Genetic and quantitative assessment of Vibrio vulnificus populations in oyster (Crassostrea virginica) tissues

Abstract

Vibrio vulnificus is a leading cause of shellfish-associated food-borne illness. US regulations stipulate shellfish processing procedures to limit V. vulnificus densities; however, the effect of these procedures on V. vulnificus strain distribution and/or genetic diversity is unknown. Vibrio vulnificus concentrations and strain diversity were analysed in various oyster tissues stored overnight at 26°C that were subsequently divided into two treatment groups: one received post-harvest processing (PHP) via individual quick freeze and one was stored on ice. Vibrio vulnificus densities were 10-fold lower in all PHP-treated tissues compared with untreated tissues. Genetic diversity of V. vulnificus was assessed by BOX-PCR genotyping and was high in all oyster tissues, but was significantly lower in untreated compared with PHP-treated oysters. BOX-PCR discriminated strains into BOX-C (clinical-associated) and BOX-E (environmental-associated) types based on a 1.1 kb DNA band, which correlated well (83% agreement) with 16S rRNA (A/B) typing. A significantly higher proportion of BOX-C isolates were recovered from PHP oysters compared with untreated oysters (24% of all isolates versus 12%) suggesting that BOX-C strains may be more resistant to treatment. These results reveal highly diverse populations of V. vulnificus in oysters with different responses to PHP, emphasizing the need to better understand the organism's ecology and population genetics to optimize food safety practices.

Impact of Hurricane Irene on Vibrio vulnificus and Vibrio parahaemolyticus concentrations in surface water, sediment, and cultured oysters in the Chesapeake Bay, MD, USA

“…These findings are in contrast to previous, laboratory-based studies, examining the relationship between V. vulnificus’ virulence associated genes in oysters. These previous studies found no change in V. vulnificus virulence associated genes during the passage through the oyster (Groubert and Oliver, 1994; Staley et al, 2011). It is possible that the changes in virulence-associated genes percentages in this study are associated with population turnover within the oyster during the storm period.…”

Detection and differentiation of Vibrio vulnificus and V. sinaloensis in water and oysters of a Gulf of Mexico estuary

“…Shellfish, particularly oysters, are known to harbour high concentrations of Vibrio vulnificus, an autochthonous, Gram-negative, opportunistic human pathogen (Johnson et al, 2010;Staley et al, 2011). The bacterium exhibits a high degree of genetic diversity and is divided into three biotypes (1, 2 and 3) based on genotypic as well as phenotypic differences.…”

“…Water salinity is also an important factor affecting concentrations of the bacterium in water and oysters; the highest concentrations are typically detected when salinity is between 5 and 25‰ (Oliver et al, 1983;Motes et al, 1998;Pfeffer et al, 2003). Genetic diversity of V. vulnificus populations in individual oysters has also been reported to be very high, with more than 100 strains present in a single oyster (Buchrieser et al, 1995;Staley et al, 2011). Genetic diversity of V. vulnificus populations in individual oysters has also been reported to be very high, with more than 100 strains present in a single oyster (Buchrieser et al, 1995;Staley et al, 2011).…”

“…Under favourable temperature and salinity conditions, V. vulnificus concentrations have been reported to vary from > 10 5 cfu (colonyforming units) g -1 to undetectable in individual oysters sampled from the same site (Birkenhauer and Oliver, 2003). Genetic diversity of V. vulnificus populations in individual oysters has also been reported to be very high, with more than 100 strains present in a single oyster (Buchrieser et al, 1995;Staley et al, 2011).…”

Integration of Vibrio vulnificus into Marine Aggregates and Its Subsequent Uptake by Crassostrea virginica Oysters

“…40 primary septicemia cases reported per year (10). Usually, oysters predominately contain the E-genotype strains of V. vulnificus, which is likely a factor in the low number of infections (12)(13)(14)(15)(16)(17)(18).…”