A field study of the survival ofLegionella pneumophilain a hospital hot–water system

Abstract

SUMMARYThe 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.

Necessity and Effect of Combating Legionella pneumophila in Municipal Shower Systems

“…Although the thermal disinfection appeared successful under laboratory conditions, the bacterial concentrations of the investigated systems are only temporarily reduced following hot water treatment. In addition, the literature also reports conflicting results regarding the success of thermal treatment [68] , [69] , [70] , [71] , [72] . This further supports our findings that it is not straight-forward to use thermal control as a long-term preventive measure against Legionella in complex systems.…”

Each water outlet is a unique ecological niche forLegionella pneumophila

“…The general consensus is that it enters in low numbers from mains water and multiplies in warm conditions of 20-45°C [6]. Once in the system the temperature of the water, < 60°C [11], presence of amoebae [12], turbidity, organic carbon, zinc, copper and algae [13] are all important factors in maintaining growth.…”

“…A number of studies of factors influencing colonization of the potable water of a hospital have been carried out [4][5][6], however little information is available on the natural history of colonization of a hospital"s water supply system by legionella. Cases of nosocomial Legionnaires" disease at our hospital [7] prompted us to investigate our water supply as the source of the legionella.…”