J. Modol, L. Mateu, M. García-Núñez, M. Pedro-Botet, N. Sopena, S. Ragull, C. Rey-Joly, M. Sabria; Hospital Germans Trias i Pujol, Badalona (Barcelona), SPAIN.

Background: Since 1983 HUGTiP has had an endemic situation of legionellosis. Hyperchlorination and superheating have not been effective in eradicating this microorganism from the water supply or decreasing the number of cases of hospital-acquired Legionella disease (HALD). In September 1999 a Cu/Ag ionisation system was implemented. However some cases of HALD were still observed in the following years. In May 2003, the dosification of the ionisation system was increased. The aim of the study was to evaluate the efficacy of the cupper-silver ionisation system on environmental colonisation by Legionella and HALD.

Methods: 1. Periods: Period A: 1/1/1998 to 9/30/1999 (21 months); disinfection methods (DM): superheating and hyperchlorination; HALD surveillance: medical and microbiology lab reports. Period B: 10/1/1999 to 5/31/2003 (44 months); DM: Cu/Ag ionisation in hot water distribution network, 0.1-0.2 Cu ppm; HALD surveillance: active daily surveillance. Period C: 6/1/2003 to 12/31/2004 (19 months). DM: Cu/Ag ionisation in hot water distribution network, 0.3- 0.4 Cu ppm; HALD surveillance: active daily surveillance. 2. Environmental studies: 407 water samples from distal points were seeded in selective MWY-BCYE-a agar. 3. Legionella tests: sputum culture, Legionella urinary antigen and serology. 4. Cu/Ag measurement: atomic absorption spectroscopy monthly (copper ions were also tested with a daily sampling kit provided by the manufacturer).

Results: Period A (3 environmental studies): 51/89 (57.3%) of samples were positive for Legionella. Mean number of CFU/L: 11,972. HALD: 81 cases. Period B (21 environmental studies): 48/230 (20.9%) of samples were positive. Mean number of CFU/L: 758 CFU/L. HALD: 20 cases (9 esporadic cases and 11 associated with 2 small outbreaks. In both outbreaks Cu/Ag ion levels were close to 0 due to technical problems). Period C (3 environmental studies): 14/88 (15.9%) of samples positive. Mean number of CFU/L: 42,982. HALD: 0 cases.

Conclusions: Cu/Ag ionisation of hot water distribution networks decreased environmental contamination by Legionella and reduced the number of cases of HALD in a hospital with an endemic situation of legionellosis. The appearance of cases was usually related to decreases in ion levels. Increasing ion levels may avoid the appearance of cases of HALD.