A nosocomial outbreak of Legionella pneumophila pneumonia serogroup 1 occurred in three patients in the liver transplant unit of Gastroenterology Surgical Center (GEC). L. pneumophilia was recovered from the hospital water supply system just before the outbreak. Following Legionella detection in the hospital water supply system, we studied the presence of Legionnaires’ disease in patients with clinically suspected hospital acquired pneumonia, between March and August 2014. Patients were tested by urinary antigen assay test and sputum culture. Results revealed Legionella pneumonia was diagnosed in three patients with incidence of 6% among liver transplant patients, and 25% among liver transplant patients with pneumonia. The outbreak was controlled by implementing the following measures; restricting tap water use and drinking, quinolones were prescribed empirically for hospital pneumonias of uncertain etiology, water decontamination with hyper-chlorination, keeping temperature of the hot water above 50°C and removing faucet aerators monthly for cleaning and disinfection. Eradication of Legionella from water and termination of the outbreak was achieved, no other cases acquired Legionella pneumonia. Thus, for hospitals with transplant programs, periodic monitoring of Legionella in hospital water supply system and introducing diagnostic tests for legionellosis for patients with nosocomial pneumonia is necessary.

Keywords: Liver transplant patients; hospital acquired pneumonia; Legionella pneumophila; outbreak; hospital water contamination.