EFFICACY OF THERMAL-TREATMENT AND COPPER-SILVER IONIZATION FOR CONTROLLING LEGIONELLA-PNEUMOPHILA IN HIGH-VOLUME HOT-WATER PLUMBING SYSTEMSIN HOSPITALS

Background: Thermal treatment and copper-silver ionization are often u sed for controlling Legionella pneumophila in high-volume hospital plu mbing systems, although the comparative efficacies of these measures i n high-volume systems are unknown. Methods: Thermal treatment of a hot water circuit was accomplished by flushing hot water (>60 degrees C) through distal fixtures for 10 minutes. Copper-silver ionization was c onducted in three circuits by installing units into return lines immed iately upstream from hot water tanks. Recovery rates of L. pneumophila were monitored by culturing swab samples from faucets, Concentrations of copper and silver in water samples were determined by atomic absor ption spectrophotometry. Results: Four heat-flush treatments failed to provide long-term control oft. pneumophila. In contrast, ionization t reatment reduced the rate of recovery of L. pneumophila from 108 fauce ts from 72% to 2% within 1 month and maintained effective control for at least 22 months. Only three samples (1.9%) of hot water from faucet s exceeded Environmental Protection Agency standards for silver, and n one exceeded the standards for copper. Of 24 samples obtained from hot water tanks, 42% and 50% exceeded the silver and copper standards, re spectively Conclusions: Copper-silver ionization effectively controls L. pneumophila in high-volume plumbing systems and is superior to ther mal treatment; however, high concentrations of copper and silver can a ccumulate at the bottom of hot water tanks.