Community-acquired Legionella pneumophila pneumonia: a single-center experience with 214 hospitalized sporadic cases over 15 years

Legionnaire's Disease: A Clinical Diagnostic Approach

Legionnaire's disease is a nonzoonotic atypical pneumonia caused by Legionella sp that occurs sporadically or in outbreaks. Legionnaire's disease pneumonia is accompanied by several extrapulmonary clinical and laboratory findings. Rather than testing all pneumonias for Legionnaire's disease, the clinical challenge is to recognize the diagnostic significance of Legionnaire's disease's. The pretest probability of Legionnaire's disease is increased if several characteristic extrapulmonary findings are present. Similarly, if certain key findings are absent, Legionnaire's disease may be eliminated from further diagnostic consideration. If characteristic clinical findings are present, then specific tests should be ordered to confirm or rule out Legionnaire's disease.

Microbiology and Epidemiology of Legionnaire's Disease

Legionnaire's disease (LD) is the pneumonic form of legionellosis caused by aerobic gram-negative bacilli of the genus Legionella. Individuals become infected when they inhale aerosolized water droplets contaminated with Legionella species. Forty years after the identification of Legionella pneumophila as the cause of the 1976 pneumonia outbreak in a hotel in Philadelphia, we have non-culture-based diagnostic tests, effective antibiotics, and preventive measures to handle LD. With a mortality rate still around 10%, underreporting, and sporadic outbreaks, there is still much work to be done. In this article, the authors review the microbiology, laboratory diagnosis, and epidemiology of LD.

Factors Shaping the Human Exposome in the Built Environment: Opportunities for Engineering Control

The "exposome" is a term describing the summation of one's lifetime exposure to microbes and chemicals. Such exposures are now recognized as major drivers of human health and disease. Because humans spend ∼90% of their time indoors, the built environment exposome merits particular attention. Herein we utilize an engineering perspective to advance understanding of the factors that shape the built environment exposome and its influence on human wellness and disease, while simultaneously informing development of a framework for intentionally controlling the exposome to protect public health. Historically, engineers have been focused on controlling chemical and physical contaminants and on eradicating microbes; however, there is a growing awareness of the role of "beneficial" microbes. Here we consider the potential to selectively control the materials and chemistry of the built environment to positively influence the microbial and chemical components of the indoor exposome. Finally, we discuss research gaps that must be addressed to enable intentional engineering design, including the need to define a "healthy" built environment exposome and how to control it.

The typical presentation of an atypical pathogen during an outbreak of Legionnaires' disease in Vila Franca de Xira, Portugal, 2014

BACKGROUND

An outbreak of Legionella pneumophila serogroup 1, with 403 cases was identified on the 7th November 2014 in Vila Franca de Xira, Portugal. Outbreak source was the wet cooling system of a local factory. Hospital Pulido Valente was one of the hospitals receiving patients with Legionnaires' disease (LD).

METHODS

We describe the clinical findings and diagnostic methods used among the 43 confirmed or probable cases admitted to our department.

RESULTS

60.5% were male, mean age was 56.1±13.5 years and tobacco smoking was the most frequent risk factor (76.7%). All patients had fever, 62.8% ≥39.5°C, 72.1% had chills and myalgia/arthralgia and 62.8% had dry cough. Extra pulmonary symptoms were frequent: confusion and headache occurred in 34.9% and gastrointestinal symptoms in 20.9%. High C-Reactive Protein (55.8% ≥30mg/dL) and hyponatremia (62.8%) were the laboratorial abnormalities most commonly found. Hypoxemia occurred in 55.8% and hypocapnia in 93%. Urinary Antigen Test (UAT) was positive in 83.7% of the cases.

CONCLUSIONS

Although not specific, a combination of risk factors, symptoms and laboratory findings can be highly suggestive of LD, even in an outbreak. This should prompt diagnosis confirmation. Routine use of UAT in less severe cases of community acquired pneumonia might contribute to earlier diagnosis.

Levofloxacin versus azithromycin for treating legionella pneumonia: a propensity score analysis

OBJECTIVES

Concerns have arisen regarding the equivalence of levofloxacin and some macrolides for treating community-acquired legionella pneumonia (LP). We aimed to compare the outcomes of current patients with LP treated with levofloxacin, azithromycin and clarithromycin.

METHODS

Observational retrospective multicentre study of consecutive patients with LP requiring hospitalization (2000-2014) conducted in two hospitals. The primary outcome assessed was 30-day mortality. To control for confounding, therapy was assessed by multivariate analysis.

RESULTS

We documented 446 patients with LP, of which 175 were treated with levofloxacin, 177 with azithromycin and 58 with clarithromycin. No significant differences in time to defervescence (2 (interquartile range (IQR) 1-4) versus 2 (IQR 1-3) days; p 0.453), time to achieve clinical stability (3 (2-5) versus 3 (2-5) days; p 0.486), length of intravenous therapy (3 (2-5.25) versus 4 (3-6) days; p 0.058) and length of hospital stay (7 (5-10) versus 6 (5-9) days; p 0.088) were found between patients treated with levofloxacin and those treated with azithromycin. Patients treated with clarithromycin had longer intravenous antibiotic treatment (3 (2-5.25) versus 5 (3-6.25) days; p 0.002) and longer hospital stay (7 (5-10) versus 9 (7-14) days; p 0.043) compared with those treated with levofloxacin. The overall mortality was 4.3% (19 patients). Neither univariate nor multivariate analysis showed a significant association of levofloxacin versus azithromycin on mortality (4 (2.3%) versus 9 (5.1%) deaths; p 0.164). The results did not change after incorporation of the propensity score into the models.

CONCLUSIONS

In our study, no significant differences in most outcomes were found between patients treated with levofloxacin and those treated with azithromycin. Due to the small number of deaths, results regarding mortality should be interpreted with caution.

Severe Pneumonia Caused by Legionella pneumophila: Differential Diagnosis and Therapeutic Considerations

Severe legionella pneumonia poses a diagnostic challenge and requires early intervention. Legionnaire's disease can have several presenting signs, symptoms, and laboratory abnormalities that suggest that Legionella pneumophila is the pathogen, but none of these are sufficient to distinguish L pneumophila pneumonia from other respiratory pathogens. L pneumophila is primarily an intracellular pathogen and needs treatment with antibiotics that efficiently enter the intracellular space.

Atypical Pneumonia: Updates on Legionella, Chlamydophila, and Mycoplasma Pneumonia

Community-acquired pneumonia (CAP) has multiple causes and is associated with illness that requires admission to the hospital and mortality. The causes of atypical CAP include Legionella species, Chlamydophila, and Mycoplasma. Atypical CAP remains a diagnostic challenge and, therefore, likely is undertreated. This article reviews the advancements in the evaluation and treatment of patients and discusses current conflicts and controversies of atypical CAP.

Impact of pneumonia and lung cancer on mortality of women with hypertension

Essential hypertension is one of the most severe women's health problems. Modern life brings more chances of pulmonary diseases to human. The purpose of the study is to investigate weather pneumonia and lung cancer are associated with the mortality of women with hypertension in different age. A cross-sectional retrospective study was conducted in women with hypertension, who were admitted into our hospital in 2004-2013. 14219 women were enrolled and 68.8 ± 12.2 year old (y). Isolated hypertension was 14.7%. The age of death was 78.1 ± 9.8 y. The mortality was 4.4% for average and 0.2%, 1.1%, 2.4%, 4.8%, 10.4% and 15.8% in group age ≦49, 50-59, 60-69, 70-79, 80-89 and ≧90 y separately. This mortality increased with age was positively significantly correlated with the increased incidences of pneumonia (P < 0.05, r = 0.77). Pneumonia was a significant risk associated with the mortality in age 55-89 y (OR = 6.4-22.5; 95% CI = 3.06-51.12). While, lung cancer was the significant risk in 70-79 y. These observations indicate that pneumonia and lung cancer are significant risk factors associated with the mortality of certain age women with hypertension, and bring an alert that pneumonia and lung cancer should be prevented and treated intensively in modern life in order to reduce the mortality.

Atypical pathogen infection in community-acquired pneumonia

Community-acquired pneumonia (CAP) is a world wide cause of morbidity and mortality. The etiology of CAP is different between countries and changes over time. With the increasing incidence, atypical pathogens are attracting more and more attention all over the world. In many countries, atypical pathogens are one of the main pathogens of CAP, and even could be the most prevalent etiology in China. Atypical pathogen infections can cause multi-system complications, which leads to a worse prognosis. Although still controversial, empirical antibiotic coverage of atypical pathogens in CAP may improve outcomes, shorten length of hospitalization, reduce mortality and lower total hospitalization costs. The macrolide resistance rate of atypical pathogens, especially Mycoplasma Pneumoniae (M. Pneumoniae) is high, so fluoroquinolones or tetracyclines should be considered as alternative therapy.

The Influence of Programmed Cell Death in Myeloid Cells on Host Resilience to Infection with Legionella pneumophila or Streptococcus pyogenes

Pathogen clearance and host resilience/tolerance to infection are both important factors in surviving an infection. Cells of the myeloid lineage play important roles in both of these processes. Neutrophils, monocytes, macrophages, and dendritic cells all have important roles in initiation of the immune response and clearance of bacterial pathogens. If these cells are not properly regulated they can result in excessive inflammation and immunopathology leading to decreased host resilience. Programmed cell death (PCD) is one possible mechanism that myeloid cells may use to prevent excessive inflammation. Myeloid cell subsets play roles in tissue repair, immune response resolution, and maintenance of homeostasis, so excessive PCD may also influence host resilience in this way. In addition, myeloid cell death is one mechanism used to control pathogen replication and dissemination. Many of these functions for PCD have been well defined in vitro, but the role in vivo is less well understood. We created a mouse that constitutively expresses the pro-survival B-cell lymphoma (bcl)-2 protein in myeloid cells (CD68(bcl2tg), thus decreasing PCD specifically in myeloid cells. Using this mouse model we explored the impact that decreased cell death of these cells has on infection with two different bacterial pathogens, Legionella pneumophila and Streptococcus pyogenes. Both of these pathogens target multiple cell death pathways in myeloid cells, and the expression of bcl2 resulted in decreased PCD after infection. We examined both pathogen clearance and host resilience and found that myeloid cell death was crucial for host resilience. Surprisingly, the decreased myeloid PCD had minimal impact on pathogen clearance. These data indicate that the most important role of PCD during infection with these bacteria is to minimize inflammation and increase host resilience, not to aid in the clearance or prevent the spread of the pathogen.

Outcomes of off- and on-hours admission in ST-segment elevation myocardial infarction patients undergoing primary percutaneous coronary intervention: A retrospective observational cohort study

Studies evaluating the outcomes of patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI) are scarce, particularly in China. The purpose of present study was therefore to compare the impact of off-hours and on-hours admission on clinical outcomes in STEMI patients from China.We retrospectively analyzed 1594 patients from 4 hospitals. Of these, 903 patients (56.65%) were admitted during off-hours (weekdays from 18:00 to 08:00, weekends and holidays) and 691 (43.35%) were during on-hours (weekdays from 08:00 to 18:00).Patients admitted during off-hours had higher thrombolysis in myocardial infarction risk score (4.67 ± 2.27 vs 4.39 ± 2.10, P = 0.012) and longer door-to-balloon time (72 [50-96] vs 64 [42-92] minutes, P < 0.001) than those admitted during on-hours. Off-hours admission had no association with in-hospital (unadjusted odds ratio 2.069, 95% confidence interval [CI] 0.956-4.480, P = 0.060) and long-term mortality (unadjusted hazards ratio [HR] 1.469, 95%CI 0.993-2.173, P = 0.054), even after adjustment for confounders. However, long-term outcomes, the composite of deaths and other adverse events, differed between groups with an unadjusted HR of 1.327 (95%CI, 1.102-1.599, P = 0.003), which remained significant in regression models. In a subgroup analysis, off-hours admission was associated with higher long-term mortality in the high-risk subgroup (unadjusted HR 1.965, 95%CI 1.103-3.512, P = 0.042), but not in low- and moderate-risk subgroups.This study showed no association between off-hours admission and in-hospital and long-term mortality. Stratified analysis indicated that off-hours admission was significantly associated with long-term mortality in the high-risk subgroup.

Community-acquired pneumonia related to intracellular pathogens

Community-acquired pneumonia (CAP) is associated with high rates of morbidity and mortality worldwide; the annual incidence of CAP among adults in Europe has ranged from 1.5 to 1.7 per 1000 population. Intracellular bacteria are common causes of CAP. However, there is considerable variation in the reported incidence between countries and change over time. The intracellular pathogens that are well established as causes of pneumonia are Legionella pneumophila, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Chlamydophila psittaci, and Coxiella burnetii. Since it is known that antibiotic treatment for severe CAP is empiric and includes coverage of typical and atypical pathogens, microbiological diagnosis bears an important relationship to prognosis of pneumonia. Factors such as adequacy of initial antibiotic or early de-escalation of therapy are important variables associated with outcomes, especially in severe cases. Intracellular pathogens sometimes appear to cause more severe disease with respiratory failure and multisystem dysfunction associated with fatal outcomes. The clinical relevance of intracellular pathogens in severe CAP has not been specifically investigated. We review the prevalence, general characteristics, and outcomes of severe CAP cases caused by intracellular pathogens.

Distinguishing complicated from uncomplicated parapneumonic effusions

PURPOSE OF REVIEW

Treatment of parapneumonic effusions (PPEs) is challenged by the decision of whether or not to insert chest tubes. This review focuses on the factors that may aid in determining which patients require an immediate drainage of the pleural space, that is, have a complicated PPE.

RECENT FINDINGS

Clinical guidelines advocate the evaluation of radiological (large effusion or loculation), bacteriological (Gram-positive stain or culture), biochemical (pH < 7.20 or glucose <60 mg/dl), and macroscopic (pus) characteristics of the pleural fluid to assist in the identification of complicated PPEs. In the past few years, a number of new pleural fluid biomarkers have been tested for the same purpose, but with the exception of C-reactive protein (CRP), they should be considered investigative. A pleural fluid CRP higher than 100 mg/l or a serum CRP higher than 200 mg/l, when combined with pleural fluid pH or glucose, may greatly increase our capability to predict the need for instituting tube thoracostomy. Although some ultrasonographic and computed tomography features favor the diagnosis of pleural infection, their role in uncomplicated-complicated PPE discrimination has not been systematically evaluated.

SUMMARY

No pleural fluid tests, other than pH or glucose, have gained wide acceptance for the assessment of patients with PPE. However, if corroborated with further studies, the measurement of pleural fluid or serum CRP, in combination with the classical fluid parameters, may have the potential to be incorporated into medical decision making.

Complex clinical and microbiological effects on Legionnaires' disease outcone; A retrospective cohort study

BACKGROUND

Legionnaires' disease (LD) is associated with high mortality rates and poses a diagnostic and therapeutic challenge. Use of the rapid urinary antigen test (UAT) has been linked to improved outcome. We examined the association between the method of diagnosis (UAT or culture) and various clinical and microbiological characteristics and outcome of LD.

METHODS

Consecutive patients with pneumonia and confirmation of Legionella infection by a positive UAT and/or a positive culture admitted between the years 2006-2012 to a university hospital were retrospectively studied. Isolated L. pneumophila strains were subject to serogrouping, immunological subtyping and sequence-based typing. Variables associated with 30-day all-cause mortality were analyzed using logistic regression as well as cox regression.

RESULTS

Seventy-two patients were eligible for mortality analyses (LD study group), of whom 15.5 % have died. Diagnosis based on positive L. pneumophila UAT as compared to positive culture (OR = 0.18, 95 % CI 0.03-0.98, p = 0.05) and administration of appropriate antibiotic therapy within 2 hospitalization days as compared to delayed therapy (OR = 0.16, 95 % CI 0.03-0.90, p = 0.04) were independently associated with reduced mortality. When controlling for intensive care unit (ICU) admissions, the method of diagnosis became non-significant. Survival analyses showed a significantly increased death risk for patients admitted to ICU compared to others (HR 12.90, 95 % CI 2.78-59.86, p = 0.001) and reduced risk for patients receiving appropriate antibiotic therapy within the first two admissions days compared to delayed therapy (HR 0.13, 95 % CI 0.04-0.05, p = 0.001). Legionella cultures were positive in 35 patients (including 29 patients from the LD study group), of whom 65.7 % were intubated and 37.1 % have died. Sequence type (ST) ST1 accounted for 50.0 % of the typed cases and ST1, OLDA/Oxford was the leading phenon (53.8 %). Mortality rate among patients in the LD study group infected with ST1 was 18.2 % compared to 42.9 % for non-ST1 genotypes (OR = 0.30, 95 % CI 0.05-1.91, p = 0.23).

CONCLUSIONS

The study confirms the importance of early administration of appropriate antibiotic therapy and at the same time highlights the complex associations of different diagnostic approaches with LD outcome. Infection with ST1 was not associated with increased mortality. Genotype effects on outcome mandate examination in larger cohorts.

Legionnaires' disease

Since first identified in early 1977, bacteria of the genus Legionella are recognised as a common cause of community-acquired pneumonia and a rare cause of hospital-acquired pneumonia. Legionella bacteria multisystem manifestations mainly affect susceptible patients as a result of age, underlying debilitating conditions, or immunosuppression. Water is the major natural reservoir for Legionella, and the pathogen is found in many different natural and artificial aquatic environments such as cooling towers or water systems in buildings, including hospitals. The term given to the severe pneumonia and systemic infection caused by Legionella bacteria is Legionnaires' disease. Over time, the prevalence of legionellosis or Legionnaires' disease has risen, which might indicate a greater awareness and reporting of the disease. Advances in microbiology have led to a better understanding of the ecological niches and pathogenesis of the condition. Legionnaires' disease is not always suspected because of its non-specific symptoms, and the diagnostic tests routinely available do not offer the desired sensitivity. However, effective antibiotics are available. Disease notification systems provide the basis for initiating investigations and limiting the scale and recurrence of outbreaks. This report reviews our current understanding of this disease.

Evolution over a 15-year period of the clinical characteristics and outcomes of critically ill patients with severe community-acquired pneumonia

OBJECTIVES

To study the characteristics and outcomes of patients in the ICU with severe community-acquired pneumonia (SCAP) over a 15-year surveillance period.

METHODS

We conducted a retrospective cohort study of episodes of SCAP, and assessed the epidemiology, etiology, treatment and outcomes of patients admitted to the ICU, comparing three periods (1999-2003, 2004-2008 and 2009-2013).

RESULTS

A total of 458 patients were diagnosed with SCAP. The overall cumulative incidence was 37.4 episodes/1000 admissions, with a progressive increase over the three periods (P<0.001). Patients fulfilling the two major IDSA/ATS criteria at admission increased from 64.2% in the first period to 82.5% in the last period (P=0.005). Streptococcus pneumoniae was the prevalent pathogen. The incidence of bacteremia was 23.1%, and a progressive significant reduction in overall incidence was observed over the three periods (P=0.02). Globally, 91% of the patients received appropriate empiric antibiotic treatment, increasing from 78.3% in the first period to 97.7% in the last period (P<0.001). Combination antibiotic therapy (betalactam+macrolide or fluoroquinolone) increased significantly from the first period (61%) to the last period (81.3%) (P<0.001). Global ICU mortality was 25.1%, and decreased over the three periods (P=0.001).

CONCLUSIONS

Despite a progressively higher incidence and severity of SCAP in our ICU, crude ICU mortality decreased by 18%. The increased use of combined antibiotic therapy and the decreasing rates of bacteremia were associated to improved patient prognosis.

Applicability assessment of ceramic microbeads coated with hydroxyapatite-binding silver/titanium dioxide ceramic composite earthplus™ to the eradication of Legionella in rainwater storage tanks for household use

Water environments appear to be the habitats of Legionella species. Legionellosis is considered as a preventable illness because bacterial reservoirs can be controlled and removed. Roof-harvested rainwater has attracted significant attention not only as a groundwater recharge but also as a potential alternative source of nonpotable water. We successfully developed ceramic microbeads coated with hydroxyapatite-binding silver/titanium dioxide ceramic composite earthplus™ using the thermal spraying method. The ceramic microbeads were demonstrated to have bactericidal activities against not only Legionella but also coliform and heterotrophic bacteria. Immersing the ceramic microbeads in household rainwater storage tanks was demonstrated to yield the favorable eradication of Legionella organisms. Not only rapid-acting but also long-lasting bactericidal activities of the ceramic microbead were exhibited against Legionella pneumophila. However, time-dependent attenuation of the bactericidal activities against Legionella were also noted in the sustainability appraisal experiment. Therefore, the problems to be overcome surely remain in constantly managing the Legionella-pollution by means of immersing the ceramic microbeads. The results of our investigation apparently indicate that the earthplus™-coated ceramic microbeads would become the favorable tool for Legionella measures in household rainwater storage tanks, which may become the natural reservoir for Legionella species. Our investigation would justify further research and data collection to obtain more reliable procedures to microbiologically regulate the Legionella in rainwater storage tanks.

The association of antibiotic treatment regimen and hospital mortality in patients hospitalized with Legionella pneumonia

BACKGROUND

Guidelines recommend azithromycin or a quinolone antibiotic for treatment of Legionella pneumonia. No clinical study has compared these strategies.

METHODS

We performed a retrospective cohort analysis of adults hospitalized in the United States with a diagnosis of Legionella pneumonia in the Premier Perspectives database (1 July 2008-30 June 2013). Our primary outcome was hospital mortality; we additionally evaluated hospital length of stay, development of Clostridium difficile colitis, and total hospital cost. We used propensity-based matching to compare patients treated with azithromycin vs a quinolone. All analyses were repeated on a subgroup of more severely ill patients, defined as requiring intensive care unit admission or mechanical ventilation or having a predicted probability of hospital mortality in the top quartile for all patients.

RESULTS

Legionella pneumonia was diagnosed in 3152 adults across 437 hospitals. Quinolones alone were used in 28.8%, azithromycin alone was used in 34.0%, and 1.8% received both. Crude hospital mortality was similar: 6.6% (95% confidence interval [CI], 5.0%-8.2%) for quinolones vs 6.4% (95% CI, 5.0%-7.9%) for azithromycin (P = .87); after propensity matching (n = 813 in each group), mortality remained similar (6.3% [95% CI, 4.6%-7.9%] vs 6.5% [95% CI, 4.8%-8.2%], P = .84 for the whole cohort, and 14.9% [95% CI, 10.0%-19.8%] vs 18.3% [95% CI, 13.0%-23.6%], P = .36 for the more severely ill). There was no difference in hospital length of stay, development of C. difficile, or total hospital cost.

CONCLUSIONS

Use of azithromycin alone or a quinolone alone for treatment of Legionella pneumonia was associated with similar hospital mortality. Few patients receive combination therapy.

Atypical pneumonia

PURPOSE OF REVIEW

We present the key advances in the infections that clinicians conventionally associate with atypical pneumonia: legionellosis, Mycoplasma pneumonia, Chlamydophila species pneumonia and Q fever.

RECENT FINDINGS

There have been significant developments in molecular diagnosis to include Mycoplasma pneumoniae and Chlamydophila pneumoniae in multiplex PCR of respiratory specimens. There are diagnostic challenges in distinguishing carriage from infection, which is recognized in C. pneumoniae and now also evident in M. pneumoniae. Macrolide-resistant M. pneumoniae has emerged in Asia. There are new antimicrobials on the horizon in the ketolide class with activity against typical and atypical pathogens and useful empirical agents.

SUMMARY

There are few advances in our knowledge of the epidemiology of atypical pathogens or the effectiveness of antimicrobial therapy--empirical or pathogen specific. However, if molecular testing becomes widely implemented, there will be an increased understanding of the epidemiology and presentation of atypical pneumonia and a shift to more targeted antimicrobial therapy.

Current and emerging Legionella diagnostics for laboratory and outbreak investigations

Legionnaires' disease (LD) is an often severe and potentially fatal form of bacterial pneumonia caused by an extensive list of Legionella species. These ubiquitous freshwater and soil inhabitants cause human respiratory disease when amplified in man-made water or cooling systems and their aerosols expose a susceptible population. Treatment of sporadic cases and rapid control of LD outbreaks benefit from swift diagnosis in concert with discriminatory bacterial typing for immediate epidemiological responses. Traditional culture and serology were instrumental in describing disease incidence early in its history; currently, diagnosis of LD relies almost solely on the urinary antigen test, which captures only the dominant species and serogroup, Legionella pneumophila serogroup 1 (Lp1). This has created a diagnostic "blind spot" for LD caused by non-Lp1 strains. This review focuses on historic, current, and emerging technologies that hold promise for increasing LD diagnostic efficiency and detection rates as part of a coherent testing regimen. The importance of cooperation between epidemiologists and laboratorians for a rapid outbreak response is also illustrated in field investigations conducted by the CDC with state and local authorities. Finally, challenges facing health care professionals, building managers, and the public health community in combating LD are highlighted, and potential solutions are discussed.

Incidence of Legionella and heterotrophic bacteria in household rainwater tanks in Azumino, Nagano prefecture, Japan

Many administrative agencies in Japan are encouraging installation of household rainwater-storage tanks for more effective use of natural rainwater. Water samples were collected periodically from 43 rainwater tanks from 40 households and tested for the presence of Legionella species and the extent of heterotrophic bacteria in Azumino city, Nagano prefecture, Japan. PCR assays indicated the presence of Legionella spp. in 12 (30%) of the 43 tank water samples. Attempts were made to identify correlations between PCR positive samples, topography, pH, chemical oxygen demand (COD), atmospheric temperature and the numbers of heterotrophic bacteria. Between June and October, 2012, the numbers of heterotrophic bacteria in rainwater tanks and the values of COD positively correlated with the presence of Legionella species. In most of the Legionella-positive cases, heterotrophic bacterial cell counts were >10(4) CFU/mL. Moreover, Legionella species were less frequently detected when the COD value was >5 mg KMnO(4)/L. Therefore, at least in Azumino, Japan between June and October 2012, both heterotrophic bacterial counts and COD values may be considered index parameters for the presence of Legionella cells in rainwater tanks. Much more accumulation of such data is needed to verify the accuracy of these findings.

Dynamics of peripheral blood lymphocyte subpopulations in the acute and subacute phase of Legionnaires' disease

STUDY OBJECTIVE

Absolute lymphocytopenia is recognised as an important hallmark of the immune response to severe infection and observed in patients with Legionnaires' disease. To explore the immune response, we studied the dynamics of peripheral blood lymphocyte subpopulations in the acute and subacute phase of LD.

METHODS AND RESULTS

EDTA-anticoagulated blood was obtained from eight patients on the day the diagnosis was made through detection of L. pneumophila serogroup 1 antigen in urine. A second blood sample was obtained in the subacute phase. Multiparametric flow cytometry was used to calculate lymphocyte counts and values for B-cells, T-cells, NK cells, CD4+ and CD8+ T-cells. Expression of activation markers was analysed. The values obtained in the subacute phase were compared with an age and gender matched control group. Absolute lymphocyte count (×10⁹/l, median and range) significantly increased from 0.8 (0.4-1.6) in the acute phase to 1.4 (0.8-3.4) in the subacute phase. B-cell count showed no significant change, while T-cell count (×10⁶/l, median and range) significantly increased in the subacute phase (495 (182-1024) versus 979 (507-2708), p = 0.012) as a result of significant increases in both CD4+ and CD8+ T-cell counts (374 (146-629) versus 763 (400-1507), p = 0.012 and 119 (29-328) versus 224 (107-862), p = 0.012). In the subacute phase of LD, significant increases were observed in absolute counts of activated CD4+ T-cells, naïve CD4+ T-cells and memory CD4+ T-cells. In the CD8+ T-cell compartment, activated CD8+ T-cells, naïve CD8+ T-cell and memory CD8+ T-cells were significantly increased (p<0.05).

CONCLUSION

The acute phase of LD is characterized by absolute lymphocytopenia, which recovers in the subacute phase with an increase in absolute T-cells and re-emergence of activated CD4+ and CD8+ T cells. These observations are in line with the suggested role for T-cell activation in the immune response to LD.

Rainfall is a risk factor for sporadic cases of Legionella pneumophila pneumonia

It is not known whether rainfall increases the risk of sporadic cases of Legionella pneumonia. We sought to test this hypothesis in a prospective observational cohort study of non-immunosuppressed adults hospitalized for community-acquired pneumonia (1995–2011). Cases with Legionella pneumonia were compared with those with non-Legionella pneumonia. Using daily rainfall data obtained from the regional meteorological service we examined patterns of rainfall over the days prior to admission in each study group. Of 4168 patients, 231 (5.5%) had Legionella pneumonia. The diagnosis was based on one or more of the following: sputum (41 cases), antigenuria (206) and serology (98). Daily rainfall average was 0.556 liters/m² in the Legionella pneumonia group vs. 0.328 liters/m² for non-Legionella pneumonia cases (p = 0.04). A ROC curve was plotted to compare the incidence of Legionella pneumonia and the weighted median rainfall. The cut-off point was 0.42 (AUC 0.54). Patients who were admitted to hospital with a prior weighted median rainfall higher than 0.42 were more likely to have Legionella pneumonia (OR 1.35; 95% CI 1.02–1.78; p = .03). Spearman Rho correlations revealed a relationship between Legionella pneumonia and rainfall average during each two-week reporting period (0.14; p = 0.003). No relationship was found between rainfall average and non-Legionella pneumonia cases (−0.06; p = 0.24). As a conclusion, rainfall is a significant risk factor for sporadic Legionella pneumonia. Physicians should carefully consider Legionella pneumonia when selecting diagnostic tests and antimicrobial therapy for patients presenting with CAP after periods of rainfall.