PHENOTYPIC AND GENOTYPIC CHARACTERIZATION OF A NEW FISH-VIRULENT VIBRIO VULNIFICUS SEROVAR THAT LACKS POTENTIAL TO INFECT HUMANS

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. For this purpose, phenotypic, serological and genetic (plasmid profiling, ribotyping and random amplified polymorphic DNA [RAPD]) techniques, as well as virulence challenges, were used. Our 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 pre-treatment with iron. Both serovars presented different biochemical profiles as well as specific patterns by ribotyping and RAPD analysis. In conclusion, SerA seems to constitute a different recently emerged clonal group within V. vulnificus species, with pathogenic potential for fish but not for humans.