Physicochemical Factors Influencing Distribution of Legionella Species in Japanese Hot Springs

We examined the relationship between the distribution of Legionella bacteria and various physicochemical characteristics of hot springs in Japan. Legionella bacteria were isolated from 52 (49.5%) out of 105 water samples, particularly from outdoor hot springs (67.3%). The bacterial count in the water samples positive for Legionella (86.5%) ranged from 101 to780mg/L, and H2SiO3: >146mg/L. The hot waterrecirculating systems were applied to 18 out of 20 (90%) hot spring facilities which were found positive for Legionella. These results indicate that Legionella species are widespread in hot springs throughout Japan, except for waters with a low pH and non-recirculating waters, and that a single strain of L. pneumophila SG 4 is predominant in a particular hot spring resort.