Vibrio in the German Bight: Spatial and temporal variations

Mesophilic bacteria of the genus Vibrio naturally exist in marine environments. Being the main water-borne human pathogens, the focus of this work was put on the species V. cholerae, V. parahaemolyticus and V. vulnificus. These are known to cause serious illnesses associated with food poisoning or wound infections. Although Vibrio infections occur mainly in tropical areas, potentially pathogenic Vibrio spp. have been detected in temperate northern European waters in recent years. Clinical cases in these regions seem to follow extreme weather events, especially heat waves. This study covers monthly samplings from spring 2015 until spring 2017 in a sampling transect between Helgoland and Cuxhaven in the German Bight. Species-specific detection and quantification was conducted using the MPN-PCR method targeting the functional genes toxR or vvhA. Additional evaluation of virulence-associated genes gave insight about the presence of pathogenic strains of these species. Besides recurring patterns of Vibrio abundances during summer seasons, the results showed an increase in pathogenic strain occurrences throughout the sampling period. This study reveals the urgency of a regulated Vibrio monitoring and an understanding of environmental dependencies of Vibrio occurrences