First Report of a Fatal Septicaemia Case Caused by Vibrio metoecus: A Comprehensive Functional and Genomic Study

Abstract

Background In recent years, we have witnessed an unprecedented increase in the incidence of vibriosis due to global warming. Vibrio metoecus is a recently described V. cholerae-like species that has not been associated with septicemia death in humans. During follow-up of human vibriosis, we received a blood isolate from a patient with secondary septicemia who died a few hours after admission. Methods Phenotypic and genotypic methods failed to identify the isolate, which could only be identified by Average Nucleotide Identity after genome sequencing. The isolate was then subjected to a series of in vitro and ex vivo assays, complemented by comparative genomics focused on the identification of unique genetic traits. Strains and genomes from the same and related species (V. cholerae and V. mimicus) were used for analyses. Results The isolate was the only one able to resist and multiply in human serum. Its genome contained virulence genes shared with V. mimicus and/or V. cholerae, with those associated with sialic acid degradation within pathogenicity island 2 standing out. However, it also presented a unique gene cluster, flanked by a transposase gene, putatively related to surface polysaccharide pseudosialyzation. Conclusion In this study, we document the first case of death from septicemia due to V. metoecus and propose that the acquisition of surface pseudosialyzation genes would explain the ability of certain isolates of this species to survive in blood. Consequently, our discovery underscores the urgent need to monitor and study new emerging pathogenic species, as climate change may be facilitating their spread and increasing the risk of serious infections in humans.