Clinical predictors for Legionella in patients presenting with community-acquired pneumonia to the emergency department.

BACKGROUND: Legionella species cause severe forms of pneumonia with high mortality and complication rates. Accurate clinical predictors to assess the likelihood of Legionella community-acquired pneumonia (CAP) in patients presenting to the emergency department are lacking. METHODS: We retrospectively compared clinical and laboratory data of 82 consecutive patients with Legionella CAP with 368 consecutive patients with non-Legionella CAP included in two studies at the same institution. RESULTS: In multivariate logistic regression analysis we identified six parameters, namely high body temperature (OR 1.67, p < 0.0001), absence of sputum production (OR 3.67, p < 0.0001), low serum sodium concentrations (OR 0.89, p = 0.011), high levels of lactate dehydrogenase (OR 1.003, p = 0.007) and C-reactive protein (OR 1.006, p < 0.0001) and low platelet counts (OR 0.991, p < 0.0001), as independent predictors of Legionella CAP. Using optimal cut off values of these six parameters, we calculated a diagnostic score for Legionella CAP. The median score was significantly higher in Legionella CAP as compared to patients without Legionella (4 (IQR 3-4) vs 2 (IQR 1-2), p < 0.0001) with a respective odds ratio of 3.34 (95%CI 2.57-4.33, p < 0.0001). Receiver operating characteristics showed a high diagnostic accuracy of this diagnostic score (AUC 0.86 (95%CI 0.81-0.90), which was better as compared to each parameter alone. Of the 191 patients (42%) with a score of 0 or 1 point, only 3% had Legionella pneumonia. Conversely, of the 73 patients (16%) with > or =4 points, 66% of patients had Legionella CAP. CONCLUSION: Six clinical and laboratory parameters embedded in a simple diagnostic score accurately identified patients with Legionella CAP. If validated in future studies, this score might aid in the management of suspected Legionella CAP.

Biodiversity of amoebae and amoebae-resisting bacteria in a drinking water treatment plant

The complex ecology of free-living amoebae (FLA) and their role in spreading pathogenic microorganisms through water systems have recently raised considerable interest. In this study, we investigated the presence of FLA and amoebae-resisting bacteria (ARB) at various stages of a drinking water plant fed with river water. We isolated various amoebal species from the river and from several points within the plant, mostly at early steps of water treatment. Echinamoeba- and Hartmannella-related amoebae were mainly recovered in the drinking water plant whereas Acanthamoeba- and Naegleria-related amoebae were recovered from the river water and the sand filtration units. Some FLA isolates were recovered immediately after the ozonation step, thus suggesting resistance of these microorganisms to this disinfection procedure. A bacterial isolate related to Mycobacterium mucogenicum was recovered from an Echinamoeba-related amoeba isolated from ozone-treated water. Various other ARB were recovered using co-culture with axenic Acanthamoeba castellanii, including mycobacteria, legionella, Chlamydia-like organisms and various proteobacteria. Noteworthy, a new Parachlamydia acanthamoebae strain was recovered from river water and from granular activated carbon (GAC) biofilm. As amoebae mainly multiply in sand and GAC filters, optimization of filter backwash procedures probably offers a possibility to better control these protists and the risk associated with their intracellular hosts

Expression of a plant-derived peptide harboring water-cleaning and antimicrobial activities.

Drinking water is currently a scarce world resource, the preparation of which requires complex treatments that include clarification of suspended particles and disinfection. Seed extracts of Moringa oleifera Lam., a tropical tree, have been proposed as an environment-friendly alternative, due to their traditional use for the clarification of drinking water. However, the precise nature of the active components of the extract and whether they may be produced in recombinant form are unknown. Here we show that recombinant or synthetic forms of a cationic seed polypeptide mediate efficient sedimentation of suspended mineral particles and bacteria. Unexpectedly, the polypeptide was also found to possesses a bactericidal activity capable of disinfecting heavily contaminated water. Furthermore, the polypeptide has been shown to efficiently kill several pathogenic bacteria, including antibiotic-resistant isolates of Staphylococcus, Streptococcus, and Legionella species. Thus, this polypeptide displays the unprecedented feature of combining water purification and disinfectant properties. Identification of an active principle derived from the seed extracts points to a range of potential for drinking water treatment or skin and mucosal disinfection in clinical settings.

Imaging of cavitary necrosis in complicated childhood pneumonia.

The aim of this study was to illustrate the chest radiographs (CR) and CT imaging features and sequential findings of cavitary necrosis in complicated childhood pneumonia. Among 30 children admitted in the Pediatric Intensive Care Unit for persistent or progressive pneumonia, respiratory distress or sepsis despite adequate antibiotic therapy, a study group of 9 children (5 girls and 4 boys; mean age 4 years) who had the radiographic features and CT criteria for cavitary necrosis complicated pneumonia was identified. The pathogens identified were Streptococcus pneumoniae( n=4), Aspergillus( n=2), Legionella( n=1), and Staphylococcus aureus( n=1). Sequential CR and CT scans were retrospectively reviewed. Follow-up CR and CT were evaluated for persistent abnormalities. Chest radiographs showed consolidations in 8 of the 9 patients. On CT examination, cavitary necrosis was localized to 1 lobe in 2 patients and 7 patients showed multilobar or bilateral areas of cavitary necrosis. In 3 patients of 9, the cavitary necrosis was initially shown on CT and visualization by CR was delayed by a time span varying from 5 to 9 days. In all patients with cavities, a mean number of five cavities were seen on antero-posterior CR, contrasting with the multiple cavities seen on CT. Parapneumonic effusions were shown by CR in 3 patients and in 5 patients by CT. Bronchopleural fistulae were demonstrated by CT alone ( n=3). No purulent pericarditis was demonstrated. The CT scan displayed persistent residual pneumatoceles of the left lower lobe in 2 patients. Computed tomography is able to define a more specific pattern of abnormalities than conventional CR in children with necrotizing pneumonia and allows an earlier diagnosis of this rapidly progressing condition. Lung necrosis and cavitation may also be associated with Aspergillus or Legionella pneumonia in the pediatric population.

Insight into cross-talk between intra-amoebal pathogens.

Abstract: Background: Amoebae are phagocytic protists where genetic exchanges might take place between amoeba-resistant bacteria. These amoebal pathogens are able to escape the phagocytic behaviour of their host. They belong to different bacterial phyla and often show a larger genome size than human-infecting pathogens. This characteristic is proposed to be the result of frequent gene exchanges with other bacteria that share a sympatric lifestyle and contrasts with the genome reduction observed among strict human pathogens.Results: We sequenced the genome of a new amoebal pathogen, Legionella drancourtii, and compared its gene content to that of a Chlamydia-related bacterium, Parachlamydia acanthamoebae. Phylogenetic reconstructions identified seven potential horizontal gene transfers (HGTs) between the two amoeba-resistant bacteria, including a complete operon of four genes that encodes an ABC-type transporter. These comparisons pinpointed potential cases of gene exchange between P. acanthamoebae and Legionella pneumophila, as well as gene exchanges between other members of the Legionellales and Chlamydiales orders. Moreover, nine cases represent possible HGTs between representatives from the Legionellales or Chlamydiales and members of the Rickettsiales order.Conclusions: This study identifies numerous gene exchanges between intracellular Legionellales and Chlamydiales bacteria, which could preferentially occur within common inclusions in their amoebal hosts. Therefore it contributes to improve our knowledge on the intra-amoebal gene properties associated to their specific lifestyle.

Genomics of "chlamydia"-related bacteria

AbstractThe Chlamydiales order is an important bacterial phylum that comprises some of the most successful human pathogens such as Chlamydia trachomatis, the leading infectious cause of blindness worldwide. Since some years, several new bacteria related to Chlamydia have been discovered in clinical or environmental samples and might represent emerging pathogens. The genome sequencing of classical Chlamydia has brought invaluable information on these obligate intracellular bacteria otherwise difficult to study due to the lack of tools to perform basic genetic manipulation. The recent emergence of high-throughput sequencing technologies yielding millions of reads in a short time lowered the costs of genome sequencing and thus represented a unique opportunity to study Chlamydia-re\ated bacteria. Based on the sequencing and the analysis of Chlamydiales genomes, this thesis provides significant insights into the genetic determinants of the intracellular lifestyle, the pathogenicity, the metabolism and the evolution of Chlamydia-related bacteria. A first approach showed the efficacy of rapid sequencing coupled to proteomics to identify immunogenic proteins. This method, particularly useful for an emerging pathogen such as Parachlamydia acanthamoebae, enabled us to discover good candidates for the development of diagnostic tools that would permit to evaluate at larger scale the role of this bacterium in disease. Second, the complete genome of Waddlia chondrophila, a potential agent of miscarriage, encodes numerous virulence factors to manipulate its host cell and resist to environmental stresses. The reconstruction of metabolic pathways showed that the bacterium possesses extensive capabilities compared to related organisms. However, it is still incapable of synthesizing some essential components and thus has to import them from its host. Third, the genome comparison of Protochlamydia naegleriophila to its closest known relative Protochlamydia amoebophila revealed a particular evolutionary dynamic with the occurrence of an unexpected genome rearrangement. Fourth, a phylogenetic analysis of P. acanthamoebae and Legionella drancourtii identified several genes probably exchanged by horizontal gene transfer with other intracellular bacteria that might occur within their amoebal host. These genes often encode mechanisms for resistance to metal or toxic compounds. As a whole, the analysis of the different genomes enabled us to highlight a large diversity in size, GC percentage, repeat content as well as plasmid organization. The abundant genomic data obtained during this thesis have a wide impact since they provide the necessary bases for detailed investigations on countless aspects of the biology and the evolution of Chlamydia-related bacteria, whether in wet lab or by bioinformatical analyses.RésuméL'ordre des Chlamydiales est un important phylum bactérien qui comprend de nombreuses espèces pathogènes pour l'homme et les animaux, dont Chlamydia trachomatis, responsable du trachome, la cause majeure de cécité d'origine infectieuse à travers le monde. Durant ces dernières décennies, de nombreuses bactéries apparentées aux Chlamydia ont été découvertes dans des échantillons environnementaux ou cliniques mais leur éventuel rôle pathogène dans le développement de maladies reste peu connu. Ces bactéries sont des intracellulaires obligatoires car elles ont besoin d'une cellule hôte pour se multiplier, ce qui rend leur étude particulièrement difficile. Le développement de nouvelles technologies permettant de séquencer le génome d'un organisme rapidement et à moindre coût ainsi que l'essor des méthodes d'analyse s'y rapportant représentent une opportunité exceptionnelle d'étudier ces organismes. Dans ce contexte, cette thèse démontre l'utilité de la génomique pour développer de nouveaux outils diagnostiques ainsi que pour étudier le métabolisme de ces bactéries, leurs facteurs de virulence et leur évolution.Ainsi, une première approche a illustré l'utilité d'un séquençage rapide pour obtenir les informations nécessaires à l'identification de protéines qui sont reconnues par des anticorps humains ou animaux. Cette méthode, particulièrement utile pour un pathogène émergent tel que Parachlamydia acanthamoebae, a permis de découvrir de bons candidats pour le développement d'un outil diagnostique qui permettrait d'évaluer à plus large échelle le rôle de cette bactérie notamment dans la pneumonie. L'analyse du contenu génique de Waddlia chondrophila, un autre germe qui pourrait être impliqué dans les avortements et tes fausses-couches, a en outre mis en évidence la présence de nombreux facteurs connus qui lui permettent de manipuler son hôte. Cette bactérie possède de plus grandes capacités métaboliques que les autres Chlamydia, mais elle est incapable de synthétiser certains composants et doit donc les importer de son hôte pour subvenir à ses besoins. La comparaison du génome de Protochlamydia naegleriophila à son plus proche parent, Protochlamydia amoebophila, a dévoilé une évolution dynamique particulière avec l'occurrence d'un réarrangement majeur inattendu après la séparation de ces deux espèces. En outre, ces études ont montré l'occurrence de plusieurs transferts de gène avec d'autres organismes plus éloignés, notamment d'autres intracellulaires d'amibes, souvent pour l'acquisition de mécanismes de résistances à des composés toxiques. Les données génomiques acquises durant ce travail posent les fondements nécessaires a de nombreuses analyses qui permettront progressivement de mieux comprendre de nombreux aspects de ces bactéries fascinantes.

TREM-1 deficiency can attenuate disease severity without affecting pathogen clearance.

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a potent amplifier of pro-inflammatory innate immune reactions. While TREM-1-amplified responses likely aid an improved detection and elimination of pathogens, excessive production of cytokines and oxygen radicals can also severely harm the host. Studies addressing the pathogenic role of TREM-1 during endotoxin-induced shock or microbial sepsis have so far mostly relied on the administration of TREM-1 fusion proteins or peptides representing part of the extracellular domain of TREM-1. However, binding of these agents to the yet unidentified TREM-1 ligand could also impact signaling through alternative receptors. More importantly, controversial results have been obtained regarding the requirement of TREM-1 for microbial control. To unambiguously investigate the role of TREM-1 in homeostasis and disease, we have generated mice deficient in Trem1. Trem1(-/-) mice are viable, fertile and show no altered hematopoietic compartment. In CD4(+) T cell- and dextran sodium sulfate-induced models of colitis, Trem1(-/-) mice displayed significantly attenuated disease that was associated with reduced inflammatory infiltrates and diminished expression of pro-inflammatory cytokines. Trem1(-/-) mice also exhibited reduced neutrophilic infiltration and decreased lesion size upon infection with Leishmania major. Furthermore, reduced morbidity was observed for influenza virus-infected Trem1(-/-) mice. Importantly, while immune-associated pathologies were significantly reduced, Trem1(-/-) mice were equally capable of controlling infections with L. major, influenza virus, but also Legionella pneumophila as Trem1(+/+) controls. Our results not only demonstrate an unanticipated pathogenic impact of TREM-1 during a viral and parasitic infection, but also indicate that therapeutic blocking of TREM-1 in distinct inflammatory disorders holds considerable promise by blunting excessive inflammation while preserving the capacity for microbial control.

Discovery of new intracellular pathogens by amoebal coculture and amoebal enrichment approaches.

Intracellular pathogens such as legionella, mycobacteria and Chlamydia-like organisms are difficult to isolate because they often grow poorly or not at all on selective media that are usually used to cultivate bacteria. For this reason, many of these pathogens were discovered only recently or following important outbreaks. These pathogens are often associated with amoebae, which serve as host-cell and allow the survival and growth of the bacteria. We intend here to provide a demonstration of two techniques that allow isolation and characterization of intracellular pathogens present in clinical or environmental samples: the amoebal coculture and the amoebal enrichment. Amoebal coculture allows recovery of intracellular bacteria by inoculating the investigated sample onto an amoebal lawn that can be infected and lysed by the intracellular bacteria present in the sample. Amoebal enrichment allows recovery of amoebae present in a clinical or environmental sample. This can lead to discovery of new amoebal species but also of new intracellular bacteria growing specifically in these amoebae. Together, these two techniques help to discover new intracellular bacteria able to grow in amoebae. Because of their ability to infect amoebae and resist phagocytosis, these intracellular bacteria might also escape phagocytosis by macrophages and thus, be pathogenic for higher eukaryotes.

Free-living amoebae: Biological by-passes in water treatment.

Free-living amoebae constitute reservoirs for many bacteria including not only well-known pathogens but also emerging pathogens responsible for respiratory diseases, and contribute to the protection, survival and dissemination of these bacteria in water systems, despite the application of disinfection or thermal treatments. In this article we review the available information on the presence of free-living amoebae and amoebae-resisting bacteria in drinking water systems, on the factors that contribute to their presence in the water and/or the biofilms, on the possible control measures and their effectiveness, and we identify some gaps in current knowledge needing further research.

Amoebae as a tool to isolate new bacterial species, to discover new virulence factors and to study the host-pathogen interactions.

Amoebae are unicellular protozoan present worldwide in several environments mainly feeding on bacteria. Some of them, the amoebae-resistant bacteria (ARBs), have evolved mechanisms to survive and replicate inside amoebal species. These mainly include legionella, mycobacteria and Chlamydia-related bacteria. Amoebae can provide a replicative niche, can act as reservoir for bacteria whereas the cystic form can protect the internalized bacteria. Moreover, the amoebae represent a Trojan horse for ARBs to infect animals. The long interaction between amoebae and bacteria has likely selected for bacterial virulence traits leading to the adaptation towards an intracellular lifestyle, and some ARBs have acquired the ability to infect mammals. This review intends to highlight the important uses of amoebae in several fields in microbiology by describing the main tools developed using amoebal cells. First, amoebae such as Acanthamoeba are used to isolate and discover new intracellular bacterial species by two main techniques: the amoebal co-culture and the amoebal enrichment. In the second part, taking Waddlia chondrophila as example, we summarize some important recent applications of amoebae to discover new bacterial virulence factors, in particular thanks to the amoebal plaque assay. Finally, the genetically tractable Dictyostelium discoideum is used as a model organism to study host-pathogen interactions, in particular with the development of several approaches to manipulate its genome that allowed the creation of a wide range of mutated strains largely shared within the Dictyostelium community.

Characterization of a plant-derived peptide displaying water clarifying and antimicrobial activities

SUMMARY Drinking water is currently a scarce world resource, the preparation of which requires complex treatments that include clarification of suspended particles and disinfection. Seed extracts of Moringa oleifera Lam., a tropical tree, have been proposed as an environment- friendly alternative, due to their traditional use for the clarification of drinking water. However, the precise nature of the active components was unknown. Here, we show that recombinant or synthetic forms of a cationic seed polypeptide mediate efficient sedimentation of suspended mineral particles and bacteria. Unexpectedly, the polypeptide was also found to possesses a bactericidal activity capable of disinfecting heavily contaminated water. Furthermore, the polypeptide has been shown to efficiently kill several pathogenic bacteria, including antibiotic-resistant isolates of Pseudomona, Streptococcus and Legionella species. Structural modeling of the peptide coupled to the functional analysis of synthetic peptide derivatives delineated distinct structural determinants for the flocculation and antibacterial activities. Our results suggest that a glutamine-rich portion of the polypeptide is involved in the sedimentation process; alternatively, the antibacterial activity depends on a amphiphilic loop. Assembly of multiple copies of this loop into a branched peptide derivative strongly enhances antibacterial activity without displaying hemolytic effect. In conclusion, this polypeptide displays the unprecedented feature of combining efficient water purification and disinfectant properties indicating different molecular mechanisms involved in each case. This work not only identified the features responsible for these activities but also provides useful information that has implications for the further development of this cationic polypeptide as a potent antibacterial agent. RESUME L'eau potable est actuellement une ressource limitée dans le monde. La production d'eau propre à la consommation exige des traitements complexes, incluant la clarification des particules en suspension ainsi que sa désinfection par des additifs chimiques. Les extraits de la graine d'un arbre tropical, Moringa oleifera, sont utilisés traditionnellement en Afrique afin de clarifier l'eau. Quoique la nature exacte des composants actifs était inconnue, on a pu mettre en évidence un polypeptide cationique contenu dans ces graines, capable de sédimenter de manière efficace des particules minérales en suspension ainsi que des bactéries. Ce travail a aussi mis en évidence que ce polypeptide a une activité bactéricide, permettant une désinfection d'eau fortement contaminée. De plus, nous avons démontré que ce polypeptide est efficace contre de nombreuses souches bactériennes pathogènes, également celles résistantes aux antibiotiques comme Pseudomonas, Streptococcus et Legionella. L'analyse de la structure moléculaire de ce polypeptide, couplée à son analyse fonctionnelle a mis en évidence deux domaines structuraux distinct, un pour l'activité de floculation et l'autre pour l'activité antibactérienne. Nos résultats suggèrent que le domaine riche en glutamine est impliqué dans le processus de sédimentation et que l'activité antimicrobienne dépend d'un domaine formant une boucle amphiphilique. En ramifiant plusieurs copies de cette boucle on a pu augmenter de manière significative l'activité antibactérienne. En conclusion, nous avons pu démontrer que ce polypeptide à la capacité unique de combiner des propriétés de purification et de désinfection de l'eau, ce qui implique des mécanismes moléculaires distincts pour ces deux activités. Ce travail a permis d'identifier les domaines du polypeptide qui sont responsables de ses activités et offre une perspective pour le développement d'un nouvel agent antimicrobien.

β-Lactam Monotherapy vs β-Lactam-Macrolide Combination Treatment in Moderately Severe Community-Acquired Pneumonia: A Randomized Noninferiority Trial.

IMPORTANCE: The clinical benefit of adding a macrolide to a β-lactam for empirical treatment of moderately severe community-acquired pneumonia remains controversial. OBJECTIVE: To test noninferiority of a β-lactam alone compared with a β-lactam and macrolide combination in moderately severe community-acquired pneumonia. DESIGN, SETTING, AND PARTICIPANTS: Open-label, multicenter, noninferiority, randomized trial conducted from January 13, 2009, through January 31, 2013, in 580 immunocompetent adult patients hospitalized in 6 acute care hospitals in Switzerland for moderately severe community-acquired pneumonia. Follow-up extended to 90 days. Outcome assessors were masked to treatment allocation. INTERVENTIONS: Patients were treated with a β-lactam and a macrolide (combination arm) or with a β-lactam alone (monotherapy arm). Legionella pneumophila infection was systematically searched and treated by addition of a macrolide to the monotherapy arm. MAIN OUTCOMES AND MEASURES: Proportion of patients not reaching clinical stability (heart rate <100/min, systolic blood pressure >90 mm Hg, temperature <38.0°C, respiratory rate <24/min, and oxygen saturation >90% on room air) at day 7. RESULTS: After 7 days of treatment, 120 of 291 patients (41.2%) in the monotherapy arm vs 97 of 289 (33.6%) in the combination arm had not reached clinical stability (7.6% difference, P = .07). The upper limit of the 1-sided 90% CI was 13.0%, exceeding the predefined noninferiority boundary of 8%. Patients infected with atypical pathogens (hazard ratio [HR], 0.33; 95% CI, 0.13-0.85) or with Pneumonia Severity Index (PSI) category IV pneumonia (HR, 0.81; 95% CI, 0.59-1.10) were less likely to reach clinical stability with monotherapy, whereas patients not infected with atypical pathogens (HR, 0.99; 95% CI, 0.80-1.22) or with PSI category I to III pneumonia (HR, 1.06; 95% CI, 0.82-1.36) had equivalent outcomes in the 2 arms. There were more 30-day readmissions in the monotherapy arm (7.9% vs 3.1%, P = .01). Mortality, intensive care unit admission, complications, length of stay, and recurrence of pneumonia within 90 days did not differ between the 2 arms. CONCLUSIONS AND RELEVANCE: We did not find noninferiority of β-lactam monotherapy in patients hospitalized for moderately severe community-acquired pneumonia. Patients infected with atypical pathogens or with PSI category IV pneumonia had delayed clinical stability with monotherapy. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00818610.

β-Lactam Monotherapy vs β-Lactam-Macrolide Combination Treatment in Moderately Severe Community-Acquired Pneumonia: A Randomized Noninferiority Trial.

IMPORTANCE: The clinical benefit of adding a macrolide to a β-lactam for empirical treatment of moderately severe community-acquired pneumonia remains controversial. OBJECTIVE: To test noninferiority of a β-lactam alone compared with a β-lactam and macrolide combination in moderately severe community-acquired pneumonia. DESIGN, SETTING, AND PARTICIPANTS: Open-label, multicenter, noninferiority, randomized trial conducted from January 13, 2009, through January 31, 2013, in 580 immunocompetent adult patients hospitalized in 6 acute care hospitals in Switzerland for moderately severe community-acquired pneumonia. Follow-up extended to 90 days. Outcome assessors were masked to treatment allocation. INTERVENTIONS: Patients were treated with a β-lactam and a macrolide (combination arm) or with a β-lactam alone (monotherapy arm). Legionella pneumophila infection was systematically searched and treated by addition of a macrolide to the monotherapy arm. MAIN OUTCOMES AND MEASURES: Proportion of patients not reaching clinical stability (heart rate <100/min, systolic blood pressure >90 mm Hg, temperature <38.0°C, respiratory rate <24/min, and oxygen saturation >90% on room air) at day 7. RESULTS: After 7 days of treatment, 120 of 291 patients (41.2%) in the monotherapy arm vs 97 of 289 (33.6%) in the combination arm had not reached clinical stability (7.6% difference, P = .07). The upper limit of the 1-sided 90% CI was 13.0%, exceeding the predefined noninferiority boundary of 8%. Patients infected with atypical pathogens (hazard ratio [HR], 0.33; 95% CI, 0.13-0.85) or with Pneumonia Severity Index (PSI) category IV pneumonia (HR, 0.81; 95% CI, 0.59-1.10) were less likely to reach clinical stability with monotherapy, whereas patients not infected with atypical pathogens (HR, 0.99; 95% CI, 0.80-1.22) or with PSI category I to III pneumonia (HR, 1.06; 95% CI, 0.82-1.36) had equivalent outcomes in the 2 arms. There were more 30-day readmissions in the monotherapy arm (7.9% vs 3.1%, P = .01). Mortality, intensive care unit admission, complications, length of stay, and recurrence of pneumonia within 90 days did not differ between the 2 arms. CONCLUSIONS AND RELEVANCE: We did not find noninferiority of β-lactam monotherapy in patients hospitalized for moderately severe community-acquired pneumonia. Patients infected with atypical pathogens or with PSI category IV pneumonia had delayed clinical stability with monotherapy. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00818610.

Amoeba/amoebal symbiont genetic transfers: lessons from giant virus neighbours.

Free-living amoebae serve as hosts for a variety of amoebae-resisting microorganisms, including giant viruses and certain bacteria. The latter include symbiotic bacteria as well as bacteria exhibiting a pathogenic phenotype towards amoebae. Amoebae-resisting bacteria have been shown to be widespread in water and to use the amoebae as a reservoir, a replication niche, a protective armour as well as a training ground to select virulence traits allowing survival in the face of microbicidal effects of macrophages, the first line of defense against invading pathogens. More importantly, amoebae play a significant role as a melting pot for genetic exchanges. These ecological and evolutionary roles of amoebae might also be at play for giant viruses and knowledge derived from the study of amoebae-resisting bacteria is useful for the study and understanding of interactions between amoebae and giant viruses. This is especially important since some genes have spread in all domains of life and the exponential availability of eukaryotic genomes and metagenomic sequences will allow researchers to explore these genetic exchanges in a more comprehensive way, thus completely changing our perception of the evolutionary history of organisms. Thus, a large part of this review is dedicated to report current known gene exchanges between the different amoebae-resisting organisms and between amoebae and the internalized bacteria.

Amoeba-resisting Chlamydiales present in domestic drinking water and their potential role in pneumonia

Chlamydia-related bacteria classified in the Chlamydiales order, are strictly intracellular bacteria and are able for the most to replicate in free-living amoebae. Amoebae, ubiquitous in the environment and especially in water, are very resistant to disinfection used in drinking water production. Thus, amoebae may reach easily the distribution and domestic water system, potentially sheltering amoeba-resisting bacteria including Legionella, mycobacteria and Chlamydiales. Indeed, some of these amoeba-resisting bacteria have been shown to cause respiratory infections in people inhaling contaminated water. Therefore, an environmental and clinical study was conducted to determine if Chlamydiales bacteria are also involved in respiratory infections and if a transmission through domestic drinking water could occur. First, large scale molecular and serological tools specific of Chlamydia-related bacteria were developed and then were applied on clinical samples from patients with and without pneumonia. Simultaneously, water and biofilm samples from households of the same patients were investigated using molecular and culture methods for the presence of Chlamydiales bacteria. Chlamydiales were detected in the nasopharyngeal flora from patients with and without pneumonia. However, no significant difference was observed between both groups. Conversely, serological investigations showed that antibody reactivity against members of the Criblamydiaceae was associated with pneumonia. The thesis provided very efficient tools that showed the presence of Chlamydiales in human nasopharyngeal flora as well as in the majority of the domestic drinking water. However, no transmission from domestic drinking water to human could be demonstrated. These tools will help in the future specifying the ecology and pathogenicity of the Chlamydia-re\ated bacteria and especially of the species belonging to the Criblamydiaceae family.