14 12 6 12 8 pneumophila species Total all 22 19 17 19 14 Legionellae
Legionella Type # in Q2 (Apr-Jun) '04 '05 '06 '07 '08 L.
Serotyping, serogrouping, typing, and subtyping legionellae
are technically challenging.
In the positive samples, the mean number of legionellae was 1.17 x [10.sup.3] CFU/L (range 25 to 8.7 x [10.sup.4] CFU/L); three samples (9.2%) contained [greater than or equal to][10.sup.4 ]CFU/L, none of which were L.
were isolated in 22.6% of domestic hot water samples, with a mean number of legionellae in positive samples of 1.17 x [10.sup.3] CFU/L (geometric mean); the highest concentration was 8.7 x [10.sup.4].
Recent studies, however, found that contamination was consistent throughout the year, both in terms of the species of legionellae isolated and in the concentration of organisms (18), suggesting that the occurrence of Legionnaires' disease most frequently in the summer is not necessarily linked to a higher water contamination.
Furthermore, compared with the other legionellae, serogroup 1 was found in water with a lower temperature, less Pseudomonas contamination, and a relatively higher residual chlorine concentration.
Amoebae, the natural hosts of legionellae, have not been controlled successfully in vitro by adding metal (42), suggesting that legionellae survive inside protozoa and are destroyed by metal ions when released into free water.
Conditions that affect the proliferation of legionellae include sludge, scale, rust, algae, and organic particulates thought to provide nutrients for growth.
Clinical cases have also occurred because of the inhalation of water droplets containing the blue-white fluorescent group of legionellae, e.g., L.
Ideally, hospital water systems should be free of legionellae, but it is exceptional for a water supply to be entirely free of aquatic organisms.
If storing water at 60 [degrees] C is not practical or acceptable or the calorifier is not in use for 1 week or more, raising the temperature of the calorifier water to 70 [degrees] C to 75 [degrees] C for 1 hour will kill legionellae. However, this technique may not be effective if the temperature of water at the bottom of the calorifier does not reach 70 [degrees] C.
Some biocides are effective against legionellae if used in sufficient concentrations for a sufficient time.