Effect of temperature and pH values on survival of Legionella longbeachae in tap water

Legionellaceae familly includes 50 strain, and more than 70 serogroups of Legionella. Natural habit of this bacteria are water and moist soil where these bacteria lives in biofilms like the parasites of protozoi. In contrast to most Legionella strain which lives in water environments, L. longbeachae is isolated from poting soil and compost. In this work we explore how different pH values affects survival of L. longbeachae. In the same time we tested if the number of bacteria or change of incubation temperature affects survival of this bacteria. In our experiments we used two different doses of L. longbeachae (A5H5 strain) of 108 CFU/ml and 1010 CFU/ml, and inoculated them in 100 ml of sterile tap water, which pH were corrected (pH 2, 5, 7 and 8). Samples were incubated on 25oC and 37oC during 60 days. We determined the number of bacteria in different time points. At pH 2 L. longbeachae survived 3 days after inoculation of 108 CFU/ml, apropos 5 days after inoculation of 1010 CFU/ml at 25oC. At incubation on 37oC Legionella survived shorter time. At pH 5, 7 and 8, after inoculation of 1010 CFU/ml at 25oC after 60 days bacteria still can be detected. If we change the temperature of incubation (37oC) and decrease number of bacteria exposed to those conditions (108 CFU/ml), bacterium lives shorter time. The number of bacteria in inoculum and the temperature of incubation affects survival of L. longbeachae at different pH values of water. The higher number of bacteria and lower temperature of incubation prolong survival of bacterium in unfavourable conditions.