Community-acquired Legionellosis Research Articles

Болезнь легионеров с неврологическими проявлениями: клинический случай

INTRODUCTION. Legionnaires' disease may be manifested by neurological symptoms along with lung damage. Cerebellar ataxia and dysarthria are rare extrapulmonary manifestations of legionellosis. These symptoms significantly reduce the quality of life of patients. AIM. To analyze the literature data on neurological manifestations of legionellosis and to present a clinical case of Legionnaires' disease manifestation with neurological symptoms. MATERIAL AND METHODS. We performed an analysis of the available literature. Twenty-four Russian and international literature sources (PubMed databases) were evaluated, describing the characteristics and prevalence of neurological manifestations in Legionnaires' disease. We also described the main theories of the pathogenesis of these clinical manifestations. Our clinical case is presented. RESULTS AND DISCUSSION. As of today, few cases of Legionnaires' disease with cerebellar symptoms have been described. Dysarthria and ataxia are the most frequent manifestations of cerebellar dysfunction in legionellosis. Cases where neurologic symptoms persisted after the resolution of pneumonia have been described previously. There are also reports of manifestation of Legionnaires' disease with cerebellar ataxia. The pathophysiology of cerebellar involvement is unknown. There are hypotheses of toxin-mediated and immune-mediated mechanisms. Recent studies have shown that L. pneumophila can activate receptors responsible for enacting the inflammasome pathway. This mechanism promotes cell death that occurs to remove the intracellular pathogen, which may be responsible for central nervous system dysfunction. CASE PRESENTATION. A 48-year-old woman was hospitalized with a suspected stroke. She works in diamond production and is in contact with aerosolized liquids. Four days before hospitalization she complained of a headache, and in the evening before she lost consciousness. Slurred speech, unsteadiness, and inability to walk were noted. At hospitalization, no instrumental evidence of stroke was obtained. Inflammatory markers were elevated. Chest computer tomography showed infiltrative changes. The rapid test for antigenuria (L. pneumophila) was positive, and community-acquired legionellosis was confirmed. Levofloxacin was administrated. After discharge, dysarthria, dysphagia, and instability in the Romberg pose persisted. CONCLUSION. The example of this clinical observation demonstrates that in rare cases Legionnaires' disease can manifest as other diseases, which requires a certain vigilance of doctors of different specialities in order to timely diagnose the disease. KEYWORDS: Legionnaires' disease, legionellosis, community-acquired pneumonia, central nervous system, infectious disease

Associations between meteorological factors, air pollution and Legionnaires’ disease in New Zealand: Time series analysis

BackgroundPrior studies have shown that meteorological factors may be associated with increases in legionellosis (Legionnaire's disease, (LD)), caused by Legionella, a globally ubiquitous bacterium found naturally in aquatic habitats, soils, and compost. The aim of this retrospective time series analysis was to examine the association between meteorological factors and air pollution parameters and the incidence of sporadic, community-acquired, laboratory confirmed LD. MethodsDaily cases of community-acquired legionellosis, meteorological and air pollution data from two urban areas, Auckland (North Island) and Christchurch (South Island) were collected from January 1, 1997 until December 31, 2020. Using Quasi-Poisson regression, associations between symptom onset and meteorological and air pollution variables were investigated using an interrupted time series analysis. ResultsThe two cities had different meteorological conditions and LD epidemiology and seasonal patterns of Legionella spp. LD incidence rates (per 100,000 population) were higher in Christchurch than Auckland for L.pneumophila (25.8 vs 10.8) and L.longbeachae (78.2 vs 4.9). Seasonal patterns were detected in Christchurch with a higher risk of LD during spring and summer (RR: 1.87, 95% CI: 1.42, 2.49) compared to autumn and winter months. In Auckland, the level of particulate matter 9–10 days prior to the onset date was positively associated with LD occurrence (RR: 1.02, 95% CI: 1.00, 1.04) compared to Christchurch, where Tmax recorded one day prior the onset (RR: 1.03, 95% CI: 1.00, 1.07) and sulphur dioxide 6 days prior to the onset date (RR: 1.27, 95% CI: 1.10, 1.45) were positively associated with LD occurrence. Atmospheric pressure 12 days prior (RR: 0.95, 95% CI: 0.90, 1.00) and wind speed 13 days prior (RR: 0.94, 95% CI: 0.89, 0.99) to the onset date were negatively associated with LD risk. In both cities, no association was detected between the level of precipitation and LD risk. ConclusionsMeteorological factors and air pollutants were associated with the risk of LD. However, different seasonal patterns and prevalent LD species seem to have distinct patterns of association between the two categories of exposures. These findings suggest the importance of considering meteorological and air quality conditions in conjunction with the source of exposure and the LD species involved. They also imply potential climate change impacts on LD and benefits from reducing air pollution, though findings need to be replicated in other geographical regions.

Water Stagnation and Flow Obstruction Reduces the Quality of Potable Water and Increases the Risk of Legionelloses

Legionella is an opportunistic waterborne pathogen associated with Legionnaires' disease and Pontiac fever. Despite improved public awareness, the incidence of Legionella associated infections has been increasing. Aerosols generated from engineered potable water systems are a demonstrated cause of both nosocomial and community-acquired legionellosis. The ecology of Legionella in these systems is complex with multiple factors impacting their colonization and persistence. Flow dynamics has been identified as an important factor and stagnation in cooling towers is an accepted risk for increased Legionella growth; however, less is known about the impact of flow dynamic on Legionella in potable water systems. This is especially complex due to the inherent intermittent and variable usage observed within outlets of a potable water system. This systematic literature review examines the role of fluid dynamics and stagnation on the colonization and growth of Legionella in potable water systems. Twenty two of 24 identified studies show a positive association between stagnation zones and increased colonization of Legionella. These zones included dead legs, dead ends, storage tanks, and obstructed water flow (such as intermittent usage or flow restriction). Prolonged stagnation in building plumbing systems also deteriorates the quality of thermally or chemically treated potable water. This stimulates the colonization of Legionella established biofilms. Such biofilms are intrinsically resistant to disinfection procedures and accelerate the rate of decay of chemical disinfectants. Sub-lethal doses of disinfectants and the presence of protozoan hosts in stationary water promote generation of viable but non-culturable Legionella cells. This results in false negatives in surveillance methods that use culture methodology. In conclusion, elimination of temporal and permanent stagnation points can improve the quality of potable water, efficacy of disinfectants, and reduce the risk of legionellosis. Current guidelines and water safety plans recognize the risks associated with permanent stagnation point (dead ends and dead legs); however, there is a need for greater emphasis on controlling temporal stagnation arising from intermittent usage.

Community-acquired pneumonia caused by Legionella pneumophila (“Legionnaire's Disease”): a brief overview and clinical observation

“Legionnaire's Disease” is an acute infectious disease caused by Legionella of the Legionellaceae family. Clinical forms of legionellosis are diverse, but the risk of severe community-acquired pneumonia (СAP) is the main clinical significance. Unfortunately, as technological progress increases, epidemiological risks of foci of infection associated with artificial water systems (favorable habitat for Legionella) are increasing, which has led to numerous epidemic outbreaks and group cases of legionellosis infection recorded in the world recently. There are no pathognomonic symptoms and signs that allow it to be reliably differentiated from CAP by another etiology for “Legionnaire's disease”. An important role in the early verification of the disease is assigned to taking into account known risk factors of infection (a recent trip accompanied by possible contact with a water spray of a centralized air conditioning system) – age over 40 years, male sex, smoking, chronic concomitant diseases (diabetes mellitus, etc.), immunosuppression and timely laboratory diagnosis. The most accessible and convenient methods of primary diagnostics of community-acquired legionellosis are tests based on the detection of soluble antigen L. pneumophila serogroup-1 in urine. The treatment of Legionellosis CAP is based on antibacterial therapy, levofloxacine and macrolides are the drugs of choice. In this article, a series of clinical observations (2017 – 2019) in one of the multidisciplinary hospitals of Moscow is given as a confirmation of the clinical significance of legionella in the etiology of CAP in hospitalized patients and the need for timely diagnosis of the disease.

Daily Reportable Disease Spatiotemporal Cluster Detection, New York City, New York, USA, 2014-2015.

Each day, the New York City Department of Health and Mental Hygiene uses the free SaTScan software to apply prospective space–time permutation scan statistics to strengthen early outbreak detection for 35 reportable diseases. This method prompted early detection of outbreaks of community-acquired legionellosis and shigellosis.

Environmental relevance of cooling towers - a systematic review of legionellosis outbreaks

Background Bioaerosols from cooling towers are often suspected to cause community-acquired legionellosis outbreaks. Uncertainty exists about the release and distribution of Legionella into the air, the occurrence of the respirable virulent form and the level of the infective dose. Aims We aimed to evaluate studies on Legionella outbreaks attributed to cooling towers. A systematic review, including data on morbidity and mortality, risk groups, diagnostic tools, meteorological conditions, maintenance actions, and comparative analysis of clinical and environmental isolates, was performed. Methods The literature search was conducted in Medline including publications from January 2001 to August 2012. Relevant findings were synthesized in form of a narrative summary. Results 19 outbreaks were identified affecting 12 countries. Recurring events were observed in Spain and Great Britain, 1609 confirmed cases of legionellosis and 102 cases of death (case-fatality rate 0-29%). Median time between onset of symptoms of first and last case was 36.5 days. The most frequent risk factors were smoking and underlying diseases in about half of the studies. The meteorological conditions varied strongly. Several studies reported a temporal association of outbreaks with technical interventions. A match of clinical and environmental isolates by serotyping and/or molecular subtyping was confirmed in 16 (84%) outbreaks. Conclusion Legionella-contaminated cooling towers as environmental trigger can cause severe health problems and even death of susceptible individuals. Consequently, public health authorities should enforce prevention and rapid risk assessment of outbreaks. Therefore, the registration of cooling towers is important to accelerate source identification and to shorten outbreak duration. To prevent and control Legionella contamination of cooling towers, maintenance actions should aim at low-emission procedures.

Assessing the environmental health relevance of cooling towers – A systematic review of legionellosis outbreaks

Bioaerosols from cooling towers are often suspected to cause community-acquired legionellosis outbreaks. Although Legionella infections can mostly be assigned to the emission sources, uncertainty exists about the release and distribution into the air, the occurrence of the respirable virulent form and the level of the infective concentration. Our study aimed to evaluate studies on legionellosis outbreaks attributed to cooling towers published within the last 11 years by means of a systematic review of the literature. 19 legionellosis outbreaks were identified affecting 12 countries. Recurring events were observed in Spain and Great Britain. In total, 1609 confirmed cases of legionellosis and a case-fatality rate of approximately 6% were reported. Duration of outbreaks was 65 days on average. For diagnosis the urinary antigen test was mainly used. Age, smoking, male sex and underlying diseases (diabetes, immunodeficiency) could be confirmed as risk factors. Smoking and underlying diseases were the most frequent risk factors associated with legionellosis in 11 and 10 of the 19 studies, respectively. The meteorological conditions varied strongly. Several studies reported a temporal association of outbreaks with inadequate maintenance of the cooling systems. A match of clinical and environmental isolates by serotyping and/or molecular subtyping could be confirmed in 84% of outbreaks. Legionella-contaminated cooling towers as environmental trigger, in particular in the neighbourhood of susceptible individuals, can cause severe health problems and even death. To prevent and control Legionella contamination of cooling towers, maintenance actions should focus on low-emission cleaning procedures of cooling towers combined with control measurements of water and air samples. Procedures allowing rapid detection and risk assessment in the case of outbreaks are essential for adequate public health measures. Systematic registration of cooling towers will facilitate the identification of the source of outbreaks and help to shorten their duration.

An unprecedented outbreak investigation for nosocomial and community-acquired legionellosis in Hong Kong.

The environmental sources associated with community-acquired or nosocomial legionellosis were not always detectable in the mainland of China and Hong Kong, China. The objective of this study was to illustrate the control measures implemented for nosocomial and community outbreaks of legionellosis, and to understand the environmental distribution of legionella in the water system in Hong Kong, China. We investigated the environmental sources of two cases of legionellosis acquired in the hospital and the community by extensive outbreak investigation and sampling of the potable water system using culture and genetic testing at the respective premises. The diagnosis of nosocomial legionellosis was suspected in a patient presenting with nosocomial pneumonia not responsive to multiple beta-lactam antibiotics with subsequent confirmation by Legionella pneumophila serogroup 1 antigenuria. High counts of Legionella pneumophila were detected in the potable water supply of the 70-year-old hospital building. Another patient on continuous ambulatory peritoneal dialysis presenting with acute community-acquired pneumonia and severe diarrhoea was positive for Legionella pneumophila serogroup 1 by polymerase chain reaction (PCR) testing on both sputum and nasopharyngeal aspirate despite negative antigenuria. Paradoxically the source of the second case was traced to the water system of a newly commissioned office building complex. No further cases were detected after shock hyperchlorination with or without superheating of the water systems. Subsequent legionella counts were drastically reduced. Point-of-care infection control by off-boiled or sterile water for mouth care and installation of water filter for showers in the hospital wards for immunocompromised patients was instituted. Territory wide investigation of the community potable water supply showed that 22.1% of the household water supply was positive at a mean legionella count of 108.56 CFU/ml (range 0.10 to 639.30 CFU/ml). Potable water systems are open systems which are inevitably colonized by bacterial biofilms containing Legionella species. High bacterial counts related to human cases may occur with stagnation of flow in both old or newly commissioned buildings. Vigilance against legionellosis is important in healthcare settings with dense population of highly susceptible hosts.

Factors associated with hospital mortality in community-acquired legionellosis in France

The aims of this study were to describe the clinical, biological and radiological features of community-acquired (CA) Legionnaires' disease (LD) and identify the predictors of mortality in hospitalised patients. Demographic data, risk factors, clinical and biological features, medical management, complications, and outcome from 540 hospitalised patients with confirmed CA LD were prospectively recorded. 8.1% of patients (44 out of 540) died. The predictors of survival after Kaplan-Meier analysis were male sex (p = 0.01), age <60 yrs (p = 0.02), general symptoms (p = 0.006), intensive care unit (ICU) stay (p<0.001), and class II-III Pneumonia Severity Index score (p = 0.004). Six predictors of death were identified by multivariate analysis: age (per 10-yr increment) (relative hazard (RH) 1.50, 95% CI 1.21-1.87), female sex (RH 2.00, 95% CI 1.08-3.69), ICU admission (RH 3.31, 95% CI 1.67-6.56), renal failure (RH 2.73, 95% CI 1.42-5.27), corticosteroid therapy (RH 2.54, 95% CI 1.04-6.20) and C-reactive protein (CRP) >500 mg · L(-1) (RH 2.14, 95% CI 1.02-4.48). Appropriate antibiotic therapy was prescribed for 70.8% (292 out of 412) of patients after admission and for 99.8% (537 out of 538) of patients after diagnosis confirmation. In conclusion, female sex, age, ICU stay, renal failure, corticosteroid treatment and increased level of CRP are significant risk factors for mortality in CA LD.

Sporadic Legionnaires' disease: the role of domestic electric hot-water tanks

Sporadic community-acquired legionellosis (SCAL) can be acquired through contaminated aerosols from residential potable water. Electricity-dependent hot-water tanks are widely used in the province of Quebec (Canada) and have been shown to be frequently contaminated with Legionella spp. We prospectively investigated the homes of culture-proven SCAL patients from Quebec in order to establish the proportion of patients whose domestic potable hot-water system was contaminated with the same Legionella isolate that caused their pneumonia. Water samples were collected in each patient's home. Environmental and clinical isolates were compared using pulsed-field gel electrophoresis. Thirty-six patients were enrolled into the study. Legionella was recovered in 12/36 (33%) homes. The residential and clinical isolates were found to be microbiologically related in 5/36 (14%) patients. Contaminated electricity-heated domestic hot-water systems contribute to the acquisition of SCAL. The proportion is similar to previous reports, but may be underestimated.

Legionella pneumophila carrying the virulence-associated lipopolysaccharide epitope possesses two functionally different LPS components

Phase-variable expression of Legionella pneumophila lipopolysaccharide (LPS) has not been described in detail for strains possessing the virulence-associated epitope recognized by the monoclonal antibody (mAb) 3/1 of the Dresden Panel. About 75 % of cases of community-acquired legionellosis are caused by mAb 3/1-positive strains. In this study, the LPS architecture of the mAb 3/1-positive Corby strain was investigated during its life cycle in broth culture and inside monocytic host cells. During the exponential growth phase in broth, the highly acetylated and therefore strongly hydrophobic mAb 3/1 epitope is expressed continuously, but only 3 % of the bacteria can be detected using mAb 59/1, which recognizes a short-chain variant of the Legionella LPS that is less hydrophobic due to missing acetylations of the O-chain. The percentage of mAb 59/1-positive legionellae increases up to 34 % in the post-exponential growth phase. LPS shed in broth during the exponential phase is mAb 59/1-negative, and mAb 3/1-positive components do not possess short-chain molecules. The LPS pattern expressed and shed inside U937 cells and A/J mouse macrophages points to the same regulatory mechanisms. During the so-called 'pregnant pause', the period for establishment of the replicative phagosomes, the mAb 3/1-positive LPS is shed into the phagosome and seems to pass through the phagosomal membrane, while mAb 59/1-positive LPS is detectable only on the bacterial surface. After egress of the legionellae into the cytoplasm followed by host cell lysis, individual bacteria are mAb 3/1-positive and mAb 59/1-negative. Intracellularly formed Legionella clusters consist of surface-located mAb 3/1-positive bacteria, which are predominantly mAb 59/1-negative. They surround less hydrophobic and therefore closely packed mAb 59/1-positive bacteria. Based on the different degrees of hydrophobicity, bacteria are able to support the expression of two functionally different LPS architectures, namely more hydrophobic LPS for surviving in aerosols and more hydrophilic LPS for close-packing of legionellae inside clusters.

P271 Sporadic community-acquired legionellosis following domestic exposure: a 93 month surveillance study

P271 Sporadic community-acquired legionellosis following domestic exposure: a 93 month surveillance study

Occurrence of Legionella in hot water systems of single-family residences in suburbs of two German cities with special reference to solar and district heating

A total of 452 samples from hot water systems of randomly selected single family residences in the suburbs of two German cities were analysed for the occurrence of Legionella. Technical data were documented using a standardized questionnaire to evaluate possible factors promoting the growth of the bacterium in these small plumbing systems. All houses were supplied with treated groundwater from public water works. Drinking water quality was within the limits specified in the German regulations for drinking water and the water was not chlorinated. The results showed that plumbing systems in private houses that provided hot water from instantaneous water heaters were free of Legionella compared with a prevalence of 12% in houses with storage tanks and recirculating hot water where maximum counts of Legionella reached 100,000 CFU/100 ml. The presence of L. pneumophila accounted for 93.9% of all Legionella positive specimens of which 71.8% belonged to serogroup 1. The volume of the storage tank, interrupting circulation for several hours daily and intermittently raising hot water temperatures to >60 °C had no influence on Legionella counts. Plumbing systems with copper pipes were more frequently contaminated than those made of synthetic materials or galvanized steel. An inhibitory effect due to copper was not present. Newly constructed systems (<2 years) were not colonized. The type of hot water preparation had a marked influence. More than 50% of all houses using district heating systems were colonized by Legionella. Their significantly lower hot water temperature is thought to be the key factor leading to intensified growth of Legionella. Although hot water systems using solar energy to supplement conventional hot water supplies operate at temperatures 3 °C lower than conventional systems, this technique does not seem to promote proliferation of the bacterium. Our data show convincingly that the temperature of the hot water is probably the most important or perhaps the only determinant factor for multiplication of Legionella. Water with a temperature below 46 °C was most frequently colonized and contained the highest concentrations of legionellae. It is evident that the same factors affecting colonization by Legionella in large buildings also exist in small residential water systems. If temperatures are low there is no difference between large and small systems and Legionella counts are high in both. Since private residences are an important source of community-acquired legionellosis, these findings emphasize the need for preventive control measures in small residential buildings. In some situations it may be necessary to install filtration devices at the point-of-use.

It’s Not the Heat, It’s the Humidity: Wet Weather Increases Legionellosis Risk in the Greater Philadelphia Metropolitan Area

Legionella species are abundant in the environment and are increasingly recognized as a cause of severe pneumonia. Increases in cases of community-acquired legionellosis in the greater Philadelphia metropolitan area (GPMA) led to concern that changing environmental factors could influence occurrence of disease. We evaluated the association between weather patterns and occurrence of legionellosis in the GPMA, using both traditional Poisson regression analysis and a case-crossover study approach. The latter approach controls for seasonal factors that could confound the relationship between weather and occurrence of disease and permits the identification of acute weather patterns associated with disease. A total of 240 cases of legionellosis were reported between 1995 and 2003. Cases occurred with striking summertime seasonality. Occurrence of cases was associated with monthly average temperature (incidence rate ratio [IRR] per degree Celsius, 1.07 [95% confidence interval [CI], 1.05-1.09]) and relative humidity (IRR per 1% increase in relative humidity, 1.09 [95% CI, 1.06-1.12]) by Poisson regression analysis. However, case-crossover analysis identified an acute association with precipitation (odds ratio [OR], 2.48 [95% CI, 1.30-3.12]) and increased humidity (OR per 1% increase in relative humidity, 1.08 [95% CI, 1.05-1.11]) 6-10 days before occurrence of cases. A significant dose-response relationship for occurrence of cases was seen with both precipitation and increased humidity. Although, in the GPMA, legionellosis occurred predominantly during summertime, the acute occurrence of disease is best predicted by wet, humid weather. This finding is consistent with the current understanding of the ecological profile of this pathogen and supports the contention that sporadic legionellosis occurs through contamination of water sources.

Levofloxacin Efficacy in the Treatment of Community-Acquired Legionellosis

Although fluoroquinolones possess excellent in vitro activity against Legionella, few large-scale clinical trials have examined their efficacy in the treatment of Legionnaires disease. Even fewer studies have applied rigorous criteria for diagnosis of community-acquired Legionnaires disease, including culture of respiratory secretions on selective media. Data from six clinical trials encompassing 1,997 total patients have been analyzed to determine the efficacy of levofloxacin (500 mg qd or 750 mg qd) in treating patients with community-acquired pneumonia (CAP) due to Legionella. Of the 1,997 total patients with CAP from the clinical trials, 75 patients had infection with a Legionella species. Demographics showed a large portion of these patients were < 55 years of age and nonsmokers. More than 90% of mild-to-moderate and severe cases of Legionella infection resolved clinically at the posttherapy visit, 2 to 14 days after treatment termination. No deaths were reported for any patient with Legionnaires disease treated with levofloxacin during the studies. Levofloxacin was efficacious at both 500 mg for 7 to 14 days and 750 mg for 5 days. Legionnaires disease is not associated only with smokers, the elderly, and the immunosuppressed, but also has the potential to affect a broader demographic range of the general population than previously thought.

Residential Water Heater Temperature: 49 or 60 Degrees Celsius?

here are two opposing risks when it comes to water tem-perature inside domestic water heaters; exposure toLegionella, the bacteria responsible for Legionnaires’ disease(pulmonary legionellosis), and the risk of scalding. In 1986,this dilemma was the subject of an editorial in the CanadianMedical Association Journal(1). A few months ago, Safe KidsCanada launched a media campaign aimed at preventingscalding by lowering domestic hot water temperature to 49°Cat the tap (2). Among the means considered to reach thisobjective, Safe Kids Canada, with the support of some publichealth organizations, suggests and seems to favour lowering thetemperature setting of domestic hot water heaters to 49°C.Like other authors (3,4), including the World HealthOrganization (WHO) who published a recent monograph onthe Legionella problem in drinking water (3), we believe thatthere is evidence for the transmission of legionellosis throughthe drinking water distribution systems in private homes. Thisis a serious illness associated with high death rates (up to 12%).Primary groups at risk (the elderly, smokers, the immunocom-promised and patients suffering from chronic respiratory ill-nesses), are groups who include a large proportion of thepopulation at home. Although we support prevention againsttap water scalds, we are against setting water heater thermo-stats at 49°C because we believe this could facilitate prolifera-tion of Legionella inside the tank and increase the risk oflegionellosis.Domestic water heaters, particularly electric devices, can cer-tainly be contaminated by Legionella. In Quebec, a study of 211homes (178 electric water heaters, 33 oil or gas water heaters)found Legionella contamination in 40% of electric water heaters.No water heaters using fossil fuels were contaminated (5). Theauthors concluded that, because of design variables, use of anelectric water heater was the most significant factor leading toLegionella contamination in hot water (5) in the home.The clinical and epidemiological significance of this find-ing is much debated. However, in a case-control study of spo-radic cases of community-acquired legionellosis, Straus et al(6) concluded that the residential drinking water supply wasresponsible for a substantial proportion of sporadic cases ofLegionnaires’ disease. These findings are supported by Stout et al(7) in a study of 20 Pittsburgh patients with culture-confirmed Legionnaires’ disease. A link with residential drink-ing water contamination was established for eight (40%)patients. This included three private homes (one singledwelling, two multidwellings), two senior-citizen homes, twoout-patient hospital clinics, and one industrial plant. Theauthors concluded that drinking water distribution systemswere a significant source of transmission of Legionnaires’ dis-ease (7).The importance of Legionnaire’s disease is underestimatedbecause it is difficult to diagnose and because it is reportedthrough a passive surveillance system. In an active surveillancestudy of pneumonia requiring hospitalization in Ohio, the inci-dence of Legionnaire’s pneumonia was estimated to be approx-imately seven cases per 100,000 people (8). With theobservations from the Stout et al (7) study, if active surveil-lance was performed, an estimated two cases of Legionnaire’sdisease per 100,000 people per year could be attributable topotable water in private homes and senior-citizen residences.This is at least of the same order of magnitude as the annualrates of 0.45 per 100,000 for hospitalization and 0.043 fordeath due to scalding by tap water in Quebec (9).The optimal temperature for Legionella proliferation inwater varies between 32°C and 35°C, but it can easily prolifer-ate at temperatures of up to 45°C. Usually, there is no growthabove 55°C, and a temperature of over 60°C has a bactericidaleffect. Thus, the WHO recommends that water be heated andstored at 60°C (3). However, studies in Quebec have shown,even when the thermostat is set at 60°C, a high percentage(approximately 40%) of electric water heaters remain contam-inated because of the lower temperature, about 30°C to 40°Cat the bottom of the tank. The probability of contaminationwill increase considerably if the temperature setting is loweredto 49°C. The risk of contamination is much lower for waterheaters operating with fossil fuels, and is practically nonexist-ent for these heaters set at 60°C.In our opinion, it is important to reduce both the risk ofscalds and the risk of legionellosis associated with domesticwater supplies (9). For water heaters servicing a single housingunit, electric water heater manufacturers need to market, asquickly as possible, water heaters resistant to proliferation ofLegionella. At the least, all new water heaters must be preset at60°C and equipped with antiscald devices to deliver water at49°C to the entire household. Electric water heaters alreadyinstalled should be set at 60°C to limit the risk of Legionellacontamination. Gas or oil water heaters already installed

Legionelosis comunitaria en las comarcas de Barcelona entre 1992 y 1999: características epidemiológicas y métodos diagnósticos

The epidemiological characteristics of community-acquired legionellosis are not well known. We present here legionellosis cases appearing in Barcelona, Spain, districts during 1992-1999. Questionnaire on socio-demographic, epidemiological, clinical and diagnostic data. 285 community-acquired cases of legionellosis were notified (67% of total). Incidence values increased from 0.03/100,000 in 1992 to 3.14 in 1999. Mostly used diagnostic method since 1996 was the urinary antigen test. The incidence of legionellosis increased sharply during the studied period. We believe that use of urinary antigen-based diagnosis allows for a better knowledge of community-acquired legionellosis.

Detecting legionellosis by unselected culture of respiratory tract secretions and developing links to hospital water strains

For a 13-month period, all respiratory tract secretions submitted for routine bacteriology from a large hospital complex were cultured for legionella, irrespective of clinical diagnosis and laboratory requests. Ten cases of legionellosis were detected in this manner, three of which met a strict epidemiological definition of hospital-acquired. Therefore, the 16 warm-water systems of the hospitals, spread out over two locations, were examined for the presence of legionella.Legionella pneumophila was found in 15 warm water systems, with a distinct pattern of serogroups between the two locations. Legionella of the same serogroups as those isolated from patients were present in each hospital water supply. The isolates were further typed by monoclonal antibodies and by genomic macrorestriction analysis. Similarity between clinical and environmental isolates was found in seven cases. In these cases, acquisition from the hospital water supply appears very likely. The strains of the remaining three patients did not match those in hospital water, suggesting that community-acquired legionellosis was occurring as well. This study suggests that routinely culturing respiratory tract secretions of pneumonia patients for legionella can help diagnose unsuspected cases of legionellosis. Typing legionella strains beyond the serogroup level with tools such as macrorestriction analysis is useful to define sources of infection, which can then be targeted for control measures.

Incidence and clinical features of community-acquired legionellosis in hospitalized patients

In a two-year prospective study of patients hospitalized because of community-acquired pneumonia, the incidence of legionellosis was found to be 3.8% (17/442 cases). After S. pneumoniae, M. pneumoniae and influenzae viruses, legionellae were the fourth most frequently identified pneumonia agents. We evaluated the clinical data from 41 cases with legionellosis, 17 diagnosed in this prospective study and 24 prior to the study. The age range of all patients (22 women, 19 men) was 24-78 yrs (median 61.3 yrs), 14 of 41 cases (34.1%) had extrapulmonary organ involvement. Twelve patients (29.3%) died. The fatality rate was 4.5% (1/22 cases) in patients treated with erythromycin, and 57.9% (11/19 cases) in patients treated with other antibiotics. Antibiotics effective in legionellosis should be added to the routine therapy of community-acquired pneumonia when this aetiology can not be excluded.

Sporadic and epidemic nosocomial legionellosis in the United States: Epidemiologic features

As of April 30, 1980, 83 nosocomial cases of sporadic legionellosis had been reported to the Centers for Disease Control (CDC). In all 83 cases the patients had pneumonia; the median age of the patients was 56.5 years. All but one patient were hospitalized at the time of onset. Of 71 patients for whom the outcome is known, 22 (31 percent) died of causes directly attributed to their infection. Eleven patients had end-stage renal disease, 28 were receiving systemic immunosuppressive medications, 17 had cancer, 12 had chronic bronchitis or emphysema, 29 were smokers, and four had diabetes mellitus. Risks of acquiring nosocomial sporadic legionellosis for patients with these conditions relative to the general United States population = 340, 26, 11, 3.7, 1.9 and 1.3, respectively. These risk factors are similar to those identified for sporadic community-acquired legionellosis and for epidemic nosocomial legionellosis. Methods for preventing nosocomial legionellosis are not known, but comparing Legionella to other water-associated organisms which have been spread from medical devices to cause pneumonia may be fruitful.