Multiplication of Legionella pneumophila in unsterilized tap water

Abstract

Naturally occurring Legionella pneumophila, an environmental isolate which had not been grown on artificial medium, was tested for the ability to multiply in tap water. A showerhead containing L. pneumophila and non-Legionellaceae bacteria was immersed in nonsterile tap water supplying this fixture. Also L. pneumophila and non-Legionellaceae bacteria were sedimented from tap water from a surgical intensive care unit. This bacterial suspension was inoculated into tap water from our laboratory. The legionellae in both suspensions multiplied in the tap water at 32, 37, and 42°C. The non-Legionellaceae bacteria multiplied at 25, 32, and 37°C. A water sample which was collected from the bottom of a hot water tank was found to contain L. pneumophila and non-Legionellaceae bacteria. These legionellae also multiplied when the water sample was incubated at 37°C. These results indicate that L. pneumophila may multiply in warm water environments such as hot water plumbing fixtures, hot water tanks, and cooling towers. Water and moist environments may be the natural habitats for Legionella pneumophila. These bacteria have been isolated from natural waters such as lakes, ponds, and streams (4, 5, 11), from cooling towers of air conditioning systems (8), and from the plumbing systems of hospitals and hotels (2, 15). Tison et al. (14) have reported growth of L. pneumophila with a mean doubling time of 2.7 h in coculture with cyanobacteria under conditions of illumination. Only slight growth of the legionellae occurred when photosynthesis was inhibited by either dark incubation or exposure to a chemical inhibitor of photosystem II. These investigators concluded that the high rate of multiplication of L. pneumophila was dependent on active photosynthesis of the cyanobacteria. Accordingly, under conditions of darkness, which occur in plumbing systems, the cyanobacteria may not be able to support the growth of L. pneumophila. Factors other than cyanobacterial photosynthesis may be involved in providing the nutrients for the growth of the legionellae in tap water in plumbing systems. The work of Highsmith et al. (Abstr. Annu. Meet. Am. Soc. Microbiol. 1979, Q71, p. 231) suggests that L. pneumophila may be able to grow in sterile water that is used for intravenous injection. These investigators found that, after incubation for 6 weeks at 25°C after inoculation with L. pneumophila, bottles of the water became turbid. Examination by Gram staining, phase-contrast microscopy, and direct immunofluores

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

“…In Fig. 1 Legionella have been reported to exhibit brief periods of growth in both autoclaved drinking water [7], and in unsterilized drinking water [20]. As shown in Fig.…”

“…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.…”

The persistence of Legionella pneumophila in non‐sterile, sterile and artificial hard waters and their growth pattern on tap washer fittings

“…The implication is that either (i) the presence of the small numbers of non-legionella organisms were not sufficient to provide the quantity of growth factors required or (ii) they were not provided by these microorganisms but were present in the natural tap water and were destroyed by autoclaving. Yee & Wadowsky (1982) also showed that L. pneumophila multiplied in non-sterile tap water in the presence of a stable population of other organisms in one of the waters tested but they made no conclusion about the possible association between the various bacterial populations.…”

Incorporating Time‐Dose‐Response into Legionella Outbreak Models

“…This collapses to the regular beta-Poisson dose-response model. If we divide Equation (20) by Equation (21), we get the following function:…”

“…(18) L. pneumophila has been shown to survive and multiply in water at temperatures between 25°C and 45°C, with an optimal temperature range of 32-42°C. (20) Water delivery systems, including cooling towers, (21,22) whirlpools, (23)(24)(25) indoor fountains, (26) air conditioning, (27) and indoor plumbing, (19,(28)(29)(30) often operate within these ranges, providing ideal conditions for Legionella growth, and have been implicated in several outbreaks. (31) Transmission to human hosts occurs when contaminated water is aerosolized, and such water delivery systems often produce aerosols, which facilitate the spread of the pathogen, and deposit the pathogen into the respiratory airways.…”