STUDIES ON THE ENTEROPATHOGENIC, FACULTATIVELY HALOPHILIC BACTERIA, VIBRIO PARAHAEMOLYTICUSI. MORPHOLOGICAL, CULTURAL AND BIOCHEMICAL PROPERTIES AND ITS TAXONOMICAL POSITION

Abstract

In the summer season, food poisoning with symptoms of acute gastro-enteritis implicating in sea-fish and fish-products breaks out in succession in Japan, where it is a custom for the people to eat raw sea-fish. Recently, a group of facultatively halophilic organisms has attracted much interest of the Japanese investigators as a causative agent of the food poisoning.
The organism in question was first reported by Fujino and his co-workers (1951, 1953) who had found the organism in autopsy materials collected from an outbreak of gastro-enteritis which involved 272 persons, including 20 fatal ones, and in“shirasuboshi”, or boiled and semi-dried young sardine, which was considered as the causative foodstuff of the outbreak.
Takikawa (1958) studied 34 strains of an enteropathogenic, facultatively halophilic organism, all of which, except one, had been isolated on ordinary agar plate containing 4 % sodium chloride from the feces of patients in several outbreaks of gastro-enteritis. The 33 strains grew profusely in/on media containing 0.5 M (2.9 %) sodium chloride and possessed similar morphological and biochemical characteristics. The remaining strain was of the organism of Fujinoet al. mentioned above. Takikawa concluded that the organism of Fujinoet al. might belong to the same group as his organism. In addition, he was able to produce gastro-enteritis in 11 human volunteers by feeding.
After Takikawa, many Japanese investigators paid attention to the organism, which has been isolated repeatedly from further outbreaks of gastro-enteritis implicating in sea-fish and its products. Now, it is said that over 50 % of the diagnosed outbreaks of bacterial gastro-enteritis in Japan may have been caused by the organism.
The organism was studied ecologically by Miyamoto and his co-workers (1960, 1961a, 1961b), Hone and his co-workers (1963), and Wagatsuma (1962) . These investigators described that the organism had been found frequently in coastal seawater and sea-fish but not in pelagic.
In spite of the description mentioned above, many important questions are still in abeyance. For example, the taxonomical position of the organism is unknown. Although Fujinoet al. and Takikawa proposed the namesPasteurella parahemolyticaandPseudomonas enteritis, respectively, for the organism, it is obvious from its morphological and biochemical properties that it belongs neither to Pasteurella nor toPseudomonas. Since the properties of the organism have been little known, they should be studied in detail.
It is not clear whether all the other members of the same group as the organism are enteropathogenic or only a few of them possess an enteritis-producing power. It has been reported by many workers that organism with the same biochemical and serological properties as the organism originated from patients were distributed widely in sea-water and sea-fish. On the other hand, Takikawa (1958, 1960) established 26 serotypes of the organisms without giving any account of antigenic analysis. He reported that no common antigens had been observed among these serotypes. Some other workers indicated, however, that some of Takikawa's strains manifested reciprocal and unilateral reactions in cross-agglutination tests. Thus, confusion has occurred in the bacteriological and serological fields of the organism.
Therefore, studies have been carried out to obtain sufficient information of its characteristics and to clarify its taxonomical position. The present paper describes the morphological, cultural, and biochemical properties of the organism. A subsequent paper will deal with its serological properties.