Abstract: This study investigated the occurrence (by means of the presence-absence test)
and level (by means of a plate count technique) of selected potentially pathogenic Vibrio
species in processed and ready-to-eat seafood, and some raw seafood normally used as raw
materials or ingredients in these products, that were commercially available in Chiang Mai,
Thailand. The level of Vibrio in raw seafood was found to range from 50 to 104 cfu/g. V.
alginolyticus was the most frequently found species, followed by V. parahaemolyticus, V.
cholerae, V. mimicus, and V. vulnificus, in that order. Processed and ready-to-eat products
were contaminated with at least one of the potentially pathogenic vibrios at significant
frequencies (25 and 17.5 % of samples, respectively), with the level as high as 103 to 104 per
gram in some samples. Incidences of vibrios revealed by the presence-absence test were
significantly higher than those revealed by the plate count assay. These data point to the
hazard potential relating to Vibrio in processed and ready-to-eat seafood and the need to
strictly apply preventive measures against Vibrio gastroenteritis through consumption of
these food products. They also suggest that analytical methods used in food safety
evaluation in relation to potentially hazardous Vibrio species should be carefully considered.