Presence of genes for type III secretion system 2 in Vibrio mimicus strains

Abstract

<p>Abstract</p> <p>Background</p> <p>Vibrios, which include more than 100 species, are ubiquitous in marine and estuarine environments, and several of them e.g. <it>Vibrio cholerae</it>, <it>V. parahaemolyticus</it>, <it>V. vulnificus </it>and <it>V. mimicus</it>, are pathogens for humans. Pathogenic <it>V. parahaemolyticus </it>strains possess two sets of genes for type III secretion system (T3SS), T3SS1 and T3SS2. The latter are critical for virulence of the organism and be classified into two distinct phylogroups, T3SS2α and T3SS2β, which are reportedly also found in pathogenic <it>V. cholerae </it>non-O1/non-O139 serogroup strains. However, whether T3SS2-related genes are present in other <it>Vibrio </it>species remains unclear.</p> <p>Results</p> <p>We therefore examined the distribution of the genes for T3SS2 in vibrios other than <it>V. parahaemolyticus </it>by using a PCR assay targeting both T3SS2α and T3SS2β genes. Among the 32 <it>Vibrio </it>species tested in our study, several T3SS2-related genes were detected in three species, <it>V. cholerae</it>, <it>V. mimicus </it>and <it>V. hollisae</it>, and most of the essential genes for type III secretion were present in T3SS2-positive <it>V. cholerae </it>and <it>V. mimicus </it>strains. Moreover, both <it>V. mimicus </it>strains possessing T3SS2α and T3SS2β were identified. The gene organization of the T3SS2 gene clusters in <it>V. mimicus </it>strains was fundamentally similar to that of <it>V. parahaemolyticus </it>and <it>V. cholerae </it>in both T3SS2α- and T3SS2β-possessing strains.</p> <p>Conclusions</p> <p>This study is the first reported evidence of the presence of T3SS2 gene clusters in <it>V. mimicus </it>strains. This finding thus provides a new insight into the pathogenicity of the <it>V. mimicus </it>species.</p