Ecological distribution of Legionella pneumophila

Abstract

Bacteria were concentrated 500-fold from 20-liter water samples collected from 67 different lakes and rivers in the United States. The data suggest that Legionella pneumophila is part of the natural aquatic environment and that the bacterium is capable of surviving extreme ranges of environmental conditions. The data further demonstrate the effectiveness of the direct fluorescent-antibody technique for detecting L. pneumophila in natural aquatic systems. Smears of the concentrated samples were screened microscopically for serogroups of L. pneumophila by the direct fluorescent-antibody technique. Virtually all of the 793 samples were found to be positive by this method. The 318 samples containing the largest numbers of positive bacteria which were morphologically consistent with L. pneumophila were injected into guinea pigs for attempted isolations. Isolates were obtained from habitats with a wide range ofphysical, chemical, and biological parameters. Samples collected monthly from a thermally altered lake and injected into guinea pigs demonstrated a seasonality of infection, with the highest frequency of infection occurring during the summer months.

Long-term survival of Legionella pneumophila serogroup 1 under low-nutrient conditions and associated morphological changes

“…The association of L. pneumophila with water and water systems is now well established [3,14,[20][21][22]. Because legionellae are ubiquitous in the natural environment, it is often difficult to 'track', the source of this organism.…”

“…A large number of microbial ecology studies have been done which have established the ubiquity of legionellae in the environment [1][2][3][4][5]. However, very few studies have involved investigating the long-term survival and morphological changes of Legionella spp.…”

“…For example, Legionella spp. isolated from a variety of environmental sources exhibit different sensitivities to disinfectants [3,6]. Thus, longterm residence in a given environmental habitat may influence many aspects of cell metabolism and structure.…”

Silver as a Disinfectant

“…One microorganism that has been commonly isolated from cooling towers is Legionella pneumophila, the causative agent of Legionnaires' disease (Fliermans et al 1981;Landeen et al 1989). Many outbreaks have been linked to cooling towers (Bentham and Broadbent 1993;Brown et al 1999;CDC 1994) and evaporative condensers (Breiman et al 1990).…”

Unusual nosocomial infections

“…Legionella is found in the soil and natural water sources. 17 In nature it appears to be associated both • 18 with blue-green algae and with amebae. Although the organisms grow quite well in natural water sources, they also seem to have a great predilection for man-made hot water systems.…”