Background. Nosocomial pneumonia caused by Legionella pneumophila serogroup 2-14 occurred in a 7-year-old patient following allogeneic hematopoietic stem cell transplantation for thalassemia major.

Case. The patient was diagnosed with nosocomial Legionella pneumophila by polymerase chain reaction (PCR) examination of the bronchoalveolar lavage and culturing Legionella pneumophila serogroup 2-14 from the patient`s room faucet water. Legionella pneumophila was eradicated from our hospital`s water distribution system by superheating and chemical eradication methods (hyper-chlorination and hydrogen peroxide). We did not detect any other case after this event.

Conclusion. Early recognition of contamination of the hospital water system with Legionella proves the importance of prevention in new cases.

Keywords: Hematopoietic stem cell transplantation, Legionella pneumophila, pneumonia