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 ◽  
...  

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.

2006 ◽  
Vol 74 (8) ◽  
pp. 4462-4473 ◽  
Author(s):  
Michelle A. Laskowski ◽  
Barbara I. Kazmierczak

ABSTRACT Pseudomonas aeruginosa is an opportunistic pathogen capable of causing both acute and chronic infections in a wide range of hosts. Expression of the type III secretion system (T3SS) proteins is correlated with virulence in models of acute infection, while downregulation of the T3SS and upregulation of genes important for biofilm formation are observed during chronic infections. RetS, a hybrid sensor kinase-response regulator protein of P. aeruginosa, plays a key role in the reciprocal regulation of virulence factors required for acute versus chronic infection and is postulated to act in concert with two other sensor kinase-response regulator hybrids, GacS and LadS. This work examines the roles of the putative sensing and signal transduction domains of RetS in induction of the T3SS in vitro and in a murine model of acute pneumonia. We identify distinct signaling roles for the tandem receiver domains of RetS and present evidence suggesting that RetS may serve as a substrate for another sensor kinase. Phenotypes associated with RetS alleles lacking periplasmic and/or transmembrane domains further indicate that the periplasmic domain of RetS may transmit a signal that inhibits RetS activity during acute infections.


2021 ◽  
Vol 22 (16) ◽  
pp. 8632
Author(s):  
Petra Pusic ◽  
Elisabeth Sonnleitner ◽  
Udo Bläsi

Pseudomonas aeruginosa (Pae) is an opportunistic pathogen showing a high intrinsic resistance to a wide variety of antibiotics. It causes nosocomial infections that are particularly detrimental to immunocompromised individuals and to patients suffering from cystic fibrosis. We provide a snapshot on regulatory RNAs of Pae that impact on metabolism, pathogenicity and antibiotic susceptibility. Different experimental approaches such as in silico predictions, co-purification with the RNA chaperone Hfq as well as high-throughput RNA sequencing identified several hundreds of regulatory RNA candidates in Pae. Notwithstanding, using in vitro and in vivo assays, the function of only a few has been revealed. Here, we focus on well-characterized small base-pairing RNAs, regulating specific target genes as well as on larger protein-binding RNAs that sequester and thereby modulate the activity of translational repressors. As the latter impact large gene networks governing metabolism, acute or chronic infections, these protein-binding RNAs in conjunction with their cognate proteins are regarded as global post-transcriptional regulators.


2007 ◽  
Vol 76 (2) ◽  
pp. 632-638 ◽  
Author(s):  
Heidi Mulcahy ◽  
Julie O'Callaghan ◽  
Eoin P. O'Grady ◽  
María D. Maciá ◽  
Nuria Borrell ◽  
...  

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.


2018 ◽  
Vol 12 (02.1) ◽  
pp. 8S
Author(s):  
Sari S Rasheed ◽  
Kohar Annie Kissoyan ◽  
Usamah Hadi ◽  
Marwan El-Sabban ◽  
Ghassan M Matar

Introduction: 1,3-β-D-glucan of the fungal cell wall and extracellular matrix (ECM) of Candida biofilm is also present as a periplasmic glucan and within the ECM of P. aeruginosa biofilm. Micafungin inhibits the synthesis of β-D-glucans. This project evaluates the effect of micafungin on P. aeruginosa biofilm formation, by determining transcription levels of biofilm formation encoding genes and measuring the thickness of biofilms in treated and untreated samples from BALB/c mice. Methodology: Rrelative gene transcription levels of P. aeruginosa biofilm-encoding pelC, algC, and ndvB genes were assessed by RT-qPCR on treated and untreated samples. Thickness calculation by Z-stacking of treated and untreated biofilms obtained from in vitro and in vivo samples was determined by confocal scanning laser microscopy (CSLM). Results: Samples from micafungin-treated mice showed decreased pelC, ndvB, and algC transcription levels with values of 260, 74, and 2-fold decreases, respectively. Reduction in biofilms thickness was confirmed with Z-stacking using CSLM that revealed a 16.8% drop in the thickness of biofilms after treatment with micafungin in vitro, and a 64% reduction in thickness post treatment with micafungin in vivo. Conclusion: Micafungin inhibits biofilm formation as measured by decrease in transcription levels of biofilm encoding genes and confocal microscopy. This reflects the events occurring in the course of an acute infection with P. aeruginosa, whereby the administration of micafungin would inhibit subsequent slime production, thus eliminating such barrier that could prevent antibacterial delivery to the core planktonic cells in biofilms. Introduction: 1,3-β-D-glucan of the fungal cell wall and extracellular matrix (ECM) of Candida biofilm is also present as a periplasmic glucan and within the ECM of P. aeruginosa biofilm. Micafungin inhibits the synthesis of β-D-glucans. This project evaluates the effect of micafungin on P. aeruginosa biofilm formation, by determining transcription levels of biofilm formation encoding genes and measuring the thickness of biofilms in treated and untreated samples from BALB/c mice. Methodology: Rrelative gene transcription levels of P. aeruginosa biofilm-encoding pelC, algC, and ndvB genes were assessed by RT-qPCR on treated and untreated samples. Thickness calculation by Z-stacking of treated and untreated biofilms obtained from in vitro and in vivo samples was determined by confocal scanning laser microscopy (CSLM). Results: Samples from micafungin-treated mice showed decreased pelC, ndvB, and algC transcription levels with values of 260, 74, and 2-fold decreases, respectively. Reduction in biofilms thickness was confirmed with Z-stacking using CSLM that revealed a 16.8% drop in the thickness of biofilms after treatment with micafungin in vitro, and a 64% reduction in thickness post treatment with micafungin in vivo. Conclusion: Micafungin inhibits biofilm formation as measured by decrease in transcription levels of biofilm encoding genes and confocal microscopy. This reflects the events occurring in the course of an acute infection with P. aeruginosa, whereby the administration of micafungin would inhibit subsequent slime production, thus eliminating such barrier that could prevent antibacterial delivery to the core planktonic cells in biofilms.


Microbiology ◽  
2009 ◽  
Vol 155 (8) ◽  
pp. 2612-2619 ◽  
Author(s):  
Lisa K. Nelson ◽  
Genevieve H. D'Amours ◽  
Kimberley M. Sproule-Willoughby ◽  
Douglas W. Morck ◽  
Howard Ceri

Pseudomonas aeruginosa frequently acts as an opportunistic pathogen of mucosal surfaces; yet, despite causing aggressive prostatitis in some men, its role as a pathogen in the prostate has not been investigated. Consequently, we developed a Ps. aeruginosa infection model in the rat prostate by instilling wild-type (WT) Ps. aeruginosa strain PAO1 into the rat prostate. It was found that Ps. aeruginosa produced acute and chronic infections in this mucosal tissue as determined by bacterial colonization, gross morphology, tissue damage and inflammatory markers. WT strain PAO1 and its isogenic mutant PAO-JP2, in which both the lasI and rhlI quorum-sensing signal systems have been silenced, were compared during both acute and chronic prostate infections. In acute infections, bacterial numbers and inflammatory markers were comparable between WT PA01 and PAO-JP2; however, considerably less tissue damage occurred in infections with PAO-JP2. Chronic infections with PAO-JP2 resulted in reduced bacterial colonization, tissue damage and inflammation as compared to WT PAO1 infections. Therefore, the quorum-sensing lasI and rhlI genes in Ps. aeruginosa affect acute prostate infections, but play a considerably more important role in maintaining chronic infections. We have thus developed a highly reproducible model for the study of Ps. aeruginosa virulence in the prostate.


2020 ◽  
Vol 64 (9) ◽  
Author(s):  
Jennifer Martynowicz ◽  
J. Stone Doggett ◽  
William J. Sullivan

ABSTRACT Toxoplasma gondii, an obligate intracellular parasite that can cause life-threatening acute disease, differentiates into a quiescent cyst stage to establish lifelong chronic infections in animal hosts, including humans. This tissue cyst reservoir, which can reactivate into an acute infection, is currently refractory to clinically available therapeutics. Recently, we and others have discovered drugs capable of significantly reducing the brain cyst burden in latently infected mice, but not to undetectable levels. In this study, we examined the use of novel combination therapies possessing multiple mechanisms of action in mouse models of latent toxoplasmosis. Our drug regimens included combinations of pyrimethamine, clindamycin, guanabenz, and endochin-like quinolones (ELQs) and were administered to two different mouse strains in an attempt to eradicate brain tissue cysts. We observed mouse strain-dependent effects with these drug treatments: pyrimethamine-guanabenz showed synergistic efficacy in C57BL/6 mice yet did not improve upon guanabenz monotherapy in BALB/c mice. Contrary to promising in vitro results demonstrating toxicity to bradyzoites, we observed an antagonistic effect between guanabenz and ELQ-334 in vivo. While we were unable to completely eliminate the brain cyst burden, we found that a combination treatment with ELQ-334 and pyrimethamine impressively reduced the brain cyst burden by 95% in C57BL/6 mice, which approached the limit of detection. These analyses highlight the importance of evaluating anti-infective drugs in multiple mouse strains and will help inform further preclinical studies of cocktail therapies designed to treat chronic toxoplasmosis.


2015 ◽  
Vol 309 (8) ◽  
pp. L902-L913 ◽  
Author(s):  
Yash R. Patankar ◽  
Rodwell Mabaera ◽  
Brent Berwin

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.


2018 ◽  
Vol 115 (42) ◽  
pp. 10714-10719 ◽  
Author(s):  
Alana Schick ◽  
Rees Kassen

Chronic infection of the cystic fibrosis (CF) airway by the opportunistic pathogen Pseudomonas aeruginosa is the leading cause of morbidity and mortality for adult CF patients. Prolonged infections are accompanied by adaptation of P. aeruginosa to the unique conditions of the CF lung environment, as well as marked diversification of the pathogen into phenotypically and genetically distinct strains that can coexist for years within a patient. Little is known, however, about the causes of this diversification and its impact on patient health. Here, we show experimentally that, consistent with ecological theory of diversification, the nutritional conditions of the CF airway can cause rapid and extensive diversification of P. aeruginosa. Mucin, the substance responsible for the increased viscosity associated with the thick mucus layer in the CF airway, had little impact on within-population diversification but did promote divergence among populations. Furthermore, in vitro evolution recapitulated traits thought to be hallmarks of chronic infection, including reduced motility and increased biofilm formation, and the range of phenotypes observed in a collection of clinical isolates. Our results suggest that nutritional complexity and reduced dispersal can drive evolutionary diversification of P. aeruginosa independent of other features of the CF lung such as an active immune system or the presence of competing microbial species. We suggest that diversification, by generating extensive phenotypic and genetic variation on which selection can act, may be a key first step in the development of chronic infections.


2014 ◽  
Vol 82 (4) ◽  
pp. 1638-1647 ◽  
Author(s):  
Ziyu Sun ◽  
Jing Shi ◽  
Chang Liu ◽  
Yongxin Jin ◽  
Kewei Li ◽  
...  

ABSTRACTPseudomonas aeruginosais an opportunistic pathogen that causes acute and chronic infections in humans. Pyocins are bacteriocins produced byP. aeruginosathat are usually released through lysis of the producer strains. Expression of pyocin genes is negatively regulated by PrtR, which gets cleaved under SOS response, leading to upregulation of pyocin synthetic genes. Previously, we demonstrated that PrtR is required for the expression of type III secretion system (T3SS), which is an important virulence component ofP. aeruginosa. In this study, we demonstrate that mutation inprtRresults in reduced bacterial colonization in a mouse acute pneumonia model. Examination of bacterial and host cells in the bronchoalveolar lavage fluids from infected mice revealed that expression of PrtR is induced by reactive oxygen species (ROS) released by neutrophils. We further demonstrate that treatment with hydrogen peroxide or ciprofloxacin, known to induce the SOS response and pyocin production, resulted in an elevated PrtR mRNA level. Overexpression of PrtR by atacpromoter repressed the endogenousprtRpromoter activity, and electrophoretic mobility shift assay revealed that PrtR binds to its own promoter, suggesting an autorepressive mechanism of regulation. A high level of PrtR expressed from a plasmid resulted in increased T3SS gene expression during infection and higher resistance against ciprofloxacin. Overall, our results suggest that the autorepression of PrtR contributes to the maintenance of a relatively stable level of PrtR, which is permissive to T3SS gene expression in the presence of ROS while increasing bacterial tolerance to stresses, such as ciprofloxacin, by limiting pyocin production.


2006 ◽  
Vol 74 (5) ◽  
pp. 2985-2995 ◽  
Author(s):  
JoAnn M. Tufariello ◽  
Kaixia Mi ◽  
Jiayong Xu ◽  
Yukari C. Manabe ◽  
Anup K. Kesavan ◽  
...  

ABSTRACT Approximately one-third of the human population is latently infected with Mycobacterium tuberculosis, comprising a critical reservoir for disease reactivation. Despite the importance of latency in maintaining M. tuberculosis in the human population, little is known about the mycobacterial factors that regulate persistence and reactivation. Previous in vitro studies have implicated a family of five related M. tuberculosis proteins, called resuscitation promoting factors (Rpfs), in regulating mycobacterial growth. We studied the in vivo role of M. tuberculosis rpf genes in an established mouse model of M. tuberculosis persistence and reactivation. After an aerosol infection with the M. tuberculosis Erdman wild type (Erdman) or single-deletion rpf mutants to establish chronic infections in mice, reactivation was induced by administration of the nitric oxide (NO) synthase inhibitor aminoguanidine. Of the five rpf deletion mutants tested, one (ΔRv1009) exhibited a delayed reactivation phenotype, manifested by delayed postreactivation growth kinetics and prolonged median survival times among infected animals. Immunophenotypic analysis suggested differences in pulmonary B-cell responses between Erdman- and ΔRv1009-infected mice at advanced stages of reactivation. Analysis of rpf gene expression in the lungs of Erdman-infected mice revealed that relative expression of four of the five rpf-like genes was diminished at late times following reactivation, when bacterial numbers had increased substantially, suggesting that rpf gene expression may be regulated in a growth phase-dependent manner. To our knowledge, ΔRv1009 is the first M. tuberculosis mutant to have a specific defect in reactivation without accompanying growth defects in vitro or during acute infection in vivo.


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