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Growth of Legionella in Nonsterilized, Naturally Contaminated Bathing Water in a System that Circulates the Water, Page 1 of 2
< Previous page Next page > /docserver/preview/fulltext/10.1128/9781555815660/9781555813901_Chap102-1.gif /docserver/preview/fulltext/10.1128/9781555815660/9781555813901_Chap102-2.gifAbstract:
In recent years, many public bathhouses introduced bathing water circulating systems for extended use, in which a sand filtration unit was installed. However, this resulted in several large scale outbreaks of legionellosis due to the microbiologically insufficient maintenance of the bathing facilities. Occurrence of Legionella in bathing water circulating systems, appears to be common and is a serious public health concern in Japan. The authors constructed a life-size model plant of a bathing water circulating system for the simulation experiment. These experiments are aimed at monitoring changes in the microbial constituents, especially a possible occurrence of Legionella in a bathing water circulating system, and developing preventive measures and intervention strategies. As a result of experiment 1, Legionella was detected in both the bathing water and the filter water at concentrations of 6.6 X 102 CFU/100 ml on the 3rd day after residual chlorine disappeared. The number of amoebae in the filter water fluctuated and amounted to 12 cells/ml at the end of the experiment. In the experiments, it was clearly demonstrated that Legionella occurred in the bathing water circulating system within a short period in a sequential manner of microbial growth. Namely, concentration of organic matter (dirt) in the bathing water can be monitored as the KMnO4 consumption value increased in correlation to the number of bathers. The deposited dirt allows bacteria to rapidly undergo multiplication in the bathing water, which consequently supports the occurrence of a large number of host amoebae.