Persistence of Pseudomonas aeruginosa in chlorinated swimming pools

Various types of swimming pools were investigated for the quantitative isolation of Pseudomonas aeruginosa. Incidence of the organism increased when the free chlorine residual dropped below 0.4 mg/L in pool water which ad a pH of 6.9-8.9. As the water pH became more alkaline the efficiency of disinfection decreased. Excessive slime production caused certain strains to become more resistent to chlorine treatment. Immunotyping and phage typing, used to study the dynamics of P. aeruginosa populations in swimming pool waters, demonstrated that high densities of the organism consisted mainly of single predominant strains.