Presence and chromosomal subtyping of Legionella species in potable water systems in 20 hospitals of Catalonia, Spain

OBJECTIVE: To investigate the presence and clonal distribution of Legionella species in the water supply of 20 hospitals in Catalonia, Spain. SETTING: 20 hospitals in Catalonia, an area of 32,000 km(2), located in northeast Spain. METHODS: Environmental cultures of 186 points of potable water supply and 10 cooling towers were performed for the presence of Legionella species. Following filtration and acid treatment, the samples were seeded in selective MWY (modified Wadowsky Yee)-buffered charcoal yeast extract-a agar. All isolates obtained were characterized microbiologically and genotyped by SfiI pulsed-field gel electrophoresis (PFGE). RESULTS: 73 of 196 water samples, representing 17 of the 20 hospitals included in the study, were positive for Legionella pneumophila (serogroups 1, 2-14, or both). The degree of contamination ranged from 200 to 74,250 colony-forming units/L. Twenty-five chromosomal DNA subtypes were detected by PFGE. A single DNA subtype was identified in 10 hospitals, 2 DNA subtypes were observed in 6 hospitals, and I hospital exhibited 3 different DNA subtypes. Each hospital had its own Legionella DNA subtype, which was not shared with any other hospitals. CONCLUSIONS: Legionella was present in the water of most of the hospitals studied: each such hospital had a unique, dominant chromosomal DNA subtype. The verification of several genomic DNA restriction profiles in such a small geographic area demonstrates the great genetic diversity of Legionella in the aquatic environment.