An in vitro hemolytic characteristic of Vibrio parahaemolyticus is closely correlated with human pathogenicity. A pathogenic halophile, Vibrio parahaemolyticus, has been well known as the causative agent of the most prevalent food poisoning in Japan. The organism has come to the attention of taxonomists outside Japan and was the subject of discussion at a recent international symposium (2, 4). In Japan, nationwide cooperative studies were initiated after the discovery of the causative agent during outbreaks of mackerel-borne food poisoning along the coast of the Pacific Ocean in 1959 (7). The 1959 outbreak was the second major occurrence since 1955 (5). Since then, extensive studies, including epidemiology and bacteriology, have been in progress, mainly by the Japanese workers. Evidence of the widespread distribution of V. parahaemolyticus in the sea of Southeast Asia and the Central Pacific has been reported by Yasunaga and Aoki et al. (personal communication), in the coastal areas of the United States by Baross and Liston (1), Colwell (personal communication), and Ward (9), and in Europe (i.e., in the Baltic Sea) by Nakanishi et al. (8).

SUMMARY : In recent years, it was demonstrated that cultures of Vibrio parahaemolyticus isolated from human diarrheal stools were different from those from sea fish and sea water in a hemolytic activity on a special blood agar, which was named the Kanagawa phenomenon.In the present studies, the finding has been confirmed by using 3370 cultures of the vibrios. Ninety-six % of the vibrios isolated from human patients gave positive (hemolytic) reaction in the test of the phenomenon, while only one % of the vibrios from sea fish and sea water gave positive results in the test.No relationship was observed between the phenomenon and serological and biochemical characteristics.Enteropathogenicity of the cultures of the vibrios positive in the Kanagawa phenomenon was evident by the results of feeding tests according to Takikawa and Aiiso and Fujiwara and by a case of laboratory infection of the culture to a male who took gastroenteritis by administration of approximately 106 viable cells of the hemolytic vibrios in the test of the phenomenon.On the other hand, feeding tests were carried out with 15 human volunteers to clarify enteropathogenicity of the negative (non-hemolytic) vibrios. None of them took illness, although over 109 cells of the vibrios were administered.Thus, the authors considered, as a rule, that the vibrios giving negative Kanagawa phenomenon may be nonpathogenic to human beings.

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A total of 1898 strains of Vibrio cholerae non-O1 non-O139, which had been collected worldwide for the past 3 year period of 1994-1996, were serogrouped. The strains were also examined for presence of cholera toxin (CT) gene (ctx) and NAG-ST gene, and strains which carried to ctx were further analyzed for their ability to produce CT. In addition, attempts were made to establish novel serogroups for those serologically untypable strains. Of those examined, 1,774 strains of V. cholerae non-O1 non-O139 was classified into 128 known serogroups while 50 strains were found to belong to R type, and the rest of the 74 strains could not be serotyped. Distribution of the serogroups did not seem to correspond to either the strains geographic distribution or sources of isolation. Of those serologically untypable strains, 38 novel serogroups (O156-O193) were established and added to our reference of V. cholerae antigenic schema. It was also found that antisera raised against many V. cholerae strains included R antibodies. This indicates that any V. cholerae antisera for diagnostic purpose should be absorbed with the reference R strains, CA385, before use. There were luminescence producing strains among those sucrose and VP reaction negative strains. Subsequent DNA/DNA homology analysis revealed that they were identified as V. cholerae. This points to a possibility that strains tentatively identified as Vibrio mimicus by conventional biochemical tests may have included luminescent strains of V. cholerae. It is thus highly recommended that strains in question should be tested for the luminescence production in order to differentiate V. cholerae from V. mimicus. Of those 1989 strains examined, 37 strains (ca. 2%) were found to produce CT. Interestingly, CT producing strains were prevalent in serogroup O141; 10 strains out of 16 strains (63%) were positive for CT. The evidence calls for a caution to possible occurrence of cholera-like diarrhea caused by V. cholerae O141 in the future.

ABSTRACT. From November 2000 to July 2002, 112 fecal samples from pet reptiles, including 18 turtles, 71 lizards and 23 snakes, sold at a pet shop were examined for the prevalence of Salmonella spp. in Japan. Salmonella spp. were isolated from 83 (74.1%) of 112 samples, and a total of 112 Salmonella isolates were identified as subspecies I to IV. The majority of isolates (62.5%) belonged to subspecies I and 54 isolates could be identified as any of 28 serovars. The predominant serovars were found to be S. Bardo, S. Newport and S. Panama, which cause human salmonellosis. These results indicate that pet reptiles may be a potential infectious source of human salmonellosis in Japan.