Identification of bacterial flora in the water of swimming pools throughout the year

Abstract

A study was conducted to identify the bacterial flora present in outdoor and indoor swimming pools of a university facility used by healthy individuals and where the water quality was appropriately controlled. Bacteria that were isolated at high frequency throughout the year were gram-positive rods, Bacillus species, and gram-positive cocci, Staphylococcus species. All of the bacteria belonging to these two genera were essentially regarded as non-pathogenic. Other bacterial groups sampled from both pools were found to be members of medically non-problematic bacterial flora on the basis of their characteristics, showing that the water quality of the two pools was appropriately controlled. The swimming pools are appropriately managed, and treated with the disinfectant sodium hypochlorite at 0.4-1.0 ppm, as specified by Japanese law. Some species of the genera Pseudomonas and Serratia have recently been attracting attention as etiological agents of opportunistic infections. Therefore, P. aeruginosa and S. marcescens isolated in this study were subjected to a step-wise sodium hypochlorite sensitivity disk-test. Both bacteria formed an inhibition zone only around (on) a disc containing sodium hypochlorite at a very high concentration of 50 ppm, showing that some species of Pseudomonas and Serratia detected in the swimming pools were resistant to sodium hypochlorite.