Hospital-acquired Legionellosis Research Articles

Prevention of legionella infections from toilet flushing cisterns

INTRODUCTIONImmunocompromised patients are at an increased risk of severe Legionella infections. We present the results of an outbreak investigation initiated following a fatal case of hospital-acquired legionellosis linked to contaminated water from a toilet-flushing cistern. Additionally, we provide experimental data on the growth of Legionella spp. in flushing cisterns and propose a straightforward protocol for prevention. METHODSWe monitored the growth of Legionella spp. in the building's hot and cold-water systems using quantitative bacterial culture on selective agar. Molecular typing of L. pneumophila isolates from the infected patient and the water system was conducted through core-genome multilocus sequence typing (cgMLST). RESULTSLegionella contamination in the hospital building’s cold-water system was significantly higher than in the hot water system and significantly higher in toilet flushing cistern’s water compared to cold water from bathroom sinks and showers. Isolates from the patient and from the flushing cistern of the patient’s bathroom were identical by cgMLST. In an experimental setting, daily toilet flushing for a period of 21 days resulted in a 67 percent reduction in the growth of Legionella spp. in the water of toilet flushing cisterns. Moreover, a one-time disinfection of cisterns with peracetic acid, followed by daily flushing, decreased Legionella growth to less than 1% over a period of at least 7 weeks in these setting. CONCLUSIONSOne-time disinfection of highly contaminated cisterns with peracetic acid and daily toilet flushing as short-term measure can significantly reduce Legionella contamination in flushing cisterns. These measures may aid in preventing Legionella infection among immunocompromised patients.

The contamination of hospital water supply systems by <i>Legionella pneumophila</i>

The risk of severe infectious complications associated with provision of medical care continues to be a pressing issue in modern surgery. Legionella pneumophila, characterized by its wide distribution in water supply systems and is highly active in film formation, represents a dangerous/important cause of hospital-acquired pneumonia. Patients requiring immunosuppression, including organ transplant recipients, are in the special risk group. Prevention of hospital-acquired legionellosis in patients at risk is essential due to severe clinical manifestations and high mortality. Objective: to summarize the practical experience in detecting contamination of water supply systems by Legionella pneumophila strains in multidisciplinary hospitals in Moscow. Materials and methods. Isolation of Legionella pneumophila strains from water and biofilms of water supply systems in multidisciplinary hospitals in Moscow and serotyping of this pathogen using bacteriological, molecular genetic and enzyme immunoassay methods. Results. Legionella pneumophila content in water reached high levels. The peculiarities of Legionella pneumophila contamination of hot water supply systems included formation of stable biofilms, in which other hospital-acquired pathogens were also identified. The share of Legionella pneumophila «SG 1», which causes up to 80% legionellosis cases in the world, was 13% in the water of the hospitals surveyed. The most effective measures for prevention of legionellosis are actions aimed at ensuring water biosecurity. Conclusion. There are potential risks of disease in the surgical wards of hospitals providing medical care, including in immunocompromised patients. Due to potential risks, prevention of hospital-acquired legionellosis is a necessary component of ensuring the safety of treatment for immunosuppressed patients.

Prevention of nosocomial legionellosis by best water management: comparison of three decontamination methods

Since 2000, the National Health System has adopted international guidelines for assessing Legionella spp. in hospital water systems. The control of water contamination by Legionella spp. is still a matter of research concerning the most effective method in preventing nosocomial infections. To compare three different decontamination methods by monitoring colony-forming unit count and number of hospital-acquired legionellosis cases. A secondary objective was to evaluate the long-term effects of the preventive measures on the water pipes. A protocol was developed for the selection of high-risk sampling sites and for the testing of three disinfection methods over the course of 19 years: hyperchlorination and thermal shock (period A, 2000-2005); copper-silver ionization (period B, 2006-2010); and integration of pre-filtering, filtering, pipe-protecting products, and remote control with chlorine dioxide (ClO2) (period C, 2011-2018). The use of shock disinfection and hyperchlorination led to a decrease in contamination level immediately after the procedure, but then it rose again to the previous level in two months. Both copper-silver ionization and ClO2 disinfection showed a stable and durable decrease in contamination level. Throughout these three phases, six cases of Legionella spp. occurred during period A, six cases during period B, and three cases during period C. With regard to the damage of water pipes, effective copper-silver levels caused corrosion and calcification in water pipes. Both copper-silver ionization and ClO2 properly controlled Legionella spp. contamination. ClO2 significantly reduced the number of positive sites (P < 0.001) without damaging the pipelines.

Legionella control in a tertiary care hospital in Italy: adapting solutions to changing scenarios

Abstract Background Legionella contamination of hospital water distribution system still remains a critical issue in healthcare settings, despite the disputed relationship between environmental legionella and hospital-acquired legionellosis. We report the experience of our 1200-beds hospital, where a new water safety plan (WSP) has been applied since 2017, and the results obtained with the application of different methods to control Legionella water contamination, especially in critical areas. Methods Policlinico San Martino is the referral tertiary acute-care university hospital in Liguria region, North-West Italy. It’s made of 21 buildings of different dimensions, 7 of which host high risk patients, according to Italian Guidelines for legionellosis prevention and control. A sampling plan for Legionella detection was implemented in 2017, focusing on the water network critical points. Different secondary disinfection procedures were used, including systemic (chlorine dioxide, monochloramine), focal (point-of-use filtration) and short-term methods (hyperchlorination), the last in case of contamination higher than 10^4 CFU/l. Results Respectively, during 2017 and 2018 a total of 201 and 119 hot water samples were collected, distributed among the 7 critical buildings of the hospital. Negative samples raised from 69.7% to 74.8%, while positive samples &amp;gt;10^3 CFU/l (recommended cut-off for acute disinfection according to Italian guidelines) lowered from 21.9% to 9.2% of total samples. Out of 55 positive samples, Legionella sg 3 accounted for 98.2% of the total. Conclusions The new WSP determined a significant reduction of Legionella contamination of water distribution networks in our hospital critical buildings. The continuous surveillance of critical water system points provided evidence to elaborate an effective protocol for routine and extraordinary disinfection interventions, as result of a close collaboration between hospital hygiene unit and engineering and technical services. Key messages The implementation of an effective water safety plan and different disinfection procedures in hospital critical areas allow us to reduce and control the risk of hospital-acquired Legionella infection. Continuous surveillance cultures of drinking water to detect Legionella are necessary to adapt disinfection methods to local results.

1622. Clinical and Environmental Surveillance of Legionella pneumophila in a Tertiary Healthcare Center in India

BackgroundLegionellosis is a form of pneumonia caused by Gram-negative bacilli belonging to the Legionella genus. In India, sporadic cases of legionellosis have been reported, but the incidence of this infection is still believed to be underestimated. We conducted a proactive clinical–environmental surveillance in a tertiary healthcare center to determine the frequency of legionellosis, and to identify the pathogen in the hospital water systems.MethodsDuring February 2015–February 2019, we enrolled 533 cases (310 males, 223 females) with a diagnosis of pneumonia; a respiratory secretion was collected from each patient and tested for L.pneumophila by using a real-time PCR targeting mip gene. To identify Legionella spp. present in hospital water systems, we collected 201 hospital water samples and were analyzed by cultivation in BCYE agar. Legionella speciation and identification of Lp1 was done by real-time PCR assay.ResultsAmong 533 cases, 11(2.1%) [6 male, 5 female] tested positive for L.pneumophila by real-time PCR. Of these, all were community-acquired sporadic cases not associated with a cluster or outbreak. Risk factors including smoking, alcohol use, malignancy, underlying respiratory disease, hypertension were identified in 8 (72.7%) cases. The duration of hospitalization for Legionella patients was 8–24 days; 5/11 (45.5%) patients were admitted to intensive care units. Of 11 patients 8 (72.7%) survived, and 3(27.3%) died. Among the 201 water samples tested, 38 (18.9%) tested positive for L.pneumophila by culture. The presence of Lp1 was detected in 25 (12.4%) water samples. Legionella spp. was recurrently isolated from patient areas, cooling towers, residential areas, and other areas inside the hospital campus.ConclusionThe study indicates a low prevalence of legionellosis in this region. Even though Legionella colonization was detected in the hospital water system, no cases of hospital-acquired legionellosis were discovered during the study period. However, considering the risk of nosocomial legionellosis to patients we formulated Legionella control strategies in this hospital. Point-of-use filters were installed to the potable water units from where Legionella was isolated and repeat sampling from these sites were found to be negative for the contagion.Disclosures All authors: No reported disclosures.

Environmental surveillance of Legionella pneumophila in distal water supplies of a hospital for early identification & prevention of hospital-acquired legionellosis.

Background & objectives:Legionella pneumophila, a ubiquitous aquatic organism is found to be associated with the development of the community as well as hospital-acquired pneumonia. Diagnosing Legionella infection is difficult unless supplemented with, diagnostic laboratory testing and established evidence for its presence in the hospital environment. Hence, the present study was undertaken to screen the hospital water supplies for the presence of L. pneumophila to show its presence in the hospital environment further facilitating early diagnosis and prevention of hospital-acquired legionellosis.Methods:Water samples and swabs from the inner side of the same water taps were collected from 30 distal water outlets present in patient care areas of a tertiary care hospital. The filtrate obtained from water samples as well as swabs were inoculated directly and after acid buffer treatment on plain and selective (with polymyxin B, cycloheximide and vancomycin) buffered charcoal yeast extract medium. The colonies grown were identified using standard methods and confirmed for L. pneumophila by latex agglutination test.Results:About 6.66 per cent (2/30) distal water outlets sampled were found to be contaminated with L. pneumophila serotype 2-15. Isolation was better with swabs compared to water samples.Interpretation & conclusions:The study showed the presence of L. pneumophila colonization of hospital water outlets at low levels. Periodic water sampling and active clinical surveillance in positive areas may be done to substantiate the evidence, to confirm or reject its role as a potential nosocomial pathogen in hospital environment.

Energy Conservation and the Promotion of Legionella pneumophila Growth: The Probable Role of Heat Exchangers in a Nosocomial Outbreak.

OBJECTIVE To determine the source of a Legionella pneumophila serogroup 5 nosocomial outbreak and the role of the heat exchanger installed on the hot water system within the previous year. SETTING A 400-bed tertiary care university hospital in Sherbrooke, Canada. METHODS Hot water samples were collected and cultured for L. pneumophila from 25 taps (baths and sinks) within wing A and 9 taps in wing B. Biofilm (5) and 2 L water samples (3) were collected within the heat exchangers for L. pneumophila culture and detection of protists. Sequence-based typing was performed on strain DNA extracts and pulsed-field gel electrophoresis patterns were analyzed. RESULTS Following 2 cases of hospital-acquired legionellosis, the hot water system investigation revealed a large proportion of L. pneumophila serogroup 5 positive taps (22/25 in wing A and 5/9 in wing B). High positivity was also detected in the heat exchanger of wing A in water samples (3/3) and swabs from the heat exchanger (4/5). The outbreak genotyping investigation identified the hot water system as the source of infections. Genotyping results revealed that all isolated environmental strains harbored the same related pulsed-field gel electrophoresis pattern and sequence-based type. CONCLUSIONS Two cases of hospital-acquired legionellosis occurred in the year following the installation of a heat exchanger to preheat hospital hot water. No cases were reported previously, although the same L. pneumophila strain was isolated from the hot water system in 1995. The heat exchanger promoted L. pneumophila growth and may have contributed to confirmed clinical cases. Infect. Control Hosp. Epidemiol. 2016;1475-1480.

Virulence of Legionella pneumophila strains isolated from hospital water system and healthcare-associated Legionnaires' disease in Northern Italy between 2004 and 2009.

BackgroundWorldwide, L. pneumophila sg 1 is the most common agent of Legionnaires’ disease ( 80 to 90% of the reported cases). In contrast, L. pneumophila sg 2–14 account for only 15 to 20% of community-acquired cases, although they account for over 50% of the environmental isolates. The discrepancy between environmental isolates and clinical cases of disease suggested that there are differences in virulence.We decided to subtype the environmental Legionella strains isolated from health care facilities (HCFs) and to compare the distribution of strains with the occurrence of hospital-acquired legionellosis.MethodsObservational ecological study based on the data provided by the regional surveillance of legionellosis and on data obtained from hospitals environmental monitoring.Using the monoclonal antibody MAb 3/1 of the Dresden Panel we collected and typed environmental strains of L. pneumophila sg 1 obtained during routine testing in 56 health care facilities from 2004 to 2009.The results of the laboratory analyses of the environmental samples were compared with the number of cases that each health care facility reported during the study period.ResultsThe association between the type of colonisation (L. pneumophila sg 1 vs others serogroups) and the incidence of reported cases was statistically significant (p = 0.03 according to the χ2 test).Legionella strains with the virulence–associated epitope recognised by MAb 3/1 were isolated in 8 of the 26 HCFs colonised by L. pneumophila sg 1; 7 of the HCFs colonised by MAb 3/1-positive strains accounted for 85% of the cases of hospital-acquired legionellosis reported during the 6-year study period. There was a statistically significant association (p = 0.003) between the presence of cases and colonisation by MAb 3/1-positive Legionella strains.ConclusionThis study suggests that hospitals colonised by more virulent strains should be aware of the increased risk and consider the opportunities of increase their monitoring efforts and implement more effective contamination control strategies.

Risk of hospital-acquired Legionellosis from microbial contamination of potable water at a Bone Marrow Transplant Unit in a Czech University Hospital

The investigated of the potable water treatment room and the sanitary facilities of patient boxes was held. The potable water treatment room had three collection points (ball valves), while in the sanitary facilities potable water was collected from the tap, shower, and the flush tank. A swab was taken from the inside wall of the toilet tank. The samples and swabs of the flush tank water were Legionella pneumophila sg 1 and sg 6A positive. Disinfection of flush tanks with chlorine agents was recommended.

Nosocomial Legionnaires’ Disease: Risque and Prevention

In 1977, Fraser et al. described an outbreak of pneumonia among legionnaires attending a convention at a hotel in Philadelphia in 1976. Legionnaires’ disease (LD) can be nosocomial, community acquired or travel related. The incidence of hospital-acquired legionellosis appears to be increasing. Colonization of water systems by <i>Legionella</i> spp. is ubiquitous in hospitals throughout the world. The outbreak, which later became known as legionnaires’ disease, was caused by a new pleomorphic, faintly staining gram-negative bacillus, <i>L.</i><i> </i><i>pneumophila</i>, which was isolated at the Center for Disease Control from lung tissues of legionnaires who died. Risk assessment for this disease forms the basis for the institution of control measures. Detection and quantification of <i>Legionella</i> spp. in the environment, in particular in the hospital water distribution system is one of the cornerstones of risk assessment. This review summarizes the current state-of-the-art regarding these aspects and points out important areas which require further study. The environmental surveillance revealed that the centralized hot water distribution system of the hospital was colonized with <i>Legionella</i>. Methods of prevention of the organisms for eradication involved in hospital water systems.

Plan for the control of Legionella infections in long-term care facilities: Role of environmental monitoring

In accordance with the international and national guidelines, the Emilia-Romagna Region (Italy) has established regional guidelines for the surveillance and prevention of legionellosis based on the concept of risk assessment, with particular attention to environmental monitoring. The aim of this study was to verify how environmental surveillance in the context of risk assessment plans could help to guide decisions about preventive strategies against Legionella infections in Long Term Care Facilities (LTCF). In six LTCFs in the city of Bologna (Emilia-Romagna Region) a self-control plan was implemented that included the environmental monitoring of Legionella spp. and the surveillance of hospital-acquired Legionnaires' Disease. At baseline, four hot water systems were colonized by Legionella pneumophila (3 LCTFs) and Legionella londiniensis (1 LCTF). In each establishment specific control measures were adopted based on the characteristics of the system, the virulence of the strain and the level of the contamination. The monitoring, carried out for around two years, was also extended to the ways in which the system and the distal water distribution points were used and maintained with respect to the good practices in operation and management. The adopted actions (shock and/or continuous disinfection treatments) and the implementation of the good practice measures reduced the contamination to acceptable and stable levels. No cases of hospital-acquired legionellosis occurred during the period of study. The environmental surveillance was successful in evaluating the risk and identifying the most suitable preventive strategies.

Prevention of hospital-acquired legionellosis

The incidence of hospital-acquired legionellosis appears to be increasing. Presence of Legionella in the hospital drinking water is the only risk factor known with certainty to be predictive of risk for contracting Legionnaires' disease. Given the high frequency of infection by nonpneumophila and nonserogroup 1 species, both Legionella respiratory culture on selective media and urine antigen testing should be available in the hospital clinical microbiology laboratory. If the drinking water is contaminated by nonpneumophila or nonserogroup 1 species, Legionella culture on selective media must be available for patients with hospital-acquired pneumonia. The impact of PCR application for environmental water specimen remains to be elucidated. Its advantage is that it is a rapid test and its weakness is its low specificity. Copper-silver ionization disinfection and point-of-use (POU) filters have proved effective. Chlorine dioxide and monochloramine are under evaluation and their ultimate role remains to be elucidated. Routine Legionella cultures in concert with disinfectant levels are the best indicators for ensuring long-term efficacy. Percentage distal site positivity for Legionella in drinking water is accurate in predicting risk. Quantitative criteria (CFU/ml) have proven inaccurate and should be abandoned. Infection control professionals, not healthcare facility personnel or engineers, should play the leadership role in selecting and evaluating the specific disinfection modality. Proactive measures of routine environmental cultures for hospital water and disinfection modalities allow for effective prevention of this high-profile hospital-acquired infection.

Environmental culturing for Legionella: Can we build a better mouse trap?

The drinking water of hospitals has been directly linked to the occurrence of hospital-acquired legionellosis. In addition, the mode of transmission is now known to be primarily aspiration rather than aerosolization. Legionellosis is now recognized as a patient safety concern for nosocomial infection. In 2009, Centers for Medicaid and Medicare Services raised the issue that hospitals might no longer be reimbursed for charges incurred when caring for patientswithhealth care-associated legionellosis based on the argument that this infection is largely preventable. Unfortunately, opposition from the US Centers for Disease Control and Prevention (CDC) and other organizations prevented the measure from passing, but the issue will be revisited next year. Given the direct link between drinking water colonization by Legionella and hospital-acquired legionellosis, national public health agencies have mandated routine environmental surveillance as a preventive measure. On the other hand, some public health agencies, including the CDC, mandate culturing of the hospital drinking water in acute care hospitals only after 1 to 2 cases have been identified. The obvious flaw in this approach is the fact that legionellosis diagnosis requires some index of suspicion. Knowledge that Legionella is within the hospital drinking water raises that index of suspicion. Without this knowledge, hospital-acquired legionellosis has gone undetected to the extent that numerous hospitals have claimed that they have never seen a case of hospital-acquired legionellosis. This commonplace belief has been refuted in numerous prospective studies and most dramatically in Maryland, when hospital-acquired legionellosis abruptly appeared in 2 academic tertiary care health centers in Baltimore within weeks of adopting the Maryland guidelines for proactive surveillance. The table of International Guidelines for Legionella Prevention summarized in the Ditomasso article shows that the guidelines of Australia, France, United Kingdom, and Italy use quantitation (colony-forming units/liter) as a guide for remediation. However, quantitative cultures have not proven to be predictive of the occurrence of hospital-acquired legionellosis. The reasons for this are intuitively obvious. Swabbing of the distal site can remove the biofilm and artifactually affect the quantitation numbers. The biofilm may also be affected by water usage and stagnation. In contrast, the extent of Legionella colonization has proven to be surprisingly robust in predicting the occurrence of hospital-acquired Legionellosis. Extent of colonization is calculated based on the percent distal site positivity (ie, the percent of water faucets that yield Legionella as compared with the total number of cultures taken). Ifmore than 30%of the sampled outlets are positive (especially for Legionella pneumophila), actions should be taken tomitigate the risk to hospitalized patients. Publicity in the newspapers and television complicates the process. In addition, lawsuits based on allegations of negligence have become commonplace for hospitals experiencing nosocomial Legionella infection. A study by the Association for Professionals in Infection Control and Epidemiology-Three Rivers Chapter (TRAPIC) and the Allegheny County (Pittsburgh) Health Department showed that, once proactive surveillance cultures for hospital drinking water were implemented in Pittsburgh, adverse publicity and the incidence of hospital-acquired legionellosis plummeted because preventive measures had been instituted. Ditomasso et al present a sophisticated and comprehensive investigation of a topical issue: improvement of an approach and methodology for performing From the University of Pittsburgh, Pittsburgh, PA; and Special Pathogens Laboratory, Pittsburgh, PA.

Clinical features and predictors of mortality in admitted patients with community- and hospital-acquired legionellosis: A Danish historical cohort study

BackgroundLegionella is a common cause of bacterial pneumonia. Community-acquired [CAL] and hospital-acquired legionellosis [HAL] may have different presentations and outcome. We aimed to compare clinical characteristics and examine predictors of mortality for CAL and HAL.MethodsWe identified hospitalized cases of legionellosis in 4 Danish counties from January 1995 to December 2005 using the Danish national surveillance system and databases at departments of clinical microbiology. Clinical and laboratory data were retrieved from medical records; vital status was obtained from the Danish Civil Registration System. We calculated 30- and 90-day case fatality rates and identified independent predictors of mortality using logistic regression analyses.ResultsWe included 272 cases of CAL and 60 cases of HAL. Signs and symptoms of HAL were less pronounced than for CAL and time from in-hospital symptoms to legionellosis diagnosis was shorter for CAL than for HAL (5.5 days vs. 12 days p < 0.001). Thirty-day case fatality was 12.9% for CAL and 33.3% for HAL; similarly 90-day case fatalities in the two groups were 15.8% and 55.0%, respectively. In a logistic regression analysis (excluding symptoms and laboratory tests) age >65 years (OR = 2.6, 95% CI: 1.1-5.9) and Charlson comorbidty index ≥2 (OR = 2.7, 95% CI: 1.1-6.5) were associated with an increased risk of death in CAL. We identified no statistically significant predictors of 30-day mortality in HAL.ConclusionsSigns and symptoms were less pronounced in HAL compared to CAL. Conversely, 30-day case fatality was almost 3 times higher. Clinical awareness is important for the timely diagnosis and treatment especially of HAL. There is a need for further studies of prognostic factors in order to improve the therapeutic approach to legionellosis and potentially reduce mortality.

Gestion des risques liés aux légionelles dans un centre hospitalier multisites : retour d’expérience de plus de six années

To reduce the Legionella-link risk in the several sites of Sud-Francilien Hospital, following a hospital-acquired legionellosis case, a multidisciplinary working group performed an action plan monitored through Legionella pneumophila counts in hot water supply. From 2003 to the first half year 2009, positive points for Legionella pneumophila on the main sites of the hospital decreased from 85.71 to 28.00%, representing a significant reduction of 67.33%. Similar results were observed for three of the four establishments, whereas the last did not describe a pronounced reduction of Legionella pneumophila counts and showed constantly serogroup 1 strains. During this period, investigations of additional cases of legionellosis demonstrated a nosocomial transmission in one case in this last site. Multidisciplinary mobilization in management of Legionella-link risk contributed to these results.

The high prevalence of Legionella pneumophila contamination in hospital potable water systems in Taiwan: implications for hospital infection control in Asia

The major sources of Legionnaires' disease (LD) are the potable water systems of large buildings including hospitals, nursing homes, and hotels. Culturing the hospital water system for Legionella allows a preventive approach for hospital-acquired LD. However, hospital-acquired LD is rarely reported in Taiwan, and environmental cultures of Legionella in hospital water systems in Taiwan have never been systematically performed. The objective of this study was to determine if Legionella is present in hospital water systems in Taiwan. Water quality analysis was also performed to determine if geographic differences in water quality result in different Legionella positivity rates. The water systems of 16 hospitals throughout Taiwan were tested for Legionella by culture. Standardized culture procedures were followed. Legionella pneumophila was isolated from 63% (10/16) of the hospital water systems; 19% (3/16) of the hospitals had an L. pneumophila positive rate greater than 30%. L. pneumophila serogroups 1 and 6 (strains that are most responsible for Legionella infections) were isolated from 80% (8/10) and 60% (6/10), respectively, of the hospitals that yielded L. pneumophila in their water distribution systems. As was shown in epidemiological studies in the USA and Spain, hospital-acquired legionellosis may be prevalent but underdiagnosed in Taiwan.

Hospital-acquired legionellosis originating from a cooling tower during a period of thermal inversion

A case of hospital-acquired legionellosis occurred in a 75-year-old male patient who underwent surgery due to malignant melanoma. Legionellosis was proven by culture of Legionella pneumophila serogroup 1 from bronchoalveolar lavage (BAL) fluid. Being a chronic smoker the patient used to visit the sickroom balcony that was located about 90 m to the west of a hospital cooling tower. Routine cooling tower water samples drawn during the presumed incubation period revealed 1.0x10(4) CFU/100 ml (L. pneumophila serogroup 1). One of three isolates from the cooling tower water matched the patient's isolate by monoclonal antibody (mab)- and genotyping (sequence-based typing). Horizontal transport of cooling tower aerosols probably was favoured by meteorological conditions with thermal inversion. The case report stresses the importance of routine maintenance and microbiological control of hospital cooling towers.

Role of Environmental Surveillance in Determining the Risk of Hospital-Acquired Legionellosis: A National Surveillance Study With Clinical Correlations

Hospital-acquired Legionella pneumonia has a fatality rate of 28%, and the source is the water distribution system. Two prevention strategies have been advocated. One approach to prevention is clinical surveillance for disease without routine environmental monitoring. Another approach recommends environmental monitoring even in the absence of known cases of Legionella pneumonia. We determined the Legionella colonization status of water systems in hospitals to establish whether the results of environmental surveillance correlated with discovery of disease. None of these hospitals had previously experienced endemic hospital-acquired Legionella pneumonia. Cohort study. Twenty US hospitals in 13 states. Hospitals performed clinical and environmental surveillance for Legionella from 2000 through 2002. All specimens were shipped to the Special Pathogens Laboratory at the Veterans Affairs Pittsburgh Medical Center. Legionella pneumophila and Legionella anisa were isolated from 14 (70%) of 20 hospital water systems. Of 676 environmental samples, 198 (29%) were positive for Legionella species. High-level colonization of the water system (30% or more of the distal outlets were positive for L. pneumophila) was demonstrated for 6 (43%) of the 14 hospitals with positive findings. L. pneumophila serogroup 1 was detected in 5 of these 6 hospitals, whereas 1 hospital was colonized with L. pneumophila serogroup 5. A total of 633 patients were evaluated for Legionella pneumonia from 12 (60%) of the 20 hospitals: 377 by urinary antigen testing and 577 by sputum culture. Hospital-acquired Legionella pneumonia was identified in 4 hospitals, all of which were hospitals with L. pneumophila serogroup 1 found in 30% or more of the distal outlets. No cases of disease due to other serogroups or species (L. anisa) were identified. Environmental monitoring followed by clinical surveillance was successful in uncovering previously unrecognized cases of hospital-acquired Legionella pneumonia.

Detection of Legionella pneumophila serogroup 7 strain from bathwater samples in a Japanese hospital

Hospital-acquired legionellosis is one of the serious problems in nosocomial infection. For risk assessment of nosocomial Legionella infection, we surveyed samples from bathrooms for public use in three hospitals and two nursing homes to determine whether Legionella pneumophila was present. A total of 70 hot bathwater samples and samples wiped from bathtubs were collected at 1-h intervals. Fifteen shower-water and 15 inner-head samples were obtained at the start of a bath. Water samples were cultured using the Legionella spp. selective medium, and discrimination between L. pneumophila and other Legionella spp. was performed by PCR analysis. L. pneumophila serogroup 7 was detected in 1 bathwater and 1 wiped sample, both of which were collected 1 h after daily use from the same bathtub in a hospital. However, L. pneumophila SG7 was not detected in any other samples. Furthermore, the concentrations of free residual chlorine in most bath- and shower-water samples were lower than 0.1 mg/l. These results suggest that L. pneumophila has become a potential pathogen for nosocomial infections in public-type hospital baths. From the point of view of an infection-control program, it might be advisable to hold the concentration of free residual chlorine at 0.2-0.4 mg/l, which is generally required for public baths in Japan.

Resolving the Controversy on Environmental Cultures for Legionella: A Modest Proposal

The two rigorous reports in this issue by investigators at the Centers for Disease Control and Prevention (CDC) make for exciting reading.',2 These two reports demonstrate the importance of shoe-leather epidemiology, highlight the power of the new molecular biology with its subtyping capabilities, and deal with the drama of a disease that has, in the two hospitals described, a mortality of 35% to 40%. When one reads Kool et al's description of the intense attempts to track down the source of the organism and the heroic effort to disinfect the water supply, it is no wonder that legionnaires' disease continues to command such attention 22 years after the outbreak at the 1976 American Legion Convention. Are there any new lessons to be gleaned from these two reports? After all, the major conclusions in these two reports have been reiterated in numerous publications and are standard knowledge in medicine textbooks: they include the link to water distribution systems, the link to intubation and the possibility of aspiration; the recognition that the clinical presentation of legionnaires' disease is nonspecific, such that special laboratory tests are needed; and the high risk for contracting legionnaires' disease in transplant recipients and in patients administered corticosteroids. However, there are a number of salient points that illustrate the need for prevention, and I will focus on them. What is remarkable to me is the number of outbreaks of hospital-acquired legionnaires' disease that still are occurring. How can this be after so many reports, dating back to 1982, have linked the contamination of water distribution systems by Legionella to subsequent discovery of legionnaires' disease on the hospital ward? More reports with the same theme will be published in 1999. The epidemiological version of Koch's postulates3 have been fulfilled for linking Legionella colonization in hospital water supplies to hospital-acquired legionnaires' disease.4,5 (Koch's postulates have not been fulfilled for linking cooling tower reservoirs to legionnaires' disease). Since the reservoir for dissemination has been so well established, as in the two CDC reports in this issue, why have measures not been enacted to prevent this disease? Pittsburgh investigators have recommended routine environmental cultures of the hospital water supply since 1986, so as to screen for the possibility of occult legionnaires' disease in the hospital (Figures 1 and 2).6 Obtaining surveillance cultures of water distribution systems in hospitals performing transplants is mandatory, in our opinion.7,8 This is a proactive, scientifically based approach that is inexpensive and focuses attention on those patients and hospitals at the highest risk. The two CDC articles both conclude that intensive surveillance for hospital-acquired legionellosis is necessary for prevention. Conspicuous by its absence is the alternative approach suggested by Pittsburgh investigators and mandated by the Allegheny County Health Department guidelines for prevention of Legi'onella infections9 (Figures 1 and 2). I am concerned that to perform patient surveillance without environmental cultures is to ignore the epidemiological data that have been collected by so many investigators, including the CDC. Knowledge of the reservoir for the organism can be applied to prevention! It makes little sense to me to initiate environmental cultures after cases of hospital-acquired legionnaires' disease have been discovered, as recommended by the CDC. Lepine et al make the telling points that hospital-acquired legionel-