The use of Matrix-assisted laser desorption ionization-time of flight mass spectrometry in the identification of Francisella tularensis

Abstract

Francisella tularensis is the cause of the zoonotic disease tularemia and is classified among highly pathogenic bacteria (HPB) due to its low infection dose and potential for airborne transmission. In the case of HBP, there is a pressing need for rapid, accurate and reliable identification. Phenotypic identification of Francisella species is inappropriate for clinical microbiology laboratories because it is time-consuming, hazardous and subject to variable interpretation. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was recently evaluated as a useful tool for the rapid identification of a variety of microorganisms. In this study, we evaluated the use of MALDI-TOF MS for the rapid identification of Francisella tularensis and differentiation of its subspecies. Using national collection of Francisella isolates from the National Tularemia Reference Laboratory (Public Health Institution of Turkey, Ankara), a total of 75 clinical isolates were investigated by species and subspecies-specific polymerase chain reaction (PCR) test and MALDI-TOF MS. All isolates were originally identified as F. tularensis subsp. holarctica according to region of difference 1 (RD1) subspecies-specific PCR results. For all isolates MALDI-TOF MS provided results in concordance with subspecies-specific PCR analysis. Although PCR-based methods are effective in identifying Francisella species, they are labor-intensive and take longer periods of time to obtain the results when compared with MALDI-TOF MS. MALDI-TOF MS appeared to be a rapid, reliable and cost-effective identification technique for Francisella spp. Shorter analysis time and low cost make this an appealing new option in microbiology laboratories.

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

“…novicida (also referred to as F. novicida ) were misidentified as F. tularensis . A study by Karatuna et al [ 31 ], in Turkey, evaluated a large number ( n = 75) of clinical isolates of F. tularensis subsp. holarctica .…”

Tularemia: a re-emerging tick-borne infectious disease

“…Accuracy of this analysis highly depends on available mass spectrum databases. However, MALDI-ToF MS-analysis provides results in accordance with the PCR assay (Afanas’ev et al 2015 ; Karatuna et al 2016 ).…”

Identification of Francisella tularensis Subspecies in a Clinical Setting Using MALDI-TOF MS: An In-House Francisella Library and Biomarkers

“…The 5182-5185 mass was excluded by BioNumerics as not being (sub)species specific. It is however included as a Francisella genus-specific marker because it was identified as such earlier [13][14][15][16][17][18].…”

“…To overcome this, an in-house library was created to distinguish F. tularensis subspecies [13]. Francisella-specific biomarkers were studied for F. tularensis, with and without subspecies differentiation, and for F. philomiragia, F. halioticida and F.salimarina [13][14][15][16][17][18][19]. An in-house database was also described limited to F. tularensis ssp.…”