COLONIZATION OF TRANSPLANT UNIT WATER-SUPPLIES WITH LEGIONELLA AND PROTOZOA - PRECAUTIONS REQUIRED TO REDUCE THE RISK OF LEGIONELLOSIS

Organ transplant recipients and other immunosuppressed patients are kn own to be at increased risk of nosocomial Legionnaires' disease. Altho ugh the ecology of Legionella in hospital water storage and distributi on systems (including a protozoonotic relationship with free-living pr otozoa) has been well documented, little is known regarding the qualit y of water supplied to high-risk units. Hot-and cold-water samples (tw o first draw and one run to waste for 5 min) were taken from 69 (85%) of the 81 United Kingdom organ transplant units (31 renal, 24 bone mar row, nine cardiopulmonary and five liver transplant units) and culture d for Legionella and protozoa. Legionella spp. were isolated from the water supplies of 38 (55%) units and Legionella pneumophila from 31 (4 5%). The blue-white fluorescent group of Legionella (Legionella gorman ii, Legionella bozemanii and others) was isolated from 18 (26%) units. Free-living protozoa were isolated from 47 units (68%) and genera of the protozoa known to permit the intracellular growth of Legionella (P GIGL), from 40 units (58%). Possible associations between Legionella a nd the variables Protozoa; PGIGL; water pH; and circulating water temp erature (recorded after running to waste for 5 min) were examined by l ogistic regression analysis. In cold-water supplies, a significant ass ociation was found between the isolation of Legionella and PGIGL (P=0. 032; OR=1.81; 95% CI 1.1-3.1). In hot-water supplies, an inverse assoc iation was found between the isolation of Legionella and circulating w ater temperature (P=0.034; OR=1.0719 per degrees C 95% CI 1.0052-1.143 2). (We failed to isolate Legionella when the circulating hot water wa s >58 degrees C). No other associations were significant. We recommend the active surveillance of water quality in high-risk patient areas, and that transplant units, either with a history of nosocomial Legionn aires' disease, or where active surveillance indicates a persistently high Legionella colony count, take remedial action. The quality of col d water may be improved by provision of a dedicated supply taken direc tly from the incoming mains; and of hot water by the use of a dedicate d calorifier, able to maintain a minimum circulating hot water return temperature of 60 degrees C.