Comparative Phenotypic, Molecular, and Virulence Characterization of \u3cem\u3eVibrio parahaemolyticus\u3c/em\u3e O3:K6 Isolates

Historically, Vibrio parahaemolyticus infections have been characterizedby sporadic cases caused by multiple, diverse serotypes. However,since 1996, V. parahaemolyticus serotype O3:K6 strains havebeen associated with several large-scale outbreaks of illness,suggesting the emergence of a new group of organisms withenhanced virulence. We have applied three different molecularsubtyping techniques to identify an appropriate method for differentiatingO3:K6 isolates from other serotypes. Pulsed-field gel electrophoresis(PFGE) following NotI digestion differentiated seven closelyrelated subtypes among O3:K6 and related strains, which weredistinct from PFGE patterns for non-O3:K6 isolates. Ribotypingand tdh sequencing were less discriminatory than PFGE, but furtherconfirmed close genetic relationships among recent O3:K6 isolates.In vitro adherence and cytotoxicity studies with human epithelialcells showed that O3:K6 isolates exhibited statistically higherlevels of adherence and cytotoxicity to host cells than non-O3:K6isolates. Epithelial cell cytotoxicity patterns were determinedwith a lactate dehydrogenase release assay. At 3 h postinfection,high relative cytotoxicities (\u3e50% maximum lactate dehydrogenaseactivity) were found among a greater proportion of recentlyisolated O3:K6 and closely related strains (75%) than amongthe non-O3:K6 isolates (23%). A statistically significant relationshipbetween adherence and cytotoxicity suggests that the pathogenicpotential of some isolates may be associated with increasedadherence to epithelial cells. Our findings suggest that enhancedadherence and cytotoxicity may contribute to the apparent uniquepathogenic potential of V. parahaemolyticus O3:K6 strains

Sequence Polymorphism of the 16S rRNA Gene of Vibrio vulnificus Is a Possible Indicator of Strain Virulence

Vibrio vulnificus exhibits considerable strain-to-strain variation in virulence. Attempts to associate phenotypic or genotypic characteristics with strain virulence have been largely unsuccessful. Based on a 17-nucleotide difference throughout the sequence of the small subunit 16S rRNA gene, there are two major groups of V. vulnificus designated types A and B. In a survey of the 16S rRNA genotype in 67 V. vulnificus human clinical and nonclinical strains, we determined that the majority of nonclinical isolates are type A (31 of 33) and that there is a statistically significant association between the type B genotype and human clinical strains (26 of 34)

Comparison of Direct Genome Restriction Enzyme Analysis and Pulsed-Field Gel Electrophoresis for Typing of Vibrio vulnificus and Their Correspondence with Multilocus Sequence Typing Data▿

We compared the potential of direct genome restriction enzyme analysis (DGREA) and pulsed-field gel electrophoresis (PFGE) for discriminating Vibrio vulnificus isolates from clinical (23) and environmental (17) sources. The genotypes generated by both methodologies were compared to previous multilocus sequence typing (MLST) data. DGREA established clearer relationships among V. vulnificus strains and was more consistent with MLST than with PFGE. DGREA is a very promising tool for epidemiological and ecological studies of V. vulnificus