A FIELD-STUDY OF THE SURVIVAL OF LEGIONELLA-PNEUMOPHILA IN A HOSPITAL HOT-WATER SYSTEM

The colonization, survival and control of Legionella pneumophila in a hospital hot–water system was examined. The organism was consistently isolated from calorifier drain–water samples at temperatures of 50°C or below, despite previous chlorination of the system. When the temperature of one of two linked calorifiers was raised to 60°C, by closing off the cold–water feed, the legionella count decreased from c. 104 c.f.u./l to an undetectable level. However, 10 min after turning on the cold–water feed which produced a fall in calorifier temperature, the count in the calorifier drain water returned to its original level. Investigations revealed that the cold–water supply was continually feeding the calorifiers with L. pneumophila. Simple modifications in the design of the system were made so that the cold–water feed no longer exceeds 20°C; these measures have considerably reduced the number of L. pneumophila reaching the calorifiers. © 1990, Cambridge University Press. All rights reserved.