Characterization of Type III Secretion System 2 (T3SS2) and TDH Toxin in Vibrio mimicus within an Integrative Conjugative Element Context

Author(s): Sergio Mascarenhas Morgado, Erica Lourenço da Fonseca, Ana Carolina Paulo Vicente

Objectives: Identify possible virulence factors in the genomes of Vibrio mimicus that may be determinants of diarrheal cases/outbreaks.

Methods: All V. mimicus genomes from Genbank were retrieved and their virulome was searched with Abricate using the VFDB database. Genomic islands (GIs) and integrative conjugative elements (ICEs) were identified using IslandViewer and ICEberg, respectively.

Results: Five ctx-negative V. mimicus genomes carrying the Type III Secretion System 2 (T3SS2) and the TDH/TRH toxin from Vibrio parahaemolyticus were identified. The T3SS-positive genomes presented the phylotypes T3SS2α and T3SS2β and formed two clusters and one singleton throughout the V. mimicus phylogeny. Genomes carrying T3SS2α and T3SS2β were associated with the tdh and trh genes, respectively. Genomic analyses characterized an integrative conjugative element (ICE) with a size of ~150 kb carrying both V. parahaemolyticus virulence determinants.

Conclusions: Although cholera toxin is primarily associated with V. mimicus cases/outbreaks, it is also important to consider Vibrio parahaemolyticus toxins in these cases. Furthermore, an ICE was identified and characterized in V. mimicus, being associated with T3SS2 and the TDH toxin, which is worrying, as it can disseminate these virulence factors among Vibrio spp.