In vivo survey of Vibrio spp. in artificially contaminated Mytilus edulis. VibrioNet-Project

All studies performed on the appearance of Vibrio spp. in mussels onpre-harvest and retail level in Germany so far showed high loads withthese microorganisms. As far as food safety is concerned Vibrio (V.)parahaemolyticus, V. vulnificus and V. cholerae are the mostimportant species within this genus.In our study, 106 retail mussel samples of different species and originwere investigated for the presence of Vibrio. Vibrio spp. was found in54.8 % of the samples investigated. In approx. 59 % of Vibriopositivesamples V. alginolyticus was detected, in 12 % V. cholerae(non 01, non 0139) and in 6 % V. parahaemolyticus. In addition,single V. metschnikovii, Photobacterium damselae and Listonellaanguillarum were found.One of the most frequently consumed mussel species in Germanyand world wide is Mytilus edulis. This mussel species filtrates approx.1.5 l of water per hour, thus an effective clarification occurs in itssurrounding. Along with the water, microorganisms such as V.parahaemolyticus and V. cholerae are affiliated. This potentialaccumulation of Vibrio spp. could cause food borne infections ifmussels are not properly heated before consumption. The aim of thestudy was to determine the clearance rate of Mytilus edulis afterartificial contamination with V. cholerae or V. parahaemolyticus.Additionally, the change of Vibrio loads in mussels during storage onice (3°C) or at 15°C were investigated, to simulate post-harvestconditions. Quantitative and semi-quantitative methods were used todescribe Vibrio concentrations within contamination- and clearancepondsas well as mussel lumen water, digestive gland and theremaining mussel meat. The contamination assays in Mytilus edulisshowed in a seven days period an enrichment of Vibrio withindigestive glands. During clearance a slow but continuously reductionof Vibrio concentrations was found. Within 10 days of storage on iceor at 15°C almost no reduction of the Vibrio load occurred in Mytilusedulis except for variations in a 2 log interval.