Seasonal Distribution of Vibrio parahaemolyticus Serotypes Along the Oyster Beds in Hiroshima Coast

1988年4月から、1989年3月までの1年間にわたって、広島県沿岸部のカキ養殖海域5地点から表層水、セジメントおよびカキ(冬季間のみ)を採取し、腸炎ビブリオの季節分布を調べ、分離菌の血清型別を行った。さらに物理的化学的各種困子の影響と汚染指標菌との関係についても検討した。腸炎ビブリオは夏季にはすべての地点で多数検出された。しかし、冬季になるに従って減少し、1～3月には検出されなくなった。腸炎ビブリオの出現と菌数は河口域地点で多く、出現する血清型も多かった.分離菌317株のうち、53.9%は型別可能で41の血清型に分類されたが、残りは型別できなかった。分離株を同定の結果、地点によって常時出現する血清型とセジメントやカキからのみ分離されて、同地点の海水から出現しないような血清型もみられた。分離した腸炎ビブリオ株はすべて神奈川現象陰性株であった。しかし、陰性株の中にも病原性を示すものがあるとの報告がみられることから、カキ養殖場における腸炎ビブリオの検査は重要である。

The seasonal distribution of Vibrio parahaemolyticus serotypes was studied from April 1988 to March 1989 in the coast of Hiroshima Prefecture where oyster culture is carried out. The influence of various physico-chemical parameters and microbial indicators of pollution on the distribution of this halophile was investigated. The organism was frequently isolated in all the study area during the warmer months and its density declined towards the winter season remaining undetectable in months of January through March. The incidence and counts of V. parahaemolyticus were consistently higher in estuarine area (salinity 15.5‰) with the highest incidence of various serotypes. Totally 41 serotypes were identified whereas 46.1% of the total isolated strains (317) in this study were untypable. Some serotypes were constantly isolated from a particular area whereas some were found only in oysters or sediments but not in the water column of the same area. All the strains were Kanagawa phenomenon-negative. As some Kanagawa phenomenon-negative strains have been reported to be pathogenic, the presence of a diverse number of V. parahaemolyticus serotypes isolated in an area which is economically important in oyster culture should be of concern to health authorities.