Posted on by Cyrille Goarant

Maldi-tof Leptospire identification

Maldi-Tof identification of Leptospira spp.
Principal investigator Cyrille Goarant
Focal point IPNC Dominique Girault, Cyrille Goarant
Collaborators at IPNC Roman Thibeaux, Julien Colot
Other Collaborators Anna Rettinger, Faculty of Veterinary Medicine, LMU Munich, Germany
Total budget of project 1 000 euros Budget devoted to IPNC : NA
Funding IPNC
Timeline Start date: 2015 End date: 2018
Context
IPNC has implemented MALDI-ToF mass spectrometry for routine identification of bacterial isolates. We aimed to use this system to identify bacteria of the genus Leptospira.
Objectives
The objectives were to create a database of mass spectra of reference strains of the genus Leptospira and then to use it to control the identification of strains used for MAT serology as well as unknown isolates.
Methods

A bibliographic review identified 3 teams that had a mass spectra database of Leptospira spp. The corresponding authors of the articles were asked to share their database. Dr. Anna Rettinger (University of Munich) agreed to transmit her reference spectra.

We have also created reference spectra of known collection strains belonging to different species. Unknown (patient isolates) or known strains (from the MAT serology panel) were then identified blindly.

 
Results

The preliminary tests made it possible to optimize the technique of preparation of the leptospires for reading their mass spectrum on the Maldi-Tof Bruker. The reference spectra of 57 strains representing all 22 known Leptospira species were created and grouped into a dedicated “research” database.

Blind analysis of strains shows very good reliability for species-level identification, but insufficient precision to identify individual strains used as antigens for MAT serology. The strains isolated from patients were properly identified at the species-level with high scores considered as diagnostic.
Perspectives
The reference spectrum of Leptospira venezuelensis (currently being described) will also be created. The transfer of the MALDI-TOF and computer breakdowns slowed down the work. This database will be incremented with novel species and used to identify unknown isolates. Threshold scores for species identification will be determined.
Valorisation 
These data should be included in a draft publication on the identification of leptospires.