Viability of C. trachomatis in thermal waters collected from 5 spas was examined by inclusion forming ability in HeLa cells. In the acid springs (pH 2.0-2.2), the organisms lost their infectivity within 0.5hr when they were incubated at 37°C and no inclusion were detected when incubated at 42°C. In weak alkaline springs (pH 8.0-8.8), the organisms could be detected after incubation at 37°C for 2hr or at 42°C for 1hr, but number of inclusions were significantly decreased.

Viability of Pseudomonas aeruginosa was examined by putting it into hot spring collected from seven places. In the acid waters (pH 2.0 to 2.2), the organisms lost their viability immediately at both cultivation temperatures of 37°C and 42°C. In alkaline waters (pH 8.0 to 9.1), the organisms were detected and increased after cultivation for 2 hours at 37°C.
The above result suggests that Pseudomonas aeruginosa may be present in whirlpools and/or indoor swimming pools of alkaline waters having a large number of bathers in a relatively small volume of water.