Survival and multiplication of Legionella pneumophila in municipal drinking water systems

S J States, L F Conley, J M Kuchta, B M Oleck, M J Lipovich, R S Wolford, R M Wadowsky, A M McNamara, J L Sykora, G Keleti
1987 Applied and Environmental Microbiology  
Studies were conducted to investigate the survival and multiplication of Legionella spp. in public drinking water supplies. An attempt was made, over a period of several years, to isolate legionellae from a municipal system. Sampling sites included the river water supply, treatment plant, finished water reservoir system, mains, and distribution taps. Despite the use of several isolation techniques, Legionella spp. could not be detected in any of the samples other than those collected from the
more » ... ver. It was hypothesized that this was due to the maintenance of a chlorine residual throughout this system. To investigate the potential for Legionella growth, additional water samples, collected from throughout the system, were dechlorinated, pasteurized, and inoculated with Legionella pneumophila. Subsequent growth indicated that many of these samples, especially those collected from areas affected by an accumulation of algal materials, exhibited a much greater ability to support LegioneUa multiplication than did river water prior to treatment. Chemical analyses were also performed on these samples. Correlation of chemical data and experimental growth results indicated that the chemical environment significantly affects the ability of the water to support multiplication, with turbidity, organic carbon, and certain metals being of particular importance. These studies indicate that the potential exists for Legionella growth within municipal systems and support the hypothesis that public water supplies may contaminate the plumbing systems of hospitals and other large buildings. The results also suggest that useful methods to control this contamination include adequate treatment plant filtration, maintenance of a chlorine residual throughout the treatment and distribution network, and effective covering of open reservoirs. 979 Vol. 53, No. 5 on May 4, 2020 by guest Downloaded from APPL. ENVIRON. MICROBIOL. legionellae has been demonstrated in a number of earlier studies (28, 38, 39) . These naturally occurring L. pneumophila and associated microbiota were maintained in the laboratory as a water stock culture by periodic transfer into membrane-filtered tap water which had been collected from a tap in the laboratory. A cellulosic nitrate membrane (Micro Filtration Systems, Dublin, Calif.) with a pore size of 0.20 lim was used to filter
doi:10.1128/aem.53.5.979-986.1987 fatcat:jvqy4pypivh5jgzcia2we5bx3e