Investigation of relationship between contamination with Legionella in potable water and Legionella infection in patients with nosocomial pneumonia

Objective To investigate the relationship between contamination by Legionella in water supply system(potable water)and Legionella infection in patients with nosocomial pneumonia.Methods Sixty-five samples from potable water were collected and cultivated for Legionella.Slide agglutination test was used for identification of Legionella.The clinical and environmental strains of Legionella pneumophila serogroup 1(LP1)were identified.Legionella urinary antigen,sputum and bronchoalveolar lavage fluid (BALF)culture were used for the detection of Legionella in 38 patients with nosocomial pneumonia.Results Nine samples were contaminated by Legionella in 65 potable water samples.LP1,LP6 and LP7 were six,one and one isolate,respectively.Legionella micdadei was detected only one isolate.LP1 was all environmental isolate.Legionella urinary antigen,sputum and BALF culture were all negative in the detection.Conclusions The water supply system in the hospital is contaminated by Legionella.LP1 is the most common isolate.No case of hospital-acquired Legionella pneumonia has been found in the hospital by now.It can prevent the outbreak and epidemic of hospital-acquired Legionella pneumonia by monitoring Legionella in the potable water of hospital and taking preventive measures. Key words: Potable water; Legionella; Nosocomial pneumonia; Legionella urinary antigen