Uncovering the geographical and host impacts on the classification of Vibrio vulnificus

Vibrio vulnificus causes human sickness throughout the world via the consumption of undercooked seafood or exposure to contaminated water. Previous attempts at phylogenetic analyses of V. vulnificus have proven unsuccessful, mainly due to the poorly understood impact of factors on its divergence. In this study, we used advanced statistical and phylogenetic methods to strengthen the classification of V. vulnificus. This updated classification included the impact of geographical and host factors. The results demonstrate the existence of hierarchies and multidimensional effects in the classification of V. vulnificus, from the molecular level using biotypes, to the distributional level using geographical location, to the adaptational level through host immune response. These findings have implications for the classification of bacteria, bacterial evolution, and public health.

Occurrence of Vibrio vulnificus in mussel farms from the Varano lagoon environment

AIMS

Monitoring the occurrence of the human pathogen Vibrio vulnificus in a mussel farm located in the lagoon of Varano (Italy).

METHODS AND RESULTS

A total of 72 samples of mussel, water and sediment, collected from two locations of Varano lagoon in the Gargano peninsula, during a 7-month survey, were analysed. Isolation and PCR characterization of six V. vulnificus environmental genotype strains revealed that this pathogen was isolated when with T was above 22 °C and salinity ranged between 22.7 and 26.4‰. No significant correlation of the occurrence of V. vulnificus with water pH or salinity was observed. Moreover, 8% of mussel samples were found to be contaminated by V. vulnificus. All of that positive mussel samples originated from the same sampling station.

CONCLUSION

It is suggested that warmer season are risky to eat raw or undercooked bivalve molluscs in the local area.

SIGNIFICANCE AND IMPACT OF THE STUDY

To increase knowledge about environmental conditions that may affect the occurrence of waterborne pathogen Vibrio vulnificus in seafood.

Immunomagnetic separation of Vibrio vulnificus with antiflagellar monoclonal antibody

Raw oysters are primary vectors for Vibrio vulnificus infections, and a rapid detection method for V. vulnificus in raw oysters before distribution would be an indispensable tool for the seafood industry. One approach to improving the recovery and detection of V. vulnificus without sacrificing assay time is through the use of immunomagnetic separation (IMS). The aim of this study was to develop and optimize an IMS protocol using anti-H (antiflagellar) antibody for determining the level of V. vulnificus in phosphate-buffered saline (PBS) suspensions and spiked oyster homogenate. Six monoclonal antibodies were produced by immunizing mice at 2-week intervals by injection of 50 microg of purified V. vulnificus ATCC 27562 flagellin. Antibodies that exhibited high anti-H titers were coated onto Cowan I Staphylococcus aureus cells and sheep anti-mouse immunoglobulin G immunomagnetic beads. The two reagents were used to determine the species specificity of the selected antibodies, which positively identified and coagglutinated 70 isolates identified genetically as V. vulnificus and did not react with 40 Vibrio parahaemolyticus isolates or nine other Vibrio species. The IMS protocol was optimized for PBS and oyster homogenate spiked with three different strains of V. vulnificus. IMS with V. vulnificus-spiked PBS yielded binding of 19 to 57%, and IMS with spiked oyster homogenate carried out at two V. vulnificus levels exhibited binding of 25 to 57%. The IMS protocol for V. vulnificus could be used to concentrate and detect V. vulnificus in seawater and shellfish homogenate.

Thermal factors influencing detection of Vibrio vulnificus using real-time PCR

Five thermal factors, including initial denaturation temperature, cycling denaturation temperature, annealing temperature, extension temperature and the temperature at which the intensity of the fluorescent signal is read, were evaluated for their effects on the detection of Vibrio vulnificus via real-time PCR. Fluorescent signal detection after extension was set between the Tm value of the primer-dimers (79 degrees C) and that of the PCR target amplicons (84 degrees C). This effectively eliminated the overestimation of the yield of PCR amplicons due to the presence of primer-dimers which otherwise led to erroneously lower Ct values (1.91+/-0.22 cycles lower). The annealing and extension steps were combined to convert a three-step PCR to a two-step PCR. This consisted of initial denaturation at 95 degrees C for 3 min, cycling denaturation at 94 degrees C for 15 s and a combined annealing and extension step at 60 degrees C for 5 s in each PCR cycle. One genomic target per real-time PCR reaction was detected with the simplified two-step PCR.

Rapid quantification of Vibrio vulnificus in clams (Protochaca staminea) using real-time PCR

We used a rapid DNA extraction and purification method to obtain the DNA from Vibrio vulnificus seeded into clam tissue homogenates for real-time PCR quantification of the organism. Without enrichment, the limit of detection was 1 x 10(2) cfu/g of tissue with a linear detection range of 1 x 10(2) to 1 x 10(8) cfu/g. With a 5 h non-selective enrichment, the limit of detection was 1 cfu/g of tissue with a linear detection range of 1 to 1 x 10(6) cfu/g of tissue. We found a 10-fold higher detection limit with seeded clam tissue homogenates compared to pure culture in TSB(+). The detection limits with pure broth culture and seeded tissue homogenates were identical, 1 cfu/ml and 1 cfu/ml, respectively, following 5 h non-selective enrichment. However, the Ct value with tissue homogenates was about 3 threshold cycles higher than with pure culture.