Environmental factors affecting the survival of soil dwelling Legionella longbeachae in water

Introduction. Legionella longbeachae, a causative agent of Legionnaire's disease, has often been associated with potting soil and gardening, a feature quite distinct from other Legionella species. The precise transmission mechanism is still unknown, although due to the ecological coherence of the soil and water there is a potential risk of infection by contaminated stagnant water in the garden. Objective. The aim of the study was to explore the ability of L.longbeachae to survive in stagnant tap water usually used for watering in gardens. The influence of different factors (temperature, pH and NaCl concentration) on L.longbeachae survival in stagnant tap water was also tested. Results. The result showed that L.longbeachae is viable in stagnant tap water over 100 days at 4 degrees C and 25 degrees C. The survival of L.longbeachae exposed to different pH and NaCl concentration suggests resistance to low pH values (pH2 and pH5) and all tested NaCl concentrations at temperatures lower than 25 degrees C. The ability of L.longbeachae to persist in stagnant tap water should be taken seriously in the risk assessments as a possible hidden reservoir of infection.