Prevalence, characteristics and ecology of Vibrio vulnificus found in New Zealand shellfish

Abstract

Aims: In New Zealand, there have been no known cases of foodborne diseases linked to Vibrio vulnificus and shellfish consumption, but two cases of wound infection have been reported. We evaluated the distribution, the effect of environmental parameters, the pheno-genotypic profile and the growth characteristics of strains isolated from shellfish.

Methods and results: Vibrio vulnificus was present in 13·6% of Pacific oysters and not found in any dredge oyster or Greenshell(™) mussel samples. Eleven isolates belonged to biotype 1 while nine appeared to be variants of biotype 1. Nineteen isolates were genotype E (type A) and just one was genotype C (type B). Some isolates were more resistant to high salt concentrations (>30‰) than others, but not different from ATCC 27562.

Conclusions: Vibrio vulnificus were low in numbers, mostly belonging to genotype E, 16S rRNA type A and biotype 1. No relationship or adaptability to high salinity was observed, but seawater temperature was a strong predictor of bacterial numbers in shellfish.

Significance and impact of the study: We report, for the first time, the characterization of V. vulnificus isolated from New Zealand shellfish and its long-term distribution and prevalence. This information will help the authorities on risk assessments.

Keywords: Greenshell™ mussel (Perna canaliculus); Pacific oyster (Crassostrea gigas); Vibrio vulnificus; biotype; dredge oyster (Ostrea chilensis); salinity.