- Email: [email protected]
LEGIONELLA PNEUMOPHILA IN HOSPITAL HOT WATER CYLINDERS
1073 LEGIONELLA PNEUMOPHILA IN HOSPITAL HOT WATER CYLINDERS
SIR,-In the 1980 outbreak of legionnaires’ disease at Kingston Hospital the cooling tower and the water supply of the new building were implicated as sources of infection. The cooling tower was replaced by an air cooler. The cold water supply was treated by continuous chlorination, to 1-2 parts per million (ppm), and the hot water
temperature
was
maintained
at
55-60°C.
Continuing surveillance revealed a further hospital-acquired case of the disease in August, 1981. The patient, a 37-year-old male of previous good health, had been an inpatient for routine investigation for 7 days. 3 days after discharge pneumonia developed and he was readmitted 2 days later. He was treated with erythromycin and made a good recovery. At the time of readmission, his antibody titre to Legionella pneumophila serogroup 1 was < 16 and this rose 5 days later to 1028. As recent evidence2,3 suggests that hot rather than cold water is important in the dissemination of L. pneumophila, we examined those parts of the water system in detail. The new building is fitted with three 1300 gallon (6000 litre) cylinders for the supply of hot water, but one, or sometimes two, are adequate for normal requirements. The water is heated in the cylinders by two internal, closed, steam-heated coils; cold water enters at the bottom and hot water leaves the top, and circulating hot water is also returned to each cylinder through a feed pipe at the side (figure). During the summer of 1981, the heating coils of only the middle cylinder were switched on. The second cylinder had its heating coils switched off but it remained in open connection with the hot water system and immediately available for use whenever needed; the water in this cylinder, when the heating is off, is stagnant. The third cylinder was disconnected and drained. In August, 1981, there was increased demand for hot water, and the second cylinder was switched on. This was during the period of first admission of the patient, and on the very day that he took a bath and a shower. After the second cylinder was turned on, and for several weeks after, the hot water supply in the wards showed a brownish discolouration. At that time, 25 ml samples were taken for culture and L. pneumophila serogroup 1 was isolated. In November, 1981, suspicion turned to the cylinders and 5 litre water samples were collected from the inlet, outlet, and return feed pipes of the two cylinders in use. At the inlets of both cylinders the had a temperature of 12 OC and a free residual chlorine content of I - 5 ppm, and at the outlet and return feed pipes the water was at 60°C and had no detectable free chlorine (figure). The third cylinder, empty of water, contained a thick brown liquid deposit at the bottom and this was also sampled for culture; as the cylinders are angled and the draincocks are not at the lowest point, they cannot be completely drained. The water samples were filtered through 142 mm 0’ 2 !-1m nylon filters (Pall) and the residues were resuspended in 5 ml amounts of filtrate. These suspensions andthe deposit from the third cylinder were cultured, neat and as 10-fold dilutions, on selective medium. 4,5 The deposit from the third cylinder and the brown tap water were also analysed, by atomic absorption spectrophotometry, for metal content. The water samples from the two in-use cylinders did not grow L. pneumophila. However, the deposit from the disconnected cylinder contained 54 x 107 organisms/I of L. pneumophila serogroup 1, the same organism as isolated from the discoloured tap water in August, 1981. The iron, zinc, and copper content of the deposit from the cylinder closely resembled that of the discoloured hot water. In January, 1982, the second in-use cylinder was emptied. It too contained a thickish deposit at the bottom but L. pneumophila could water
1 Fisher-Hoch SP, Bartlett
outbreak of
CLR, Tobin J O’H, et al Investigation and control of an an legionnaires’ disease in a district general hospital Lancet 1981, i:
932-36 2 Dennis
PJ, Taylor JA, Fitzgeorge RB, et al.Legionella pneumophila in water plumbing system Lancet (in press) 3 Tobin J O’H, Beare J, Dunnill MS, et al Legionnaires’ disease in a transplant unit: isolation of the causative agent from shower baths Lancet 1980, ii 118-21 4 Edelstein PH Improved semiselective medium for isolation of Legionella pneumophila from contaminated clinical and environmental specimens. J Clin Microbiol 1981; 14: 298-303
5 Dennis
PJ, Taylor JA, Barrow GI The isolation of Legionella pneumophila from environmental water samples Trans Roy Soc Trop Med Hyg 1981, 76: 884
Arrangement of hot water cylinders. TITRES OF L PNEUMOPHILA IN CYLINDER DEPOSIT
be isolated. However, this was after the cylinder had been in use for about 5 months, with continuous heating and chlorination of the water. The metal content of the deposit was similar to that of the deposit from the disconnected cylinder. The second water cylinder was brought into use on the day the patient took a bath and shower. From the metal-content analyses, this was obviously responsible for the discolouration of the hot water supply to the wards, following disturbance and release of the deposit that had accumulated in the cylinder during the stagnant period. Our results from the disconnected cylinder show that L. pneumophila can grow to high titre in such stagnant deposits. It is likely, therefore, that the patient was exposed to large numbers of the organism during his bath and shower. Hot water supply cylinders should be regarded as potential sources ofL. pneumophila, and should be examined whenever otherwise unexplained cases of legionnaires’ disease occur, or where hot tap water is found to contain the organisms. Filling the disconnected cylinder with water containing chlorine at 50 ppm for 24 h, followed by thorough descaling, failed to eliminate the organism, but maintaining a constant water temperature of 70’C throughout the cylinder for 1 h was successful (table). not
We thank Dr I. Strickland for permission to report this case; Dr Mike Dart for permission to include data provided by the Thames Water Authority; and Mr David Harper of Kingston Hospital engineering department for his assistance.
Department of Microbiology, St Georges’ Hospital Medical School, London SW17 0RE, and Kingston Hospital,
Kingston,Surrey
S. P. FISHER-HOCH M. G. SMITH
Thames Water
J. S. COLBOURNE
Authority
LEGIONELLA PNEUMOPHILA NOT A CATEGORY B1 PATHOGEN
SIR,-The ubiquity of Legionella pneumophila in aqueous environments, without causing clinical illness, reaffirmed by Mr Dennis and his colleagues (April 24, p. 949) in their study of hotel
plumbing systems, surely makes nonsense of its continued laboratory categorisation as a B 1 pathogen. Although no one denies its occasional function as an opportunist in the aetiology of pneumonia, experience supports a lesser role both in incidence and certainly in severity than that well known category C pathogen, the pneumococcus. Public Health
Laboratory, University Hospital, Queen’s Medical Centre, Nottingham NG7 2UH
A. D. MACRAE
SIR,-In the 1980 outbreak of legionnaires’ disease at Kingston Hospital the cooling tower and the water supply of the new building were implicated as sources of infection. The cooling tower was replaced by an air cooler. The cold water supply was treated by continuous chlorination, to 1-2 parts per million (ppm), and the hot water
temperature
was
maintained
at
55-60°C.
Continuing surveillance revealed a further hospital-acquired case of the disease in August, 1981. The patient, a 37-year-old male of previous good health, had been an inpatient for routine investigation for 7 days. 3 days after discharge pneumonia developed and he was readmitted 2 days later. He was treated with erythromycin and made a good recovery. At the time of readmission, his antibody titre to Legionella pneumophila serogroup 1 was < 16 and this rose 5 days later to 1028. As recent evidence2,3 suggests that hot rather than cold water is important in the dissemination of L. pneumophila, we examined those parts of the water system in detail. The new building is fitted with three 1300 gallon (6000 litre) cylinders for the supply of hot water, but one, or sometimes two, are adequate for normal requirements. The water is heated in the cylinders by two internal, closed, steam-heated coils; cold water enters at the bottom and hot water leaves the top, and circulating hot water is also returned to each cylinder through a feed pipe at the side (figure). During the summer of 1981, the heating coils of only the middle cylinder were switched on. The second cylinder had its heating coils switched off but it remained in open connection with the hot water system and immediately available for use whenever needed; the water in this cylinder, when the heating is off, is stagnant. The third cylinder was disconnected and drained. In August, 1981, there was increased demand for hot water, and the second cylinder was switched on. This was during the period of first admission of the patient, and on the very day that he took a bath and a shower. After the second cylinder was turned on, and for several weeks after, the hot water supply in the wards showed a brownish discolouration. At that time, 25 ml samples were taken for culture and L. pneumophila serogroup 1 was isolated. In November, 1981, suspicion turned to the cylinders and 5 litre water samples were collected from the inlet, outlet, and return feed pipes of the two cylinders in use. At the inlets of both cylinders the had a temperature of 12 OC and a free residual chlorine content of I - 5 ppm, and at the outlet and return feed pipes the water was at 60°C and had no detectable free chlorine (figure). The third cylinder, empty of water, contained a thick brown liquid deposit at the bottom and this was also sampled for culture; as the cylinders are angled and the draincocks are not at the lowest point, they cannot be completely drained. The water samples were filtered through 142 mm 0’ 2 !-1m nylon filters (Pall) and the residues were resuspended in 5 ml amounts of filtrate. These suspensions andthe deposit from the third cylinder were cultured, neat and as 10-fold dilutions, on selective medium. 4,5 The deposit from the third cylinder and the brown tap water were also analysed, by atomic absorption spectrophotometry, for metal content. The water samples from the two in-use cylinders did not grow L. pneumophila. However, the deposit from the disconnected cylinder contained 54 x 107 organisms/I of L. pneumophila serogroup 1, the same organism as isolated from the discoloured tap water in August, 1981. The iron, zinc, and copper content of the deposit from the cylinder closely resembled that of the discoloured hot water. In January, 1982, the second in-use cylinder was emptied. It too contained a thickish deposit at the bottom but L. pneumophila could water
1 Fisher-Hoch SP, Bartlett
outbreak of
CLR, Tobin J O’H, et al Investigation and control of an an legionnaires’ disease in a district general hospital Lancet 1981, i:
932-36 2 Dennis
PJ, Taylor JA, Fitzgeorge RB, et al.Legionella pneumophila in water plumbing system Lancet (in press) 3 Tobin J O’H, Beare J, Dunnill MS, et al Legionnaires’ disease in a transplant unit: isolation of the causative agent from shower baths Lancet 1980, ii 118-21 4 Edelstein PH Improved semiselective medium for isolation of Legionella pneumophila from contaminated clinical and environmental specimens. J Clin Microbiol 1981; 14: 298-303
5 Dennis
PJ, Taylor JA, Barrow GI The isolation of Legionella pneumophila from environmental water samples Trans Roy Soc Trop Med Hyg 1981, 76: 884
Arrangement of hot water cylinders. TITRES OF L PNEUMOPHILA IN CYLINDER DEPOSIT
be isolated. However, this was after the cylinder had been in use for about 5 months, with continuous heating and chlorination of the water. The metal content of the deposit was similar to that of the deposit from the disconnected cylinder. The second water cylinder was brought into use on the day the patient took a bath and shower. From the metal-content analyses, this was obviously responsible for the discolouration of the hot water supply to the wards, following disturbance and release of the deposit that had accumulated in the cylinder during the stagnant period. Our results from the disconnected cylinder show that L. pneumophila can grow to high titre in such stagnant deposits. It is likely, therefore, that the patient was exposed to large numbers of the organism during his bath and shower. Hot water supply cylinders should be regarded as potential sources ofL. pneumophila, and should be examined whenever otherwise unexplained cases of legionnaires’ disease occur, or where hot tap water is found to contain the organisms. Filling the disconnected cylinder with water containing chlorine at 50 ppm for 24 h, followed by thorough descaling, failed to eliminate the organism, but maintaining a constant water temperature of 70’C throughout the cylinder for 1 h was successful (table). not
We thank Dr I. Strickland for permission to report this case; Dr Mike Dart for permission to include data provided by the Thames Water Authority; and Mr David Harper of Kingston Hospital engineering department for his assistance.
Department of Microbiology, St Georges’ Hospital Medical School, London SW17 0RE, and Kingston Hospital,
Kingston,Surrey
S. P. FISHER-HOCH M. G. SMITH
Thames Water
J. S. COLBOURNE
Authority
LEGIONELLA PNEUMOPHILA NOT A CATEGORY B1 PATHOGEN
SIR,-The ubiquity of Legionella pneumophila in aqueous environments, without causing clinical illness, reaffirmed by Mr Dennis and his colleagues (April 24, p. 949) in their study of hotel
plumbing systems, surely makes nonsense of its continued laboratory categorisation as a B 1 pathogen. Although no one denies its occasional function as an opportunist in the aetiology of pneumonia, experience supports a lesser role both in incidence and certainly in severity than that well known category C pathogen, the pneumococcus. Public Health
Laboratory, University Hospital, Queen’s Medical Centre, Nottingham NG7 2UH
A. D. MACRAE