Control of nosocomial Legionnaires' disease by keeping the circulating hot water temperature above 55 degrees C: experience from a 10-year surveillance programme in a district general hospital

After a nosocomial outbreak of Legionnaires' disease in a 450-bed district general hospital in 1991, the circulating hot water temperature was kept above 55 degrees C as the sole control measure. From 1991 to 2000, all cases of nosocomial pneumonia were clinically monitored and tested for Legionella pneumophila serogroup 1 by serology or urinary antigen detection. Water samples from peripheral tap sites were cultured for Legionella spp. twice a year. An infection with L. pneumophila serogroup 1 was diagnosed in four out of 366 (1.1%) patients treated for nosocomial pneumonia, representing one case per 26,000 admissions. All patients were cured without complications. L. pneumophila serogroup 1 was isolated in 30 of 251 (12%) cultured hospital water samples during the monitoring period. We conclude that control of nosocomial Legionnaires' disease in a primary referral hospital is possible by keeping the circulating hospital hot water temperature above 55 degrees C, together with careful clinical surveillance. Complete eradication of Legionella spp. from the hot water system does not seem necessary.     

Potable water and nosocomial Legionnaires' disease--check water from all rooms in which patient has stayed.

We studied 7 patients with nosocomial Legionnaires'' disease to determine the relationship between isolates of Legionella pneumophila recovered from potable water and those recovered from patients. Potable water was cultured from all rooms in which patients had stayed prior to the diagnosis of Legionnaires'' disease. The 38 isolates of L. pneumophila (31 environmental, 7 patient) were resolved into 9 distinct patterns by pulse-field gel electrophoresis (PFGE), 3 by plasmid content and 2 each with monoclonal antibodies and conventional agarose gel electrophoresis of small fragments of DNA. Using PFGE it was determined that 4 of the 7 patients were infected with L. pneumophila identical to an isolate recovered from the potable water supply in one of the rooms each had occupied prior to the diagnosis of Legionnaires'' disease. Patients had resided in a mean of 3.57 rooms before a diagnosis of nosocomial Legionnaires'' disease. We conclude that in the setting of contaminated potable water and nosocomial Legionnaires'' disease water from all the rooms which the patient has occupied prior to this diagnosis should be cultured. PFGE of large DNA fragments discriminated best among the isolates of L. pneumophila.     

北京市某宾馆一起军团病爆发的调查报告

1992年2、3月,北京市郊某宾馆发生了一起上呼吸道感染(上感样)流行。流行病学调查及细菌学检查证明:这是一起嗜肺军团菌血清10型(简称Lp10)引起的宾馆军团菌病小规模爆发,患病率为13.51%(5/37)。由Lp10引起的军团病爆发在国内属首次报道。     

Phenotypic variation amongst genotypically homogeneous Legionella pneumophila serogroup 1 isolates: implications for the investigation of outbreaks of Legionnaires' disease.

One hundred and seventy-nine isolates of Legionella pneumophila serogroup 1, obtained from a site associated with an outbreak of Legionnaires'' disease, were examined by monoclonal antibody subgrouping, restriction fragment length polymorphism typing, restriction endonuclease analysis and plasmid content. Nine distinct phenotypes were detected but at the genotypic level all strains were closely related. The data presented indicate that phenotypic variation of a single parent strain can occur within an environmental site. The implications of these findings are discussed in relation to the investigation of outbreaks of Legionnaires'' disease.     

Legionella spp. in a hospital hot water system: effect of control measures

Potential sources of Legionella spp. in a university hospital were investigated over 3 years in order to gain better understanding of the ecology and transmission of this organism to hospitalized patients. The survey highlighted the contamination of the hot water system with high concentrations of legionellas (up to 10(6) cfu 1(-1]. Legionella pneumophila serogroup 6 was predominant followed by L. pneumophila serogroup 10. Serogroup 1 and other species (L. longbeachae, L. micdadei) were rarely isolated. Serogroup 6 was also the predominant cause of nosocomial legionellosis in 15 sporadic cases in immunocompromised patients from 1981 to 1987. In light of this problem, several control measures were tried consecutively. A disinfection cycle with 6 ppm free chlorine failed to eradicate legionellas because of difficulties with the plumbing system. Raising the temperature in hot water tanks to 80 degrees C was effective locally, but mixer tanks where cold and hot water (60-65 degrees C) are mingled in order to achieve 45 degrees C became the principal reservoirs. Disconnecting the mixer tanks, maintaining a temperature of 60 degrees C in the heating tanks and accelerating the flow rate in the hot water system proved to be the most useful measures.     

Prevention and control of Legionella infection in the hospital environment

An outbreak of nosocomial legionnaires' disease in a hospital of Northern Italy is described, together with the epidemiological survey and the control measures adopted. Two patients developed Legionella pneumophila (serogroup 1) pneumonia, one (immunodepressed) died. The Task Group organised by the Health Service excluded other previous nosocomial infections, and made controls on patients and personnel of at risk units (all negative). An intensive programme of environmental sampling and educational activities on personnel have been carried out. The environmental surveillance revealed that the centralised hot water distribution system of the hospital was colonised with Legionella. Shock heating and hyperchlorination of water were applied, which reduced the number of contaminated sites short term, but recolonisation took place two months later. We underline the difficulties encountered to control Legionella by active surveillance of water quality; once the system is contamined, Legionella eradication may be difficult and expensive, and cases of hospital-acquired legionnaieres' disease are likely to occur.     

Disconnecting central hot water and using electric showers to avoid colonization of the water system by Legionella pneumophila: an 11-year study

Legionella spp. can be difficult to control in hospitals. The objective of this study was to describe an 11-year experience with the use of electric showers in the control of Legionella pneumophila. From June 1989 to March 1990 there was an outbreak of pneumonia caused by L. pneumophila in a 20-bed renal transplant unit in a university-associated tertiary-care hospital. Control measures included hyperchlorination, heating and flushing of the water system with limited results. In November 1993 the central hot water was disconnected and water for bathing was heated using electric showers. From January 1992 to June 1995 water was collected from showers and water faucets and cultured for L. pneumophila every two weeks. Surveillance cultures were then collected every month until May 1999. During this seven-year surveillance period, 1115 samples of water were cultured. Water cultures were positive on 24 of 429 occasions (without cases of legionellosis) during the pre-shower period (22 months). In the post-shower period (67 months) only one of 686 cultures was positive. Subsequently there have been no new cases of nosocomial pneumonia by L. pneumophila although surveillance continues. In conclusion, disconnecting the central hot water was effective in avoiding colonization of the water system by L. pneumophila. Heating was possible by using electric showers, which are effective, easy to maintain and cheap.     

Fatal nosocomial Legionnaires' disease: relevance of contamination of hospital water supply by temperature-dependent buoyancy-driven flow from spur pipes.

The investigation, epidemiology, and effectiveness of control procedures during an outbreak of Legionnaires'' disease involving three immunosuppressed patients are described. The source of infection appeared to be a network of fire hydrant spurs connected directly to the incoming hospital mains water supply. Removal of these hydrants considerably reduced, but failed to eliminate, contamination of water storage facilities. As an emergency control procedure the incoming mains water was chlorinated continuously. Additional modifications to improve temperature regulation and reduce stagnation also failed to eliminate the legionellae. A perspex test-rig was constructed to model the pre-existing hospital water supply and storage system. This showed that through the hydraulic mechanism known as ''temperature buoyancy'', contaminated water could be efficiently and quickly exchanged between a stagnant spur pipe and its mains supply. Contamination of hospital storage tanks from such sources has not previously been considered a risk factor for Legionnaires'' disease. We recommend that hospital water storage tanks are supplied by a dedicated mains pipe without spurs.     

Isolation of Legionella pneumophila from water supplies: comparison of methods based on the guinea-pig and culture media.

The detection of Legionella pneumophila in water via guinea-pig intraperitoneal injection has been compared with direct isolation of these organisms on semiselective BCYE alpha media. Both techniques were of similar sensitivity, detecting as few as 10(2) L. pneumophila in 10 ml of water. However, at this concentration, detection using guinea-pig intraperitoneal injection was via the indirect parameters of antibody production and immunofluorescent microscopy. Isolation of L. pneumophila from guinea-pig tissue for further investigation required greater than 10(7) organisms injected and in this respect is relatively much less sensitive than direct isolation on semiselective BCYE alpha media. Since L. micdadei and L. longbeachae are inhibited by one of the selective supplements used, other supplements and techniques need to be developed in order to avoid possible inhibition of other Legionella species. This work is based on simulated water samples containing strains of L. pneumophila defined in terms of pneumonic Legionnaires'' disease in the guinea-pig. As such, this work serves as a guide to technique and the need to test large numbers of naturally infected water samples in parallel by techniques outlined in this work is emphasized.     

Legionnaires' disease outbreak,Fairfield 1992: public health aspects

Abstract: An investigation of an outbreak of Legionnaires' disease in 1992 in Fairfield, a municipality of Sydney, was carried out to determine the source of the outbreak. Cases of Legionnaires' disease with onset of symptoms between 11 and 20 April 1992 were included. Definite cases were individuals with a history consistent with Legionnaires' disease, confirmed by direct fluorescent antibody testing plus serology or culture. There were two control groups: patients admitted to the same hospital as the cases, matched for age and sex, and patients admitted to hospital with a presumptive diagnosis of Legionnaires' disease, in whom the diagnosis was subsequently excluded. There were 26 definite cases with onset of symptoms between 11 and 20 April 1992. Six (23 per cent) died. Twenty-two cases (85 per cent) reported visiting the Fairfield business district during the ten days prior to the onset of symptoms. They were 20 times more likely to have visited Fairfield than were matched controls. Matching of Legionella pneumophila serogroup 1 from environmental and clinical samples was achieved by cytogenetic fingerprinting. Fourteen cases were linked to a single environmental sample. The epidemiological findings were consistent with a point source of Legionella in the Fairfield business district. It is most likely that the exposure occurred on 10 April 1992.     

Persistence of the same strain of Legionella pneumophila in the water system of an Italian hospital for 15 years.

In 2004, an outbreak of legionnaires disease occurred in a hospital in northern Italy with a water system that had been disinfected multiple times since 1990 and equipped with a continuous disinfecting system. Molecular typing linked the outbreak to contamination of the hospital water system and demonstrated the persistence of a predominant strain of Legionella pneumophila for 15 years.     

Hygienic assessment of the characteristics of centralized hot water supply in case of Moscow

The paper considers the characteristics of domestic hot water consumption by Moscow dwellers. It gives the results of questionnaire surveys in 100 respondents aged 20-80 years about the modes and intensity of hot water use, by indicating the time and frequency of contact with hot water complaints about hot water supply. According to the authors'studies, the daily consumption of hot water per capita was 1.1-2 times greater than that of cold water; at the same time the total water use remained to be 1.3-3 times less than the Moscow standard levels. Top stationary point measurements of water temperature showed the noncompliance with its hygienic requirements: 95 of 98 hot water samples had a temperature of 5-22 degrees C less than the standard temperature (60 degrees C). A decrease in hot water temperature in the centralized hot water supply systems creates conditions for Legionella pneumophila propagation and ensures no hot water safety with regards to the possible development of Legionella pneumonia.     

Relationship between Legionella spp. and antibody titres at a therapeutic thermal spa in Portugal.

The presence of Legionella spp. in the water of a Portuguese spa was ascertained during the spa season, between May and November. Simultaneously the prevalence of anti-legionella antibodies in people attending the spa was also investigated. The antibody titres of 172 randomly selected patients and 42 therapists were determined, and compared with a control group of 503 blood donors. Legionellae were present in the spa water at low concentrations, generally lower than 10(3) c.f.u./l. A total of 92 strains representing eight different species or serogroups were isolated; the predominant isolates belonged to Legionella pneumophila serogroup 6 and to L. londiniensis. During the study, no clinical cases of Legionnaires'' disease were observed, and the antibody titres were generally low in the groups studied. However, the antibody titres of the patients increased slightly during their stay at the spa, approaching the values for the therapists. Mean antibody titres in the groups related with the spa were significantly higher than those in the blood donors against five of the seven legionella antigens tested. The largest number of elevated antibody titres in the exposed groups were to the L. pneumophila sg 5 and sg 6 antigens.     

A community hospital outbreak of legionellosis. Transmission by potable hot water

Seven cases of nosocomial legionellosis occurred between February and September 1982 in a small community hospital in Upstate New York. All seven were cases of Legionella pneumophila serogroup 1; six were hospital patients and one a hospital employee. None of the cases died. During the peak of the outbreak, the incidence of nosocomial legionellosis was 1.2 cases per 100 patient discharges. An epidemiologic comparison of the six patient cases with 21 matched patient controls suggested that longer hospital stay (chi 1(2) = 24.2, p less than 0.001) and the proximity of patients' rooms to ward showers (chi 1(2) = 4.4, p less than 0.04) were significant risk factors for acquiring legionellosis. An environmental investigation demonstrated that the ward showers and the hospital hot water system were contaminated with L. pneumophila serogroup 1. Monoclonal antibody subtyping performed on isolates obtained during the outbreak investigation confirmed that the hot water system and patient isolates had an identical pattern of reactivity. The outbreak demonstrates that legionellosis can be a significant cause of nosocomial pneumonia in a community hospital and that transmission can occur from contaminated potable hot water sources, potentially via shower aerosols.     

Legionella pneumophila in a hospital water system following a nosocomial outbreak: prevalence, monoclonal antibody subgrouping and effect of control measures

Swabs and water samples from a hospital water system were cultured for legionellae over an extended period. Legionella pneumophila serogroup 1, including outbreak associated strains, were isolated in small numbers from approximately 5% of these samples despite implementation of the current DHSS/Welsh Office regulations. No cases of nosocomial legionnaires' disease were proven during the study. Physical cleaning and chemical sterilization of taps, and replacement of washers with 'approved' brands did not eradicate the organisms. Eradication of legionellae in hospital water supplies appears to be unnecessary in preventing nosocomial legionnaires' disease provided the current DHSS/Welsh Office recommendations are implemented.     

Control of Legionella pneumophila contamination in a respiratory hydrotherapy system with sulfurous spa water.

OBJECTIVE: To evaluate the effectiveness of different disinfection treatments in a spa water system contaminated by Legionella pneumophila and associated with a case of Legionella pneumonia. DESIGN: During an 18-month period, the spa water was analyzed by taking samples from the well, the recirculation line, and the final distribution devices (nebulizers and nasal irrigators). Various attempts were made to eradicate Legionella organisms by chemical and thermal shock. The final protocol consisted of heat shock treatment at 70 degrees C-75 degrees C for 3 hours, 2 nights per week, followed by a lowering of the water temperature to 30 deg C+/-1 deg C for use in the plant. In addition, 3 times a week superheated steam (at a pressure of 1 atmosphere) was introduced for 1 hour into the nebulization machines. SETTING: A spa at which sulfurous water was used for hydrotherapy by means of aerosol and nasal irrigation. PATIENT: A 74-year-old woman with legionnaires disease. RESULTS: After the case of infection occurred, L. pneumophila was isolated from the recirculation line at a concentration of 400,000 cfu/L and from the nebulizers and nasal irrigators at levels ranging from 3,300 to 1,800,000 cfu/L. The colonizing organisms consisted of a mixture of L. pneumophila serogroup 1 (12%) and serogroup 5 (88%). The shock treatment with chlorine dioxide and peracetic acid resulted in the eradication of Legionella organisms from the recirculation line but not from the water generated from the final distribution devices. After the restructuring of the plant and the application of thermal shock protocol, an evaluation after 12 months revealed no evidence of Legionella contamination. CONCLUSION: To prevent Legionella colonization, disinfection treatment is effective if associated with carefully selected materials, good circuit design, and good maintenance practices.     

Epidemiological survey of a major outbreak of nosocomial legionellosis

Forty-seven nosocomial cases of legionellosis due to Legionella pneumophila serogroup 1 were diagnosed in one major outbreak from November 1982 to March 1983 in a 960-bed teaching hospital. Contaminated water was considered to be a possible source of infection because, during that period, monthly samples were found to be positive with averages of 10(4) CFU/l. After chlorination of hot water associated with flushing of outlets, nearly all samples taken in the next two years were found to be negative. A case-control study was performed to examine potential risk factors. Three groups of controls were randomly selected among eligible patients. In a multivariate analysis, only three clinical factors were found to be associated with legionellosis patients: malignant illness (relative risk, RR = 3.5), presence of an ultimately fatal disease (RR = 2.6), and exposure to corticosteroids prior to admission (RR = 7.9). Investigations of in-hospital exposures suggest that during this nosocomial outbreak diagnostic or therapeutic respiratory procedures had not increased the risk of illness. Although the epidemiological association between water contamination and disease remains unclear, the eradication of L. pneumophila from the identified supply seems to have been effective in preventing disease in this hospital.     

Endemicity of Legionella pneumophila serogroup 3 in a hospital water supply

A microbiological and epidemiological investigation at the Infectious Diseases Hospital in Turin, Italy, demonstrated Legionella pneumophila serogroup 3 at 10(2) to greater than 4 X 10(3) cfu l-1 from 24 of 32 hot water samples collected from hand-basins in six separate buildings. A sample taken from the public water supply, and a hot water sample (80 degrees C) collected from hot water tanks, did not yield legionellas. Legionella pneumophila serogroup 3 was found in samples taken at the first point of mixed hot and cold water (50 degrees C) at 3 X 10(2) cfu l-1. 12 of 26 samples from the shower-heads yielded 10(3) to 2.5 X 10(5) cfu l-1 and one of 12 water samples from oxygen bubble humidifiers tested yielded 1.6 X 10(4) cfu l-1. No other legionellas species or serogroups of Legionella pneumophila were isolated during the study. No cases of nosocomial pneumonia were detected among 3653 patients' records, nor was there serological evidence of Legionella infection in the 180 patients tested.     

Decreasing trend of Legionella isolation in a long-term microbial monitoring program in Greek hospitals

Legionnaires' disease is a known cause of severe pneumonia in a nosocomial setting. This study examined Legionella isolation in Greek hospitals. Water samples and swabs of showerheads from 41 hospitals were collected over a four-year period (2004-2007) from hot and cold water systems and cooling towers in Greece. In total, 1058 samples were examined for the presence of Legionella. From the hot water samples examined, 166 out of 607 (27.3%) were positive for Legionella, including 111 (18.3%) positive for Legionella pneumophila sg1 samples. The temperature of hot water samples less than 55°C was statistically significant, associated with Legionella spp. isolation (RR 4.01, 95%CI 2.33-6.92). Ten out of 17 (58.8%) hospital cooling towers required remedial actions due to Legionella colonization. Reemergence of Legionella spp. colonization was evident in more than half of the hospitals where frequent monitoring and appropriate risk assessment plans were absent or lacking. Hospitals that were monitored continuously over the study period presented a decreasing trend of Legionella colonization. Environmental risk assessment together with Legionella isolation should be enforced systematically in hospitals.     

广州某展馆空调冷却塔水军团菌污染状况调查

目的了解广州某展馆军团菌污染状况,提出相应的防制对策。方法对2008-2009年在广州某展馆采集的44份空调冷却塔水样进行军团菌的分离培养与鉴定,并对检测结果进行统计学分析。结果 44份水样中分离出15株军团菌,军团菌阳性检出率为34.1%。展馆A、B、C区的空调系统运行年限不同,但军团菌阳性检出率差异无统计学意义(2χ=0.143,P0.05)。军团菌检出率在春秋两季差异有统计学意义(2χ=4.130,P0.05),其中秋季军团菌检出率较高,为50.0%,而春季检出率则相对较低,为20.8%。结论广州某展馆空调冷却塔水军团菌污染状况较为严重,对其危险性应引起高度重视并进行有效控制,以防止军团病的暴发流行。