Investigation article published in Aquaculture (Amsterdam, Netherlands)

November 1^st, 2016

Photobacterium damselae is a well-recognized fish pathogen comprising two subspecies (damselae and piscicida) with significant clinical and epidemiological differences. We explored the suitability of MALDI-TOF MS for discriminating P. damselae subspecies in a panel of 45 isolates from diseased fish. MALDI Biotyper approach correctly identified all isolates at species level with average scores values of 2.271 although identification at subspecies level was not reliable. Visual inspection of the spectra using FlexAnalysis revealed five specific peaks (m/z 4183 and 8367 for subsp. damselae and 4197, 8397 and 8856 for subsp. piscicida) that may allow their differentiation. A classification model (GA-5A) was constructed based on these peaks using a genetic algorithm (ClinProTools software). Cross-validation and recognition capability values of this model were 100%. Validation of this model was confirmed by blind identification of 21 isolates of both subspecies resulting in sensitivity and specificity values of 100%. This is the first study describing a classification algorithm for MALDI-TOF MS identification of both P. damselae subspecies. This approach proved to be an effective and reliable tool in discriminating within the P. damselae subspecies that might be easily integrated into the workflow of microbiological diagnosis laboratories

Perez-Sancho M., Vela AI., Awad M., Kostrzewa M., Dominguez L. and Fernandez-Garayzabal JF..

Differentiation of Photobacterium damselae subspecies using Matrix-Assisted Laser-Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) in fish isolates

	Servicio de Identificación y Caracterización Microbiana (ICM). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).
	CEI Campus Moncloa.
	Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM).
	Bruker Daltonik GmbH (BRUKER).