered unreliable. Real-time PCR-based methods for rapid detection and accurate identification of F. tularensis are not available in many laboratories. As a national reference center for tularemia, we developed a MALDI TOF database allowing accurate identification of the species F. tularensis and its differentiation from the closely related neighbor species F. tularensis subsp. novicida and F. philomiragia. The sensitivity and specificity of this database were validated by testing 71 F. tularensis strains and 165 strains from 63 species not belonging to the Francisella genus. We obtained accurate identification at the species level and differentiation of all the tested bacterial strains. In particular, F. tularensis could be accurately differentiated from other small Gram-negative bacilli occasionally isolated from human samples, including species of the HACEK group and Brucella melitensis.

Establishment and Application of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry for Detection of Shewanella Genus

“…Multiple Shewanella species are frequently isolated from food products and clinical specimens as opportunistic pathogens ( Pagani et al, 2003 ; Liu et al, 2013 ; Janda and Abbott, 2014 ). Commercial systems, such as Vitek and MALDI-TOF MS (bioMérieux, Bruker), are available for species identification in clinical laboratories ( Regoui et al, 2020 ; Sánchez-Juanes et al, 2020 ). However, only a few species, like S. putrefaciens and S. algae , were recorded in the database ( Liu et al, 2013 ; Janda and Abbott, 2014 ; Zhang et al, 2018 ).…”

“Omic” Approaches to Bacteria and Antibiotic Resistance Identification

“…Regoui et al, on the other hand, developed a database to identify Francisella tularensis and distinguished it from the closely related species F. tularensis subsp. novicida and Francisella philomiragia [ 77 ]. They also found that incubation on chocolate agar plates supplemented with PolyViteX ® at 30 or 37 °C in an aerobic or 5% CO 2 -enriched atmosphere for less than 72 h allows for the accurate identification of F. tularensis subsp.…”

MALDI-TOF MS: application in diagnosis, dereplication, biomolecule profiling and microbial ecology

“…A study suggested that some isolates belonging to various genera such as Bacillus, Stenotrophomonas, Pseudomonas, and Rhodococcus were grouped and were differentiated upto strain level by using MALDI-TOF MS however, rep-PCR failed to produce such results (Ghyselinck et al 2011 ). MALDI-TOF MS can classify serotypes of Listeria monocytogenes in three lineages (Ojima-Kato et al 2016 ), differentiated subspecies of Francisellatularensis (Regoui et al 2020 ) as well as discriminated the strains of Legionella (Blanco et al 2021 ). Tanigawa et al ( 2010 ) used mass spectral analysis of ribosomal proteins to distinguish between different Lactococcus species and subspecies.…”