Isolation of Vibrio vulnificus and atypical Vibrio from surface water of the Baltic Sea in Germany

From 1995 to 1997 several defined species like V. alginolyticus, V. anguillarum, V. cholerae (non O1 and non O139), V. mimicus, V. parahaemolyticus and V. vulnificus were isolated during a survey to determine the presence of V. vulnficus in the brackish water of the Baltic Sea in Germany. Moreover atypical Vibrio isolates were detected. Four isolates belonging to a group of atypical Vibrio and possibly representing a new species in the genus Vibrio were characterized in detail. All four strains were isolated from surface costal waters. Based on 16S rDNA sequence analysis they showed the highest relatedness to the species V. navarrensis and V. vulnificus. The strains did not harbor the species specific hemolysin gene whA from V. vulnificus as shown by PCR and hybridization experiments. Moreover, they differed in at least two biochemical parameters tested from the hitherto described Vibrio species. All these strains induced hemolysis on washed blood agar dishes and showed phase variations on Luria Bertani agar dishes. Because of the similarity to the eel pathogen V. vulnificus, we infected eels with one of the four atypical strains (CH-291), but no pathogenicity for eels could be detected. Furthermore, Vero cell tests with supernatants of bacterial cultures did not reveal secreted Vero cell cytotoxic compounds. This indicates a nonpathogenic nature of these strains.