The Emergence of a Virulent Clade of Vibrio vulnificus and Correlation with the Presence of a 33-Kb Genomic Island

Department of Biological Sciences, University of Delaware, Newark, DE 19716,USA; Department of Microbiology, National University of Ireland, Cork, Ireland, Department of Biology, University of North Carolina at Charlotte, Charlotte, NC 28223, USA, Gulf Coast Seafood Laboratory, U. S. Food and Drug Administration, Dauphin Island, Alabama 36528, USA, Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK

^* To whom correspondence should be addressed. Email: fboyd{at}udel.edu.

	Abstract

Vibrio vulnificus is a ubiquitous inhabitant of the marine coastal environment, and an important pathogen of humans. We characterized a globally distributed sample of environmental isolates from a range of habitats and hosts, and compared these with isolates recovered from cases of human infection. Multilocus sequence typing (MLST) data using six housekeeping genes divided 63/67 of the isolates in to the two main lineages previously noted for this species, and this division was also confirmed using the 16S rRNA and ORF VV0401 markers. Lineage I was comprised exclusively of biotype 1 isolates whereas lineage II contained biotype 1 and all biotype 2 isolates. Four isolates did not cluster within either lineage; two biotype 3 and two biotype 1 isolates. A higher proportion of isolates recovered from a clinical setting was noted in lineage I than in lineage II. Lineage I isolates were also associated with a 33 Kb genomic island (Region XII), one of three regions identified by genome comparisons as unique to the species. Region XII contained an arylsulfatase gene cluster, a sulfate reduction system, two chondroitinase genes and an oligopeptide ABC transport system, that are absent from the majority of lineage II isolates. Arylsulfatases and the sulfate reduction system, along with performing a scavenging role, have also been hypothesized to play a role in pathogenic processes in other bacteria. Our data suggests that lineage I may have a higher pathogenic potential and that region XII, along with other regions, may give isolates a selective advantage either in the human host or in the aquatic environment or both.