外洋のプランクトンおよび魚類における腸炎ビブリオの分布について

Abstract

In the previous oceanographic survey conducted by HORIE et al.3) it was revealed that Biotype 1 organisms of Vibrio parahaemolyticus distribute in coastal sea area. It was also noted that Biotype 1 organisms can be more frequently isolated from plankton or marine mud than from sea water sample. The present study was undertaken to investigate the occurrence of Biotype 1 or 2 organisms in the plankton or fish inhabiting in the pelagic ocean. The survey was carried out aboard the Umitaka-maru, a research vessel of Tokyo University of Fisheries in the sea off Southern Kanto and Tokai districts late in July 1963. The location of sampling stations is shown in Fig. 1. Plankton samples were obtained at all the 13 stations, whereas young fish were caught only at 3 stations. At the station 9, particularly, several samples of sizable fish and squid could be caught using flyingfish drift net, and the gastric contents of these organ-isms were tested. A selective liquid medium, 3% NaCl containing arabinose ethyl violet broth (AE medium), as shown in Table 1, was used. In order to get higher rate of detection of Biotype 1 organisms, ME medium, 3% NaCl containing mannitol ethyl violet broth was employed, and the said medium of pH 7.8 was used in parallel with that of pH 9.0. No bacteria belonging to Biotype 1 could be detected from the samples collected in the pelagic ocean, whereas Biotype 2 were found to be widely distributed in the plankton samples. Biotype 3 bacteria was not isolated from the plankton, but detected in the samples of young fish and in the gastric contents of fish and squid. Some strains isolated from the flying fish could be classified as Biotype 2 on account of the salt resistance, positive Voges-Proskauer reaction and sucrose fermentation, however, they were differentiated from the typical organisms of Biotype 2 by other biological features.