A survey of urease-positive Vibrio parahaemolyticus strains isolated from traveller's diarrhea, sea water and imported frozen sea foods.

The frequency of urease-positive Vibrio parahaemolyticus among isolates from patients, imported frozen sea foods and the environment (sea water) was studied. The highest isolation frequency of urease-positive V. parahaemolyticus was found in clinical isolates (11.2% out of 204 strains examined). Urease-positive V. parahaemolyticus was found in 5.7% of 88 frozen sea food-isolates examined, but no strains isolated from sea water were urease-positive. The isolates were further examined for the production of thermostable direct hemolysin (Vp-TDH) and its related hemolysin (Vp-TRH). Both are possible pathogenic toxins produced by mostly clinical isolates of V. parahaemolyticus. Urease-positive strains have a tendency to associate with clinical isolates producing both or neither Vp-TDH and Vp-TRH. Rabbit ligated ileal loops test was performed with several strains of urease-positive and -negative clinical isolates, and we found that some strains producing urease, even those which do not produce Vp-TDH or Vp-TRH, caused intestinal fluid accumulation.