Colonization factor of thermostable direct hemolysinproducing Vibrio parahaemolyticus in the alimentary tract of a gastropod, Clithon retropictus

用扫描电子显微镜观察了耐热的副溶血性弧菌在河口腹足动物消化道内的定植情况，以及腹足动物对消化道微生物的防御反应。在冲绳岛北部河口微咸水水域，调查了冲绳和三江县河口4种网纹腹足类和腹足类中产三氢呋喃的菌株的生态。在与前四种腹足类分布地点相邻的淡水区发现了反枝线虫，但在半咸水区几乎没有见到腹足类个体。由于副溶血弧菌不能在淡水中存活，副溶血弧菌可能与冲绳河口的前4种腹足类有关，而不是冲绳河口的逆行螺旋体。1996年8月，在三叶县三屋河和五十铃河口的逆行螺旋体中分别检出2.1×10^5/g和3.0/g的TDH菌，但从蚕豆、冠冠、铅和波塞纳4种腹足类中未检出。在冲绳，利用TDH基因进行聚合酶链式反应，逆转录弧菌D3菌株经口接种，并保存在盐度为20*的紫外线照射的循环人工海水中。以适当的时间间隔取出腹足动物的消化道，用2.5%的戊二醛固定，乙醇脱水，涂铂，在扫描电子显微镜下观察，粘膜上看不到微生物。由于通过菌落计数法从消化道检测到的有机体的水平在个别情况下是高度可变的，因此可能需要进一步的观察。

Colonization of thermostable direct hemolysin (TDH)-producing Vibrio parahaemolyticus in the alimentary tract of an estuarine neritid gastropod, Clithon retropictus, and defense reaction of the gastropod to the organism in the alimentary tract was investigated under scanning electron microscope (SEM). Ecology of neritid gastropods and of the TDH-producing strains in the gastropods were surveyed at estuaries in Okinawa and Mie Prefectures.Four neritid gastropods, Clithon faba, C.corona, Neritina plumbea and Septaria porcellana, ranged at the brackish water areas of estuaries of the northern part of Okinawa island. C.retropictus was seen at the freshwater areas adjacent to the sites where the former four neritid gastropods ranged, though few individuals of the gastropod were seen at the brackishwater area. As V.parahaemolyticus cannot survive in freshwater, V.parahaemolyticus was supposed to be associated with the former four gastropods rather than C.retropictus at estuaries in Okinawa.TDH-producing strain was detected from C.retropictus at estuaries of Miya and Isuzu rivers in Mie Prefecture at a level of 2.1*10^5/g and 3.0/g, respectively, in August, 1996, but not from the four neritid gastropods, C.faba, C.corona, N.plumbea and S.porcellana, in Okinawa by Polymerase Chain Reaction using tdh gene.C.retropictus was inoculated per os by V.parahaemolyticus strain D3 and maintained in UV-irradiated recirculating artificial seawater with a salinity of 20*. At appropriate time intervals, the alimentary tract of the gastropod were removed, fixed with 2.5% glutaraldehyde, dehydrated with ethanol, coated with platinum and observed under SEM.The organism was not seen on the mucous membrane. As the level of the organism detected from the alimentary tract by the colony count method is known to be highly variable individually, further observations might be necessary.