Isolation of legionella pneumophila from environment and water system samples and evaluation of immuno-protective efficiency of its whole killed cell in mice model

Legionella pneumophila is a cause of pneumonia in human beings. The purpose of this study was to separate L.pneumophila from stagnant and waste water, city squares, coolers and faucets and evaluation of the immuno-protective efficiency of its whole killed cells in mice model. Water samples were prepared, concentrated and then cultured on selective (GVPC) media. After identification of L.pneomophila the biomass of the organism was fixed with 0.5% formalin in sterile saline at 37ºC for 24 hours in order to prepare whole killed cells. Four groups of female BALB/c mices (each group consisted of 15 mices) were selected. Two groups of mice were immunized by three intraperitoneal administrations of prepared antigen in a dose of 4×108 CFU from whole killed cells at two week intervals and control groups received only sterile saline injections. Two weeks after the last injection, one group of immunized mice and one of the control groups were challenged with the lethal dose of virulent strain of L.pneuophila and also the two other groups of mice were challenged six weeks after the last immunization. From 120 water samples 27 samples were contaminated with L.pneumophila. Challenge results showed that the immune efficiency of whole killed cell was 93.33% after two weeks of the last immunization, and 86.66% after six weeks of the last immunization. This study showed that, stagnant water had the highest rate of contamination with L.pneumophila and the whole killed cell of L.pneumophila is a proper candidate for L.pneumophila vaccine studies.