Characterisation of a haemolysin related to Vp-TDH produced by a Kanagawa phenomenon-negative clinical isolate of Vibrio parahaemolyticus.

The production of a family of haemolysins--thermostable direct haemolysin (Vp-TDH), Vp-TDH-related haemolysin (Vp-TRH) and Vp-TDH/I--has been reported in clinical isolates of Vibrio parahaemolyticus. This paper describes a fourth type of haemolysin--Vp-TDH/II--produced by a Kanagawa phenomenon-negative clinical isolate of V. parahaemolyticus (O13:K, untypable). Vp-TDH/II was purified by ammonium sulphate precipitation and successive filtrations on DEAE-cellulose, hydroxyapatite, Sepharose 4B and Mono Q columns. Vp-TDH/II was biophysicochemically and immunologically similar to, but not identical to Vp-TDH, Vp-TRH and Vp-TDH/I. Vp-TDH/II stimulated vascular permeability in rabbit skin and was lethal to mice. Purified Vp-TDH/II and viable cells of the Vp-TDH/II-producing strain both induced fluid accumulation in ligated rabbit intestine. The plasmid-determined structural gene for Vp-TDH/II was cloned and the nucleotide sequence determined. The deduced amino acid sequence of Vp-TDH/II differed from those of Vp-TDH, Vp-TRH and Vp-TDH/I.