河川水中におけるAeromonasの分布

太田川水系および小田川水系を選んで生活用水源あるいは内水面漁場としての河川水中におけるAeromonasの分布状況について調査し検討した。その結果, (1) Aeromonasは表流水中よりもアユなどの餌ともなる苔類にはるかに多く分布していた。 (2) この分布状況は水温に大きく影響され,27℃以上の温度域では試料の80%において1mlあたり10^3以上の菌数が存在し,水温の低下と共に減少する傾向を示した。 (3) この減少傾向は表流水で顕著で,20℃以下では1mlあたり10以下まで減少した。 (4) 分離されたAeromonasの病原性と密接な関係にある溶血能も,やはり水温に影響され,特に29℃以上では病原菌としての可能性を思わせる強い溶血能を持った菌株が60～80%を占めていた。 (5) しかし,水温の低下に伴って溶血能の弱い菌株や非溶血株が増える傾向にあった。

Aeromonas (A. hydrophila, A. salmonicida etc.) are well known as being Vibrio associated with food poisoning or diseases among humans, fish including ayu (sweetfish) and other animals. The summer in 1978, a large number of Ayu died of illness in the Ohta river. At that time we examined and discussed the distribution of Aeromonas in the Ohta and Oda rivers. 1) Larger quantities of Aeromonas were distributed in algae which are Ayu and other fishes food than in the surface water itself. 2) The distribution of the Aeromonas depended on the water temperature largely. In 80% of the algae tested, the number of Aeromonas was 10^3 cells per ml in the temperature range of over 27°C. This number decreased gradually as the temperature decreased. 3) The decreasing tendency of Aeromonas was notable in the surface water. The number of Aeromonas per ml was less than 10 cells in the temperature range of below 20°C. 4) The haemolytic activity of the isolated Aeromonas also depended on the water temperature. Especially, in the temperature range, of over 29°C, 60-80% of the isolated Aeromonas had strong haemolytic activity which is connected with the cause of food poisoning or diseases among humans, fish and other snimals. 5) However, as the temperature decreased, the isolated Aeromonas had weak haemolytic activity. Still others had no haemolytic activity increased tendencies.