SUMMARY Vibrio parahaemolyticus is recognized as a cause of food-borne gastroenteritis, particularly in the Far East, where raw seafood consumption is high. An unusual increase in admissions of V. parahaemolyticus cases was observed at the Infectious Diseases Hospital in Calcutta, a city in the northeastern part of India, beginning February 1996. Analysis of the strains revealed that a unique serotype, O3:K6, not previously isolated during the surveillance in Calcutta accounted for 50 to 80% of the infections in the following months. After this report, O3:K6 isolates identical to those isolated in Calcutta were reported from food-borne outbreaks and from sporadic cases in Bangladesh, Chile, France, Japan, Korea, Laos, Mozambique, Peru, Russia, Spain, Taiwan, Thailand, and the United States. Other serotypes, such as O4:K68, O1:K25, and O1:KUT (untypeable), that had molecular characteristics identical to that of the O3:K6 serotype were subsequently documented. These serotypes appeared to have diverged from the O3:K6 serotype by alteration of the O:K antigens and were defined as “serovariants” of the O3:K6 isolate. O3:K6 and its serovariants have now spread into Asia, America, Africa, and Europe. This review traces the genesis, virulence features, molecular characteristics, serotype variants, environmental occurrence, and global spread of this unique clone of V. parahaemolyticus.

The site of action of a Vero toxin (VT2 or Shiga-like toxin 11) from enterohemorrhagic Escherichia coli and Shiga toxin from Shigella dysenteriae 1 on eukaryotic ribosomes was studied. Treatment of eukaryotic ribosomes with either toxin caused the release of a fragment of 400 nucleotides from 28s ribosomal RNA when the isolated ribosomal RNA was treated with aniline. Release of this fragment with aniline treatment was accompanied by inhibition of protein synthesis and of elongation-factor-1-dependent aminoacyl-tRNA binding to ribosomes. Analysis of the nucleotide sequence of the 3'-terminal fragment of 553 nucleotides of 28s rRNA of rat liver 60s ribosomal subunits suggested that an adenine base at position 4324 (A-4324) was absent in toxin-treated 28s rRNA. Further analysis by thin-layer chromatography demonstrated quantitative release of adenine from rat liver ribosomes on treatment with the toxins. These results indicate that both VT2 and Shiga toxin inactivate 60s ribosomal subunits by cleaving the N-glycosidic bond at A-4324 in 28s ribosomal RNA. (T. Ogasawara et al., unpublished results) were recently shown to inactivate 60s ribosomal subunits and thereby inhibit EF-1-dependent binding of aminoacyl-tRNA to ribosomes, in this study we examined whether these bacterial cytotoxins inactivate 60s ribosomal subunits by the same mechanism as that of other plant and fungal cytotoxins. MATERIALS AND METHODS Purqications of Shiga toxin and VT2Shiga toxin was isolated and purified from the culture supernatant of S. dysenteriae 1 (RIMD 3101010) by ammonium sulfate fractionation, DEAE-cellulose column chromatography and repeated chromatofocusing column chromatographies, as described previously [28, 291. VT2, which has been shown to be immunologically unrelated to the Shiga toxin, but has similar biological activities to the latter, was isolated and purified from an enterohemorrhagic E. cali 0157:H7 strain J-2 as described earlier [12]. Both purified toxins gave a single band staining for protein on conventional polyacrylamide disc gel electrophoresis and polyacrylamide gel isoelectrofocusing. Preparation of anti-toxin sera against Shiga toxin and VT2Anti-toxin sera against Shiga toxin and VT2 were prepared by immunizing rabbits with purified Shiga toxin and purified VT2 as described previously [12, 281. Immunoglobulins

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We have characterized a nontoxic mutant of cholera toxin (