Legionnaires' disease

Genetic evidence for a regulated cysteine protease catalytic triad in LegA7, a Legionella pneumophila protein that impinges on a stress response pathway

Legionella pneumophila grows within membrane-bound vacuoles in phylogenetically diverse hosts. Intracellular growth requires the function of the Icm/Dot type-IVb secretion system, which translocates more than 300 proteins into host cells. A screen was performed to identify L. pneumophila proteins that stimulate mitogen-activated protein kinase (MAPK) activation, using Icm/Dot translocated proteins ectopically expressed in mammalian cells. In parallel, a second screen was performed to identify L. pneumophila proteins expressed in yeast that cause growth inhibition in MAPK pathway-stimulatory high-osmolarity medium. LegA7 was shared in both screens, a protein predicted to be a member of the bacterial cysteine protease family that has five carboxyl-terminal ankyrin repeats. Three conserved residues in the predicted catalytic triad of LegA7 were mutated. These mutations abolished the ability of LegA7 to inhibit yeast growth. To identify other residues important for LegA7 function, a generalizable selection strategy in yeast was devised to isolate mutants that have lost function and no longer cause growth inhibition on a high-osmolarity medium. Mutations were isolated in the two carboxyl-terminal ankyrin repeats, as well as an inter-domain region located between the cysteine protease domain and the ankyrin repeats. These mutations were predicted by AlphaFold modeling to localize to the face opposite from the catalytic site, arguing that they interfere with the positive regulation of the catalytic activity. Based on our data, we present a model in which LegA7 harbors a cysteine protease domain with an inter-domain and two carboxyl-terminal ankyrin repeat regions that modulate the function of the catalytic domain.

IMPORTANCE

Legionella pneumophila grows in a membrane-bound compartment in macrophages during disease. Construction of the compartment requires a dedicated secretion system that translocates virulence proteins into host cells. One of these proteins, LegA7, is shown to activate a stress response pathway in host cells called the mitogen-activated protein kinase (MAPK) pathway. The effects on the mammalian MAPK pathway were reconstructed in yeast, allowing the development of a strategy to identify the role of individual domains of LegA7. A domain similar to cysteine proteases is demonstrated to be critical for impinging on the MAPK pathway, and the catalytic activity of this domain is required for targeting this path. In addition, a conserved series of repeats, called ankyrin repeats, controls this activity. Data are provided that argue the interaction of the ankyrin repeats with unknown targets probably results in activation of the cysteine protease domain.

Epidemiological Analysis of Legionella Pneumonia in Japan: A National Inpatient Database Study

BACKGROUND

Legionella pneumonia, a severe form of pneumonia, is caused by Legionella bacteria. The epidemiology of Legionnaires' disease in Japan, including seasonal trends, risk factors for severe disease, and fatality rates, is unclear. This study examined the epidemiology of Legionella pneumonia in Japan.

METHODS

This retrospective cohort study included data of adult patients hospitalized for Legionella pneumonia (identified using the International Classification of Diseases, 10th revision code, A481) in the Japanese Diagnosis Procedure Combination inpatient database, from April 2011 to March 2021. We performed multivariable logistic regression analysis to explore the prognostic factors of in-hospital mortality.

RESULTS

Of 7,370 enrolled hospitalized patients from 1,140 hospitals (male, 84.4%; aged >50 years, 87.9%), 469 (6.4%) died during hospitalization. The number of hospitalized patients increased yearly, from 658 in 2016 to 975 in 2020. Multivariable logistic regression analysis revealed that higher in-hospital mortality was associated with older age, male sex, lower body mass index, worsened level of consciousness, comorbidities (congestive heart failure, chronic renal diseases, and metastasis), hospitalization from November to May, and ambulance use. However, lower in-hospital mortality was associated with comorbidity (liver diseases), hospitalization after 2013, and hospitalization in hospitals with higher case volume.

CONCLUSION

The characterized epidemiology of Legionella pneumonia in Japan revealed a high mortality rate of 6.4%. To the best of our knowledge, this is the first study to demonstrate a higher mortality rate in winter and in patients with congestive heart failure and metastasis. Further research is needed to understand the complex interplay between the prognostic factors of Legionella pneumonia.

Environmentally relevant concentrations of naphthenic acids initiate intestinal injury and gut microbiota dysbiosis in marine medaka (Oryzias melastigma)

Naphthenic acids (NAs) are important pollutants in marine crude oils and have obvious toxic effects on marine organisms. However, the effects of NAs on the intestine are largely unknown. Thus, we evaluated the effects of NAs exposure in the intestines of marine medaka. Fish were experimentally exposed to NAs (0.5 mg/L, 5 mg/L, and 10 mg/L) for 96 h and monitored for changes in intestinal histology, markers of oxidative stress, and intestinal microbiome responses. Significant mucosal damage, inflammation, and oxidative stress were observed in the intestines of marine medaka after exposure to NAs. In addition, significant changes in the gut microbiota were observed. Specifically, the relative abundance of Proteobacteria decreased, while that of Verrucomicrobiota increased in the high-concentration exposure group. In addition, nutrient synthesis and metabolism in the gut were affected. The results of this study contribute to a better understanding of the ecological risk of different concentrations of NAs to marine organisms. CAPSULE ABSTRACT: Changes in the gut microbial community of marine medaka (Oryzias melastigma) caused by naphthenic acids in the marine environment were investigated through the assessment of gut inflammatory factors and comprehensive analysis using 16S rDNA high-throughput sequencing. The results indicated the induction of intestinal inflammation and changes in the structural composition of the intestinal flora.

Concordance between IDEXX Legiolert® (liquid culture assay) and plate culture (ISO 11731:2017) for the detection and quantification of Legionella pneumophila in water samples

BACKGROUND

Legionella pneumophila is a water-borne bacterium that can cause Legionnaires' disease. Legiolert® (IDEXX, USA) is a low-labour liquid culture assay for the detection and enumeration of L. pneumophila (SG1-15) from water.

AIM

To analyse concordance between Legiolert and ISO 11731:2017 plate culture method (membrane filtration and culture on selective agars) using hospital water samples (N = 100).

METHODS

Incubation was at 39 °C and 36 °C, respectively, for seven days, followed by most-probable enumeration for Legiolert and subculturing and serogrouping of suspected Legionella colonies, with plate culture.

FINDINGS

L. pneumophila (SG1-15) was isolated from 25 out of 100 samples when using Legiolert or plate culture. Fourteen additional Legiolert samples tested positive for L. pneumophila; analysis of the same samples by plate culture was negative (12 out of 14) or yielded only Legionella rubrilucens (two out of 14; confirmed via matrix-assisted ionization/desorption time-of-flight mass spectrometry). L. pneumophila was not captured from Quanti-Tray/Legiolert pouch wells of these positive samples after subculture of puncture aliquots on buffered charcoal yeast-extract agar. Both methods in concordance did not detect L. pneumophila in 61 out of 100 samples.

CONCLUSION

Legiolert and plate culture are both satisfactory methods to detect L. pneumophila from water samples, and both to detect isolated L. pneumophila in 25% of the sample population. Legiolert provides a faster time to result, and is less resource-demanding and labour-intensive; however, there may be a low risk of cross-reactivity with other organisms. Both methods are suitable for the analysis of water in healthcare settings, where the monitoring of L. pneumophila is imperative in preventing cases of Legionnaires' disease.

Legionella maceachernii pneumonia: a case report and literature review

BACKGROUND

Legionella maceachernii pneumonia is a severe respiratory infection with low incidence but high mortality. However, the optimal treatment for this disease remains unclear. We report a case of successful treatment of Legionella maceachernii pneumonia, which is the first report of such a case in China.

CASE PRESENTATION

An 87-year-old man with concomitant chronic obstructive pulmonary disease, liver cirrhosis, and history of left nephrectomy was diagnosed with Legionella maceachernii pneumonia using Dano-seq pathogen metagenomic testing. After two weeks of treatment with cefoperazone/sulbactam combined with quinolone antibiotics, the patient showed improvement and was discharged. The patient continued to take oral quinolone antibiotics for one week after discharge and recovered during outpatient follow-up.

CONCLUSIONS

Dano-seq pathogen metagenomic testing can rapidly diagnose Legionella maceachernii pneumonia, and taking quinolone antibiotics is an effective treatment.

Legionella pneumophila cell surface RtxA release by LapD/LapG and its role in virulence

BACKGROUND

Legionella pneumophila is a Gram-negative intracellular bacillus and is the causative agent of a severe form of pneumonia called Legionnaires' disease which accounts for 2-9% of cases of community acquired pneumonia. It produces an extremely large protein belonging to the RTX (Repeats in ToXin) family, called RtxA, and we previously reported that RtxA is transported by a dedicated type 1 secretion system (T1SS) to the cell surface. RTX proteins have been shown to participate in the virulence or biofilm formation of various bacteria, the most studied models being the pore forming hemolysin A (HlyA) of Escherichia coli and the biofilm associated protein LapA of P. fluorescens. LapA localization depends on the enzymatic release by LapD/LapG complex activity. This study aimed to elucidate the dual localization (cell surface associated or released state) of L. pneumophila RTX protein (RtxA) and whether this released versus sequestered state of RtxA plays a role in L. pneumophila virulence.

RESULTS

The hereby work reveals that, in vitro, LapG periplasmic protease cleaves RtxA N-terminus in the middle of a di-alanine motif (position 108-109). Consistently, a strain lacking LapG protease maintains RtxA on the cell surface, whereas a strain lacking the c-di-GMP receptor LapD does not exhibit cell surface RtxA because of its continuous cleavage and release, as in the LapA-D-G model of Pseudomonas fluorescens. Interestingly, our data point out a key role of RtxA in enhancing the infection process of amoeba cells, regardless of its location (embedded or released); therefore, this may be the result of a secondary role of this surface protein.

CONCLUSIONS

This is the first experimental identification of the cleavage site within the RTX protein family. The primary role of RtxA in Legionella is still questionable as in many other bacterial species, hence it sounds reasonable to propose a major function in biofilm formation, promoting cell aggregation when RtxA is embedded in the outer membrane and facilitating biofilm dispersion in case of RtxA release. The role of RtxA in enhancing the infection process may be a result of its action on host cells (i.e., PDI interaction or pore-formation), and independently of its status (embedded or released).

Sde Proteins Coordinate Ubiquitin Utilization and Phosphoribosylation to Establish and Maintain the Legionella Replication Vacuole

The Legionella pneumophila Sde family of translocated proteins promotes host tubular endoplasmic reticulum (ER) rearrangements that are tightly linked to phosphoribosyl-ubiquitin (pR-Ub) modification of Reticulon 4 (Rtn4). Sde proteins have two additional activities of unclear relevance to the infection process: K63 linkage-specific deubiquitination and phosphoribosyl modification of polyubiquitin (pR-Ub). We show here that the deubiquitination activity (DUB) stimulates ER rearrangements while pR-Ub protects the replication vacuole from cytosolic surveillance by autophagy. Loss of DUB activity is tightly linked to lowered pR-Ub modification of Rtn4, consistent with the DUB activity fueling the production of pR-Ub-Rtn4. In parallel, phosphoribosyl modification of polyUb, in a region of the protein known as the isoleucine patch, prevents binding by the autophagy adapter p62. An inability of Sde mutants to modify polyUb results in immediate p62 association, a critical precursor to autophagic attack. The ability of Sde WT to block p62 association decays quickly after bacterial infection, as predicted by the presence of previously characterized L. pneumophila effectors that inactivate Sde and remove polyUb. In sum, these results show that the accessory Sde activities act to stimulate ER rearrangements and protect from host innate immune sensing in a temporal fashion.

Antimicrobial susceptibility testing reveals reduced susceptibility to azithromycin and other antibiotics in Legionella pneumophila serogroup 1 isolates from Portugal

BACKGROUD

Although not fully investigated, studies show that Legionella pneumophila can develop antibiotic resistance. As there is limited data available for Portugal, we determined the antibiotic susceptibility profile of Portuguese L. pneumophila serogroup 1 (LpnSg1) isolates against antibiotics used in the clinical practice in Portugal.

METHODS

Minimum inhibitory concentrations (MICs) were determined for LpnSg1 clinical (n = 100) and related environmental (n = 7) isolates, collected between 2006-2022 in the context of the National Legionnaire´s Disease Surveillance Programme, against azithromycin, clarithromycin, erythromycin, levofloxacin, ciprofloxacin, moxifloxacin, rifampicin, doxycycline, tigecycline, and amoxicillin/clavulanic acid, using three different assays. Isolates were also PCR-screened for the presence of the lpeAB gene.

RESULTS

Twelve isolates had azithromycin MICs above the EUCAST tentative highest WT MIC, 9 of which were lpeAB negative; for erythromycin and clarithromycin, all isolates tested within the susceptible range. The number of isolates with MICs above the tentative highest WT MIC for the remaining antibiotics was: ciprofloxacin: 7; levofloxacin: 17; moxifloxacin: 8; rifampicin: 11; doxycycline: 82; tigecycline: 4. EUCAST breakpoints are not available for amoxicillin/clavulanic acid. We estimated the ECOFFs and one isolate had a MIC eightfold higher than the E-test ECOFF. Additionally, a clinical isolate generated three colonies growing on the E-test inhibition zone that resulted in MICs fourfold higher than for the parental isolate.

CONCLUSIONS

We report, for the first time, elevated MICs against first-line and other antibiotics (including azithromycin, fluoroquinolones and amoxicillin/clavulanic acid commonly used to treat pneumonia patients in Portugal) in Portuguese L. pneumophila strains. Results point towards decreased susceptibility in circulating strains, justifying further investigation.

Genetic evidence for a regulated cysteine protease catalytic triad in LegA7, a Legionella pneumophila protein that impinges on a stress response pathway

Legionella pneumophila grows within membrane-bound vacuoles in phylogenetically diverse hosts. Intracellular growth requires the function of the Icm/Dot type-IVb secretion system, which translocates more than 300 proteins into host cells. A screen was performed to identify L. pneumophila proteins that stimulate MAPK activation, using Icm/Dot translocated proteins ectopically expressed in mammalian cells. In parallel, a second screen was performed to identify L. pneumophila proteins expressed in yeast that cause growth inhibition in MAPK pathway-stimulatory high osmolarity medium. LegA7 was shared in both screens, a protein predicted to be a member of the bacterial cysteine protease family that has five carboxyl-terminal ankyrin repeats. Three conserved residues in the predicted catalytic triad of LegA7 were mutated. These mutations abolished the ability of LegA7 to inhibit yeast growth. To identify other residues important for LegA7 function, a generalizable selection strategy in yeast was devised to isolate mutants that have lost function and no longer cause growth inhibition on high osmolarity medium. Mutations were isolated in the two carboxyl-terminal ankyrin repeats, as well as an inter-domain region located between the cysteine protease domain and the ankyrin repeats. These mutations were predicted by AlphaFold modeling to localize to the face opposite from the catalytic site, arguing that they interfere with the positive regulation of the catalytic activity. Based on our data, we present a model in which LegA7 harbors a cysteine protease domain with an inter-domain and two carboxyl-terminal ankyrin repeat regions that modulate the function of the catalytic domain.

Omadacycline for the treatment of patients with Legionella pneumophila pneumonia after experiencing liver dysfunction: case series

Introduction

Antibiotics frequently induce abnormal liver function. Omadacycline is a novel aminomethylcycline antibiotic, which shows potent activity against Gram-positive and Gram-negative aerobic, anaerobic, and atypical (including Legionella pneumophila) bacteria. Of note, omadacycline is tolerable in most patients with liver impairment. However, evidence regarding the application of omadacycline in patients with Legionella pneumophila pneumonia after experiencing liver dysfunction is scarce.

Methods

The current study reported 6 cases of patients with Legionella pneumophila pneumonia receiving omadacycline as subsequent antibiotics after experiencing liver dysfunction.

Results

These 6 cases were admitted to the hospital for pneumonia and received antibiotic therapy, including piperacillin-tazobactam, imipenem, meropenem, and moxifloxacin. After receiving these antibiotics, increased liver enzymes were noted. Although hepatoprotective therapy (such as magnesium isoglycyrrhizinate and glutathione) was given, the liver function was still abnormal. According to metagenomic next-generation sequencing, these patients were diagnosed with Legionella pneumophila pneumonia. Considering the abnormal liver function, the antibiotic therapy was switched to omadacycline-containing antibiotic therapy. After that, liver function was improved, and the infection was ameliorated. Ultimately, all patients discharged from the hospital, including 2 patients who achieved complete clinical symptomatic improvement and 4 patients who achieved partial clinical symptomatic improvement.

Discussion

This study emphasizes the successful treatment of switching to omadacycline after experiencing abnormal liver function in patients with Legionella pneumophila pneumonia. This study suggests that omadacycline may serve as an optional antibiotic for patients with Legionella pneumophila pneumonia, especially when occurring liver dysfunction. However, more clinical studies are required to validate our findings.

Metagenomic next-generation sequencing reveals co-infection with Legionella pneumophila and Fusobacterium necrophorum in a patient with severe pneumonia: a case report

BACKGROUND

Legionella pneumonia is one of the most severe types of atypical pneumonia, impairing multiple organ systems, posing a threat to life. Diagnosing Legionella pneumonia is challenging due to difficulties in culturing the bacteria and limitations in immunoassay sensitivity and specificity.

CASE PRESENTATION

This paper reports a rare case of sepsis caused by combined infection with Legionella pneumophila and Fusobacterium necrophorum, leading to respiratory failure, acute kidney injury, acute liver injury, myocardial damage, and electrolyte disorders. In addition, we systematically reviewed literature on patients with combined Legionella infections, analyzing their clinical features, laboratory results and diagnosis.

CONCLUSIONS

For pathogens that require prolonged incubation periods and are less sensitive to conventional culturing methods, metagenomic next-generation sequencing (mNGS) can be a powerful supplement to pathogen screening and plays a significant role in the auxiliary diagnosis of complex infectious diseases.

Adherence to Legionella control regulations and guidelines in Norwegian nursing homes: a cross-sectional survey

BACKGROUND

Infection by Legionella bacteria is a risk to elderly individuals in health care facilities and should be managed by preventing bacterial proliferation in internal water systems. Norwegian legislation calls for a mandatory Legionella-specific risk assessment with the subsequent introduction of an adapted water management programme. The present study investigates adherence to legislation and guidelines on Legionella control and prevention in Norwegian nursing homes.

METHODS

A cross-sectional survey was distributed to Norwegian municipalities to investigate the status of Legionella specific risk assessments of internal water distribution systems and the introduction of water management programmes in nursing homes.

RESULTS

A total of 55.1% (n = 228) of the participating nursing homes had performed Legionella-specific risk assessments, of which 55.3% (n = 126) stated that they had updated the risk assessment within the last year. 96.5% introduced a water management programme following a risk assessment, whereas 59.6% of the ones without a risk assessment did the same. Nursing homes with risk assessments were more likely to monitor Legionella levels than those without (61.2% vs 38.8%), to remove dead legs (44.7% vs 16.5%), and to select biocidal preventive treatment over hot water flushing (35.5% vs 4.6%).

CONCLUSIONS

This study presents novel insight into Legionella control in Norway, suggesting that adherence to mandatory risk assessment in nursing homes is moderate-low. Once performed, the risk assessment seems to be advantageous as an introduction to future Legionella prevention in terms of the scope and contents of the water management programme.

CRP under 130 mg/L rules out the diagnosis of Legionella pneumophila serogroup 1 (URINELLA Study)

INTRODUCTION

In case of pneumonia, some biological findings are suggestive for Legionnaire's disease (LD) including C-reactive protein (CRP). A low level of CRP is predictive for negative Legionella Urinary-Antigen-Test (L-UAT).

METHOD

Observational retrospective study in Nord-Franche-Comté Hospital with external validation in Besançon University Hospital, France which included all adults with L-UAT performed during January 2018 to December 2022. The objective was to determine CRP optimal threshold to predict a L-UAT negative result.

RESULTS

URINELLA included 5051 patients (83 with positive L-UAT). CRP optimal threshold was 131.9 mg/L, with a negative predictive value (NPV) at 100%, sensitivity at 100% and specificity at 58.0%. The AUC of the ROC-Curve was at 88.7% (95% CI, 86.3-91.1). External validation in Besançon Hospital patients showed an AUC at 89.8% (95% CI, 85.5-94.1) and NPV, sensitivity and specificity was respectively 99.9%, 97.6% and 59.1% for a CRP threshold at 131.9 mg/L; after exclusion of immunosuppressed patients, index sensitivity and NPV reached also 100%.

CONCLUSION

In case of pneumonia suspicion with a CRP level under 130 mg/L (independently of the severity) L-UAT is useless in immunocompetent patients with a NPV at 100%. We must remain cautious in patients with symptoms onset less than 48 h before CRP dosage.

Metal-Organic Framework-Based Antimicrobial Touch Surfaces to Prevent Cross-Contamination

Infection diseases are a major threat to global public health, with nosocomial infections being of particular concern. In this context, antimicrobial coatings emerge as a promising prophylactic strategy to reduce the transmission of pathogens and control infections. Here, antimicrobial door handle covers to prevent cross-contamination are prepared by incorporating iodine-loaded UiO-66 microparticles into a potentially biodegradable polyurethane polymer (Baycusan eco E 1000). These covers incorporate MOF particles that serve as both storage reservoirs and delivery systems for the biocidal iodine. Under realistic touching conditions, the door handle covers completely inhibit the transmission of Gram-positive bacterial species (Staphylococcus aureus, and Enterococcus faecalis), Gram-negative bacterial species (Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii), and fungi (Candida albicans). The covers remain effective even after undergoing multiple contamination cycles, after being cleaned, and when tinted to improve discretion and usability. Furthermore, as the release of iodine from the door handle covers follow hindered Fickian diffusion, their antimicrobial lifetime is calculated to be as long as approximately two years. Together, these results demonstrate the potential of these antimicrobial door handle covers to prevent cross-contamination, and underline the efficacy of integrating MOFs into innovative technologies.

Efficacy of omadacycline in the treatment of Legionella pneumonia: a case report

Legionella, one of the main pathogens that causes community-acquired pneumonia, can lead to Legionella pneumonia, a condition characterized predominantly by severe pneumonia. This disease, caused by the bacterium Legionella pneumophila, can quickly progress to critical pneumonia and is often associated with damage to multiple organs. As a result, it requires close attention in terms of clinical diagnosis and treatment. Omadacycline, a new type of tetracycline derivative belonging to the aminomethylcycline class of antibiotics, is a semi-synthetic compound derived from minocycline. Its key structural feature, the aminomethyl modification, allows omadacycline to overcome bacterial resistance and broadens its range of effectiveness against bacteria. Clinical studies have demonstrated that omadacycline is not metabolized in the body, and patients with hepatic and renal dysfunction do not need to adjust their dosage. This paper reports a case of successful treatment of Legionella pneumonia with omadacycline in a patient who initially did not respond to empirical treatment with moxifloxacin. The patient also experienced electrolyte disturbance, as well as dysfunction in the liver and kidneys, delirium, and other related psychiatric symptoms.

Legionella uses host Rab GTPases and BAP31 to create a unique ER niche

Upon entry into host cells, the facultative intracellular bacterium Legionella pneumophila ( L.p .) uses its type IV secretion system, Dot/Icm, to secrete ~330 bacterial effector proteins into the host cell. Some of these effectors hijack endoplasmic reticulum (ER)-derived vesicles to form the Legionella -containing vacuole (LCV). Despite extensive investigation over decades, the fundamental question persists: Is the LCV membrane distinct from or contiguous with the host ER network? Here, we employ advanced photobleaching techniques, revealing a temporal acquisition of both smooth and rough ER (sER and rER) markers on the LCV. In the early stages of infection, the sER intimately associates with the LCV. Remarkably, as the infection progresses, the LCV evolves into a distinct niche comprising an rER membrane that is independent of the host ER network. We discover that the L.p. effector LidA binds to and recruits two host proteins of the Rab superfamily, Rab10, and Rab4, that play significant roles in acquiring sER and rER membranes, respectively. Additionally, we identify the pivotal role of a host ER-resident protein, BAP31, in orchestrating the transition from sER to rER. While previously recognized for shuttling between sER and rER, we demonstrate BAP31's role as a Rab effector, mediating communication between these ER sub-compartments. Furthermore, using genomic deletion strains, we uncover a novel L.p. effector, Lpg1152, essential for recruiting BAP31 to the LCV and facilitating its transition from sER to rER. Depletion of BAP31 or infection with an isogenic L.p. strain lacking Lpg1152 results in a growth defect. Collectively, our findings illuminate the intricate interplay between molecular players from both host and pathogen, elucidating how L.p. orchestrates the transformation of its residing vacuole membrane from a host-associated sER to a distinct rER membrane that is not contiguous with the host ER network.

An outbreak of Legionnaires' disease linked to a municipal and industrial wastewater treatment plant, The Netherlands, September-October 2022

Wastewater treatment plants (WWTPs) are increasingly identified as Legionnaires' disease (LD) sources. An outbreak investigation was initiated following five LD cases reported in September 2022 in Houten, the Netherlands. Case identification was based on the European LD case definition, with symptom onset from 1 September 2022, residence in or within 5 km of Houten, or visit to Houten within the incubation period, without other likely sources. We sampled potential sources and genotyped environmental and clinical isolates. We identified 15 LD cases with onset between 13 September and 23 October 2022. A spatial source identification and wind direction model suggested an industrial (iWWTP) and a municipal WWTP (mWWTP) as potential sources, with the first discharging water into the latter. Both tested positive for Legionella pneumophila serogroups 1 and 6 with multiple sequence types (ST). We detected L. pneumophila sg1 ST42 in the mWWTP, matching with one of three available clinical isolates. Following control measures at the WWTPs, no further cases were observed. This outbreak underlines that municipal and industrial WWTPs can play an important role in community LD cases and outbreaks, especially those with favourable conditions for Legionella growth and dissemination, or even non-favourable conditions for growth but with the influx of contaminated water.

Interactions between chaperone and energy storage networks during the evolution of Legionella pneumophila under heat shock

Waterborne transmission of the bacterium Legionella pneumophila has emerged as a major cause of severe nosocomial infections of major public health impact. The major route of transmission involves the uptake of aerosolized bacteria, often from the contaminated hot water systems of large buildings. Public health regulations aimed at controlling the mesophilic pathogen are generally concerned with acute pasteurization and maintaining high temperatures at the heating systems and throughout the plumbing of hot water systems, but L. pneumophila is often able to survive these treatments due to both bacterium-intrinsic and environmental factors. Previous work has established an experimental evolution system to model the observations of increased heat resistance in repeatedly but unsuccessfully pasteurized L. pneumophila populations. Here, we show rapid fixation of novel alleles in lineages selected for resistance to heat shock and shifts in mutational profile related to increases in the temperature of selection. Gene-level and nucleotide-level parallelisms between independently-evolving lineages show the centrality of the DnaJ/DnaK chaperone system in the heat resistance of L. pneumophila. Inference of epistatic interactions through reverse genetics shows an unexpected interaction between DnaJ/DnaK and the polyhydroxybutyrate-accumulation energy storage mechanism used by the species to survive long-term starvation in low-nutrient environments.

Opportunistic Pathogens in Drinking Water Distribution Systems-A Review

In contrast to "frank" pathogens, like Salmonella entrocolitica, Shigella dysenteriae, and Vibrio cholerae, that always have a probability of disease, "opportunistic" pathogens are organisms that cause an infectious disease in a host with a weakened immune system and rarely in a healthy host. Historically, drinking water treatment has focused on control of frank pathogens, particularly those from human or animal sources (like Giardia lamblia, Cryptosporidium parvum, or Hepatitis A virus), but in recent years outbreaks from drinking water have increasingly been due to opportunistic pathogens. Characteristics of opportunistic pathogens that make them problematic for water treatment include: (1) they are normally present in aquatic environments, (2) they grow in biofilms that protect the bacteria from disinfectants, and (3) under appropriate conditions in drinking water systems (e.g., warm water, stagnation, low disinfectant levels, etc.), these bacteria can amplify to levels that can pose a public health risk. The three most common opportunistic pathogens in drinking water systems are Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa. This report focuses on these organisms to provide information on their public health risk, occurrence in drinking water systems, susceptibility to various disinfectants, and other operational practices (like flushing and cleaning of pipes and storage tanks). In addition, information is provided on a group of nine other opportunistic pathogens that are less commonly found in drinking water systems, including Aeromonas hydrophila, Klebsiella pneumoniae, Serratia marcescens, Burkholderia pseudomallei, Acinetobacter baumannii, Stenotrophomonas maltophilia, Arcobacter butzleri, and several free-living amoebae including Naegleria fowleri and species of Acanthamoeba. The public health risk for these microbes in drinking water is still unclear, but in most cases, efforts to manage Legionella, mycobacteria, and Pseudomonas risks will also be effective for these other opportunistic pathogens. The approach to managing opportunistic pathogens in drinking water supplies focuses on controlling the growth of these organisms. Many of these microbes are normal inhabitants in biofilms in water, so the attention is less on eliminating these organisms from entering the system and more on managing their occurrence and concentrations in the pipe network. With anticipated warming trends associated with climate change, the factors that drive the growth of opportunistic pathogens in drinking water systems will likely increase. It is important, therefore, to evaluate treatment barriers and management activities for control of opportunistic pathogen risks. Controls for primary treatment, particularly for turbidity management and disinfection, should be reviewed to ensure adequacy for opportunistic pathogen control. However, the major focus for the utility's opportunistic pathogen risk reduction plan is the management of biological activity and biofilms in the distribution system. Factors that influence the growth of microbes (primarily in biofilms) in the distribution system include, temperature, disinfectant type and concentration, nutrient levels (measured as AOC or BDOC), stagnation, flushing of pipes and cleaning of storage tank sediments, and corrosion control. Pressure management and distribution system integrity are also important to the microbial quality of water but are related more to the intrusion of contaminants into the distribution system rather than directly related to microbial growth. Summarizing the identified risk from drinking water, the availability and quality of disinfection data for treatment, and guidelines or standards for control showed that adequate information is best available for management of L. pneumophila. For L. pneumophila, the risk for this organism has been clearly established from drinking water, cases have increased worldwide, and it is one of the most identified causes of drinking water outbreaks. Water management best practices (e.g., maintenance of a disinfectant residual throughout the distribution system, flushing and cleaning of sediments in pipelines and storage tanks, among others) have been shown to be effective for control of L. pneumophila in water supplies. In addition, there are well documented management guidelines available for the control of the organism in drinking water distribution systems. By comparison, management of risks for Mycobacteria from water are less clear than for L. pneumophila. Treatment of M. avium is difficult due to its resistance to disinfection, the tendency to form clumps, and attachment to surfaces in biofilms. Additionally, there are no guidelines for management of M. avium in drinking water, and one risk assessment study suggested a low risk of infection. The role of tap water in the transmission of the other opportunistic pathogens is less clear and, in many cases, actions to manage L. pneumophila (e.g., maintenance of a disinfectant residual, flushing, cleaning of storage tanks, etc.) will also be beneficial in helping to manage these organisms as well.

Identification rate of Legionella species in non-purulent sputum culture is comparable to that in purulent sputum culture in Legionella pneumonia

Many Legionella pneumonia patients do not produce sputum, and it is unknown whether purulent sputum is required for the identification of Legionella species. This study aimed to evaluate the identification rate of Legionella species based on sputum quality and the factors predictive of Legionella infection. This study included Legionella pneumonia patients at Kurashiki Central Hospital from November 2000 to December 2022. Sputum quality, based on gram staining, was classified as the following: Geckler 1/2, 3/6 and 4/5. Geckler 4/5 was defined as purulent sputum. The sputa of 104 of 124 Legionella pneumonia patients were cultured. Fifty-four patients (51.9%) were identified with Legionella species, most of which were Legionella pneumophila serogroup 1 (81.5%). The identification rates of Legionella species according to sputum quality were 57.1% (16/28) in Geckler 1/2 sputum, 50.0% (34/68) in Geckler 3/6 sputum, and 50.0% (4/8) in Geckler 4/5 sputum, which were not significantly different (P = 0.86). On multivariate analysis, pre-culture treatment with anti-Legionella antimicrobials (odds ratio [OR] 0.26, 95% confidence interval [CI] 0.06-0.91), Pneumonia Severity Index class ≥IV (OR 2.57 [95% CI 1.02-6.71]), and intensive care unit admission (OR 3.08, 95% CI 1.06-10.09) correlated with the ability to identify Legionella species, but sputum quality did not (OR 0.88, 95% CI 0.17-4.41). The identification rate of Legionella species in non-purulent sputum was similar to that in purulent sputum. For the diagnosis of Legionella pneumonia, sputum should be collected before administering anti-Legionella antibiotics and cultured regardless of sputum quality.

Severe Legionnaires' disease

BACKGROUND

Legionnaires' disease (LD) is a common but under-diagnosed cause of community-acquired pneumonia (CAP), although rapid detection of urine antigen testing (UAT) and advances in molecular testing have improved the diagnosis. LD entails intensive care unit (ICU) admission in almost one-third of cases, and the mortality rate ranges from 4% to 40%. This review aims to discuss recent advances in the study of this condition and to provide an update on the diagnosis, pathogenesis and management of severe LD.

RESULTS

The overall incidence of LD has increased worldwide in recent years due to the higher number of patients with risk factors, especially immunosuppression, and to improvements in diagnostic methods. Although LD is responsible for only around 5% of all-cause CAP, it is one of the three most common causes of CAP requiring ICU admission. Mortality in ICU patients, immunocompromised patients or patients with a nosocomial source of LD can reach 40% despite appropriate antimicrobial therapy. Regarding pathogenesis, no Legionella-specific virulence factors have been associated with severity; however, recent reports have found high pulmonary Legionella DNA loads, and impairments in immune response and lung microbiome in the most severe cases. The clinical picture includes severe lung injury requiring respiratory and/or hemodynamic support, extrapulmonary symptoms and non-specific laboratory findings. LD diagnostic methods have improved due to the broad use of UAT and the development of molecular methods allowing the detection of all Lp serogroups. Therapy is currently based on macrolides, quinolones, or a combination of the two, with prolonged treatment in severe cases.

CONCLUSIONS

Numerous factors influence the mortality rate of LD, such as ICU admission, the underlying immune status, and the nosocomial source of the infection. The host immune response (hyperinflammation and/or immunoparalysis) may also be associated with increased severity. Given that the incidence of LD is rising, studies on specific biomarkers of severity may be of great interest. Further assessments comparing different regimens and/or evaluating host-directed therapies are nowadays needed.

Correlation between bacterial microbiome and Legionella species in water from public bath facilities by 16S rRNA gene amplicon sequencing

Public bath facilities are a major source of Legionella infections in Japan. In this study, we performed 16S rRNA gene amplicon sequencing to characterize the bacterial community in bath and shower water from public bath facilities, along with chemical parameters, and investigated the effect of the bacterial microbiome on the presence of Legionella species. Although no significant difference in bacterial community richness was observed between bath and shower water samples, there was a remarkable difference in the bacterial community structure between them. Distance-based redundancy analysis revealed that several factors (free residual chlorine, pH, and conductivity) were correlated with the bacterial community in bath water. The most abundant bacterial genera in the samples were Pseudomonas (13.7%) in bath water and Phreatobacter (13.6%) in shower water, as indicated by the taxonomic composition, and the dominant bacteria differed between these environmental samples. Legionella pneumophila was the most frequently detected Legionella species, with additional 15 other Legionella species detected in water samples. In Legionella-positive water samples, several unassigned and uncultured bacteria were enriched together. In addition, the co-occurrence network showed that Legionella was strongly interconnected with two uncultured bacteria. Corynebacterium and Sphingomonas negatively correlated with Legionella species. The present study reveals the ecology of Legionella species, especially their interactions with other bacteria that are poorly understood to date.

IMPORTANCE

Public bath facilities are major sources of sporadic cases and outbreaks of Legionella infections. Recently, 16S rRNA gene amplicon sequencing has been used to analyze bacterial characteristics in various water samples from both artificial and natural environments, with a particular focus on Legionella bacterial species. However, the relationship between the bacterial community and Legionella species in the water from public bath facilities remains unclear. In terms of hygiene management, it is important to reduce the growth of Legionella species by disinfecting the water in public bath facilities. Our findings contribute to the establishment of appropriate hygiene management practices and provide a basis for understanding the potential health effects of using bath and shower water available in public bath facilities.

A Case of Legionella pneumophila Serogroup 13 Pneumonia Based on the Detection of Serogroup-Specific Genes in Culture-Negative Sputum

Legionella pneumophila serogroup (SG) 1, the main cause of Legionnaires' disease, can be diagnosed using urinary antigen testing kits. However, lower respiratory tract specimen cultures are required to identify L. pneumophila SG 2-15. We attempted to detect L. pneumophila SG-specific genes in a culture-negative sputum specimen from a patient with pneumonia who was suspected to have Legionnaires' disease. Two multiplex PCR methods targeting L. pneumophila were modified and amplicons considered to be SG13 specific were detected. Direct sequencing revealed that the amplicons were identical to the nucleotide sequence of L. pneumophila SG13. Based on the presentation and clinical course (fever, muscle pain, disturbance of consciousness, high C-reactive protein titer, rhabdomyolysis, hypophosphatemia, and symptomatic improvement with levofloxacin treatment), in combination with the detection of L. pneumophila SG-specific genes, we suspected L. pneumophila SG13 pneumonia. L. pneumophila non-SG1 pneumonia is thought to be underestimated because of its difficult laboratory diagnosis. The modified multiplex PCR system for lower respiratory tract specimens revealed in this study is likely to improve the diagnosis of Legionnaires' disease caused by L. pneumophila SG13 and other SGs.

Legionella-induced dysarthria and rhabdomyolysis with acute renal failure achieving recovery

Key Clinical Message

Legionnaires' disease, often presenting as pneumonia, can uncommonly manifest with extrapulmonary symptoms such as cerebellar involvement and rhabdomyolysis. This case emphasizes the successful resolution of dysarthria and renal dysfunction with prompt Legionella treatment, underscoring the importance of vigilance for diverse manifestations in Legionella infections.

Abstract

Legionnaires' disease usually presents with pneumonia and a few extrapulmonary manifestations, such as neurological, musculoskeletal, and cutaneous manifestations. However, cerebellar involvement and rhabdomyolysis as an association with Legionella are not frequently encountered. We present a case of Legionella-induced rhabdomyolysis requiring hemodialysis and dysarthria that resolved with Legionella treatment.

Multiple pulmonary cavities in an immunocompetent patient: a case report and literature review

Legionella pneumonia (LP) is a relatively uncommon yet well-known type of atypical community-acquired pneumonia (CAP). It is characterized by a rapid progression to severe pneumonia and can be easily misdiagnosed. In most patients, chest computed tomography (CT) showed patchy infiltration, which may progress to lobar infiltration or even lobar consolidation. While pulmonary cavities are commonly observed in immunocompromised patients with LP, they are considered rare in immunocompetent individuals. Herein, we present a case of LP in an immunocompetent patient with multiple cavities in both lungs. Pathogen detection was performed using metagenomic next-generation sequencing (mNGS). This case highlights the unusual radiographic presentation of LP in an immunocompetent patient and emphasizes the importance of considering LP as a possible diagnosis in patients with pulmonary cavities, regardless of their immune status. Furthermore, the timely utilization of mNGS is crucial for early pathogen identification, as it provides multiple benefits in enhancing the diagnosis and prognosis of LP patients.

The LysR-type transcriptional regulator LelA co-regulates various effectors in different Legionella species

The intracellular pathogen Legionella pneumophila translocates more than 300 effector proteins into its host cells. The expression levels of the genes encoding these effectors are orchestrated by an intricate regulatory network. Here, we introduce LelA, the first L. pneumophila LysR-type transcriptional regulator of effectors. Through bioinformatic and experimental analyses, we identified the LelA target regulatory element and demonstrated that it directly activates the expression of three L. pneumophila effectors (legL7, legL6, and legU1). We further found that the gene encoding LelA is positively regulated by the RpoS sigma factor, thus linking it to the known effector regulatory network. Examination of other species throughout the Legionella genus revealed that this regulatory element is found upstream of 34 genes encoding validated effectors, putative effectors, and hypothetical proteins. Moreover, ten of these genes were examined and found to be activated by the L. pneumophila LelA as well as by their orthologs in the corresponding species. LelA represents a novel type of Legionella effector regulator, which coordinates the expression of both adjacently and distantly located effector-encoding genes, thus forming small groups of co-regulated effectors.

Legionella pneumonia in hospitalized adults with respiratory failure: Quinolones or macrolides?

The optimal antimicrobial regimen for adults with respiratory failure due to Legionella pneumonia remains controversial. A systematic review was performed to assess the impact on outcomes comparing quinolones versus macrolides. A literature search was conducted in PubMed, Cochrane Library and Web of Science between 2012 and 2022. It yielded 124 potentially articles and ten observational studies met the inclusion criteria. A total of 4271 patients were included, 2879 (67 %) were male. A total of 1797 (42 %) subjects required intensive care unit (ICU) admission and 942 (52 %) mechanical ventilation. Fluoroquinolones and macrolides alone were administered in 1397 (33 %) and 1500 (35 %) subjects, respectively; combined therapy in 204 (4.8 %) patients. Overall mortality was 7.4 % (319 patients), with no difference between antibiotics. When data from the three studies with severe pneumonia were pooled together, mortality with fluoroquinolones alone was statistically superior to macrolides alone (72.8 % vs 30.8 %, p value 0.027). Hospital length of stay and complications were comparable. Our findings suggest that macrolides and quinolones were comparable for hospitalized Legionella pneumonia. However, in severe pneumonia, a randomized clinical trial is an unmet clinical need. PROSPERO registration number: CRD42023389308.

An Epidemiological Study on Legionnaires' Disease in Gyeonggi Province, Korea: Occurrence, Infection Routes, and Risk Factors for Mortality (2016-2022)

Background and Objectives: Legionnaires' disease (LD) is an acute respiratory disease with increasing annual numbers of reported domestic and global cases. This study aimed to establish foundational data for the prevention and control of LD by investigating the occurrence and infection routes of reported and suspected cases of LD in Gyeonggi Province, Korea, from January 2016 to December 2022, and by and analyzing the risk factors for death. Materials and Methods: A sex-and-age standardization was performed on LD patients and suspected cases reported in Gyeonggi Province. The monthly average number of confirmed cases was visualized using graphs, and a survival analysis was performed using Kaplan-Meier survival curves. The mortality risk ratio was estimated using the Cox proportional hazards model. Results: The incidence of LD in Gyeonggi Province mirrored the national trend, peaking in July with the highest number of confirmed and suspected cases. While there was no significant difference in survival rates by age, the survival rate was higher for suspected cases when analyzed separately. Comparing the death ratio by infection route, nosocomial infections showed the highest death ratio, and intensive care unit (ICU) admission and the presence of coinfections were significantly correlated with mortality. Factors such as nosocomial infection, admission within 1 to 3 days following diagnosis, and the development of complications were factors contributing to a higher risk of death. Conclusions: The general characteristics of patients with LD were similar to those suggested by previous studies. The proportion of community-acquired infections was lower than in previous studies, but the length of hospital stay was similar for survivors and the deceased, and the mortality rate within 30 days after diagnosis was higher for nosocomial infections. In conclusion, nosocomial infection, a period of up to 3 days from admission to diagnosis, and complications were significantly related to the mortality rate of LD.

Venovenous extracorporeal membrane oxygenation after cardiac arrest for acute respiratory distress syndrome caused by Legionella: a case report

BACKGROUND

Legionella remains underdiagnosed in the intensive care unit and can progress to acute respiratory distress syndrome (ARDS), multiorgan failure and death. In severe cases, venovenous extracorporeal membrane oxygenation (VV-ECMO) allows time for resolution of disease with Legionella-targeted therapy. VV-ECMO outcomes for Legionella are favorable with reported survival greater than 70%. Rapid molecular polymerase chain reaction (PCR) testing of the lower respiratory tract aids in diagnosing Legionella with high sensitivity and specificity. We present a unique case of a patient with a positive COVID-19 test and ARDS who suffered a cardiac arrest. The patient was subsequently cannulated for VV-ECMO, and after lower respiratory tract PCR testing, Legionella was determined to be the cause. She was successfully treated and decannulated from VV-ECMO after eight days.

CASE PRESENTATION

A 53-year-old female presented with one week of dyspnea and a positive COVID-19 test. She was hypoxemic, hypotensive and had bilateral infiltrates on imaging. She received supplemental oxygen, intravenous fluids, vasopressors, broad spectrum antibiotics, and was transferred to a tertiary care center. She developed progressive hypoxemia and suffered a cardiac arrest, requiring ten minutes of CPR and endotracheal intubation to achieve return of spontaneous circulation. Despite mechanical ventilation and paralysis, she developed refractory hypoxemia and was cannulated for VV-ECMO. Dexamethasone and remdesivir were given for presumed COVID-19. Bronchoscopy with bronchoalveolar lavage (BAL) performed with PCR testing was positive for Legionella pneumophila and negative for COVID-19. Steroids and remdesivir were discontinued and she was treated with azithromycin. Her lung compliance improved, and she was decannulated after eight days on VV-ECMO. She was discharged home on hospital day 16 breathing room air and neurologically intact.

CONCLUSIONS

This case illustrates the utility of rapid PCR testing to diagnose Legionella in patients with respiratory failure and the early use of VV-ECMO in patients with refractory hypoxemia secondary to Legionella infection. Moreover, many patients encountered in the ICU may have prior COVID-19 immunity, and though a positive COVID-19 test may be present, further investigation with lower respiratory tract PCR testing may provide alternative diagnoses. Patients with ARDS should undergo Legionella-specific testing, and if Legionella is determined to be the causative organism, early VV-ECMO should be considered in patients with refractory hypoxemia given reported high survival rates.

Safeguarding drinking water: A brief insight on characteristics, treatments and risk assessment of contamination

Water pollution stands as a critical worldwide concern, bearing extensive repercussions that extend to human health and the natural ecosystem. The sources of water pollution can be diverse, arising from natural processes and human activities and the pollutants may range from chemical and biological agents to physical and radiological contaminants. The contamination of water disrupts the natural functioning of the system, leading to both immediate and prolonged health problems. Various technologies and procedures, ranging from conventional to advanced, have been developed to eliminate water impurities, with the choice depending on the type and level of contamination. Assessing risks is a crucial element in guaranteeing the safety of drinking water. Till now, research is continuing the removal of contaminates for the sake of supplying safe drinking water. The study examined physical, inorganic, organic, biological and radiological contaminants in drinking water. It looked at where these contaminants come from, their characteristics, the impact they have and successful methods used in real-world situations to clean the contaminated water. Risk assessment methodologies associated with the use of unsafe drinking water as future directives are also taken into consideration in the present study for the benefit of public concern. The manuscript introduces a comprehensive study on water pollution, focusing on assessing and mitigating risks associated with physical, inorganic, organic, biological and radiological contaminants in drinking water, with a novel emphasis on future directives and sustainable solutions for public safety.

Estimating the burden of illness caused by domestic waterborne Legionnaires' disease in Canada: 2015-2019

Legionellosis is a disease caused by the bacterium Legionella that most commonly presents as Legionnaires' disease (LD), a severe form of pneumonia. From 2015 to 2019, an average of 438 LD cases per year were reported in Canada. However, it is believed that the actual number of cases is much higher, since LD may be underdiagnosed and underreported. The purpose of this study was to develop an estimate of the true incidence of illnesses, hospitalizations, and deaths associated with LD in Canada. Values were derived using a stochastic model, based on Canadian surveillance data from 2015 to 2019, which were scaled up to account for underdiagnosis and underreporting. Overall, there were an estimated 1,113 (90% CrI: 737-1,730) illnesses, 1,008 (90% CrI: 271-2,244) hospitalizations, and 34 (90% CrI: 4-86) deaths due to domestically acquired waterborne LD annually in Canada from 2015 to 2019. It was further estimated that only 36% of illnesses and 39% of hospitalizations and deaths were captured in surveillance, and that 22% of illnesses were caused by Legionella serogroups and species other than Legionella pneumophila serogroup 1 (non-Lp1). This study highlights the true burden and areas for improvement in Canada's surveillance and detection of LD.

Assessing the Impacts of Lead Corrosion Control on the Microbial Ecology and Abundance of Drinking-Water-Associated Pathogens in a Full-Scale Drinking Water Distribution System

Increases in phosphate availability in drinking water distribution systems (DWDSs) from the use of phosphate-based corrosion control strategies may result in nutrient and microbial community composition shifts in the DWDS. This study assessed the year-long impacts of full-scale DWDS orthophosphate addition on both the microbial ecology and density of drinking-water-associated pathogens that infect the immunocompromised (DWPIs). Using 16S rRNA gene amplicon sequencing and droplet digital PCR, drinking water microbial community composition and DWPI density were examined. Microbial community composition analysis suggested significant compositional changes after the orthophosphate addition. Significant increases in total bacterial density were observed after orthophosphate addition, likely driven by a 2 log 10 increase in nontuberculous mycobacteria (NTM). Linear effect models confirmed the importance of phosphate addition with phosphorus concentration explaining 17% and 12% of the variance in NTM and L. pneumophila density, respectively. To elucidate the impact of phosphate on NTM aggregation, a comparison of planktonic and aggregate fractions of NTM cultures grown at varying phosphate concentrations was conducted. Aggregation assay results suggested that higher phosphate concentrations cause more disaggregation, and the interaction between phosphate and NTM is species specific. This work reveals new insight into the consequences of orthophosphate application on the DWDS microbiome and highlights the importance of proactively monitoring the DWDS for DWPIs.

Therapeutical strategies in cavitary legionnaires' disease, two cases from the field and a systematic review

BACKGROUND

Legionnaires' Disease (LD) rarely evolves into pulmonary abscesses. The current systematic review has been designed to explore therapeutical strategies in pulmonary cavitary LD.

METHODS

A research strategy was developed and applied to the databases Embase, Pubmed, and Web of Science from the 1st of January 2000 to the 1st of November 2022. Original articles, case series, case reports, and guidelines written in English, French, German, Italian, and Dutch were considered. Furthermore, medical records of patients treated at the University Hospital UZ Brussel for LD cavitary pneumonia, between the 1st of January 2016 to the 1st of January 2022, were reviewed.

RESULTS

Two patients were found by the UZ Brussel's medical records investigation. Through the literature review, 23 reports describing 29 patients, and seven guidelines were identified. The overall evidence level was low.

RESULT OF SYNTHESIS (CASE REPORTS)

The median age was 48 years and 65% were male. A polymicrobial infection was detected in 11 patients (44%) with other aerobic bacteria being the most commonly found. At diagnosis, 52% of patients received combination therapy, and fluoroquinolones were the preferred antimicrobial class. Anaerobic coverage was neglected in 33% of patients.

RESULT OF SYNTHESIS (GUIDELINES)

Three guidelines favor monotherapy with fluoroquinolones or macrolides, while one suggested an antimicrobial combination in case of severe LD. Four guidelines recommended anaerobic coverage in case of lung abscesses.

CONCLUSION

To date, the evidence supporting cavitary LD treatment is low. Monotherapy lowers toxicity and might be as effective as combination therapy. Finally, anaerobes should not be neglected.

A meta-analysis of Legionella pneumophila contamination in hospital water systems

BACKGROUND

Legionella pneumophila is a common cause of community-acquired pneumonia. We aimed to determine the pooled rates of L pneumophila contamination in the water environment of the hospital.

METHODS

We searched PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure, WangFang and Science Direct, The Cochrane Library, and Science Finder, for relevant studies published until December 2022. Stata 16.0 software was used to determine pooled contamination rates, publication bias, and subgroup analysis.

RESULTS

Forty-eight eligible articles with a total of 23,640 samples of water were evaluated, and the prevalence of L pneumophila was 41.6%. The results of the subgroup analysis showed that the pollution rate of L pneumophila in hot water (47.6%) was higher than that in other water bodies. The rates of L pneumophila contamination were higher in developed countries (45.2%), culture methods (42.3%), published between 1985 and 2015 (42.9%), and studies with a sample size of less than 100 (53.0%).

CONCLUSIONS

L pneumophila contamination in medical institutions is still very serious and should be paid attention to, especially in developed countries and hot water tanks.

A 38-Year-Old Man With Persistent Fever and Progressive Shortness of Breath

CASE PRESENTATION

A 38-year-old man presented to the ED complaining of persistent fever, dry cough, shortness of breath, and diarrhea for 7 days. He reported a history of OSA with inconsistent CPAP use, tobacco use of less than one pack per day, and daily e-cigarette use or "vaping." He denied any contact with ill people or recent travels and was up to date on recommended COVID-19 vaccinations. Prior to his presentation, he had been seen at an urgent care facility twice in the last week, where he was given IV fluids and prescribed steroids without improvement.

Prevalence and genetic distribution of Legionella spp. in public bath facilities in Kobe City, Japan

Legionella is an important waterborne pathogen that causes legionellosis. Public baths are considered the primary cause of legionellosis infection in Japan. We investigated the prevalence and genetic distribution of 338 Legionella spp. isolates from 81 public bath facilities, including 35 hot springs and 46 other facilities, through annual periodic surveillance in Kobe, Japan, from 2016 to 2021. In addition, the genotypes of nine clinical strains of unknown infectious source from the same period were compared to those of bathwater isolates. We elucidated the differences in the distribution of Legionella species, serogroups, and genotypes between hot springs and other public baths. Legionella israelensis, L. londiniensis, and L. micdadei colonized hot springs along with L. pneumophila. The minimum spanning tree analysis based on multiple-locus variable number tandem repeat analysis (MLVA) also identified four major clonal complexes (CCs) in L. pneumophila SG1 and found that CC1 of the four CCs is a specific novel genotype with the lag-1 gene in hot springs. The same MLVA genotypes and sequence types as those of the clinical strains were not present among the strains isolated from bath water. Thus, our surveillance is useful for estimating the sources of legionellosis infection in Japan and developing prevention strategies.

L. pneumophila resists its self-harming metabolite HGA via secreted factors and collective peroxide scavenging

IMPORTANCE

Before environmental opportunistic pathogens can infect humans, they must first successfully grow and compete with other microbes in nature, often via secreted antimicrobials. We previously discovered that the bacterium Legionella pneumophila, the causative agent of Legionnaires' disease, can compete with other microbes via a secreted molecule called HGA. Curiously, L. pneumophila strains that produce HGA is not wholly immune to its toxicity, making it a mystery how these bacteria can withstand the "friendly fire" of potentially self-targeting antimicrobials during inter-bacterial battles. Here, we identify several strategies that allow the high-density bacterial populations that secrete HGA to tolerate its effects. Our study clarifies how HGA works. It also points to some explanations of why it is difficult to disinfect L. pneumophila from the built environment and prevent disease outbreaks.

Assessing residential activity in a home plumbing system simulator: monitoring the occurrence and relationship of major opportunistic pathogens and phagocytic amoebas

Opportunistic premise plumbing pathogens (OPPPs) have been detected in buildings' plumbing systems causing waterborne disease outbreaks in the United States. In this study, we monitored the occurrence of OPPPs along with free-living amoeba (FLA) and investigated the effects of residential activities in a simulated home plumbing system (HPS). Water samples were collected from various locations in the HPS and analyzed for three major OPPPs: Legionella pneumophila, nontuberculous mycobacterial species (e.g., Mycobacterium avium, M. intracellulare, and M. abscessus), and Pseudomonas aeruginosa along with two groups of amoebas (Acanthamoeba and Vermamoeba vermiformis). A metagenomic approach was also used to further characterize the microbial communities. Results show that the microbial community is highly diverse with evidence of spatial and temporal structuring influenced by environmental conditions. L. pneumophila was the most prevalent pathogen (86% of samples), followed by M. intracellulare (66%) and P. aeruginosa (21%). Interestingly, M. avium and M. abscessus were not detected in any samples. The data revealed a relatively low prevalence of Acanthamoeba spp. (4%), while V. vermiformis was widely detected (81%) across all the sampling locations within the HPS. Locations with a high concentration of L. pneumophila and M. intracellulare coincided with the highest detection of V. vermiformis, suggesting the potential growth of both populations within FLA and additional protection in drinking water. After a period of stagnation lasting at least 2-weeks, the concentrations of OPPPs and amoeba immediately increased and then decreased gradually back to the baseline. Furthermore, monitoring the microbial population after drainage of the hot water tank and partial drainage of the entire HPS demonstrated no significant mitigation of the selected OPPPs. This study demonstrates that these organisms can adjust to their environment during such events and may survive in biofilms and/or grow within FLA, protecting them from stressors in the supplied water.

Legionnaires' disease in Switzerland: rationale and study protocol of a prospective national case-control and molecular source attribution study (SwissLEGIO)

Switzerland has one of the highest annual Legionnaires' disease (LD) notification rates in Europe (7.8 cases/100,000 population in 2021). The main sources of infection and the cause for this high rate remain largely unknown. This hampers the implementation of targeted Legionella spp. control efforts. The SwissLEGIO national case-control and molecular source attribution study investigates risk factors and infection sources for community-acquired LD in Switzerland. Over the duration of one year, the study is recruiting 205 newly diagnosed LD patients through a network of 20 university and cantonal hospitals. Healthy controls matched for age, sex, and residence at district level are recruited from the general population. Risk factors for LD are assessed in questionnaire-based interviews. Clinical and environmental Legionella spp. isolates are compared using whole genome sequencing (WGS). Direct comparison of sero- and sequence types (ST), core genome multilocus sequencing types (cgMLST), and single nucleotide polymorphisms (SNPs) between clinical and environmental isolates are used to investigate the infection sources and the prevalence and virulence of different Legionella spp. strains detected across Switzerland. The SwissLEGIO study innovates in combining case-control and molecular typing approaches for source attribution on a national level outside an outbreak setting. The study provides a unique platform for national Legionellosis and Legionella research and is conducted in an inter- and transdisciplinary, co-production approach involving various national governmental and national research stakeholders.

Development of heat-shock resistance in Legionella pneumophila modeled by experimental evolution

Because it can grow in buildings with complex hot water distribution systems (HWDS), healthcare facilities recognize the waterborne bacterium Legionella pneumophila as a major nosocomial infection threat and often try to clear the systems with a pasteurization process known as superheat-and-flush. After this treatment, many facilities find that the contaminating populations slowly recover, suggesting the possibility of in situ evolution favoring increased survival in high-temperature conditions. To mimic this process in a controlled environment, an adaptive laboratory evolution model was used to select a wild-type strain of L. pneumophila for survival to transient exposures to temperatures characteristic of routine hot water use or failed pasteurization processes in HWDS. Over their evolution, these populations became insensitive to exposure to 55°C and developed the ability to survive short exposures to 59°C heat shock. Heat-adapted lineages maintained a higher expression of heat-shock genes during low-temperature incubation in freshwater, suggesting a pre-adaptation to heat stress. Although there were distinct mutation profiles in each of the heat-adapted lineages, each acquired multiple mutations in the DnaJ/DnaK/ClpB disaggregase complex, as well as mutations in chaperone htpG and protease clpX. These mutations were specific to heat-shock survival and were not seen in control lineages included in the experimental model without exposure to heat shock. This study supports in situ observations of adaptation to heat stress and demonstrates the potential of L. pneumophila to develop resistance to control measures. IMPORTANCE As a bacterium that thrives in warm water ecosystems, Legionella pneumophila is a key factor motivating regulations on hot water systems. Two major measures to control Legionella are high circulating temperatures intended to curtail growth and the use of superheat-and-flush pasteurization processes to eliminate established populations. Facilities often suffer recolonization of their hot water systems; hospitals are particularly at risk due to the severe nosocomial pneumoniae caused by Legionella. To understand these long-term survivors, we have used an adaptive laboratory evolution model to replicate this process. We find major differences between the mutational profiles of heat-adapted and heat-naïve L. pneumophila populations including mutations in major heat-shock genes like chaperones and proteases. This model demonstrates that well-validated treatment protocols are needed to clear contaminated systems and-in an analog to antibiotic resistance-the importance of complete eradication of the resident population to prevent selection for more persistent bacteria.

Early discontinuation of combination antibiotic therapy in severe community-acquired pneumonia: a retrospective cohort study

BACKGROUND

Severe community-acquired pneumonia (SCAP) is commonly treated with an empiric combination therapy, including a macrolide, or a quinolone and a β-lactam. However, the risk of Legionella pneumonia may lead to a prolonged combination therapy even after negative urinary antigen tests (UAT).

METHODS

We conducted a retrospective cohort study in a French intensive care unit (ICU) over 6 years and included all the patients admitted with documented SCAP. All patients received an empirical combination therapy with a β-lactam plus a macrolide or quinolone, and a Legionella UAT was performed. Macrolide or quinolone were discontinued when the UAT was confirmed negative. We examined the clinical and epidemiological features of SCAP and analysed the independent factors associated with ICU mortality.

RESULTS

Among the 856 patients with documented SCAP, 26 patients had atypical pneumonia: 18 Legionella pneumophila (LP) serogroup 1, 3 Mycoplasma pneumonia (MP), and 5 Chlamydia psittaci (CP). UAT diagnosed 16 (89%) Legionella pneumonia and PCR confirmed the diagnosis for the other atypical pneumonia. No atypical pneumonia was found by culture only. Type of pathogen was not associated with a higher ICU mortality in the multivariate analysis.

CONCLUSION

Legionella pneumophila UAT proved to be highly effective in detecting the majority of cases, with only a negligible percentage of patients being missed, but is not sufficient to diagnose atypical pneumonia, and culture did not provide any supplementary information. These results suggest that the discontinuation of macrolides or quinolones may be a safe option when Legionella UAT is negative in countries with a low incidence of Legionella pneumonia.

Sde Proteins Coordinate Ubiquitin Utilization and Phosphoribosylation to Promote Establishment and Maintenance of the Legionella Replication Vacuole

The Legionella pneumophilaSde family of translocated proteins promote host tubular endoplasmic reticulum (ER) rearrangements that are tightly linked to phosphoribosyl-ubiquitin (pR-Ub) modification of Reticulon 4 (Rtn4). Sde proteins have two additional activities of unclear relevance to the infection process: K63 linkage-specific deubiquitination and phosphoribosyl modification of polyubiquitin (pR-Ub). We show here that the deubiquitination activity (DUB) stimulates ER rearrangements while pR-Ub protects the replication vacuole from cytosolic surveillance by autophagy. Loss of DUB activity was tightly linked to lowered pR-Ub modification of Rtn4, consistent with the DUB activity fueling the production of pR-Ub-Rtn4. In parallel, phosphoribosyl modification of polyUb, in a region of the protein known as the isoleucine patch, caused an absolute block in binding by the autophagy adapter p62. An inability of Sde mutants to modify polyUb resulted in immediate p62 association, a critical precursor to autophagic attack. The ability of Sde WT to block p62 association decayed quickly after bacterial infection, as predicted by the presence of previously characterized L. pneumophila effectors that inactivate Sde and remove polyUb. In sum, these results show that the accessory Sde activities act to stimulate ER rearrangements and protect from host innate immune sensing in a temporal fashion.

Impacts of weather and air pollution on Legionnaires' disease in Switzerland: A national case-crossover study

BACKGROUND

The number of reported cases of Legionnaires' disease (LD) has risen markedly in Switzerland (6.5/100,000 inhabitants in 2021) and abroad over the last decade. Legionella, the causative agent of LD, are ubiquitous in the environment. Therefore, environmental changes can affect the incidence of LD, for example by increasing bacterial concentrations in the environment or by facilitating transmission.

OBJECTIVES

The aim of this study is to understand the environmental determinants, in particular weather conditions, for the regional and seasonal distribution of LD in Switzerland.

METHODS

We conducted a series of analyses based on the Swiss LD notification data from 2017 to 2021. First, we used a descriptive and hotspot analysis to map LD cases and identify regional clusters. Second, we applied an ecological model to identify environmental determinants on case frequency at the district level. Third, we applied a case-crossover design using distributed lag non-linear models to identify short-term associations between seven weather variables and LD occurrence. Lastly, we performed a sensitivity analysis for the case-crossover design including NO2 levels available for the year 2019.

RESULTS

Canton Ticino in southern Switzerland was identified as a hotspot in the cluster analysis, with a standardised notification rate of 14.3 cases/100,000 inhabitants (CI: 12.6, 16.0). The strongest association with LD frequency in the ecological model was found for large-scale factors such as weather and air pollution. The case-crossover study confirmed the strong association of elevated daily mean temperature (OR 2.83; CI: 1.70, 4.70) and mean daily vapour pressure (OR: 1.52, CI: 1.15, 2.01) 6-14 days before LD occurrence.

DISCUSSION

Our analyses showed an influence of weather with a specific temporal pattern before the onset of LD, which may provide insights into the effect mechanism. The relationship between air pollution and LD and the interplay with weather should be further investigated.

[Respiratory infections: Additional transmission-based precautions in healthcare facilities]

INTRODUCTION

In health care, measures against cross-transmission of microorganisms are codified by standard precautions, and if necessary, they are supplemented by additional precautions.

STATE OF THE ART

Several factors impact transmission of microorganisms via the respiratory route: size and quantity of the emitted particles, environmental conditions, nature and pathogenicity of the microorganisms, and degree of host receptivity. While some microorganisms necessitate additional airborne or droplet precautions, others do not.

PROSPECTS

For most microorganisms, transmission patterns are well-understood and transmission-based precautions are well-established. For others, measures to prevent cross-transmission in healthcare facilities remain under discussion.

CONCLUSIONS

Standard precautions are essential to the prevention of microorganism transmission. Understanding of the modalities of microorganism transmission is essential to implementation of additional transmission-based precautions, particularly in view of opting for appropriate respiratory protection.

Legionella pneumophila Rhizoferrin Promotes Bacterial Biofilm Formation and Growth within Amoebae and Macrophages

Previously, we showed that Legionella pneumophila secretes rhizoferrin, a polycarboxylate siderophore that promotes bacterial growth in iron-deplete media and the murine lung. Yet, past studies failed to identify a role for the rhizoferrin biosynthetic gene (lbtA) in L. pneumophila infection of host cells, suggesting the siderophore's importance was solely linked to extracellular survival. To test the possibility that rhizoferrin's relevance to intracellular infection was missed due to functional redundancy with the ferrous iron transport (FeoB) pathway, we characterized a new mutant lacking both lbtA and feoB. This mutant was highly impaired for growth on bacteriological media that were only modestly depleted of iron, confirming that rhizoferrin-mediated ferric iron uptake and FeoB-mediated ferrous iron uptake are critical for iron acquisition. The lbtA feoB mutant, but not its lbtA-containing complement, was also highly defective for biofilm formation on plastic surfaces, demonstrating a new role for the L. pneumophila siderophore in extracellular survival. Finally, the lbtA feoB mutant, but not its complement containing lbtA, proved to be greatly impaired for growth in Acanthamoeba castellanii, Vermamoeba vermiformis, and human U937 cell macrophages, revealing that rhizoferrin does promote intracellular infection by L. pneumophila. Moreover, the application of purified rhizoferrin triggered cytokine production from the U937 cells. Rhizoferrin-associated genes were fully conserved across the many sequenced strains of L. pneumophila examined but were variably present among strains from the other species of Legionella. Outside of Legionella, the closest match to the L. pneumophila rhizoferrin genes was in Aquicella siphonis, another facultative intracellular parasite of amoebae.

Waterborne Infectious Diseases Associated with Exposure to Tropical Cyclonic Storms, United States, 1996-2018

In the United States, tropical cyclones cause destructive flooding that can lead to adverse health outcomes. Storm-driven flooding contaminates environmental, recreational, and drinking water sources, but few studies have examined effects on specific infections over time. We used 23 years of exposure and case data to assess the effects of tropical cyclones on 6 waterborne diseases in a conditional quasi-Poisson model. We separately defined storm exposure for windspeed, rainfall, and proximity to the storm track. Exposure to storm-related rainfall was associated with a 48% (95% CI 27%-69%) increase in Shiga toxin-producing Escherichia coli infections 1 week after storms and a 42% (95% CI 22%-62%) in increase Legionnaires' disease 2 weeks after storms. Cryptosporidiosis cases increased 52% (95% CI 42%-62%) during storm weeks but declined over ensuing weeks. Cyclones are a risk to public health that will likely become more serious with climate change and aging water infrastructure systems.

Trends of legionellosis reported in Jeju Province, Republic of Korea, 2015-2022

BACKGROUND

The number of reported cases of Legionnaires' disease (LD) in the Republic of Korea surged nationally in 2016; however, in 2022, this number was higher in Jeju Province than the previous national peak. A descriptive epidemiological study was conducted to analyze trends in the incidence of reported LD cases in Jeju Island from 2015 to 2022.

METHODS

The data for this study were obtained from case reports submitted to the Korea Disease Control and Prevention Agency through its Disease and Health Integrated Management System. The selection criteria were cases or suspected cases of LD reported among Jeju residents between 2015 and 2022. The 95% confidence interval of the crude incidence rate was calculated using the Poisson distribution.

RESULTS

Since 2020, the incidence rate of LD in Jeju has risen sharply, showing a statistically significant difference from the national incidence rate. A particular medical institution in Jeju reported a significant number of LD cases. Screening with the urine antigen test (UAT) also increased significantly.

CONCLUSION

Our findings indicate that the rapid increase in cases of LD in Jeju Province since 2020 was due to the characteristics of medical-care use among Jeju residents, which were focused on a specific medical institution. According to their clinical practice guidelines, this medical institution conducted UATs to screen patients suspected of pneumonia.

Legionellosis on the rise: A scoping review of sporadic, community-acquired incidence in the United States

Over the past two decades, the incidence of legionellosis has been steadily increasing in the United States though there is noclear explanation for the main factors driving the increase. While legionellosis is the leading cause of waterborne outbreaks in the US, most cases are sporadic and acquired in community settings where the environmental source is never identified. This scoping review aimed to summarise the drivers of infections in the USA and determine the magnitude of impact each potential driver may have. A total of 1,738 titles were screened, and 18 articles were identified that met the inclusion criteria. Strong evidence was found for precipitation as a major driver, and both temperature and relative humidity were found to be moderate drivers of incidence. Increased testing and improved diagnostic methods were classified as moderate drivers, and the ageing U.S. population was a minor driver of increasing incidence. Racial and socioeconomic inequities and water and housing infrastructure were found to be potential factors explaining the increasing incidence though they were largely understudied in the context of non-outbreak cases. Understanding the complex relationships between environmental, infrastructure, and population factors driving legionellosis incidence is important to optimise mitigation strategies and public policy.

Contamination of Hotel Water Distribution Systems by Legionella Species: Environmental Surveillance in Campania Region, South Italy

The COVID-19 pandemic period was marked by the absence or reduced circulation of some infectious diseases. Legionellosis may have been affected by the prevention measures adopted to counter COVID-19. Legionellosis is a form of pneumonia interstitial that is normally transmitted via aerosol-containing bacteria (genus Legionella), that could be present in contaminated water sources and is often associated with travel and with staying in hotels. In this work, the data of the environmental surveys carried out by ARPA Campania in accommodation facilities since 2019 were analyzed for a better understanding of the dispersion patterns of L. pneumophila associated with the environment and to evaluate the variation of the data during the pandemic period. The aim was to provide a better understanding of Legionella at different geographic scales and to define a predictive epidemiological method. Results: In 2019, the Legionella genus contaminated 37.7% of all tourist facilities evaluated. In 2020, the Legionella genus contaminated 44.4% of all tourist facilities evaluated. In 2021, the Legionella genus contaminated 54.2% of all tourist facilities evaluated. Conclusions: Legionella pneumophila was the most prevalent species in our community, serogroup 1 was the most frequently isolated and the most implicated risk factor of contamination was the temperature of water in circulation.