Identification and characterization of Clostridium botulinum group III field strains by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS)

Luca Bano; Ilenia Drigo; Elena Tonon; Simone Pascoletti; Cinzia Puiatti; Fabrizio Anniballi; Bruna Auricchio; Florigio Lista; Cesare Montecucco; Fabrizio Agnoletti

doi:10.1016/j.anaerobe.2017.08.004

Identification and characterization of Clostridium botulinum group III field strains by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS)

Anaerobe. 2017 Dec:48:126-134. doi: 10.1016/j.anaerobe.2017.08.004. Epub 2017 Aug 10.

Authors

Affiliations

¹ Diagnostic and Microbiology Veterinary Laboratory, Istituto Zooprofilattico Sperimentale delle Venezie, Villorba di Treviso, Italy. Electronic address: lbano@izsvenezie.it.
² Diagnostic and Microbiology Veterinary Laboratory, Istituto Zooprofilattico Sperimentale delle Venezie, Villorba di Treviso, Italy.
³ National Reference Center for Botulism, Department of Veterinary Public Health and Food Safety, Istituto Superiore di Sanità, Roma, Italy.
⁴ Army Medical and Veterinary Research Center, Roma, Italy.
⁵ Department of Biomedical Sciences, University of Padova, Padova, Italy.

PMID: 28802703
DOI: 10.1016/j.anaerobe.2017.08.004

Abstract

Animal botulism is primarily due to botulinum neurotoxin (BoNT) types C, D or their chimeric variants C/D or D/C, produced by Clostridium botulinum group III, which appears to include the genetically indistinguishable Clostridium haemolyticum and Clostridium novyi. In the present study, we used matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI TOF MS) to identify and characterize 81 BoNT-producing Clostridia isolated in 47 episodes of animal botulism. The instrument's default database, containing no entries for Clostridium botulinum, permitted reliable identification of 26 strains at the genus level. Although supplementation of the database with reference strains enhanced the instrument's ability to identify the neurotoxic strains at the genus level, resolution was not sufficient to recognize field strains at species level. Characterization by MALDI TOF confirmed the well-documented phenotypic and genetic differences between Clostridium botulinum strains of serotypes normally implicated in human botulism (A, B, E, F) and other Clostridium species able to produce BoNTs type C and D. The chimeric and non-chimeric field strains grouped separately. In particular, very low similarity was found between two non-chimeric type C field strains isolated in the same outbreak and the other field strains. This difference was comparable with the differences among the various Clostridia species included in the study. Characterization by MALDI TOF confirmed that BoNT-producing Clostridia isolated from animals are closely related and indistinguishable at the species level from Clostridium haemolyticum and Clostridium novyi reference strains. On the contrary, there seem to be substantial differences among chimeric and some non-chimeric type C strains.

Keywords: Animal botulism; Clostridium botulinum group III; MALDI-TOF MS.

MeSH terms

Animal Diseases / epidemiology
Animal Diseases / microbiology
Animals
Bacterial Typing Techniques* / methods
Botulism / veterinary
Clostridium botulinum / classification*
Cluster Analysis
Databases, Factual
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization* / methods