Genotypic and phenotypic profiling of 127 Legionella pneumophila strains: Insights into regional spread.

Given the recent global surge in Legionnaires' disease cases, the monitoring of Legionella pneumophila becomes increasingly crucial. Epidemiological cases often stem from local outbreaks rather than widespread dissemination, emphasizing the need to study the characteristics of this pathogen at a local level. This study focuses on isolates of L. pneumophila in the Italian region of Friuli Venezia Giulia to assess specific genotype and phenotype distribution over time and space. To this end, a total of 127 L. pneumophila strains isolated between 2005 and 2017 within national surveillance programs were analysed. Rep-PCR, RAPD, and Sau-PCR were used for genotypic characterization, while phenotypic characterization was conducted through fatty acids analysis. RAPD and Sau-PCR effectively assessed genetic characteristics, identifying different profiles for the isolates and excluding the presence of clones. Although Sau-PCR is rarely used to analyse this pathogen, it emerged as the most discriminatory technique. Phenotypically, hierarchical cluster analysis categorized strains into three groups based on varying membrane fatty acid percentages. However, both phenotypic and genotypic analyses revealed a ubiquitous profile distribution at a regional level. These results suggest an absence of correlations between strain profiles, geographical location, and isolation time, indicating instead high variability and strain dissemination within this region.

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 Diversity of Legionella pneumophila Isolates from Artificial Water Sources in Brazil.

Legionella pneumophila (Lp) is a Gram-negative bacterium found in natural and artificial aquatic environments and inhalation of contaminated aerosols can cause severe pneumonia known as Legionnaires' Disease (LD). In Brazil there is hardly any information about this pathogen, so we studied the genetic variation of forty Legionella spp. isolates obtained from hotels, malls, laboratories, retail centers, and companies after culturing in BCYE medium. These isolates were collected from various sources in nine Brazilian states. Molecular identification of the samples was carried out using Sequence-Based Typing (SBT), which consists of sequencing and analysis of seven genes (flaA, pilE, asd, mip, mompS, proA, and neuA) to define a Sequence Type (ST). Eleven STs were identified among 34/40 isolates, of which eight have been previously described (ST1, ST80, ST152, ST242, ST664, ST1185, ST1464, ST1642) and three were new STs (ST2960, ST2962, and ST2963), the former identified in five different cooling towers in the city of São Paulo. The ST1 that is widely distributed in many countries was also the most prevalent in this study. In addition, other STs that we observed have also been associated with legionellosis in other countries, reinforcing the potential of these isolates to cause LD in Brazil. Unfortunately, no human isolates could be characterized until presently, but our observations strongly suggest the need of surveillance implementation system and control measures of Legionella spp. in Brazil, including the use of more sensitive genotyping procedures besides ST.

Persistence of viable but nonculturable Legionella pneumophila state in hospital water systems: A hidden enemy?

There is little evidence of the long-term consequences of maintaining sanitary hot water at high temperatures on the persistence of Legionella in the plumbing system. The aims of this study were to describe the persistence and genotypic variability of L. pneumophila in a hospital building with two entirely independent hot water distribution systems, and to estimate the thermotolerance of the genotypic variants by studying the quantity of VBNC L. pneumophila. Eighty isolates from 55 water samples obtained between the years 2012-2017 were analyzed. All isolates correspond to L. pneumophila serogroup 6. The isolates were discriminated in four restriction patterns by pulsed-field gel electrophoresis. In one installation, pattern A + Aa predominated, accounting for 75.8 % of samples, while the other installation exhibited pattern B as the most frequent (81.8 % of samples; p < 0.001). The mean temperature of the isolates was: 52.6 °C (pattern A + Aa) and 55.0 °C (pattern B), being significantly different. Nine strains were selected as representative among patterns to study their thermotolerance by flow-cytometry after 24 h of thermic treatment. VBNC bacteria were detected in all samples. After thermic treatment at 50 °C, 52.0 % of bacteria had an intact membrane, and after 55 °C this percentage decreased to 23.1 %. Each pattern exhibited varying levels of thermotolerance. These findings indicate that the same hospital building can be colonized with different predominant types of Legionella if it has independent hot water installations. Maintaining a minimum temperature of 50 °C at distal points of the system would allow the survival of replicative L. pneumophila. However, the presence of Legionella in hospital water networks is underestimated if culture is considered as the standard method for Legionella detection, because VBNC do not grow on culture plates. This phenomenon can carry implications for the Legionella risk management plans in hospitals that adjust their control measures based on the microbiological surveillance of water.

Recurrence, Microevolution, and Spatiotemporal Dynamics of Legionella pneumophila Sequence Type 1905, Portugal, 2014-2022.

We investigated molecular evolution and spatiotemporal dynamics of atypical Legionella pneumophila serogroup 1 sequence type 1905 and determined its long-term persistence and linkage to human disease in dispersed locations, far beyond the large 2014 outbreak epicenter in Portugal. Our finding highlights the need for public health interventions to prevent further disease spread.

Evaluating Fourier-transform infrared spectroscopy with IR Biotyper as a faster and simpler method for investigating the sources of an outbreak of legionellosis.

Fourier-transform infrared (FTIR) spectroscopy using the IR Biotyper and core genome single nucleotide polymorphism (cgSNP) analysis were performed on 12 Legionella isolates associated with an outbreak at a spa house in Kanagawa Prefecture, Japan, and 3 non-outbreak isolates. The discriminative power of FTIR spectroscopy for 48-h incubation conditions of L. pneumophila in this outbreak was lower than cgSNP-based typing but higher than serogroup typing. FTIR spectroscopy could screen outbreak isolates from a group of genetically related isolates and may be useful as an initial typing method in Legionella outbreak investigations.

Population analysis of Legionella pneumophila reveals a basis for resistance to complement-mediated killing.

Legionella pneumophila is the most common cause of the severe respiratory infection known as Legionnaires' disease. However, the microorganism is typically a symbiont of free-living amoeba, and our understanding of the bacterial factors that determine human pathogenicity is limited. Here we carried out a population genomic study of 902 L. pneumophila isolates from human clinical and environmental samples to examine their genetic diversity, global distribution and the basis for human pathogenicity. We find that the capacity for human disease is representative of the breadth of species diversity although some clones are more commonly associated with clinical infections. We identified a single gene (lag-1) to be most strongly associated with clinical isolates. lag-1, which encodes an O-acetyltransferase for lipopolysaccharide modification, has been distributed horizontally across all major phylogenetic clades of L. pneumophila by frequent recent recombination events. The gene confers resistance to complement-mediated killing in human serum by inhibiting deposition of classical pathway molecules on the bacterial surface. Furthermore, acquisition of lag-1 inhibits complement-dependent phagocytosis by human neutrophils, and promoted survival in a mouse model of pulmonary legionellosis. Thus, our results reveal L. pneumophila genetic traits linked to disease and provide a molecular basis for resistance to complement-mediated killing.

Investigation of the presence of Legionella pneumophila in water samples from Erzurum and surrounding provinces in Turkey.

INTRODUCTION AND OBJECTIVE: Legionnaires' disease, which is a waterborne disease leading to pneumonia that can result in death, is one of the major health issues today. The study aims to carry out a three-year retrospective review of routine Legionella follow-up analyses in various samples taken mostly from hospitals in the province of Erzurum and nearby provinces, and to discover a the frequency of isolation of the agent and serogroups from each kind of media. MATERIAL AND METHODS: The study included a total of 2,025 water samples taken from hospitals, hotels, Turkish baths and shopping malls in Erzurum,and 13 nearby cities between 2016 and 2018. Samples were filtered by 0.45 µm-diameter membrane filter paper in the Public Health Laboratory of Erzurum and examined for L. pneumophila using culture method, according to the criteria set out in ISO 11731-2. RESULTS: The presence of L. pneumophila was found in 65 of the 2,025 water samples taken in hospitals, and in none of 40 samples taken in hotels, Turkish baths and shopping malls. L. pneumophila serogroup 2-14 was detected in 46 (70.8%) of 65 samples found positive, whereas L. pneumophila serogroup 1 was detected in 18 (27.7%). Furthermore, both the L. pneumophila serogroup 2-14 and L. pneumophila serogroup 1 were detected simultaneously in one example (1.5%). The first three samples indicate that the highest positivity rates were in hot water taps (11.6%), hot water tanks (6.1%) and shower heads (4.8%). CONCLUSIONS: The Prevalence rat of L. pneumophila was found to be quite low compared to other studies conducted in the western regions of Turkey. Legionella positivity was found to be higher in the hot water systems of hospitals and related points, compared to the other sample points.

Comparative study of Legiolert with ISO 11731-1998 standard method-conclusions from a Public Health Laboratory.

BACKGROUND: Legionella pneumophila (L. pneumophila) is responsible for 96% of Legionnaires' disease (LD) and 10% of all worldwide pneumonia cases. Legiolert™, a liquid culture method for most probable number (MPN) enumeration of L. pneumophila, was developed by IDEXX Laboratories. The method detects all serogroups of L. pneumophila in potable and non-potable water samples. OBJECTIVE: The goal of this study is to establish that Legiolert is a suitable alternative method to meet testing requirements in Spain for the enumeration of Legionella in water samples. METHODOLOGY: The laboratory analyzed 118 environmental water samples from the Barcelona region (56 potable and 62 non-potable) in parallel by the Standard method for detection and enumeration of Legionella (ISO 11731:1998) and by Legiolert. Comparison of the recovery of the alternative method (Legiolert) and the Standard was made using ISO 17994:2014 and McNemar's binomial test statistical methods. RESULTS: 44 samples were positive for Legionella (36 potable and 8 non-potable). Legiolert and the Standard method detected a similar percentage of positive samples, with Legiolert being slightly higher (31 vs 30%) and detecting higher concentrations of Legionella within the samples. ISO 17994:2014 analysis of the potable water samples found Legiolert was more sensitive than the Standard at detecting Legionella, even when complete Legionella species (L. spp.) results were considered for both methods. The two methods also demonstrated equivalent detection of L. spp. according to the McNemar's test. The comparison is significantly more in favor of Legiolert when only L. pneumophila results are considered. Each confirmation run with material extracted from positive Legiolert wells contained L. pneumophila, giving the method a specificity of 100%. Although statistical results for non-potable waters are not included because of the low number of samples, the two methods trended towards equivalence. CONCLUSIONS: Relative to the Standard method, Legiolert has a greater sensitivity and selectivity, and appears to have higher recovery for L. pneumophila, and equivalent recovery when L. spp. is included in the comparison. Legiolert also has high specificity. The procedural advantages of Legiolert allow laboratories to save on resources, costs, and time and consequently to test more frequently. In conclusion, the study finds IDEXX Legiolert a suitable alternative to ISO 11731:1998.

Cross-reactivity of the IDEXX Legiolert method with other Gram-negative bacteria and waterborne pathogens leads to false-positive assay results.

Legionella species are the causative agent of Legionnaires' disease, a potentially fatal bacterial pneumonia. New regulations and standards have prioritized the development of water safety plans to minimize the growth and spread of Legionella species in buildings. To determine the presence and type of Legionella in a water system, microbiological culturing is the gold standard method. However, recently new methodologies have been developed that claim to be sensitive and specific for Legionella at the genus or L. pneumophila at the species level. Published and anecdotal reports suggest that one of these newer culture-based, enzyme-substrate methods, the IDEXX Legiolert test, may exhibit false positivity with other microbes common to water sources. We experimentally evaluated the IDEXX Legiolert method using these other waterborne bacteria including Elizabethkingia meningoseptica, Pseudomonas aeruginosa, Proteus mirabilis and Serratia marcescens at real-world environmental concentrations. We saw false-positive results for the Legiolert test with several of these organisms, at sample concentrations as low as 60 CFU per ml. False-positive Legionella results can trigger costly remediation and water-use restrictions, that may be implemented while waiting for additional, confirmatory microbiological testing that could, in this case, yield no L. pneumophila.

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.

Large community-acquired Legionnaires' disease outbreak caused by Legionella pneumophila serogroup 1, Italy, July to August 2018.

In July 2018, a large outbreak of Legionnaires' disease (LD) caused by Legionella pneumophila serogroup 1 (Lp1) occurred in Bresso, Italy. Fifty-two cases were diagnosed, including five deaths. We performed an epidemiological investigation and prepared a map of the places cases visited during the incubation period. All sites identified as potential sources were investigated and sampled. Association between heavy rainfall and LD cases was evaluated in a case-crossover study. We also performed a case-control study and an aerosol dispersion investigation model. Lp1 was isolated from 22 of 598 analysed water samples; four clinical isolates were typed using monoclonal antibodies and sequence-based typing. Four Lp1 human strains were ST23, of which two were Philadelphia and two were France-Allentown subgroup. Lp1 ST23 France-Allentown was isolated only from a public fountain. In the case-crossover study, extreme precipitation 5-6 days before symptom onset was associated with increased LD risk. The aerosol dispersion model showed that the fountain matched the case distribution best. The case-control study demonstrated a significant eightfold increase in risk for cases residing near the public fountain. The three studies and the matching of clinical and environmental Lp1 strains identified the fountain as the source responsible for the epidemic.

Fatal Case of Legionnaires' Disease After Home Exposure to Legionella pneumophila Serogroup 3 - Wisconsin, 2018.

In January 2018, the Wisconsin Department of Health Services, Division of Public Health (DPH), received a report of a culture-confirmed case of Legionnaires' disease. The patient, who was immunocompromised, had died at a local hospital 10 days after being admitted. DPH and an infection preventionist from the hospital investigated to determine the source of the infection and prevent additional cases. Because the case was suspected to be nosocomial, health care facility water samples were tested for Legionella. When these samples were negative, water sources in the patient's home were tested. These tested positive for Legionella pneumophila, and the bacteria remained after an attempt to remediate. The patient and home isolates were identified as L. pneumophila serogroup 3, sequence type 93, by whole-genome multilocus sequence typing. A second resident of the home did not become ill. This case highlights the potential for immunocompromised persons and others at risk for Legionnaires' disease to be exposed to Legionella through home water systems containing the bacteria and demonstrates the difficulty of home remediation. This case also illustrates the role of lower respiratory tract specimens in the identification of less common Legionella infections (e.g., L. pneumophila serogroup 3) and confirmation of the infection source.

Distribution of Legionella species and serogroups in patients with culture-confirmed Legionella pneumonia.

Legionella species are consistently identified as some of the most common causative agents of severe community-acquired pneumonia (CAP) or nosocomial pneumonia. Although the number of reported Legionella infection cases is gradually increasing in Japan, most cases are diagnosed by a urinary antigen test, which identifies only L. pneumophila serogroup 1. Therefore, assessment of pneumonia-causing Legionella species and serogroups would be important. The Japan Society for Chemotherapy Legionella committee has collected the isolates and clinical information on cases of sporadic community-acquired Legionella pneumonia throughout Japan. Between December 2006 and March 2019, totally 140 sporadic cases were identified, in which L. pneumophila was the most frequently isolated species (90.7%) followed by L. bozemanae (3.6%), L. dumofii (3.6%), L. micdadei (1.4%), and L. longbeachae (0.7%). Among 127 isolates of L. pneumophila, 111 isolates were of serogroup 1, two of serogroup 2, four of serogroup 3, one of serogroup 4, one of serogroup 5, seven of serogroup 6, and one was of serogroup 10. We also assessed in vitro activity of antibiotics against these isolates and showed that quinolones and macrolides have potent anti-Legionella activity. Our study showed that pneumonia-causing Legionella species and serogroup distribution was comparable to that reported in former surveillances. L. pneumophila was the most common etiologic agent in patients with community-acquired Legionella pneumonia, and L. pneumophila serogroup 1 was the predominant serogroup.

Legionella pneumophila occurrence in drinking water supplied by private wells.

Unregulated private wells are understudied potential sources of community-acquired Legionnaires' disease. Here we conducted a comprehensive survey of 44 homes supplied by private wells in Wake County, North Carolina, quantifying Legionella spp. DNA, Legionella pneumophila DNA, and total bacterial 16S rRNA genes via real-time polymerase chain reaction in hot and cold drinking water samples, along with culturable L. pneumophila via IDEXX Legiolert in cold drinking water samples. Legionella spp. DNA, L. pneumophila DNA and culturable L. pneumophila were detected in 100, 65·5 and 15·9% of the 44 homes, respectively, and culturable levels were comparable to some municipal surveys applying the same methods. Total coliforms and Escherichia coli were monitored as representative faecal indicators and were found in 20·4 and 0·0% of homes. Within certain sample types, Legionella spp. and L. pneumophila gene copy numbers were positively associated with total bacteria (i.e. total 16S rRNA genes) and water softener use, but were not associated with faecal indicator bacteria, inorganic water parameters or other well characteristics. These findings confirm that occurrence of Legionella and L. pneumophila is highly variable in private wells. SIGNIFICANCE AND IMPACT OF THE STUDY: Legionella is the leading identified cause of waterborne disease outbreaks associated with US municipal water systems. While Legionella is known to occur naturally in groundwater, prior efforts to characterize its occurrence in unregulated private wells are limited to sampling at the wellhead and not in the home plumbing where Legionella can thrive. This work documents much higher levels of Legionella in home plumbing versus water directly from private wells and examines factors associated with higher Legionella occurrence.

Combinatorial selection in amoebal hosts drives the evolution of the human pathogen Legionella pneumophila.

Virulence mechanisms typically evolve through the continual interaction of a pathogen with its host. In contrast, it is poorly understood how environmentally acquired pathogens are able to cause disease without prior interaction with humans. Here, we provide experimental evidence for the model that Legionella pathogenesis in humans results from the cumulative selective pressures of multiple amoebal hosts in the environment. Using transposon sequencing, we identify Legionella pneumophila genes required for growth in four diverse amoebae, defining universal virulence factors commonly required in all host cell types and amoeba-specific auxiliary genes that determine host range. By comparing genes that promote growth in amoebae and macrophages, we show that adaptation of L. pneumophila to each amoeba causes the accumulation of distinct virulence genes that collectively allow replication in macrophages and, in some cases, leads to redundancy in this host cell type. In contrast, some bacterial proteins that promote replication in amoebae restrict growth in macrophages. Thus, amoebae-imposed selection is a double-edged sword, having both positive and negative impacts on disease. Comparing the genome composition and host range of multiple Legionella species, we demonstrate that their distinct evolutionary trajectories in the environment have led to the convergent evolution of compensatory virulence mechanisms.

A Novel Legionella Genomic Island Encodes a Copper-Responsive Regulatory System and a Single Icm/Dot Effector Protein Transcriptionally Activated by Copper.

The intracellular pathogen Legionella pneumophila utilizes the Icm/Dot type IV secretion system to translocate >300 effector proteins into host cells during infection. The regulation of some of these effector-encoding genes was previously shown to be coordinated by several global regulators, including three two-component systems (TCSs) found in all the Legionella species examined. Here, we describe the first Legionella genomic island encoding a single Icm/Dot effector and a dedicated TCS, which regulates its expression. This genomic island, which we named Lci, undergoes horizontal gene transfer in the Legionella genus, and the TCS encoded from this island (LciRS) is homologous to TCSs that control the expression of various metal resistance systems found in other bacteria. We found that the L. pneumophila sensor histidine kinase LciS is specifically activated by copper via a unique, small periplasmic sensing domain. Upon activation by LciS, the response regulator LciR directly binds to a conserved regulatory element and activates the expression of the adjacently located lciE effector-encoding gene. Thus, LciR represents the first local regulator of effectors identified in L. pneumophila Moreover, we found that the expression of the lciRS operon is repressed by the Fis1 and Fis3 regulators, leading to Fis-mediated effects on copper induction of LciE and silencing of the expression of this genomic island in the absence of copper. This island represents a novel type of effector regulation in Legionella, shedding new light on the ways by which the Legionella pathogenesis system evolves its effector repertoire and expands its activating signals.IMPORTANCELegionella pneumophila is an intracellular human pathogen that utilizes amoebae as its environmental host. The adaptation of L. pneumophila to the intracellular environment requires coordination of expression of its multicomponent pathogenesis system, which is composed of a secretion system and effector proteins. However, the regulatory factors controlling the expression of this pathogenesis system are only partially uncovered. Here, we discovered a novel regulatory system that is activated by copper and controls the expression of a single effector protein. The genes encoding both the regulatory system and the effector protein are located on a genomic island that undergoes horizontal gene transfer within the Legionella genus. This regulator-effector genomic island represents the first reported case of local regulation of effectors in Legionella The discovery of this regulatory mechanism is an important step forward in the understanding of how the regulatory network of effectors functions and evolves in the Legionella genus.

What is the risk of missing legionellosis relying on urinary antigen testing solely? A retrospective Belgian multicenter study.

Currently, diagnosis of legionellosis relies mainly on urinary antigen testing (UAT) for Legionella pneumophila serogroup 1 (Lp1). However, this test has several limitations, particularly missing non-Lp1 infections. The purpose of this large multicenter study was to investigate the risk of missing legionellosis relying on UAT solely. Molecular results of Legionella detection as part of a first-line (syndromic) testing algorithm for severe respiratory tract infections were investigated retrospectively and compared with UAT results in 14 Belgian laboratories. Overall, 44.4% (20/45) UAT results appeared false negative and were reclassified as legionellosis based on PCR findings [Legionnaires' disease, 37.5% (15/40); Pontiac fever, 100% (5/5)]. A total of 39.4% (26/66) diagnosis probably would have been missed or delayed without a syndromic approach, as UAT or specific molecular testing for Legionella was not requested by the clinician. Furthermore, we confirmed the higher sensitivity of molecular Legionella detection in lower respiratory tract compared with upper respiratory tract specimens (p = 0.010).