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Vibrio vulnificus (Vv) is a bacterial pathogen native to warm and brackish water ecosystems that can cause fatal septicemia (Vv-vibriosis) in humans and various farmed fish species. From a One Health perspective, controlling Vv-vibriosis outbreaks on farms is essential not only for animal but also for human health, as it reduces the risk of Vv transmission to humans. Electrolyzed water (EW) is a sustainable control method, exhibiting transient disinfectant properties due to the formation of hypochlorous acid (HOCl). We hypothesized that EW could effectively reduce Vv populations in aquaculture facilities, preventing outbreak emergence. To test this hypothesis, survival assays in EW were conducted under varying conditions of salinity, pH, and free available chlorine (FAC). The results indicated that an intermediate concentration of FAC had a significant bactericidal effect on Vv populations regardless of the condition and tested strain. Consequently, the strategic use of EW could serve as an eco-friendly preventive and control measure against Vv-vibriosis by significantly decreasing the bacterial load in farm water. [ABSTRACT FROM AUTHOR]

Vibrio vulnificus is a heterogeneous bacterial species that can be virulent for humans and fish. Virulence in fish seems to rely on a recently described plasmid that can be transmitted between strains, aided by a conjugative plasmid. The main objective of this work was to analyse the plasmid content of a wide collection of strains from the three biotypes of the species, as well as to identify putative conjugative and virulence plasmids by means of Southern hybridization with specific probes and sequence analysis of selected gene markers. We found 28 different plasmid profiles in a total of 112 strains, which were relatively biotype- or serovar-specific. Biotype 1 lacked high-molecular-mass plasmids, with the exception of a putative conjugative plasmid of 48 kb that was present in 42.8% of clinical and environmental strains isolated worldwide. All biotype 2 strains possessed the virulence plasmid, whose molecular mass ranged between 68 and 70 kb, and 89.65% of these strains also had a putative conjugative plasmid with a molecular size of 52-56 kb. Finally, a 48 kb putative conjugative plasmid was present in all biotype 3 strains. Data from partial sequencing of traD, tral and the whole vep07 (a recently described plasmid-borne virulence gene) from a selection of strains suggest that the plasmids of 48-56 kb probably belong to the same family of F-plasmids as pYJ016 and that the gene vep07 is absolutely essential for fish virulence. Additional cryptic plasmids of low molecular mass were present in the three biotypes. In conclusion, plasmids are widespread among V. vulnificus species and could contribute substantially to genetic plasticity of the species.

Strains of Vibrio vulnificus, a marine bacterial species pathogenic for humans and eels, are divided into three biotypes, and those virulent for eels are classified as biotype 2. All biotype 2 strains possess one or more plasmids, which have been shown to harbor the biotype 2-specific DNA sequences. In this study we determined the DNA sequences of three biotype 2 plasmids: pR99 (68.4 kbp) in strain CECT4999 and pC4602-1 (56.6 kb) and pC4602-2 (66.9 kb) in strain CECT4602. Plasmid pC4602-2 showed 92% sequence identity with pR99. Curing of pR99 from strain CECT4999 resulted in loss of resistance to eel serum and virulence for eels but had no effect on the virulence for mice, an animal model, and resistance to human serum. Plasmids pC4602-2 and pR99 could be transferred to the plasmid-cured strain by conjugation in the presence of pC4602-1, which was self-transmissible, and acquisition of pC4602-2 restored the virulence of the cured strain for eels. Therefore, both pR99 and pC4602-2 were virulence plasmids for eels but not mice. A gene in pR99, which encoded a novel protein and had an equivalent in pC4602-2, was further shown to be essential, but not sufficient, for the resistance to eel serum and virulence for eels. There was evidence showing that pC4602-2 may form a cointegrate with pC4602-1. An investigation of six other biotype 2 strains for the presence of various plasmid markers revealed that they all harbored the virulence plasmid and four of them possessed the conjugal plasmid in addition.

Vibrio vulnificus is a bacterial species that is virulent for humans and fish. Human isolates are classified into biotypes 1 and 3 (BT1 and BT3) and fish isolates into biotype 2 (BT2). However, a few human infections caused by BT2 isolates have been reported worldwide (zoonosis). These BT2 human isolates belong to serovar E (SerE), which is also present in diseased fish. The aim of the present work was to characterize a new BT2 serovar [serovar A (SerA)], which emerged in the European fish-farming industry in 2000, by means of phenotypic, serological and genetic [plasmid profiling, ribotyping and random amplified polymorphic DNA (RAPD)] methodologies. The results confirmed that SerA constitutes a homogeneous O-serogroup within the species that shares plasmidic information with SerE. Like SerE, this new serogroup was resistant to fresh fish serum, as well as being highly virulent for fish. In contrast, it was sensitive to human serum and avirulent for mice, even after pretreatment with iron. The two serovars presented different biochemical profiles as well as specific patterns by ribotyping and RAPD analysis. In conclusion, SerA seems to constitute a different clonal group that has recently emerged within the species V. vulnificus, with pathogenic potential for fish but not for humans.

Vibrio vulnificus biotype 3 has been implicated as the causative pathogen of an ongoing disease outbreak that erupted in Israel in 1996. Recent work based on multi-locus sequence typing (MLST) showed that V. vulnificus biotype 3 is genetically homogeneous. The aim of this study was to investigate the existence of subpopulations within this homogeneous biotype by characterizing the surface antigens and analysing the sequence diversity of selected outer-membrane protein (OMP)-encoding genes. Rabbit antisera were prepared against biotype 1, 2 and 3 strains. The results of the slide-agglutination test, dot-blot assay (using fresh and boiled cells), and immunoblotting of lipopolysaccharides (LPS) and OMPs were evaluated. By slide-agglutination and dot-blot assays all biotype 3 strains agglutinated with the selected biotype 3 strain. This homogeneity was supported by immunoblot analysis of the LPS. Analysis of OMP patterns revealed that all three biotypes share a considerable number of common bands that are antigenically related. Cluster analysis of DNA sequence data from selected OMP-encoding genes showed that biotype 3 strains form a genetically distinct and homogeneous clone. The homogeneity of surface antigens and the lack of any sequence diversity among both housekeeping and OMP-encoding genes reaffirms the highly clonal nature of biotype 3 and suggests that it has only recently descended from the parent population of V. vulnificus.

Vibrio vulnificus serovar E can form biofilms on the skin of eels and appears to gain entry via the gills or in contaminated food. The microorganism was also found in tank water during a natural outbreak in an eel farm.

Vibrio vulnificus serovar E strains from aquatic habitats in Taiwan that are not virulent to eels have been isolated. Polymerase chain reaction of the cytolysin-hemolysin gene was used in studying the strains. Tryptone soya agar and tryptone soya broth were used as culture substrates. The Vibrio samples were obtained from water and oysters and are different from eel virulent strains in their fermentation, utilization of mannitol, ribotyping after HindIII digestion and susceptibility to eel serum.

Twenty-one Vibrio vulnificus isolates which are mostly from northern Europe, were phenotypically and genotypically characterized by comparing them with reference strains of the two biotypes to search for new isolates of biotype 2. Findings indicated that the majority of the isolates virulent for eels had phenotypic characteristics which have been formerly considered to be traits of biotype 2 and specific ribotypes with HindIII. However, from the new isolates, a serogroup E strain virulent for eels but indole positive and one isolate which is not a member of serogroup E but pathogenic for eels were found.

An enzyme-linked immunosorbent assay based on the specificity of lipopolyasaccharide (LPS) can detect Vibrio vulnificus biotype 2 pathogen successfully in infected eels and asymptomatic carriers. This pathogen consists of LPS-based homogeneous O serogroup and eels act as a reservoir for this pathogen. The accurate detection and identification of this pathogen has important implications for sanitary controls, and ecological and clinical studies.

The extracellular products (ECPs) of Vibrio vulnificus biotype 2 contribute to bacterial virulence for eels and other warm-water and cold-water fish. The ECPs of biotypes 1 and 2 show significant proteolytic, phospholipasic and hemolytic activities. There is a loss of the enzymatic activities after heat treatment, indicating that the heat-labile molecules are proteins. The hydrolytic and cytotoxic capabilities and lethality of the type 1 and 2 ECPs for eels are similar but biotype 1 is avirulent for eels.

The Vibrio vulnificus biotype 2 is an opportunist pathogen for humans under favourable circumstances. The strain ATCC 33817 initially isolated from a human leg wound has been identified as V. vulnificus biotype 2. The strain gives negative results in the indole test and is pathogenic for eels and mice. It belongs to the serogroup E and has two plasmids. V. vulnificus has phenotypically different strains some of which are pathogenic for humans but only the serogroup E infects eels.

A study was conducted on the ability of Vibrio vulnificus biotype 2 to acquire iron through various mechanisms. Siderophore-mediated mechanisms and the role of free iron in vibriosis were analyzed. The role of capsule in iron acquisition was also examined by using capsulated and acapsulated original isolates. Results showed that the biotype 2 expresses an iron uptake mechanism dependent on siderophores. The chelator triggering iron acquisition from transferrins was postulated to be the hydroxamic type.

Vibrio vulnificus biotype 2 isolates from diseased European eels have been extensively characterized to determine their taxonomic status and clarify differences between biotype 1 and biotype 2. Serological and molecular characterization, 123 biochemical, physiological and morphological tests and a virulence study were conducted. Data indicated that the biotype 2 constitutes a lipopolysaccharide-based O serogroup phenotypically homogeneous and pathogenic for eels.

The eel pathogen Vibrio vulnificus biotype 2 survives for nearly two months in artificial seawater (ASW) at low temperatures in a nonculturable but viable state. The cells regain culturability when the temperature is increased to 15 degrees celsius (C). The cultured cells are infectious in eel and mice. The bacteria survives in a free-living form in ASW at 25 degrees celsius. An aquatic environment helps in the transmission of the pathogen. The pathogen is able to survive away from its host. It multiplies under favorable conditions in marine water until it is ready to cause infection.