Clustering of Vibrio vulnificus Isolates Derived from the Coast of Nagasaki Prefecture and Clinical Samples Based on Restriction Fragment Length Polymorphism of 16S–23S rRNA Gene ITS Region (rITS-RFLP)

Abstract

Vibrio vulnificus is widely present in brackish water area and can cause fatal infections in patients with chronic liver diseases and other symptoms through raw seafood consumption and/or seawater exposure. A number of serious cases of Vibrio vulnificus infection have been reported along coastal area of the Ariake Sea in Japan. In the present study, we report on a sensitive typing method to V. vulnificus on the bases of restriction fragment length polymorphism (RFLP) of the intergenic spacer (ITS) region between 16S and 23S ribosomal RNA operons of the bacterial genomes. A total of 158 strains of V. vulnificus derived from coastal area of Nagasaki prefecture including the Ariake Sea and patients in northern Kyushu were examined. Among the resultant 7 clusters (I to VII), 57% (16/28) of the clinically derived strain was fallen into the cluster III and 96% (47/49) of the strains contained in the cluster III had clinical-type of virulence-correlated genes (vcg). Strains derived from the Ariake Sea were distributed across all the 7 clusters, and 64% of the strains had clinical type vcg genes, and 53% of them were fallen into the cluster III. This was in contrast to the characteristics of strains derived in coastal areas other than the Ariake Sea in Nagasaki Prefecture. These results indicate that (1) the rITS-RFLP method presented here is sensitive enough to detect V. vulnificus strains with high risk of infection, and (2) coastal area of the Ariake Sea holds greater diversity of V. vulnificus compared with other coastal areas of Nagasaki prefecture.