Survival and multiplication of Legionella pneumophila in municipal drinking water systems

Abstract

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 river. 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.

A laboratory apparatus for the generation and biocide efficacy testing of Legionella biofilms

“…The proliferation of legionellas and especially of Legionella pneumophila in cooling tower waters (Dondero et al 1980;Ikedo et al 1986), potable water supplies (States et al 1987;Vickers et al 1987), humidifiers (Marrie et al 1987) and various other aerosol generating devices has aroused interest and concern in recent years. The regular isolation of legionellas from such environments, particularly those associated with hospitals or other institutions where the ill or elderly are involved, is of particular importance.…”

Comparison of Detection Methods for Legionella Species in Environmental Water by Colony Isolation, Fluorescent Antibody Staining, and Polymerase Chain Reaction

“…Survey and monitoring of legionellae in environments are needed to prevent and control legionellosis. Legionella species are recovered from aquatic environments, such as rivers (18), lakes and ponds (8), cooling towers (13,21), and even tapwater (15). In water samples from these environments, cell numbers of legionellae were 102 to 105 cell/ml by direct counting with fluorescent antibody (FA) staining (8,18).…”

“…Legionella species are recovered from aquatic environments, such as rivers (18), lakes and ponds (8), cooling towers (13,21), and even tapwater (15). In water samples from these environments, cell numbers of legionellae were 102 to 105 cell/ml by direct counting with fluorescent antibody (FA) staining (8,18). On the other hand, colony numbers of legionellae from the water samples were usually lower than the number detected by direct counting (18,21).…”

“…In water samples from these environments, cell numbers of legionellae were 102 to 105 cell/ml by direct counting with fluorescent antibody (FA) staining (8,18). On the other hand, colony numbers of legionellae from the water samples were usually lower than the number detected by direct counting (18,21). Several surveys also reported that legionellae were not isolated from many FA-positive samples, cooling tower water (13), tap-water (15), or river water (18).…”

“…On the other hand, colony numbers of legionellae from the water samples were usually lower than the number detected by direct counting (18,21). Several surveys also reported that legionellae were not isolated from many FA-positive samples, cooling tower water (13), tap-water (15), or river water (18). FA staining is generally accepted to detect legionellae from environmental samples.…”