scholarly journals Differential ASC requirements reveal a key role for neutrophils and a noncanonical IL-1β response to Pseudomonas aeruginosa

2015 ◽  
Vol 309 (8) ◽  
pp. L902-L913 ◽  
Author(s):  
Yash R. Patankar ◽  
Rodwell Mabaera ◽  
Brent Berwin
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Acute Infection ◽  
Adaptor Protein ◽  
Ocular Infection ◽  
Lethal Challenge ◽  
Type Three Secretion System ◽  
Acute Pneumonia ◽  
Marked Deficit

The NLRC4 inflammasome is responsible for IL-1β processing by macrophages in response to Pseudomonas aeruginosa infection. We therefore hypothesized that mice that lack ASC, an NLRC4 inflammasome adaptor protein necessary for in vitro IL-1β production by macrophages, would be preferentially protected from a hyperinflammatory lethal challenge that is dependent on bacterial type three secretion system (T3SS) activity. We report herein that lack of ASC does not confer preferential protection in response to P. aeruginosa acute infection and that ASC−/− mice are capable of producing robust amounts of IL-1β comparable with C57BL/6 mice. We now identify that neutrophils represent the ASC-independent source of IL-1β production during the acute phases of infection both in models of acute pneumonia and peritonitis. Consequently, depletion of neutrophils in ASC−/− mice leads to a marked deficit in IL-1β production in vivo. The pulmonary neutrophil IL-1β response is predominantly dependent on caspase-1, which contrasts with data derived from ocular infection. These studies therefore identify a noncanonical mechanism of IL-1β production by neutrophils independent of ASC and demonstrate the first physiological contribution of neutrophils as an important source of IL-1β in response to acute P. aeruginosa infection during acute pneumonia and peritonitis.

scholarly journals Could Azithromycin Be Part of Pseudomonas aeruginosa Acute Pneumonia Treatment?

2021 ◽  
Vol 12 ◽  
Author(s):  
Anne-Gaëlle Leroy ◽  
Jocelyne Caillon ◽  
Nathalie Caroff ◽  
Alexis Broquet ◽  
Stéphane Corvec ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Clinical Trials ◽  
Respiratory Infections ◽  
Direct Interaction ◽  
Membered Ring ◽  
Careful Examination ◽  
Major Interest ◽  
Acute Pneumonia

Azithromycin (AZM) is a 15-membered-ring macrolide that presents a broad-spectrum antimicrobial activity against Gram-positive bacteria and atypical microorganisms but suffers from a poor diffusion across the outer-membrane of Gram-negative bacilli, including Pseudomonas aeruginosa (PA). However, AZM has demonstrated clinical benefits in patients suffering from chronic PA respiratory infections, especially cystic fibrosis patients. Since the rise of multidrug-resistant PA has led to a growing need for new therapeutic options, this macrolide has been proposed as an adjunctive therapy. Clinical trials assessing AZM in PA acute pneumonia are scarce. However, a careful examination of the available literature provides good rationales for its use in that context. In fact, 14- and 15-membered-ring macrolides have demonstrated immunomodulatory and immunosuppressive effects that could be of major interest in the management of acute illness. Furthermore, growing evidence supports a downregulation of PA virulence dependent on direct interaction with the ribosomes, and based on the modulation of several key regulators from the Quorum Sensing network. First highlighted in vitro, these interesting properties of AZM have subsequently been confirmed in the animal models. In this review, we systematically analyzed the literature regarding AZM immunomodulatory and anti-PA effects. In vitro and in vivo studies, as well as clinical trials were reviewed, looking for rationales for AZM use in PA acute pneumonia.

scholarly journals Pseudomonas aeruginosa Cytotoxin ExoU Is Injected into Phagocytic Cells during Acute Pneumonia

2010 ◽  
Vol 78 (4) ◽  
pp. 1447-1456 ◽  
Author(s):  
Maureen H. Diaz ◽  
Alan R. Hauser
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Immune Cells ◽  
Type Iii Secretion ◽  
Cell Types ◽  
Secretion System ◽  
Host Cells ◽  
Phagocytic Cells ◽  
Acute Pneumonia

ABSTRACT ExoU, a cytotoxin translocated into host cells via the type III secretion system of Pseudomonas aeruginosa, is associated with increased mortality and disease severity. We previously showed that impairment of recruited phagocytic cells allowed survival of ExoU-secreting P. aeruginosa in the lung. Here we analyzed types of cells injected with ExoU in vivo using translational fusions of ExoU with a β-lactamase reporter (ExoU-Bla). Cells injected with ExoU-Bla were detectable in vitro but not in vivo, presumably due to the rapid cytotoxicity induced by the toxin. Therefore, we used a noncytotoxic ExoU variant, designated ExoU(S142A)-Bla, to analyze injection in vivo. We determined that phagocytic cells in the lung were frequently injected with ExoU(S142A). Early during infection, resident macrophages constituted the majority of cells into which ExoU was injected, but neutrophils and monocytes became the predominant types of cells into which ExoU was injected upon recruitment into the lung. We observed a modest preference for injection into neutrophils over injection into other cell types, but in general the repertoire of injected immune cells reflected the relative abundance of these cells in the lung. Our results indicate that phagocytic cells in the lung are injected with ExoU and support the hypothesis that ExoU-mediated impairment of phagocytes has a role in the pathogenesis of pneumonia caused by P. aeruginosa.

scholarly journals Two Novel Bacteriophages Improve Survival in Galleria mellonella Infection and Mouse Acute Pneumonia Models Infected with Extensively Drug-Resistant Pseudomonas aeruginosa

2019 ◽  
Vol 85 (9) ◽  
Author(s):  
Jongsoo Jeon ◽  
Dongeun Yong
Keyword(s):  
Pseudomonas Aeruginosa ◽  
In Silico ◽  
Galleria Mellonella ◽  
Drug Resistant ◽  
Content Type ◽  
Bacteriolytic Activity ◽  
Extensively Drug Resistant ◽  
Acute Pneumonia

ABSTRACT Extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) is a life-threatening pathogen that causes serious global problems. Here, we investigated two novel P. aeruginosa bacteriophages (phages), Bϕ-R656 and Bϕ-R1836, in vitro, in silico, and in vivo to evaluate the potential of phage therapy to control XDR-PA clinical strains. Bϕ-R656 and Bϕ-R1836 belong to the Siphoviridae family and exhibited broad host ranges which could lyse 18 (64%) and 14 (50%) of the 28 XDR-PA strains. In addition, the two phages showed strong bacteriolytic activity against XDR-PA host strains from pneumonia patients. The whole genomes of Bϕ-R656 and Bϕ-R1836 have linear double-stranded DNA of 60,919 and 37,714 bp, respectively. The complete sequence of Bϕ-R656 had very low similarity to the previously discovered P. aeruginosa phages in GenBank, but phage Bϕ-R1836 exhibited 98% and 91% nucleotide similarity to Pseudomonas phages YMC12/01/R24 and PA1/KOR/2010, respectively. In the two in vivo infection models, treatment with Bϕ-R656 and Bϕ-R1836 enhanced the survival of Galleria mellonella larvae (50% and 60%, respectively) at 72 h postinfection and pneumonia-model mice (66% and 83%, respectively) at 12 days postinfection compared with untreated controls. Treatment with Bϕ-R656 or Bϕ-R1836 also significantly decreased the bacterial load in the lungs of the mouse pneumonia model (>6 log10 CFU and >4 log10 CFU, respectively) on day 5. IMPORTANCE In this study, two novel P. aeruginosa phages, Bϕ-R656 and Bϕ-R1836, were evaluated in vitro, in silico, and in vivo for therapeutic efficacy and safety as an alternative antibacterial agent to control XDR-PA strains collected from pneumonia patients. Both phages exhibited potent bacteriolytic activity and greatly improved survival in G. mellonella larva infection and a mouse acute pneumonia model. Based on these results, we strongly predict that these two new phages could be used as fast-acting and safe alternative biological weapons against XDR-PA infections.

scholarly journals Pseudomonas aeruginosa Forms Biofilms in Acute Infection Independent of Cell-to-Cell Signaling

2007 ◽  
Vol 75 (8) ◽  
pp. 3715-3721 ◽  
Author(s):  
J. Andy Schaber ◽  
W. Jeffrey Triffo ◽  
Sang Jin Suh ◽  
Jeffrey W. Oliver ◽  
Mary Catherine Hastert ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Bacterial Colonization ◽  
Acute Infection ◽  
Opportunistic Pathogen ◽  
Confocal Scanning Laser Microscopy ◽  
Chronic Infections ◽  
Signaling Mechanism ◽  
Confocal Scanning Laser

ABSTRACT Biofilms are bacterial communities residing within a polysaccharide matrix that are associated with persistence and antibiotic resistance in chronic infections. We show that the opportunistic pathogen Pseudomonas aeruginosa forms biofilms within 8 h of infection in thermally injured mice, demonstrating that biofilms contribute to bacterial colonization in acute infections as well. Using light, electron, and confocal scanning laser microscopy, P. aeruginosa biofilms were visualized within burned tissue surrounding blood vessels and adipose cells. Although quorum sensing (QS), a bacterial signaling mechanism, coordinates differentiation of biofilms in vitro, wild-type and QS-deficient P. aeruginosa strains formed similar biofilms in vivo. Our findings demonstrate that P. aeruginosa forms biofilms on specific host tissues independently of QS.

scholarly journals The LbcA lipoprotein and CtpA protease assemble an oligomeric complex to control peptidoglycan hydrolases in Pseudomonas aeruginosa

2021 ◽  
Author(s):  
Huilin Li ◽  
Hao-Chi Hsu ◽  
Michelle Wang ◽  
Amanda Kovach ◽  
Andrew J Darwin
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Molecular Mechanisms ◽  
Adaptor Protein ◽  
Activation Mechanism ◽  
Peptidoglycan Hydrolase ◽  
Tetratricopeptide Repeats ◽  
Active Protease ◽  
Processing Protease

Pseudomonas aeruginosa CtpA is a carboxyl terminal–processing protease that partners with the outer membrane lipoprotein LbcA to degrade cell wall cross-link hydrolases. This activity plays an important role in supporting P. aeruginosa virulence. However, almost nothing is known about the molecular mechanisms underlying CtpA and LbcA function. Here, we used structural analysis to show that CtpA alone assembles into an inactive hexamer comprising a trimer of dimers, which limits its substrate access and prevents nonspecific degradation. The adaptor protein LbcA is a right-handed open spiral with 11 tetratricopeptide repeats, which might wrap around a substrate to deliver it to CtpA for degradation. We found that up to three LbcA molecules can bind to one CtpA hexamer to assemble a giant, active protease complex that degrades its peptidoglycan hydrolase substrates both in vitro and in vivo. This work reveals an intricate protease activation mechanism that is substrate delivery-dependent and enables targeted removal of the peptidoglycan hydrolase substrates.

scholarly journals Pseudomonas aeruginosa Gene Products PilT and PilU Are Required for Cytotoxicity In Vitro and Virulence in a Mouse Model of Acute Pneumonia

1999 ◽  
Vol 67 (7) ◽  
pp. 3625-3630 ◽  
Author(s):  
James C. Comolli ◽  
Alan R. Hauser ◽  
Leslie Waite ◽  
Cynthia B. Whitchurch ◽  
John S. Mattick ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Epithelial Cell ◽  
Mouse Model ◽  
Cell Lines ◽  
Twitching Motility ◽  
Wild Type ◽  
Epithelial Cell Lines ◽  
Acute Pneumonia

ABSTRACT Type IV pili of the opportunistic pathogen Pseudomonas aeruginosa mediate twitching motility and act as receptors for bacteriophage infection. They are also important bacterial adhesins, and nonpiliated mutants of P. aeruginosa have been shown to cause less epithelial cell damage in vitro and have decreased virulence in animal models. This finding raises the question as to whether the reduction in cytotoxicity and virulence of nonpiliated P. aeruginosa mutants are primarily due to defects in cell adhesion or loss of twitching motility, or both. This work describes the role of PilT and PilU, putative nucleotide-binding proteins involved in pili function, in mediating epithelial cell injury in vitro and virulence in vivo. Mutants of pilT and pilU retain surface pili but have lost twitching motility. In three different epithelial cell lines, pilT or pilU mutants of the strain PAK caused less cytotoxicity than the wild-type strain but more than isogenic, nonpiliated pilA or rpoN mutants. ThepilT and pilU mutants also showed reduced association with these same epithelial cell lines compared both to the wild type, and surprisingly, to a pilA mutant. In a mouse model of acute pneumonia, the pilT and pilUmutants showed decreased colonization of the liver but not of the lung relative to the parental strain, though they exhibited no change in the ability to cause mortality. These results demonstrate that pilus function mediated by PilT and PilU is required for in vitro adherence and cytotoxicity toward epithelial cells and is important in virulence in vivo.

scholarly journals Pseudomonas aeruginosa RsmA Plays an Important Role during Murine Infection by Influencing Colonization, Virulence, Persistence, and Pulmonary Inflammation

2007 ◽  
Vol 76 (2) ◽  
pp. 632-638 ◽  
Author(s):  
Heidi Mulcahy ◽  
Julie O'Callaghan ◽  
Eoin P. O'Grady ◽  
María D. Maciá ◽  
Nuria Borrell ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Environmental Conditions ◽  
Pulmonary Inflammation ◽  
Acute Infection ◽  
Regulatory Protein ◽  
Airway Epithelial Cells ◽  
Virulence Determinants ◽  
Chronic Infections

ABSTRACT The ability of Pseudomonas aeruginosa to cause a broad range of infections in humans is due, at least in part, to its adaptability and its capacity to regulate the expression of key virulence genes in response to specific environmental conditions. Multiple two-component response regulators have been shown to facilitate rapid responses to these environmental conditions, including the coordinated expression of specific virulence determinants. RsmA is a posttranscriptional regulatory protein which controls the expression of a number of virulence-related genes with relevance for acute and chronic infections. Many membrane-bound sensors, including RetS, LadS, and GacS, are responsible for the reciprocal regulation of genes associated with acute infection and chronic persistence. In P. aeruginosa this is due to sensors influencing the expression of the regulatory RNA RsmZ, with subsequent effects on the level of free RsmA. While interactions between an rsmA mutant and human airway epithelial cells have been examined in vitro, the role of RsmA during infection in vivo has not been determined yet. Here the function of RsmA in both acute and chronic models of infection was examined. The results demonstrate that RsmA is involved in initial colonization and dissemination in a mouse model of acute pneumonia. Furthermore, while loss of RsmA results in reduced colonization during the initial stages of acute infection, the data show that mutation of rsmA ultimately favors chronic persistence and results in increased inflammation in the lungs of infected mice.

scholarly journals A Novel Infection Protocol in Zebrafish Embryo to Assess Pseudomonas aeruginosa Virulence and Validate Efficacy of a Quorum Sensing Inhibitor In Vivo

Pathogens ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 401
Author(s):  
Pauline Nogaret ◽  
Fatima El El Garah ◽  
Anne-Béatrice Blanc-Potard
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Animal Model ◽  
Quorum Sensing ◽  
Drug Testing ◽  
Drug Efficacy ◽  
Embryo Viability ◽  
Immersion Method ◽  
Opportunistic Human Pathogen

The opportunistic human pathogen Pseudomonas aeruginosa is responsible for a variety of acute infections and is a major cause of mortality in chronically infected cystic fibrosis patients. Due to increased resistance to antibiotics, new therapeutic strategies against P. aeruginosa are urgently needed. In this context, we aimed to develop a simple vertebrate animal model to rapidly assess in vivo drug efficacy against P. aeruginosa. Zebrafish are increasingly considered for modeling human infections caused by bacterial pathogens, which are commonly microinjected in embryos. In the present study, we established a novel protocol for zebrafish infection by P. aeruginosa based on bath immersion in 96-well plates of tail-injured embryos. The immersion method, followed by a 48-hour survey of embryo viability, was first validated to assess the virulence of P. aeruginosa wild-type PAO1 and a known attenuated mutant. We then validated its relevance for antipseudomonal drug testing by first using a clinically used antibiotic, ciprofloxacin. Secondly, we used a novel quorum sensing (QS) inhibitory molecule, N-(2-pyrimidyl)butanamide (C11), the activity of which had been validated in vitro but not previously tested in any animal model. A significant protective effect of C11 was observed on infected embryos, supporting the ability of C11 to attenuate in vivo P. aeruginosa pathogenicity. In conclusion, we present here a new and reliable method to compare the virulence of P. aeruginosa strains in vivo and to rapidly assess the efficacy of clinically relevant drugs against P. aeruginosa, including new antivirulence compounds.

Antimicrobial and antibiofilm activities of meropenem loaded-mesoporous silica nanoparticles against carbapenem-resistant Pseudomonas aeruginosa

2021 ◽  
pp. 088532822110038
Author(s):  
Mohammad Yousef Memar ◽  
Mina Yekani ◽  
Hadi Ghanbari ◽  
Edris Nabizadeh ◽  
Sepideh Zununi Vahed ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Mesoporous Silica ◽  
Silica Nanoparticles ◽  
Mesoporous Silica Nanoparticles ◽  
Carbapenem Resistant ◽  
Toxicity In Vitro ◽  
Different Levels

The aims of the present study were the determination of antimicrobial and antibiofilm effects of meropenem-loaded mesoporous silica nanoparticles (MSNs) on carbapenem resistant Pseudomonas aeruginosa ( P. aeruginosa) and cytotoxicity properties in vitro. The meropenem-loaded MSNs had shown antibacterial and biofilm inhibitory activities on all isolates at different levels lower than MICs and BICs of meropenem. The viability of HC-04 cells treated with serial concentrations as MICs and BICs of meropenem-loaded MSNs was 92–100%. According to the obtained results, meropenem-loaded MSNs display the significant antibacterial and antibiofilm effects against carbapenem resistant and biofilm forming P. aeruginosa and low cell toxicity in vitro. Then, the prepared system can be an appropriate option for the delivery of carbapenem for further evaluation in vivo assays.

scholarly journals Exogenous Alginate Protects Staphylococcus aureus from Killing by Pseudomonas aeruginosa

2019 ◽  
Vol 202 (8) ◽  
Author(s):  
Courtney E. Price ◽  
Dustin G. Brown ◽  
Dominique H. Limoli ◽  
Vanessa V. Phelan ◽  
George A. O’Toole
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Physical Space ◽  
Late Time ◽  
Protective Effects ◽  
Content Type ◽  
Alginate Production ◽  
The Impact

ABSTRACT Cystic fibrosis (CF) patients chronically infected with both Pseudomonas aeruginosa and Staphylococcus aureus have worse health outcomes than patients who are monoinfected with either P. aeruginosa or S. aureus. We showed previously that mucoid strains of P. aeruginosa can coexist with S. aureus in vitro due to the transcriptional downregulation of several toxic exoproducts typically produced by P. aeruginosa, including siderophores, rhamnolipids, and HQNO (2-heptyl-4-hydroxyquinoline N-oxide). Here, we demonstrate that exogenous alginate protects S. aureus from P. aeruginosa in both planktonic and biofilm coculture models under a variety of nutritional conditions. S. aureus protection in the presence of exogenous alginate is due to the transcriptional downregulation of pvdA, a gene required for the production of the iron-scavenging siderophore pyoverdine as well as the downregulation of the PQS (Pseudomonas quinolone signal) (2-heptyl-3,4-dihydroxyquinoline) quorum sensing system. The impact of exogenous alginate is independent of endogenous alginate production. We further demonstrate that coculture of mucoid P. aeruginosa with nonmucoid P. aeruginosa strains can mitigate the killing of S. aureus by the nonmucoid strain of P. aeruginosa, indicating that the mechanism that we describe here may function in vivo in the context of mixed infections. Finally, we investigated a panel of mucoid clinical isolates that retain the ability to kill S. aureus at late time points and show that each strain has a unique expression profile, indicating that mucoid isolates can overcome the S. aureus-protective effects of mucoidy in a strain-specific manner. IMPORTANCE CF patients are chronically infected by polymicrobial communities. The two dominant bacterial pathogens that infect the lungs of CF patients are P. aeruginosa and S. aureus, with ∼30% of patients coinfected by both species. Such coinfected individuals have worse outcomes than monoinfected patients, and both species persist within the same physical space. A variety of host and environmental factors have been demonstrated to promote P. aeruginosa-S. aureus coexistence, despite evidence that P. aeruginosa kills S. aureus when these organisms are cocultured in vitro. Thus, a better understanding of P. aeruginosa-S. aureus interactions, particularly mechanisms by which these microorganisms are able to coexist in proximal physical space, will lead to better-informed treatments for chronic polymicrobial infections.

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