Epidemiology and clinical management of Legionnaires' disease

The effect of seasonal and extreme floods on hospitalizations for Legionnaires' disease in the United States, 2000-2011

BACKGROUND

An increasing severity of extreme storms and more intense seasonal flooding are projected consequences of climate change in the United States. In addition to the immediate destruction caused by storm surges and catastrophic flooding, these events may also increase the risk of infectious disease transmission. We aimed to determine the association between extreme and seasonal floods and hospitalizations for Legionnaires' disease in 25 US states during 2000-2011.

METHODS

We used a nonparametric bootstrap approach to examine the association between Legionnaires' disease hospitalizations and extreme floods, defined by multiple hydrometeorological variables. We also assessed the effect of extreme flooding associated with named cyclonic storms on hospitalizations in a generalized linear mixed model (GLMM) framework. To quantify the effect of seasonal floods, we used multi-model inference to identify the most highly weighted flood-indicator variables and evaluated their effects on hospitalizations in a GLMM.

RESULTS

We found a 32% increase in monthly hospitalizations at sites that experienced cyclonic storms, compared to sites in months without storms. Hospitalizations in months with extreme precipitation were in the 89^th percentile of the bootstrapped distribution of monthly hospitalizations. Soil moisture and precipitation were the most highly weighted variables identified by multi-model inference and were included in the final model. A 1-standard deviation (SD) increase in average monthly soil moisture was associated with a 49% increase in hospitalizations; in the same model, a 1-SD increase in precipitation was associated with a 26% increase in hospitalizations.

CONCLUSIONS

This analysis is the first to examine the effects of flooding on hospitalizations for Legionnaires' disease in the United States using a range of flood-indicator variables and flood definitions. We found evidence that extreme and seasonal flooding is associated with increased hospitalizations; further research is required to mechanistically establish whether floodwaters contaminated with Legionella bacteria drive transmission.

Case Report: First Report of Fatal Legionella pneumophila and Klebsiella pneumoniae Coinfection in a Kidney Transplant Recipient

A very rare case of pulmonary Klebsiella pneumoniae-Legionella pneumophila coinfection in a double kidney transplanted man affected by the chronic renal disease is described. Cases of Legionnaires' disease with an incubation period of 14 days have rarely been documented. Despite the long period of hospitalization, typing of clinical and environmental L. pneumophila strains demonstrated that the patient's home water distribution system was the source of infection, highlighting that Legionella house contamination can be a hidden risk, especially for immune-compromised people.

The Legionella pneumophila Dot/Icm type IV secretion system and its effectors

To prevail in the interaction with eukaryotic hosts, many bacterial pathogens use protein secretion systems to release virulence factors at the host–pathogen interface and/or deliver them directly into host cells. An outstanding example of the complexity and sophistication of secretion systems and the diversity of their protein substrates, effectors, is the Defective in organelle trafficking/Intracellular multiplication (Dot/Icm) Type IVB secretion system (T4BSS) of Legionella pneumophila and related species. Legionella species are facultative intracellular pathogens of environmental protozoa and opportunistic human respiratory pathogens. The Dot/Icm T4BSS translocates an exceptionally large number of effectors, more than 300 per L. pneumophila strain, and is essential for evasion of phagolysosomal degradation and exploitation of protozoa and human macrophages as replicative niches. Recent technological advancements in the imaging of large protein complexes have provided new insight into the architecture of the T4BSS and allowed us to propose models for the transport mechanism. At the same time, significant progress has been made in assigning functions to about a third of L. pneumophila effectors, discovering unprecedented new enzymatic activities and concepts of host subversion. In this review, we describe the current knowledge of the workings of the Dot/Icm T4BSS machinery and provide an overview of the activities and functions of the to-date characterized effectors in the interaction of L. pneumophila with host cells.

Acute fibrinous and organizing pneumonia in a patient with Sjögren's syndrome and Legionella pneumonia: a case report and literature review

Background

Acute fibrinous and organizing pneumonia (AFOP) is a rare clinicopathological condition. Studies in the literature have reported that AFOP may be associated with respiratory infections, such as respiratory syncytial virus, influenza virus, Pneumocystis jirovecii, Penicillium citrinum, and Chlamydia infections. However, AFOP associated with Legionella infection has not been reported previously. Here, we report a case of a patient with AFOP secondary to Sjögren’s syndrome and Legionella infection.

Case presentation

A 47-year-old man was admitted to the hospital because of fever, expectoration, and shortness of breath. Lung imaging showed irregular patchy consolidation. A diagnosis of Legionella pneumonia was initially considered on the basis of the patient’s history of exposure to soil before disease onset, signs of extrapulmonary involvement, and a positive Legionella urine antigen test result. However, the patient’s symptoms and lung imaging did not improve after treatment with levofloxacin, moxifloxacin, and tigecycline for Legionella infection. In addition, Sjögren’s syndrome was diagnosed on the basis of clinical manifestations and immunological indicators. Pathological changes associated with AFOP were confirmed from the results of ultrasound-guided percutaneous lung biopsy. The patient’s clinical symptoms improved rapidly after a short course of low-dose corticosteroid therapy, and lung imaging showed significant improvement.

Conclusions

The possibility of secondary AFOP should be considered when Legionella pneumonia does not improve after standard antibiotic therapy. Lung biopsy and histopathological examination are important for the adjustment of treatment strategy. Our case also highlights the importance of screening for autoimmune diseases in patients with AFOP.

Validating a clinical prediction score for Legionella-related community acquired pneumonia

BACKGROUND

Legionella-related community acquired pneumonia (CAP) is a disease with an increasing incidence and a high mortality rate, especially if empirical antibiotic therapy is inadequate. Antibiotic treatment highly relies on clinical symptoms, although proven non-specific, because currently available diagnostic techniques provide insufficient accuracy for detecting Legionella CAP on admission. This study validates a diagnostic scoring system for detection of Legionella-related CAP, based on six items on admission (Legionella prediction score).

METHODS

We included patients with Legionella-related CAP admitted to five large Dutch hospitals between 2006 and 2016. Controls were non-Legionella-related CAP patients. The following six conditions were rewarded one point if present: fever > 39.4 °C; dry cough; hyponatremia (sodium) < 133 mmol/L; lactate dehydrogenase (LDH) > 225 mmol/L; C-reactive protein (CRP) > 187 mg/L and platelet count < 171 × 10⁹/L. The accuracy of the prediction score was assessed by calculating the area under the curve (AUC) through logistic regression analysis.

RESULTS

We included 131 cases and 160 controls. A score of 0 occurred in non-Legionella-related CAP patients only, a score of 5 and 6 in Legionella-related CAP patients only. A cut-off ≥ 4 resulted in a sensitivity of 58.8% and a specificity of 93.1%. The AUC was 0.89 (95% CI 0.86-0.93). The strongest predictors were elevated LDH, elevated CRP and hyponatremia.

CONCLUSIONS

This multi-centre study validates the Legionella prediction score, an easily applicable diagnostic scoring system, in a large group of patients and finds high diagnostic accuracy. The score shows promise for future prospective validation and could contribute to targeted antibiotic treatment of suspected Legionella CAP.

An outbreak of Legionnaires' disease in newborns in Serbia

Legionnaires' disease is an atypical pneumonia caused by inhaling small droplets of water containing the bacterium Legionella spp. In newborns, it is a rare event, usually associated with water births and the use of air conditioning systems or air humidifiers. A nosocomial outbreak of Legionnaires' disease in the maternity ward of a secondary-care hospital in Arandjelovac, Serbia is described.Two male newborns were found to be infected with Legionnella pneumophila. On Days 7 and 6 of life, respectively, they were transferred to a tertiary-care hospital with signs of severe pneumonia which was radiologically confirmed. L. pneumophila was detected in tracheal secretions from both infants by RT-PCR, and its antigens were also positive in urine samples. The source of infection in the secondary-care hospital was the internal hot water heating system, and the main contributory factor to the emergence of the infection was the low temperature of the hot water which did not kill the bacteria during the available exposure time.These two cases highlight the importance of being cautious about possible Legionnaires' disease in maternity wards with outdated or irregularly maintained internal water supply systems. The adoption of official guidelines for the control and regular maintenance of water supply systems, including the multidisciplinary cooperation of all relevant parties, forms the basis for direct monitoring for Legionella and the prevention of new outbreaks.Abbreviations: BCYE: buffered charcoal yeast extract agar; GVPC: glycine vancomycin polymyxin cycloheximide agar; LD - Legionnaires' disease; TR-PCR: Reverse transcription polymerase chain reaction.

Association of Natural Waterways and Legionella pneumophila Infection in Eastern Wisconsin: A Case-Control Study

Preliminary research has suggested possible associations between natural waterways and Legionella infection, and we previously explored these associations in eastern Wisconsin using positive L. pneumophila serogroup 1 urine antigen tests (LUAT) as diagnostic. This case-control study was a secondary analysis of home address data from patients who underwent LUAT at a single eastern Wisconsin health system from 2013 to 2017. Only zip codes within the health system's catchment area that registered ≥3 positive cases and ≥50 completed tests, as well as geographically adjacent zip codes with ≥2 positive cases and ≥50 tests, were included. A 1:3 ratio of cases to randomly selected controls was used. Home addresses were geocoded and mapped using ArcGIS software (Esri); nearest waterway and distance to home was identified. Distance to nearest waterway according to ArcGIS was verified/corrected using Google Maps incognito. Distances were analyzed using chi-squared and 2-sample t-tests. Overall, mean distance to nearest waterway did not differ between cases (2958 ± 2049 ft) and controls (2856 ± 2018 ft; P=0.701). However, in a subset of nonurban zip codes, cases were closer to nearest waterway than controls (1165 ± 905 ft vs 2113 ± 1710 ft; P=0.019). No association was found between cases and type of waterway. Further research is needed to investigate associations and differences between natural and built environmental water sources in relation to legionellosis.

Extensive epigenetic modification with large-scale chromosomal and plasmid recombination characterise the Legionella longbeachae serogroup 1 genome

Legionella longbeachae is an environmental bacterium that is the most clinically significant Legionella species in New Zealand (NZ), causing around two-thirds of all notified cases of Legionnaires’ disease. Here we report the sequencing and analysis of the geo-temporal genetic diversity of 54 L. longbeachae serogroup 1 (sg1) clinical isolates, derived from cases from around NZ over a 22-year period, including one complete genome and its associated methylome. The 54 sg1 isolates belonged to two main clades that last shared a common ancestor between 95 BCE and 1694 CE. There was diversity at the genome-structural level, with large-scale arrangements occurring in some regions of the chromosome and evidence of extensive chromosomal and plasmid recombination. This includes the presence of plasmids derived from recombination and horizontal gene transfer between various Legionella species, indicating there has been both intra- and inter-species gene flow. However, because similar plasmids were found among isolates within each clade, plasmid recombination events may pre-empt the emergence of new L. longbeachae strains. Our complete NZ reference genome consisted of a 4.1 Mb chromosome and a 108 kb plasmid. The genome was highly methylated with two known epigenetic modifications, m⁴C and m⁶A, occurring in particular sequence motifs within the genome.

Four-Year Environmental Surveillance Program of Legionella spp. in One of Palermo’s Largest Hospitals

Legionella is a ubiquitous bacterium that lives in freshwater environments and colonizes human-made water systems. Legionella pneumophila is the most virulent species, and risk factors for Legionnaires’ disease include increasing age, smoking, chronic diseases, and immunodeficiency. For this reason, it is very important to assess and monitor hospital water systems in order to prevent legionellosis. We have monitored a large hospital in Palermo for four years. To determine the presence of microorganisms, according to national guidelines, we used the culture method, which is considered the gold standard for Legionella detection. Sampling was divided into five macro-areas, and a total of 251 samples were collected during the period of investigation, 49% of which were Legionella spp.-positive and 51% were Legionella spp.-negative. Positive samples with L. pneumophila. sgr 2-15 were most frequent in the Underground (55.6%, p = 0.0184), Medicine (42.9%, p = 0.0184) and Other (63.2%, p = 0.002) areas; while positive samples for L. pneumophila sgr 1 were less frequent in the Underground (0.0%, p = 0.0184) and Surgery areas (4.5%, p = 0.033), and for Legionella anisa, were less frequent in the Medicine (4.1%, p = 0.021), Oncohematology (0.0%, p = 0.0282), and Other (0.0%, p = 0.016) areas. Finally, no significant differences were observed among the areas for each isolate considered. The surveillance carried out in these years demonstrates the importance of monitoring, which allows us to analyze the conditions of hospital facilities and, therefore, prevent Legionella spp. infections.

Legionella pneumophila Subspecies fraseri Infection after Allogeneic Hematopoietic Stem Cell Transplant, China

We describe an immunosuppressed patient with bacteremia and pneumonia caused by Legionella pneumophila subspecies fraseri in China. We confirmed this diagnosis by using nanopore sequencing of positive blood cultures and subsequent recovery from buffered-charcoal yeast extract culture. Nanopore sequencing is an effective tool for early diagnosis of atypical infections.

GVPC Medium Manufactured without Oxygen Improves the Growth of Legionella spp. and Exhibits Enhanced Selectivity Properties

Glycine-vancomycin-polymyxin-cycloheximide agar (GVPC) is a recommended medium for the detection of Legionella spp. in water samples. However, its quality could be improved in terms of recovery of Legionella spp. and selectivity properties. Modifications were introduced in GVPC manufacture: autoclaving conditions (115°C, 15 min) and atmosphere during component-stirring (removal of oxygen and N₂ injection). The use of softer autoclaving conditions (115°C, 15 min) improved the growth of Legionella anisa by the spiral method and Legionella pneumophila after membrane filtration. The medium manufactured with O₂ removal and autoclaving for 15 min at 115°C allowed a faster growth of L. pneumophila (colonies visible at day 2) and a notable increase of L. anisa growth (colonies appearing at day 3, and statistically significant numbers of CFU at day 5). After 3 to 5 days of incubation, the improved media showed higher selectivity properties, particularly for Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 9027. A further improvement was achieved by the addition of N₂ during ingredient stirring, leading to a statistically significant faster growth of L. pneumophila at days 2 and 3 and L. anisa at day 3. Selectivity properties were also enhanced, resulting in the complete inhibition of both E. faecalis strains and Escherichia coli and complete-partial inhibition of P. aeruginosa. Oxygen removal during GVPC manufacture using a vacuum pump system promotes the growth of L. pneumophila and L. anisa, and markedly inhibits the growth of E. coli, P. aeruginosa, and E. faecalis. IMPORTANCE Currently, GVPC is a recommended medium for the detection of Legionella spp. in water samples. However, recovery of Legionella spp. and selectivity properties can be improved. GVPC medium manufactured without oxygen improved the growth of Legionella pneumophila and Legionella anisa. Oxygen removal during GVPC manufacture also improved selectivity properties. A further improvement was achieved by the addition of N₂ during ingredient stirring, leading to a faster growth of L. pneumophila at days 2 and 3 and L. anisa at day 3 and enhancement of selectivity properties. The introduction of the modified GVPC medium in routine practice can allow a better detection of Legionella spp. in water samples.

Risk Exposure to Legionella pneumophila during Showering: The Difference between a Classical and a Water Saving Shower System

The increase in legionellosis incidence in the general population in recent years calls for a better characterization of the sources of infection, such as showering. Water-efficient shower systems that use water-atomizing technology have been shown to emit slightly more inhalable particles in the range of bacterial sizes than the traditional systems; however, the actual rate of bacterial emission remains poorly documented. The aim of this study was to assess the aerosolisation rate of the opportunistic water pathogen Legionella pneumophila during showering with one shower system representative of each technology. To achieve this objective, we performed controlled experiments inside a glove box and determined the emitted dose and viability of airborne Legionella. The bioaerosols were sampled with a Coriolis^® Delta air sampler and the total number of viable (cultivable and noncultivable) Legionella was determined by flow cytometry and culture. We found that the rate of viable and cultivable Legionella aerosolized from the water jet was similar between the two showerheads: the viable fraction represents 0.02% of the overall bacteria present in water, while the cultivable fraction corresponds to only 0.0005%. The two showerhead models emitted a similar ratio of airborne Legionella viable and cultivable per volume of water used. Therefore, the risk of exposure to Legionella is not expected to increase significantly with the new generation of water-efficient showerheads.

Global Perspective of Legionella Infection in Community-Acquired Pneumonia: A Systematic Review and Meta-Analysis of Observational Studies

Legionnaires’ disease (LD) (Legionella) is a common cause of community-acquired pneumonia (CAP) in those requiring hospitalization. Geographical variation in the importance of Legionella species as an aetiologic agent of CAP is poorly understood. We performed a systematic review and meta-analysis of population-based observational studies that reported the proportion of Legionella infection in patients with CAP (1 January 1990 to 31 May 2020). Using five electronic databases, articles were identified, appraised and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The quality of the included studies was assessed using the Newcastle–Ottawa Scale. Univariate and multivariate meta-regression analyses were conducted using study design, WHO region, study quality and healthcare setting as the explanatory variables. We reviewed 2778 studies, of which 219 were included in the meta-analysis. The mean incidence of CAP was 46.7/100,000 population (95% CI: 46.6–46.8). The mean proportion of Legionella as the causative agent for CAP was 4.6% (95% CI: 4.4 to 4.7). Consequently, the mean Legionella incidence rate was 2.8/100,000 population (95% CI: 2.7–2.9). There was significant heterogeneity across all studies I² = 99.27% (p < 0.0001). After outliers were removed, there was a decrease in the heterogeneity (I² = 43.53%). Legionella contribution to CAP has a global distribution. Although the rates appear highest in high income countries in temperate regions, there are insufficient studies from low- and middle-income countries to draw conclusions about the rates in these regions. Nevertheless, this study provides an estimate of the mean incidence of Legionella infection in CAP, which could be used to estimate the regional and global burden of LD to support efforts to reduce the impact of this infection as well as to fill important knowledge gaps.

Bacterial Antagonistic Species of the Pathogenic Genus Legionella Isolated from Cooling Tower

Legionella pneumophila is the causative agent of Legionnaires' disease, a severe pneumonia. Cooling towers are a major source of large outbreaks of the disease. The growth of L. pneumophila in these habitats is influenced by the resident microbiota. Consequently, the aim of this study was to isolate and characterize bacterial species from cooling towers capable of inhibiting several strains of L. pneumophila and one strain of L. quinlivanii. Two cooling towers were sampled to isolate inhibiting bacterial species. Seven inhibitory isolates were isolated, through serial dilution plating and streaking on agar plates, belonging to seven distinct species. The genomes of these isolates were sequenced to identify potential genetic elements that could explain the inhibitory effect. The results showed that the bacterial isolates were taxonomically diverse and that one of the isolates may be a novel species. Genome analysis showed a high diversity of antimicrobial gene products identified in the genomes of the bacterial isolates. Finally, testing different strains of Legionella demonstrated varying degrees of susceptibility to the antimicrobial activity of the antagonistic species. This may be due to genetic variability between the Legionella strains. The results demonstrate that though cooling towers are breeding grounds for L. pneumophila, the bacteria must contend with various antagonistic species. Potentially, these species could be used to create an inhospitable environment for L. pneumophila, and thus decrease the probability of outbreaks occurring.

Case Report: Community-Acquired Legionella gormanii Pneumonia in an Immunocompetent Patient Detected by Metagenomic Next-Generation Sequencing

Background

Legionella spp. has been well-recognized as an important cause of community-acquired pneumonia. Current community-acquired pneumonia guidelines recommended covering the treatment of Legionella because of the high mortality associated with inadequate antibiotic treatments. However, the symptom of Legionella pneumonia is non-specific, and routine diagnostic tests exhibit low sensitivity for Legionella spp., especially for non-Legionella pneumophila serogroup 1 strains.

Case Presentation

We report a 53-year-old man without underlying diseases admitted to respiratory intensive care unit because of severe community-acquired pneumonia and respiratory failure. Although, the results of routine culture of bronchoalveolar lavage fluid and the Legionella urinary antigen test were all negative, metagenomic next-generation sequencing (mNGS) identified a great amount of DNA and RNA sequences of Legionella gormanii in bronchoalveolar lavage fluid while negative in blood sample. The presence of Legionella gormanii in bronchoalveolar lavage fluid was further confirmed by polymerase-chain-reaction and Sanger sequencing.

Conclusion

Legionella gormanii has rarely been reported in patients with community-acquired pneumonia mainly due to lack of diagnostic test for non-Legionella pneumophila serogroup 1 strains. This is the first report of Legionella gormanii pneumonia in an immunocompetent patient detected by mNGS, which indicates that mNGS is a high-resolution and sensitive assay for the diagnosis and surveillance of Legionella infection.

A Community Outbreak of Legionnaires' Disease with Two Strains of L. pneumophila Serogroup 1 Linked to an Aquatic Therapy Centre

An outbreak of Legionnaires' disease affected 18 people in Montpellier, a town of the south of France, between December 2016 and July 2017. All cases were diagnosed by a positive urinary antigen test. No deaths were reported. Epidemiological, environmental and genomic investigations (nested Sequence-Based Typing (nSBT) and whole genome sequencing) were undertaken. For the cases for which we had information, four had a new isolate (ST2471), one had a different new isolate (ST2470), one had a genomic pattern compatible with the ST2471 identified by nSBT (flaA = 3), and one had a genomic pattern not compatible with two previous identified STs (pilE = 6). The analysis conducted on the pool of an aquatic therapy center revealed seven isolates of Legionella pneumophila. Whole genome analysis confirmed the link between the environmental and clinical isolates for both ST2470 and ST2471. As the outbreak occurred slowly, with several weeks between new cases, it was not possible to immediately identify a common source. The sixth case was the first to report having aquatic therapy care. Of the 18 cases, eight had attended the aquatic therapy center and the other 10 were inhabitants who lived, worked or walked close to the center. The main cause for this outbreak was the lack of facility maintenance. This investigation highlights the risk to public health of aquatic therapy centers for users and nearby populations, and emphasizes the need for risk reduction measures with specific guidelines to improve health and safety in aquatic facilities.

Investigation of Legionella bacteria in water and cooling systems of a university in Turkey

Objectives: Colonization of Legionella in water systems is among the factors affecting the incidence of community and hospital-acquired pneumonia. In this study, it was aimed to investigate the presence of Legionella in the water and cooling systems of the inpatient services of the faculty of medicine hospital and the faculties of the university. Material and Methods: The presence of Legionella was investigated in 418 water and swab samples were taken from the water and cooling systems of the inpatient services of X University Faculty of Medicine Research and Practice Hospital and 11 faculties of the university between February-October 2020. Collected water and swab samples were inoculated into BCYE medium and identification at the species and serogroups by latex agglutination test. In addition, rpoB sequencing was used to confirm these isolates. Results: Legionella were isolated in four (4.1%) of the samples collected from the inpatient services of the hospital and in three (0.9%) of the samples collected from the faculties (n=321), in total seven (1.67%) samples. One of these isolates (14.3%) was grouped as L.pneumophila serogroup 2-14 and six (85.7%) as L.pneumophila serogroup 1 by latex agglutination test. Species identifications were consistent with sequence analysis results. Conclusion: The isolation of L.pneumophila in samples taken from inpatient services at a higher rate than in faculties poses a great risk. Although the detection rate of Legionella in our study was low, we think that regular disinfection, follow-up and inspection of water and cooling systems may be effective in reducing Legionella-related pneumonias.

Using Genomic Deletion Mutants to Investigate Effector-Triggered Immunity During Legionella pneumophila Infection

Legionella pneumophila is an intracellular bacterial pathogen that uses a type IV secretion system (T4SS), termed Dot/Icm, to secrete more than 330 virulence effector proteins into the infected host cell. Many Dot/Icm effectors are involved in biogenesis of the Legionella-containing vacuole (LCV), which allows intracellular bacterial replication in environmental amoebae and alveolar macrophages. Through their activity, some effectors trigger the mammalian host immune response in a phenomenon termed effector-triggered immunity (ETI). Here, we describe a protocol to create and use L. pneumophila genome deletion mutants to identify effector(s) that alter pro-inflammatory cytokine production and bacterial clearance in the lungs of mice.

Clinical features of patients with Legionnaires disease showing initial clinical improvement but radiological deterioration: A retrospective single-center analysis

Patients with Legionnaires disease occasionally experience initial clinical improvement but radiological progression. However, data on this issue are so far limited. The aim of this study was to investigate changes in chest radiograph findings in patients with Legionnaires disease who showed initial clinical improvement and to identify risk factors and outcomes in these patients.All patients diagnosed with Legionnaires disease at a tertiary hospital in South Korea between March 2011 and May 2020 were retrospectively enrolled. Legionnaires disease was defined as abnormal chest radiographs accompanied by a positive finding on at least one of the following tests: urinary antigen test, sputum Legionella polymerase chain reaction, and sputum Legionella culture. Clinical improvement was defined as defervescence and decreased C-reactive protein level. Clinical and radiological records were reviewed on treatment days 7 and 14 and at discharge. We describe the characteristics of patients with clinical improvement but radiological deterioration on treatment for Legionnaires disease and compared them with patients with initial clinical improvement and stable or resolving chest radiograph findings.Of 140 patients with Legionnaires disease, 33 (24%) showed initial clinical deterioration, while the remaining 107 (76%) showed initial clinical improvement on day 7. The latter 107 patients were analyzed in this study; 22 (21%) showed radiological progression despite the clinical improvement. Risk factors for these patients were a high pneumonia severity index score and the use of mechanical ventilation. Mortality did not significantly differ between those with initial clinical improvement but radiological deterioration and those with both initial clinical and radiological improvement (28% vs 12%, P = .49).About one-fifth of patients with Legionnaires disease, especially those who had a high pneumonia severity index score and underwent mechanical ventilation, showed radiological deterioration despite of clinical improvement 1 week after appropriate treatment, while outcomes were not significantly worse in these patients. Therefore, our findings support that close monitoring without modification of antibiotics use is warranted in those who have clinical improvement regardless of radiologic findings.

Interleukin-36 Cytokines in Infectious and Non-Infectious Lung Diseases

The IL-36 family of cytokines were identified in the early 2000’s as a new subfamily of the IL-1 cytokine family, and since then, the role of IL-36 cytokines during various inflammatory processes has been characterized. While most of the research has focused on the role of these cytokines in autoimmune skin diseases such as psoriasis and dermatitis, recent studies have also shown the importance of IL-36 cytokines in the lung inflammatory response during infectious and non-infectious diseases. In this review, we discuss the biology of IL-36 cytokines in terms of how they are produced and activated, as well as their effects on myeloid and lymphoid cells during inflammation. We also discuss the role of these cytokines during lung infectious diseases caused by bacteria and influenza virus, as well as other inflammatory conditions in the lungs such as allergic asthma, lung fibrosis, chronic obstructive pulmonary disease, cystic fibrosis and cancer. Finally, we discuss the current therapeutic advances that target the IL-36 pathway and the possibility to extend these tools to treat lung inflammatory diseases.

Lefamulin in Patients with Community-Acquired Bacterial Pneumonia Caused by Atypical Respiratory Pathogens: Pooled Results from Two Phase 3 Trials

Lefamulin was the first systemic pleuromutilin antibiotic approved for intravenous and oral use in adults with community-acquired bacterial pneumonia based on two phase 3 trials (Lefamulin Evaluation Against Pneumonia [LEAP]-1 and LEAP-2). This pooled analysis evaluated lefamulin efficacy and safety in adults with community-acquired bacterial pneumonia caused by atypical pathogens (Mycoplasma pneumoniae, Legionella pneumophila, and Chlamydia pneumoniae). In LEAP-1, participants received intravenous lefamulin 150 mg every 12 h for 5–7 days or moxifloxacin 400 mg every 24 h for 7 days, with optional intravenous-to-oral switch. In LEAP-2, participants received oral lefamulin 600 mg every 12 h for 5 days or moxifloxacin 400 mg every 24 h for 7 days. Primary outcomes were early clinical response at 96 ± 24 h after first dose and investigator assessment of clinical response at test of cure (5–10 days after last dose). Atypical pathogens were identified in 25.0% (91/364) of lefamulin-treated patients and 25.2% (87/345) of moxifloxacin-treated patients; most were identified by ≥1 standard diagnostic modality (M. pneumoniae 71.2% [52/73]; L. pneumophila 96.9% [63/65]; C. pneumoniae 79.3% [46/58]); the most common standard diagnostic modality was serology. In terms of disease severity, more than 90% of patients had CURB-65 (confusion of new onset, blood urea nitrogen > 19 mg/dL, respiratory rate ≥ 30 breaths/min, blood pressure <90 mm Hg systolic or ≤60 mm Hg diastolic, and age ≥ 65 years) scores of 0–2; approximately 50% of patients had PORT (Pneumonia Outcomes Research Team) risk class of III, and the remaining patients were more likely to have PORT risk class of II or IV versus V. In patients with atypical pathogens, early clinical response (lefamulin 84.4–96.6%; moxifloxacin 90.3–96.8%) and investigator assessment of clinical response at test of cure (lefamulin 74.1–89.7%; moxifloxacin 74.2–97.1%) were high and similar between arms. Treatment-emergent adverse event rates were similar in the lefamulin (34.1% [31/91]) and moxifloxacin (32.2% [28/87]) groups. Limitations to this analysis include its post hoc nature, the small numbers of patients infected with atypical pathogens, the possibility of PCR-based diagnostic methods to identify non-etiologically relevant pathogens, and the possibility that these findings may not be generalizable to all patients. Lefamulin as short-course empiric monotherapy, including 5-day oral therapy, was well tolerated in adults with community-acquired bacterial pneumonia and demonstrated high clinical response rates against atypical pathogens.

Water Security and Nutrition: Current Knowledge and Research Opportunities

Water is an essential nutrient that has primarily been considered in terms of its physiological necessity. But reliable access to water in sufficient quantities and quality is also critical for many nutrition-related behaviors and activities, including growing and cooking diverse foods. Given growing challenges to water availability and safety, including climate change, pollution, and infrastructure degradation, a broader conceptualization of water and its diverse uses is needed to sustainably achieve global nutrition targets. Therefore, we review empirical and qualitative evidence describing the linkages between water security (the reliable availability, accessibility, and quality of water for all household uses) and nutrition. Primary linkages include water security for drinking, food production and preparation, infant and young child feeding, and limiting exposure to pathogens and environmental toxins. We then identify knowledge gaps within each linkage and propose a research agenda for studying water security and nutrition going forward, including the concurrent quantification of both food and water availability, accessibility, use, and stability. By making explicit the connections between water security and nutritional well-being, we aim to promote greater collaboration between the nutrition and water, sanitation, and hygiene sectors. Interdisciplinary policies and programs that holistically address the water-nutrition nexus, versus those that focus on water and nutrition independently, are likely to significantly advance our ability to ensure equitable access to healthy foods and safe water for all.

Legionella pneumophila Risk from Cooling Tower Systems in China

Legionella pneumophila (LP) widely exists in natural and artificial water environments, which facilitates LP to infect people. LP infection causes Legionnaires' disease (LD), which is an important but relatively uncommon respiratory infection. Approximately 90% of LD is caused by L. pneumophila serogroup 1 (Lp1). Meteorological conditions may affect the infectivity and virulence of Lp1, but the exact relationship between them is still unclear. In this study, we evaluated the virulence of Lp1 by screening of total 156 Lp1 strains isolated from cooling tower water in different region of China by detecting their abilities to activate NF-κB signaling pathway in vitro. In addition, we screened the distribution of some selected virulence genes in these strains. The virulence, virulence gene distribution and the meteorological factors were analyzed. We found that both the virulence and the distribution of virulence genes had a certain regional and meteorological correlation. Although loss of several virulence genes showed significant effects on the virulence of Lp1 strains, the distribution of virulence genes had very limited effects on the virulence of Lp1. IMPORTANCE LD is likely to be under-recognized in many countries. Due to the widespread existence of LP in natural and artificial water environments, and to the lack of cross-protection against different strains, LP is a potentially serious threat to human health. Therefore, effective monitoring of the virulence of LP in the water environment is very important to prevent and control the prevalence of LD. Understanding the virulence of LP can not only help us to predict the risk of possible outbreaks in advance, but can also enable more targeted clinical treatment. This study highlights the importance of understanding the epidemiology and ecology of LP isolated from public facilities in terms of public health and biology. Due to the potential for water sources to harbor and disseminate LP, and to the fact that geographical conditions influence the virulence of LP, timely and accurate LP virulence surveillance is urgently needed.

Characterization of the First Cultured Psychrotolerant Representative of Legionella from Antarctica Reveals Its Unique Genome Structure

Culture-independent analysis shows that Legionella spp. inhabit a wide range of low-temperature environments, but to date, no psychrotolerant or psychrophilic strains have been reported. Here, we characterized the first cultivated psychrotolerant representative, designated strain TUM19329T, isolated from an Antarctic lake using a polyphasic approach and comparative genomic analysis. A genome-wide phylogenetic tree indicated that this strain was phylogenetically separate at the species level. Strain TUM19329T shared common physiological traits (e.g., Gram-negative, limited growth on buffered charcoal-yeast extract α-ketoglutarate [BCYEα] agar with l-cysteine requirements) with its relatives, but it also showed psychrotolerant growth properties (e.g., growth at 4°C to 25°C). Moreover, this strain altered its own cellular fatty acid composition to accumulate unsaturated fatty acid at a lower temperature, which may help maintain the cell membrane fluidity. Through comparative genomic analysis, we found that this strain possessed massive mobile genetic elements compared with other species, amounting to up to 17% of the total genes. The majority of the elements were the result of the spread of only a few insertion sequences (ISs), which were spread throughout the genome by a "copy-and-paste" mechanism. Furthermore, we found metabolic genes, such as fatty acid synthesis-related genes, acquired by horizontal gene transfer (HGT). The expansion of ISs and HGT events may play a major role in shaping the phenotype and physiology of this strain. On the basis of the features presented here, we propose a new species-Legionella antarctica sp. nov.-represented by strain TUM19329T (= GTC 22699T = NCTC 14581T). IMPORTANCE This study characterized a unique cultivated representative of the genus Legionella isolated from an Antarctic lake. This psychrotolerant strain had some common properties of known Legionella species but also displayed other characteristics, such as plasticity in fatty acid composition and an enrichment of mobile genes in the genome. These remarkable properties, as well as other factors, may contribute to cold hardiness, and this first cultivated cold-tolerant strain of the genus Legionella may serve as a model bacterium for further studies. It is worth noting that environmentally derived 16S rRNA gene phylotypes closely related to the strain characterized here have been detected from diverse environments outside Antarctica, suggesting a wide distribution of psychrotolerant Legionella bacteria. Our culture- and genome-based findings may accelerate the ongoing studies of the behavior and pathogenicity of Legionella spp., which have been monitored for many years in the context of public health.

Fatal Co-infections with SARS-CoV-2 and Legionella pneumophila, England

Both Legionella pneumophila and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause pneumonia. L. pneumophila is acquired from water sources, sometimes in healthcare settings. We report 2 fatal cases of L. pneumophila and SARS-CoV-2 co-infection in England. Clinicians should be aware of possible L. pneumophila infections among SARS-CoV-2 patients.

Environmental surveillance of Legionella pneumophila in hot water systems of hotels in Morocco

OBJECTIVE

Environmental monitoring of Legionella in hot water systems of hotels in Morocco was performed during the period from January 2016 to April 2018. A total of 149 water samples from 118 different hotels were analyzed.

METHODS

A total of 149 water samples from 118 different hotels were analyzed. Possible risk factors were prospectively recorded, and data were analyzed in connection with building and plumbing systems characteristics. Data about building and risk factors were collected through a questionnaire survey.

RESULTS

Out of the 149 samples, 77(51.7%) were positive for L. pneumophila. Serological typing of the isolates revealed that 54 (70.1%) are L. pneumophila serogroup 2-15 and 23 (29.9%) are L. pneumophila serogroup 1. 56.8% of all buildings were colonized by L. pneumophila. Counts were over 1,000 CFU/L in 44%. Contamination was strongly correlated with temperature in the circulation, the age of the premise plumbing and the size of the building.

CONCLUSIONS

The results showed a relevant exposure to L. pneumophila in the community and the identified risk factors can serve as indicators for risk assessment and relevant actions.

Clinical features of Legionnaires' disease at three Belgian university hospitals, a retrospective study

INTRODUCTION

Legionnaires' disease (LD) is a recognised cause of community-acquired pneumonia. However, Legionella is an overlooked pathogen in hospital-acquired pneumonia. The European Surveillance System 2008-2017 found 23% of the Belgian LD reported cases being healthcare-related, with a higher death-rate than in community-acquired patients. This study aims to describe patients admitted for community-acquired LD or affected by hospital-acquired LD and investigate discriminants associated with lethality.

METHODS

Medical records were retrospectively reviewed at three Belgian University Hospitals, between 1 January 2016 up to 31 January 2019. Hospital-acquired LD was defined as symptom onset at 10 days or more after admission, according to the Centres for Disease Control and prevention. Community-acquired LD was defined as diagnosis at admission or within 10 days after admission.

RESULTS

Fifty patients were included in the study, among them 26% were diagnosed with hospital-acquired LD. The case-fatality rate was 22%, with eight of the eleven deceased patients (73%) being in the hospital-acquired LD group. Medical history of asthma or chronic obstructive pulmonary disease and higher sequential organ failure assessment (SOFA) score at diagnosis were more frequently observed in the hospital-acquired LD group. Furthermore, significantly lower SOFA score at diagnosis of LD and higher rates of treatment with levofloxacin or moxifloxacin were observed in survivors.

CONCLUSION

In the current cohort, LD death-rate was mainly driven by hospital-acquired LD patients. Hospital-acquired LD might especially affect patients with chronic respiratory disease. Respiratory fluoroquinolones treatment and lower SOFA score at diagnosis may be associated with favourable outcomes.

Legionella feeleii: Ubiquitous Pathogen in the Environment and Causative Agent of Pneumonia

L. feeleii is one of the most frequent Legionella species isolated from natural pools of the central region of Spain. This study aimed to evaluate its ecology and to identify this Legionella species as a respiratory pathogen. A PCR assay for detecting the L. feeleii mip gene was developed to identify it in clinical and environmental samples. Culture and PCR were performed in environmental samples from four drinking water treatment plants (DWTPs). Free L. feeleii was only detected in raw water samples (3.4%), while L. feeleii as an Acanthamoeba endosymbiont was found in 30.7% of raw water, 11.5% of decanter biofilm, and 32% of finished water samples. Therefore, Acanthamoeba spp. plays an essential role in the multiplication, persistence, and spread of Legionella species in the environment. The first case of Legionnaires’ disease caused by L. feeleii in Spain is described in this study. The case was diagnosed in an older woman through PCR and sequencing from urine and sputum samples. A respiratory infection could be linked with health care procedures, and the patient presented several risk factors (age, insulin-dependent diabetes, and heart disease). The detection of non-L. pneumophila, such as L. feeleii, is a factor that must be considered when establishing or reviewing measures for the control and prevention of legionellosis.

Co-infection with Legionella and SARS-CoV-2: a case report

INTRODUCTION

We report a case of COVID-19 with Legionella co-infection that was treated successfully.

CASE REPORT

A 73-year-old man presented to the hospital with symptoms of fatigue that continued for the next 5 days. The patient was receiving docetaxel and prednisolone chemotherapy for prostate cancer. Laboratory findings on admission showed positive urine Legionella antigen test and SARS-CoV-2 test. He was administered antiviral and antibacterial agents, and a corticosteroid. Pneumonia exacerbated on day 2 of hospitalization. The patient underwent tracheal intubation and began receiving multidisciplinary care. On day 8 of hospitalization, his oxygenation improved, and the patient was extubated. He discharged on day 27 of hospitalization.

CONCLUSIONS

The patient had a favorable outcome with early diagnosis and early treatment of both diseases. Patients with severe COVID-19 disease need to be evaluated for co-infection. Further, early diagnosis and early treatment of the microbial bacteria causing the co-infection are important.

Advances in Environmental Detection and Clinical Diagnostic Tests for Legionella Species

Legionella is a fastidious organism that is difficult to culture in the lab but is widely distributed in environmental, domestic, and hospital settings. The clinical manifestations due to Legionella infections range from mild fever to fatal pneumonia and multiorgan pathologies. Legionella outbreaks though prevalent globally are not reported in developing countries due to difficulties in isolating this organism and the lack of simple diagnostic protocols. Here, we review the literature from across countries to present various methods used to detect Legionella from environmental and clinical samples. We compare the sensitivity and the specificity of the conventional culture-based assays with the recent methods and discuss approaches to develop better detection and diagnostic tests. With better cost-effective detection techniques and regular monitoring of the susceptible sites, which may harbor Legionella colonies, most of the Legionella infections can be prevented. As a result, considerable burden, caused by Legionella infections, on the healthcare system, in especially economically weaker countries, can be mitigated.

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In September 2018 in Brescia province, northern Italy, an outbreak of Legionnaires' disease (LD) caused by Legionella pneumophila serogroup 2 (Lp2) occurred. The 33 cases (two fatal) resided in seven municipalities along the Chiese river. All cases were negative by urinary antigen test (UAT) and most were diagnosed by real-time PCR and serology. In only three cases, respiratory sample cultures were positive, and Lp2 was identified and typed as sequence type (ST)1455. In another three cases, nested sequence-based typing was directly applied to respiratory samples, which provided allelic profiles highly similar to ST1455. An environmental investigation was undertaken immediately and water samples were collected from private homes, municipal water systems, cooling towers and the river. Overall, 533 environmental water samples were analysed and 34 were positive for Lp. Of these, only three samples, all collected from the Chiese river, were Lp2 ST1455. If and how the river water could have been aerosolised causing the LD cases remains unexplained. This outbreak, the first to our knowledge caused by Lp2, highlights the limits of UAT for LD diagnosis, underlining the importance of adopting multiple tests to ensure that serogroups other than serogroup 1, as well as other Legionella species, are identified.

Legionella pneumophila-Epidemiology and Characterization of Clinical Isolates, Slovenia, 2006-2020

Legionella pneumophila is the causative agent of severe Legionnaires’ disease (LD). Although an increasing number of LD cases have been observed, published data from Slovenia are very limited and data on molecular epidemiology are even scarcer. The present retrospective study (2006–2020) reports the results of the microbiological diagnosis of LD, as well as the epidemiology and characterization of the Legionella clinical isolates. We tested urine samples from 15,540 patients with pneumonia symptoms for L. pneumophila infection by urine antigen test, of which 717 (4.6%) tested positive. Isolation of L. pneumophila was successfully performed from 88 clinical specimens, with 82 (93.2%) being identified as L. pneumophila sg 1 and six (6.8%) as L. pneumophila sg 2–14. Sequence-based typing (SBT) identified 33 different sequence types (STs), the most frequent being ST1 and ST23. Sequence type 1 mainly comprised isolates belonging to the Philadelphia subgroup, and ST23 mostly to Allentown/France. The standard SBT scheme, as well as Dresden phenotyping for L. pneumophila, presented a high diversity among isolates.

A Legionnaires' Disease Cluster in a Private Building in Italy

Legionnaires’ disease (LD) is a severe pneumonia caused by bacteria belonging to the genus Legionella. This is a major public health concern and infections are steadily increasing worldwide. Several sources of infection have been identified, but they have not always been linked to human isolates by molecular match. The well-known Legionella contamination of private homes has rarely been associated with the acquisition of the disease, although some patients never left their homes during the incubation period. This study demonstrated by genomic matching between clinical and environmental Legionella isolates that the source of an LD cluster was a private building. Monoclonal antibodies and sequence-based typing were used to type the isolates, and the results clearly demonstrated the molecular relationship between the strains highlighting the risk of contracting LD at home. To contain this risk, the new European directive on the quality of water intended for human consumption has introduced for the first time Legionella as a microbiological parameter to be investigated in domestic water systems. This should lead to a greater attention to prevention and control measures for domestic Legionella contamination and, consequently, to a possible reduction in community acquired LD cases.

Healthcare-Associated Legionnaires' Disease, Europe, 2008-2017

Healthcare-associated Legionnaires’ disease (HCA LD) can cause nosocomial outbreaks with high death rates. We compared community-acquired LD cases with HCA LD cases in Europe during 2008−2017 using data from The European Surveillance System. A total of 29 countries reported 40,411 community-acquired and 4,315 HCA LD cases. Of the HCA LD cases, 2,937 (68.1%) were hospital-acquired and 1,378 (31.9%) were linked to other healthcare facilities. The odds of having HCA LD were higher for women, children and persons <20 years of age, and persons >60 years of age. Out of the cases caused by Legionella pneumophila with a known serotype, community-acquired LD was more likely to be caused by L. pneumophila serogroup 1 (92.3%) than was HCA LD (85.1%). HCA LD patients were more likely to die. HCA LD is associated with specific patient demographics, causative strains, and outcomes. Healthcare facilities should consider these characteristics when designing HCA LD prevention strategies.

Donnan Potential across the Outer Membrane of Gram-Negative Bacteria and Its Effect on the Permeability of Antibiotics

The cell envelope structure of Gram-negative bacteria is unique, composed of two lipid bilayer membranes and an aqueous periplasmic space sandwiched in between. The outer membrane constitutes an extra barrier to limit the exchange of molecules between the cells and the exterior environment. Donnan potential is a membrane potential across the outer membrane, resulted from the selective permeability of the membrane, which plays a pivotal role in the permeability of many antibiotics. In this review, we discussed factors that affect the intensity of the Donnan potential, including the osmotic strength and pH of the external media, the osmoregulated periplasmic glucans trapped in the periplasmic space, and the displacement of cell surface charges. The focus of our discussion is the impact of Donnan potential on the cellular permeability of selected antibiotics including fluoroquinolones, tetracyclines, β-lactams, and trimethoprim.

Evaluation of five Legionella urinary antigen detection kits including new Ribotest Legionella for simultaneous detection of ribosomal protein L7/L12

Urinary antigen tests are a widely used rapid diagnostic method for Legionella pneumonia. However, conventional urinary antigen tests are unable to detect anything other than Legionella pneumophila serogroup 1. The Ribotest Legionella (Ribotest) can detect all serogroups by using antibodies recognizing L. pneumophila ribosomal protein L7/L12 in addition to the conventional L. pneumophila serogroup 1 lipopolysaccharide. The aim of this study was to evaluate the performance of Ribotest against conventional urinary antigen tests, including the detection of Legionellaceae other than L. pneumophila. We investigated the detection sensitivity of various kits using in-vitro culture-soluble antigen extracts of ATCC strains and 22 clinical isolates collected from multiple medical facilities in the Kinki region of Japan. For L. pneumophila serogroup 1, four kits, including Ribotest, had a detection sensitivity of 10⁵ CFU/mL, with only Check Legionella having a sensitivity of 10⁶ CFU/mL. L. pneumophila non-serogroup 1 and Legionellaceae of other species were undetectable by the four conventional kits, whereas Ribotest could detect them with a sensitivity of 10⁵-10⁸ CFU/mL. The Ribotest was also able to detect other species such as Legionella hackeliae, Legionella feeleii, Legionella anisa, Fluoribacter bozemanae, and Fluoribacter dumoffii, but the detection sensitivity of L. hackeliae and L. feeleii was 10⁸ CFU/mL, which was much lower than that of the other strains. The Ribotest has high potential to be applied as a rapid diagnostic method for pneumonia caused by other species of Legionella and Fluoribacter.

Cytotoxicity, Intracellular Replication, and Contact-Dependent Pore Formation of Genotyped Environmental Legionella pneumophila Isolates from Hospital Water Systems in the West Bank, Palestine

Legionella pneumophila is the causative agent of Legionnaires’ disease. Due to the hot climate and intermittent water supply, the West Bank, Palestine, can be considered a high-risk area for this often fatal atypical pneumonia. L. pneumophila occurs in biofilms of natural and man-made freshwater environments, where it infects and replicates intracellularly within protozoa. To correlate the genetic diversity of the bacteria in the environment with their virulence properties for protozoan and mammalian host cells, 60 genotyped isolates from hospital water systems in the West Bank were analyzed. The L. pneumophila isolates were previously genotyped by high resolution Multi Locus Variable Number of Tandem Repeat Analysis (MLVA-8(12)) and sorted according to their relationship in clonal complexes (VACC). Strains of relevant genotypes and VACCs were compared according to their capacity to infect Acanthamoeba castellanii and THP-1 macrophages, and to mediate pore-forming cytotoxicity in sheep red blood cells (sRBCs). Based on a previous detailed analysis of the biogeographic distribution and abundance of the MLVA-8(12)-genotypes, the focus of the study was on the most abundant L. pneumophila- genotypes Gt4(17), Gt6 (18) and Gt10(93) and the four relevant clonal complexes [VACC1, VACC2, VACC5 and VACC11]. The highly abundant genotypes Gt4(17) and Gt6(18) are affiliated with VACC1 and sequence type (ST)1 (comprising L. pneumophila str. Paris), and displayed seroroup (Sg)1. Isolates of these two genotypes exhibited significantly higher virulence potentials compared to other genotypes and clonal complexes in the West Bank. Endemic for the West Bank was the clonal complex VACC11 (affiliated with ST461) represented by three relevant genotypes that all displayed Sg6. These genotypes unique for the West Bank showed a lower infectivity and cytotoxicity compared to all other clonal complexes and their affiliated genotypes. Interestingly, the L. pneumophila serotypes ST1 and ST461 were previously identified by in situ-sequence based typing (SBT) as main causative agents of Legionnaires’ disease (LD) in the West Bank at a comparable level. Overall, this study demonstrates the site-specific regional diversity of L. pneumophila genotypes in the West Bank and suggests that a combination of MLVA, cellular infection assays and hierarchical agglomerative cluster analysis allows an improved genotype-based risk assessment.

An outbreak investigation of Legionella non-pneumophila Legionnaires’ disease in Sweden, April to August 2018: Gardening and use of commercial bagged soil associated with infections

In early June 2018, an increase in non-travel-related cases of Legionella non-pneumophila Legionnaires’ disease (LD) was observed in Sweden and a national outbreak investigation was started. Outbreak cases were defined as notified confirmed or probable cases of L. non-pneumophila LD, with symptom onset after 1 April 2018. From April to August 2018, 41 cases were reported, 30 of whom were identified as L. longbeachae. We conducted a case–control study with 27 cases and 182 matched controls. Results from the case–control study indicated that gardening and handling commercial bagged soil, especially dusty dry soil, were associated with disease. L. longbeachae was isolated in soils from cases’ homes or gardens, but joint analysis of soil and human specimens did not identify any genetic clonality. Substantial polyclonality was noted between and within soil samples, which made finding a genetic match between soil and human specimens unlikely. Therefore, whole genome sequencing may be of limited use to confirm a specific soil as a vehicle of transmission for L. longbeachae. Handling soil for residential gardening was associated with disease and the isolation of L. longbeachae in different soils provided further evidence for Legionella non-pneumophila infection from soil.

Development of a Fluorescent Tool for Studying Legionella bozemanae Intracellular Infection

Legionnaires' disease incidence is on the rise, with the majority of cases attributed to the intracellular pathogen, Legionella pneumophila. Nominally a parasite of protozoa, L. pneumophila can also infect alveolar macrophages when bacteria-laden aerosols enter the lungs of immunocompromised individuals. L. pneumophila pathogenesis has been well characterized; however, little is known about the >25 different Legionella spp. that can cause disease in humans. Here, we report for the first time a study demonstrating the intracellular infection of an L. bozemanae clinical isolate using approaches previously established for L. pneumophila investigations. Specifically, we report on the modification and use of a green fluorescent protein (GFP)-expressing plasmid as a tool to monitor the L. bozemanae presence in the Acanthamoeba castellanii protozoan infection model. As comparative controls, L. pneumophila strains were also transformed with the GFP-expressing plasmid. In vitro and in vivo growth kinetics of the Legionella parental and GFP-expressing strains were conducted followed by confocal microscopy. Results suggest that the metabolic burden imposed by GFP expression did not impact cell viability, as growth kinetics were similar between the GFP-expressing Legionella spp. and their parental strains. This study demonstrates that the use of a GFP-expressing plasmid can serve as a viable approach for investigating Legionella non-pneumophila spp. in real time.

Community-acquired versus nosocomial Legionella pneumonia: factors associated with Legionella-related mortality

Over the past decade, changes in the diagnosis and management of Legionella pneumonia occurred and risk factors for severe infection and increased mortality were identified. Previous reports found that nosocomial infection is associated with higher mortality while others showed no differences. We aimed to evaluate the differences in the clinical course and mortality rates between hospital-acquired pneumonia (HAP) and community-acquired pneumonia (CAP) caused by Legionella pneumophila. A retrospective cohort study of patients admitted due to Legionella pneumonia between January 2012 through November 2019 was conducted in a tertiary referral center (Rambam Health Care Campus, Haifa, Israel). The primary outcome was 30-day Legionella pneumonia-related mortality. A multivariable logistic regression was performed to determine whether a nosocomial infection is an independent predictor of mortality. One hundred nine patients were included. Seventy (64.2%) had CAP and 39 (35.8%) had HAP. The groups were comparable regarding age, gender, and comorbidities. Time to diagnosis was longer and the number of patients receiving initial empiric anti-Legionella spp. treatment was smaller in the HAP group (8 days [IQR 5.5-12.5] vs. 5 days [IQR 3-8], p < 0.001 and 65.5% vs. 78.6%, p = 0.003, respectively). Patients with HAP had higher 30-day mortality, 41% vs. 18.6%, p = 0.02. In a multivariable logistic regression model, only pneumonia severity index and nosocomial source were independently associated with increased mortality. HAP caused by Legionella spp. is independently associated with increased mortality when compared to CAP caused by the same pathogen. The possible reasons for this increased mortality include late diagnosis and delayed initiation of appropriate treatment.

Evidence for multiple cases of recurrent Legionella infection: a Danish national surveillance study

While case reports have documented recurrence of Legionnaires' disease, the frequency of recurrent infections has not been systematically examined at a national level over multiple decades. Between 2000 and 2020 in Denmark, 21 individuals had repeat laboratory-identified Legionella infection, totalling 48 episodes of hospitalisation. The majority of these individuals had underlying comorbidities. In at least 3 of the 21 cases, a different Legionella serogroup was detected during the second episode of infection, which could indicate reinfection from a new source. These results emphasise that Legionella can, and does, reinfect high-risk individuals causing multiple hospitalisations.

Differential Bacterial Predation by Free-Living Amoebae May Result in Blooms of Legionella in Drinking Water Systems

Intracellular growth of pathogenic Legionella in free-living amoebae (FLA) results in the critical concentrations that are problematic in engineered water systems (EWS). However, being amoeba-resistant bacteria (ARB), how Legionella spp. becomes internalized within FLA is still poorly understood. Using fluorescent microscopy, we investigated in real-time the preferential feeding behavior of three water-related FLA species, Willaertia magna, Acanthamoeba polyphaga, and Vermamoeba vermiformis regarding Legionella pneumophila and two Escherichia coli strains. Although all the studied FLA species supported intracellular growth of L. pneumophila, they avoided this bacterium to a certain degree in the presence of E. coli and mostly fed on it when the preferred bacterial food-sources were limited. Moreover, once L. pneumophila were intracellular, it inhibited digestion of co-occurring E. coli within the same trophozoites. Altogether, based on FLA–bacteria interactions and the shifts in microbial population dynamics, we propose that FLA’s feeding preference leads to an initial growth of FLA and depletion of prey bacteria, thus increases the relative abundance of Legionella and creates a “forced-feeding” condition facilitating the internalization of Legionella into FLA to initiate the cycles of intracellular multiplication. These findings imply that monitoring of FLA levels in EWS could be useful in predicting possible imminent high occurrence of Legionella.

Closed Genome and Plasmid Sequences of Legionella pneumophila AW-13-4, Isolated from a Hot Water Loop System of a Large Occupational Building

Unused water in unoccupied buildings can become stagnant, with reductions in temperature and levels of disinfectant resulting in increased microbial growth. We report the closed and complete genome and plasmid of Legionella pneumophila strain AW-13-4 (serogroup 1), which was isolated from a hot water loop system of a large building.

Legionnaires' disease in the time of COVID-19

Due to similarities in initial disease presentation, clinicians may be inclined to repeatedly test community-acquired pneumonia cases for COVID-19 before recognizing the need to test for Legionnaires' disease. Legionnaires' disease is an illness characterized by pneumonia that has a summer/early fall seasonality due to favorable conditions for Legionella growth and exposure. Legionella proliferate in warm water environments and stagnant sections of indoor plumbing and cooling systems. During the ongoing pandemic crisis, exposures to aerosolized water from recently reopened office or retail buildings should be considered as an epidemiologic risk factor for Legionella exposure and an indication to test. The majority of Legionnaires' disease cases occurring each year are not diagnosed, and some experts recommend that all patients hospitalized with community-acquired pneumonia without a known etiology be tested for Legionella infection. Proper diagnosis can increase the likelihood of appropriate and timely antibiotic treatment, identify potential clusters of disease, and facilitate source attribution.

Chasing Waterborne Pathogens in Antarctic Human-Made and Natural Environments, with Special Reference to Legionella spp

Waterborne pathogenic diseases are public health issues, especially for people staying in remote environments, such as Antarctica. After repeated detection of Legionella by PCR from the shower room of Syowa Station, the Japanese Antarctic research station, we wanted to understand the occurrence of waterborne pathogens, especially Legionella, in the station and their potential sources. In this study, we analyzed water and biofilm samples collected from the water facilities of Syowa Station, as well as water samples from surrounding glacier lakes, by 16S rRNA gene-based amplicon sequencing. For Legionella spp., we further attempted to obtain a detailed community structure by using genus-specific primers. The results showed that potentially pathogenic genera were mostly localized in the station, while Legionella spp., Pseudomonas spp., and Mycobacterium spp. were also widely distributed in lakes. Genus-specific analysis of Legionella spp. within the lake environments confirmed the presence of diverse Legionella amplicon sequence variants (ASVs) that were distinctly different from the Legionella ASVs detected in the station. The majority of the Legionella ASVs inhabiting Antarctic lake habitats were phylogenetically distinct from known Legionella species, whereas the ASVs detected in the human-made station tended to contain ASVs highly similar to well-described mesophilic species with human pathogenicity. These data suggest that unexpected Legionella diversity exists in remote Antarctic cold environments and that environmental differences (e.g., temperature) in and around the station affect the community structure.IMPORTANCE We comprehensively examined the localization of potential waterborne pathogens in the Antarctic human-made and natural aquatic environment with special focus on Legionella spp. Some potential pathogenic genera were detected with low relative abundance in the natural environment, but most detections of these genera occurred in the station. Through detailed community analysis of Legionella spp., we revealed that a variety of Legionella spp. was widely distributed in the Antarctic environment and that they were phylogenetically distinct from the described species. This fact indicates that there are still diverse unknown Legionella spp. in Antarctica, and this genus encompasses a greater variety of species in low-temperature environments than is currently known. In contrast, amplicon sequence variants closely related to known Legionella spp. with reported pathogenicity were almost solely localized in the station, suggesting that human-made environments alter the Legionella community.

Risk Factors, Management, and Outcomes of Legionella Pneumonia in a Large, Nationally Representative Sample

BACKGROUND

American Thoracic Society/Infectious Diseases Society of America guidelines recommend against routine Legionella pneumophila testing, but recommend that hospitalized patients with community-acquired pneumonia receive empiric treatment covering Legionella. Testing, empiric treatment, and outcomes for patients with Legionella have not been well described.

RESEARCH QUESTION

Is testing for Legionella pneumophila appropriate, and could it impact treatment?

STUDY DESIGN AND METHODS

We conducted a large retrospective cohort analysis using Premier Healthcare Database data from 2010 to 2015. We included adults with a principal diagnosis code for pneumonia (or a principal diagnosis of respiratory failure or sepsis with secondary diagnosis of pneumonia) if they also received treatment for pneumonia on hospital days 1-3. We categorized Legionella-tested patients by test result, identified patient characteristics associated with testing and test result, and examined seasonal and regional patterns of Legionella pneumonia (LP) diagnoses. Empiric therapy for LP was defined as a macrolide, quinolone, or doxycycline, administered on each of the first two hospital days.

RESULTS

Of 166,689 eligible patients, 43,070 (26%) were tested for Legionella, and 642 (1.5%) tested positive. Although only 36% of tests were ordered from June to October, 70% of positive test results occurred during this time. Only 30% of patients with hyponatremia, 32% with diarrhea, and 27% in the ICU were tested. Of patients with positive test results, 495 of 642 (77%) had received empiric Legionella therapy. Patients with LP did not have more severe presentation. They had more frequent late decompensation, but similar mortality to patients without LP.

INTERPRETATION

Legionella is an uncommon cause of community-acquired pneumonia, occurring primarily from late spring through early autumn. Testing is uncommon, even among patients with risk factors, and many patients with positive test results failed to receive empiric coverage for LP.

Legionella pneumophila in Patients with Pneumonia at a Referral Hospital, New Delhi, India, 2015-2020

Legionnaires' disease (LD) is an established cause of pneumonia, and the disease remains largely underdiagnosed. Even though LD has been reported from many parts of the world, only sporadic cases have been reported in India. During February 2015-January 2020, we enrolled 597 patients with radiographically confirmed pneumonia and tested respiratory secretions for Legionella spp. by using real-time PCR, and culture. A commercial urinary antigen test (UAT) was also used to detect the Legionella pneumophila (Lp) serogroup 1 antigen in urine. An LD case was defined as a patient with pneumonia and positive results for Legionella spp. infections determined by real-time PCR (from any respiratory specimen) or culture or UAT. Demographic data, risk factors, clinical, radiological, and outcome data of Lp-positive and Lp-negative patients were compared using logistic regression. Over the study period, 14 (2.3%) patients were positive for Legionella spp. infections by real-time PCR and UAT; eight (57%) were admitted to the intensive care unit, and four (28.6%) in-hospital deaths occurred. Bivariate analysis showed that renal disease, neurological conditions, confusion, leukocytosis, and requirement of oxygen support were more common in the Lp-positive group than in the Lp-negative group. However, multivariate analysis failed to confirm most of these differences; renal disease was the only independent variable remaining significant. All test methods have intrinsic limitations in identifying Legionella; therefore, more than one testing method should be used. Application of molecular assays including real-time PCR has great value because of its high sensitivity, specificity, and rapid diagnostic potency. Increased awareness and improved diagnostic testing could facilitate early detection of cases, pathogen-directed therapy, and improved outcomes for patients.

Biogeography and Environmental Drivers of Legionella pneumophila Abundance and Genotype Composition Across the West Bank: Relevance of a Genotype-Based Ecology for Understanding Legionella Occurrence

The West Bank can be considered as a high-risk area for Legionella prevalence in drinking water due to high ambient temperature, intermittent water supply, frequent pressure loss, and storage of drinking water in roof containers. To assess occurrence of Legionella species, especially L. pneumophila, in the drinking water of the West Bank, the drinking water distribution systems of eight hospitals were sampled over a period of 2.3 years covering the seasonal cycle and the major geographic regions. To gain insight into potential environmental drivers, a set of physico-chemical and microbiological parameters was recorded. Sampling included drinking water and biofilm analyzed by culture and PCR-based methods. Cultivation led to the isolation of 180 strains of L. pneumophila that were genotyped by Multi-Locus Variable Number of Tandem Repeat Analysis (MLVA). Surprisingly, the abundance of culturable L. pneumophila was low in drinking water of the sampling sites, with only three out of eight sites where Legionella was observed at all (range: 30–500 CFU/Liter). By contrast, biofilm and PCR-based analyses showed a higher prevalence. Statistical analyses with physico-chemical parameters revealed a decrease of L. pneumophila abundance for water and biofilm with increasing magnesium concentrations (>30 mg/L). MLVA-genotype analysis of the L. pneumophila isolates and their spatial distribution indicated three niches characterized by distinct physico-chemical parameters and inhabited by specific consortia of genotypes. This study provides novel insights into mechanisms shaping L. pneumophila populations and triggering their abundance leading to an understanding of their genotype-specific niches and ecology in support of improved prevention measures.

Evaluation of a novel urinary antigen test kit for diagnosing Legionella pneumonia

OBJECTIVES

The aim of this study was to evaluate the diagnostic utility of a novel test kit that could theoretically detect all serogroups of Legionella pneumophila for diagnosing Legionella pneumonia, in comparison with existing kits.

METHODS

This study was conducted in 16 hospitals in Japan from April 2016 to December 2018. Three urinary antigen test kits were used: the novel kit (LAC-116), BinaxNOW Legionella (Binax), and Q-line Kyokutou Legionella (Q-line). In addition, sputum culture and nucleic acid detection tests and serum antibody tests were performed where possible. The diagnostic accuracy and correlations of the novel kit with the two existing kits were analyzed.

RESULTS

In total, 56 patients were diagnosed with Legionella pneumonia. The sensitivities of LAC-116, Binax, and Q-line were 79%, 84%, and 71%, respectively. The overall match rate between LAC-116 and Binax was 96.8% and between LAC-116 and Q-line was 96.4%. One patient had L. pneumophila serogroup 2, and only LAC-116 showed a positive result, whereas Binax and Q-line did not.

CONCLUSIONS

The novel Legionella urinary antigen test kit was useful for diagnosing Legionella pneumonia. In addition, it could detect Legionella pneumonia caused by non-L. pneumophila serogroup 1.