Baicalin Represses Type Three Secretion System of Pseudomonas aeruginosa through PQS System

Therapeutics that target the virulence of pathogens rather than their viability offer a promising alternative for treating infectious diseases and circumventing antibiotic resistance. In this study, we searched for anti-virulence compounds against Pseudomonas aeruginosa from Chinese herbs and investigated baicalin from Scutellariae radix as such an active anti-virulence compound. The effect of baicalin on a range of important virulence factors in P. aeruginosa was assessed using luxCDABE-based reporters and by phenotypical assays. The molecular mechanism of the virulence inhibition by baicalin was investigated using genetic approaches. The impact of baicalin on P. aeruginosa pathogenicity was evaluated by both in vitro assays and in vivo animal models. The results show that baicalin diminished a plenty of important virulence factors in P. aeruginosa, including the Type III secretion system (T3SS). Baicalin treatment reduced the cellular toxicity of P. aeruginosa on the mammalian cells and attenuated in vivo pathogenicity in a Drosophila melanogaster infection model. In a rat pulmonary infection model, baicalin significantly reduced the severity of lung pathology and accelerated lung bacterial clearance. The PqsR of the Pseudomonas quinolone signal (PQS) system was found to be required for baicalin’s impact on T3SS. These findings indicate that baicalin is a promising therapeutic candidate for treating P. aeruginosa infections.

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Virulence-Inhibiting Herbal Compound Falcarindiol Significantly Reduced Mortality in Mice Infected with Pseudomonas aeruginosa

Antibiotics ◽

10.3390/antibiotics9030136 ◽

2020 ◽

Vol 9 (3) ◽

pp. 136 ◽

Cited By ~ 2

Author(s):

Pansong Zhang ◽

Qiaolian Wu ◽

Lin Chen ◽

Kangmin Duan

Keyword(s):

Pseudomonas Aeruginosa ◽

Type Iii Secretion ◽

Pathogenic Bacteria ◽

Secretion System ◽

Chinese Herbs ◽

Drug Candidate ◽

Swarming Motility ◽

Promising Alternative ◽

Alternative Approach ◽

Herbal Compound

Antipathogenic compounds that target the virulence of pathogenic bacteria rather than their viability offer a promising alternative approach to treat infectious diseases. Using extracts from 30 Chinese herbs that are known for treating symptoms resembling infections, we identified an active compound falcarindiol from Notopterygium incisum Ting ex H. T. Chang that showed potent inhibitory activities against Pseudomonas aeruginosa multiple virulence factors. Falcarindiol significantly repressed virulence-related genes, including the type III secretion system (T3SS); quorum sensing synthase genes lasIR and rhlIR; lasB; motility-related genes fliC and fliG; and phenazine synthesis genes phzA1 and phzA2. P. aeruginosa swarming motility and pyocyanin production were reduced significantly. In a burned mouse model, falcarindiol treatment significantly reduced the mortality in mice infected with P. aeruginosa, indicating that falcarindiol is a promising antipathogenic drug candidate for treating P. aeruginosa infections.

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Cephalosporins target quorum sensing and suppress virulence of Pseudomonas aeruginosa in Caenorhabditis elegans infection model

10.1101/2020.05.15.097790 ◽

2020 ◽

Author(s):

Lokender Kumar ◽

Nathanael Brenner ◽

John Brice ◽

Judith Klein-Seetharaman ◽

Susanta K. Sarkar

Keyword(s):

Pseudomonas Aeruginosa ◽

Caenorhabditis Elegans ◽

Quorum Sensing ◽

Virulence Factors ◽

Biofilm Formation ◽

Host Cells ◽

Infection Model ◽

Host Immune System ◽

Bacterial Cells

ABSTRACTPseudomonas aeruginosa utilizes a chemical social networking system referred to as quorum sensing (QS) to strategically co-ordinate the expression of virulence factors and biofilm formation. Virulence attributes damage the host cells, impair the host immune system, and protect bacterial cells from antibiotic attack. Thus, anti-QS agents may act as novel anti-infective therapeutics to treat P. aeruginosa infections. The present study was performed to evaluate the anti-QS, anti-biofilm, and anti-virulence activity of β-lactam antibiotics (carbapenems and cephalosporins) against P. aeruginosa. The anti-QS activity was quantified using Chromobacterium violaceum CV026 as a QS reporter strain. Our results showed that cephalosporins including cefepime (CP), ceftazidime (CF), and ceftriaxone (CT) exhibited potent anti-QS and anti-virulence activities against P. aeruginosa PAO1. These antibiotics significantly impaired motility phenotypes, decreased pyocyanin production, and reduced the biofilm formation by P. aeruginosa PAO1. In the present study, we studied isogenic QS mutants of PAO1: ΔLasR, ΔRhlR, ΔPqsA, and ΔPqsR and found that the levels of virulence factors of antibiotic-treated PAO1 were comparable to QS mutant strains. Molecular docking predicted high binding affinities of cephalosporins for the ligand-binding pocket of QS receptors (CviR, LasR, and PqsR). In addition, our results showed that the anti-microbial activity of aminoglycosides increased in the presence of sub-inhibitory concentrations (sub-MICs) of CP against P. aeruginosa PAO1. Further, utilizing Caenorhabditis elegans as an animal model for the in vivo anti-virulence effects of antibiotics, cephalosporins showed a significant increase in C. elegans survival by suppressing virulence factor production in P. aeruginosa. Thus, our results indicate that cephalosporins might provide a viable anti-virulence therapy in the treatment of infections caused by multi-drug resistant P. aeruginosa.

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In VivoActivities of Ceftolozane, a New Cephalosporin, with and without Tazobactam against Pseudomonas aeruginosa and Enterobacteriaceae, Including Strains with Extended-Spectrum β-Lactamases, in the Thighs of Neutropenic Mice

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01590-12 ◽

2012 ◽

Vol 57 (4) ◽

pp. 1577-1582 ◽

Cited By ~ 88

Author(s):

W. A. Craig ◽

D. R. Andes

Keyword(s):

Pseudomonas Aeruginosa ◽

Infection Model ◽

Wild Type ◽

Gram Negative ◽

Content Type ◽

Peak Dose ◽

Extended Spectrum ◽

The Impact ◽

Primary Index

ABSTRACTCeftolozane is a new cephalosporin with potent activity againstPseudomonas aeruginosaandEnterobacteriaceae. A neutropenic murine thigh infection model was used to determine which pharmacokinetic/pharmacodynamic index and magnitude drives the efficacy of ceftolozane with Gram-negative bacilli, to compare the rates ofin vivokilling ofP. aeruginosaby ceftolozane and ceftazidime, and to determine the impact of different ratios of ceftolozane plus tazobactam onEnterobacteriaceaecontaining extended-spectrum β-lactamases (ESBLs). Neutropenic mice had 106.2-7.1CFU/thigh when treated with ceftolozane for 24 h with (i) various doses (3.12 to 1,600 mg/kg) and dosage intervals (3, 6, 12, and 24 h) against twoEnterobacteriaceaestrains, (ii) 0.39 to 800 mg/kg every 6 h for fourEnterobacteriaceaeand fourP. aeruginosastrains, and (iii) 400 or 800 mg/kg with 2:1. 4:1, and 8:1 ratios of tazobactam against fiveEnterobacteriaceaestrains with ESBLs. The pharmacokinetics of ceftolozane at 25, 100, and 400 mg/kg were linear with peak/dose values of 1.0 to 1.4 and half-lives of 12 to 14 min. T>MIC was the primary index driving efficacy. For stasis (1 log kill), T>MIC was 26.3% ± 2.1% (31.6% ± 1.6%) for wild-typeEnterobacteriaceae, 31.1% ± 4.9% (34.8% ± 4.4%) forEnterobacteriaceaewith ESBLs, and 24.0% ± 3.3% (31.5% ± 3.9%) forP. aeruginosa. At 200 mg/kg every 3 h, the rate ofin vivokilling ofP. aeruginosawas faster with ceftolozane than with ceftazidime (−0.34 to −0.41 log10CFU/thigh/h versus −0.21 to −0.24 log10CFU/thigh/h). The 2:1 ratio of ceftolozane with tazobactam was the most potent combination studied. The T>MIC required for ceftolozane is less than with other cephalosporins and may be due to more rapid killing.

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Tetradecanoic Acids With Anti-Virulence Properties Increase the Pathogenicity of Pseudomonas aeruginosa in a Murine Cutaneous Infection Model

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2020.597517 ◽

2021 ◽

Vol 10 ◽

Author(s):

Martha María Juárez-Rodríguez ◽

Humberto Cortes-López ◽

Rodolfo García-Contreras ◽

Bertha González-Pedrajo ◽

Miguel Díaz-Guerrero ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Molecular Mechanisms ◽

Cell Communication ◽

Infection Model ◽

Cutaneous Infection ◽

Complex Environments ◽

Promising Alternative ◽

Virulence Target

Blocking virulence is a promising alternative to counteract Pseudomonas aeruginosa infections. In this regard, the phenomenon of cell-cell communication by quorum sensing (QS) is an important anti-virulence target. In this field, fatty acids (FA) have gained notoriety for their role as autoinducers, as well as anti-virulence molecules in vitro, like some saturated FA (SAFA). In this study, we analyzed the anti-virulence activity of SAFA with 12 to18 carbon atoms and compared their effect with the putative autoinducer cis-2-decenoic acid (CDA). The effect of SAFA on six QS-regulated virulence factors and on the secretion of the exoenzyme ExoU was evaluated. In addition, a murine cutaneous infection model was used to determine their influence on the establishment and damage caused by P. aeruginosa PA14. Dodecanoic (lauric, C12:0) and tetradecanoic (myristic, C14:0) acids (SAFA C12-14) reduced the production of pyocyanin by 35–58% at 40 and 1,000 µM, while CDA inhibited it 62% at a 3.1 µM concentration. Moreover, the SAFA C12-14 reduced swarming by 90% without affecting biofilm formation. In contrast, CDA reduced the biofilm by 57% at 3 µM but did not affect swarming. Furthermore, lauric and myristic acids abolished ExoU secretion at 100 and 50 µM respectively, while CDA reduced it by ≈ 92% at 100 µM. Remarkably, the coadministration of myristic acid (200 and 1,000 µM) with P. aeruginosa PA14 induced greater damage and reduced survival of the animals up to 50%, whereas CDA to 500 µM reduced the damage without affecting the viability of the PA14 strain. Hence, our results show that SAFA C12-14 and CDA have a role in regulation of P. aeruginosa virulence, although their inhibition/activation molecular mechanisms are different in complex environments such as in vivo systems.

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Spatial determinants of quorum signaling in a Pseudomonas aeruginosa infection model

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1719317115 ◽

2018 ◽

Vol 115 (18) ◽

pp. 4779-4784 ◽

Cited By ~ 47

Author(s):

Sophie E. Darch ◽

Olja Simoska ◽

Mignon Fitzpatrick ◽

Juan P. Barraza ◽

Keith J. Stevenson ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Aggregate Size ◽

Spatial Arrangement ◽

Opportunistic Pathogen ◽

Human Infection ◽

Emergent Properties ◽

Infection Model ◽

Spatial Positioning ◽

The Impact

Quorum sensing (QS) is a bacterial communication system that involves production and sensing of extracellular signals. In laboratory models, QS allows bacteria to monitor and respond to their own cell density and is critical for fitness. However, how QS proceeds in natural, spatially structured bacterial communities is not well understood, which significantly hampers our understanding of the emergent properties of natural communities. To address this gap, we assessed QS signaling in the opportunistic pathogen Pseudomonas aeruginosa in a cystic fibrosis (CF) lung infection model that recapitulates the biogeographical aspects of the natural human infection. In this model, P. aeruginosa grows as spatially organized, highly dense aggregates similar to those observed in the human CF lung. By combining this natural aggregate system with a micro-3D–printing platform that allows for confinement and precise spatial positioning of P. aeruginosa aggregates, we assessed the impact of aggregate size and spatial positioning on both intra- and interaggregate signaling. We discovered that aggregates containing ∼2,000 signal-producing P. aeruginosa were unable to signal neighboring aggregates, while those containing ≥5,000 cells signaled aggregates as far away as 176 µm. Not all aggregates within this “calling distance” responded, indicating that aggregates have differential sensitivities to signal. Overexpression of the signal receptor increased aggregate sensitivity to signal, suggesting that the ability of aggregates to respond is defined in part by receptor levels. These studies provide quantitative benchmark data for the impact of spatial arrangement and phenotypic heterogeneity on P. aeruginosa signaling in vivo.

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The Long-Term Effect of a Nine Amino-Acid Antimicrobial Peptide AS-hepc3(48-56) Against Pseudomonas aeruginosa With No Detectable Resistance

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2021.752637 ◽

2021 ◽

Vol 11 ◽

Author(s):

Depeng Zhu ◽

Fangyi Chen ◽

Yan-Chao Chen ◽

Hui Peng ◽

Ke-Jian Wang

Keyword(s):

Pseudomonas Aeruginosa ◽

Mammalian Cells ◽

Bacterial Resistance ◽

Mouse Lung ◽

Infection Model ◽

Global Public Health ◽

Health Crisis

The emergence of multidrug-resistant (MDR) pathogens has become a global public health crisis. Among them, MDR Pseudomonas aeruginosa is the main cause of nosocomial infections and deaths. Antimicrobial peptides (AMPs) are considered as competitive drug candidates to address this threat. In the study, we characterized two AMPs (AS-hepc3(41-71) and AS-hepc3(48-56)) that had potent activity against 5 new clinical isolates of MDR P. aeruginosa. Both AMPs destroyed the integrity of the cell membrane, induced leakage of intracellular components, and ultimately led to cell death. A long-term comparative study on the bacterial resistance treated with AS-hepc3(41-71), AS-hepc3(48-56) and 12 commonly used antibiotics showed that P. aeruginosa quickly developed resistance to the nine antibiotics tested (including aztreonam, ceftazidime, cefepime, imipenem, meropenem, ciprofloxacin, levofloxacin, gentamicin, and piperacillin) as early as 12 days after 150 days of successive culture generations. The initial effective concentration of 9 antibiotics against P. aeruginosa was greatly increased to a different high level at 150 days, however, both AS-hepc3(41-71) and AS-hepc3(48-56) maintained their initial MIC unchangeable through 150 days, indicating that P. aeruginosa did not produce any significant resistance to both AMPs. Furthermore, AS-hepc3(48-56) did not show any toxic effect on mammalian cells in vitro and mice in vivo. AS-hepc3(48-56) had a therapeutic effect on MDR P. aeruginosa infection using a mouse lung infection model and could effectively increase the survival rate of mice by inhibiting bacterial proliferation and attenuating lung inflammation. Taken together, the short peptide AS-hepc3(48-56) would be a promising agent for clinical treatment of MDR P. aeruginosa infections.

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The Pseudomonas aeruginosa ExoY phenotype of high-copy-number recombinants is not detectable in natural isolates

Open Biology ◽

10.1098/rsob.170250 ◽

2018 ◽

Vol 8 (1) ◽

pp. 170250 ◽

Cited By ~ 5

Author(s):

Antje Munder ◽

Justin Rothschuh ◽

Bastian Schirmer ◽

Jens Klockgether ◽

Volkhard Kaever ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Copy Number ◽

Mammalian Cells ◽

Real Life ◽

High Copy Number ◽

Infection Model ◽

Loss Of Function ◽

Natural Isolates

The nucleotidyl cyclase ExoY is an effector protein of the type III secretion system of Pseudomonas aeruginosa . We compared the cyclic nucleotide production and lung disease phenotypes caused by the ExoY-overexpressing strain PA103Δ exoUexoT::Tc pUCP exoY , its vector control strain PA103Δ exoUexoT::Tc pUCP18, its loss-of-function control PA103Δ exoUexoT::Tc pUCP exoY K81M and natural ExoY-positive and ExoY-negative isolates in a murine acute airway infection model. Only the P. aeruginosa carrier of the exoY- plasmid produced high levels of cUMP and caused the most severe course of infection. The pathology ascribed to ExoY from studies using the high-copy-number plasmid on mammalian cells in vitro and in vivo was not observed with natural P. aeruginosa isolates. This indicates that the role of ExoY during infection with real-life P. aeruginosa still needs to be resolved.

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An Adenylate Cyclase-Controlled Signaling Network Regulates Pseudomonas aeruginosa Virulence in a Mouse Model of Acute Pneumonia

Infection and Immunity ◽

10.1128/iai.72.3.1677-1684.2004 ◽

2004 ◽

Vol 72 (3) ◽

pp. 1677-1684 ◽

Cited By ~ 90

Author(s):

Roger S. Smith ◽

Matthew C. Wolfgang ◽

Stephen Lory

Keyword(s):

Pseudomonas Aeruginosa ◽

Adenylate Cyclase ◽

Virulence Factors ◽

Type Iii Secretion ◽

Regulatory Network ◽

Regulatory Protein ◽

Type Iii Secretion System ◽

Secretion System ◽

Lung Pathology ◽

Type Iii

ABSTRACT Infections caused by the opportunistic pathogen Pseudomonas aeruginosa involve the interplay of several bacterial virulence factors. It has recently been established that the delivery of toxic effector proteins by the type III secretion system is an important virulence mechanism in several animal models. Furthermore, the expression of the type III secretion system and its effectors has been correlated with a poor clinical outcome during human infections. A novel cyclic AMP (cAMP) regulatory network that controls the expression of virulence factors, including the type III secretion system, was examined to determine its contribution to P. aeruginosa colonization and dissemination in a mouse pneumonia model. Mutants lacking the two genome-encoded adenylate cyclases, CyaA and CyaB, and the cAMP-dependent regulator Vfr were examined. Based on the enumeration of bacteria in lungs, livers, and spleens, as well as the assessment of mouse lung pathology, mutations in the cyaB and vfr genes resulted in a more significantly attenuated phenotype than mutations in cyaA. Moreover, in this model, expression of the type III secretion system was essential for lung colonization and pathology. Strains with mutations in the exsA gene, which encodes a type III regulatory protein, or pscC, which encodes an essential component of the secretion apparatus, were also significantly attenuated. Finally, we demonstrate that virulence can be restored in an adenylate cyclase mutant by the overexpression of exsA, which specifically restores expression of the type III secretion system in the absence of a functional cAMP-dependent regulatory network.

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Paeonol Attenuates Quorum-Sensing Regulated Virulence and Biofilm Formation in Pseudomonas aeruginosa

Frontiers in Microbiology ◽

10.3389/fmicb.2021.692474 ◽

2021 ◽

Vol 12 ◽

Author(s):

Dan Yang ◽

Suqi Hao ◽

Ling Zhao ◽

Fei Shi ◽

Gang Ye ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Virulence Factors ◽

Biofilm Formation ◽

Resistant Bacteria ◽

Infection Model ◽

Dependent Manner ◽

Gram Negative ◽

C Elegans

With the prevalence of multidrug-resistant bacteria and clinical -acquired pathogenic infections, the development of quorum-sensing (QS) interfering agents is one of the most potential strategies to combat bacterial infections and antibiotic resistance. Chinese herbal medicines constitute a valuable bank of resources for the identification of QS inhibitors. Accordingly, in this research, some compounds were tested for QS inhibition using indicator strains. Paeonol is a phenolic compound, which can effectively reduce the production of violacein without affecting its growth in Chromobacterium violaceum ATCC 12472, indicating its excellent anti-QS activity. This study assessed the anti-biofilm activity of paeonol against Gram-negative pathogens and investigated the effect of paeonol on QS-regulated virulence factors in Pseudomonas aeruginosa. A Caenorhabditis elegans infection model was used to explore the anti-infection ability of paeonol in vivo. Paeonol exhibited an effective anti-biofilm activity against Gram-negative bacteria. The ability of paeonol to interfere with the AHL-mediated quorum sensing systems of P. aeruginosa was determined, found that it could attenuate biofilm formation, and synthesis of pyocyanin, protease, elastase, motility, and AHL signaling molecule in a concentration- and time-dependent manner. Moreover, paeonol could significantly downregulate the transcription level of the QS-related genes of P. aeruginosa including lasI/R, rhlI/R, pqs/mvfR, as well as mediated its virulence factors, lasA, lasB, rhlA, rhlC, phzA, phzM, phzH, and phzS. In vivo studies revealed that paeonol could reduce the pathogenicity of P. aeruginosa and enhance the survival rate of C. elegans, showing a moderate protective effect on C. elegans. Collectively, these findings suggest that paeonol attenuates bacterial virulence and infection of P. aeruginosa and that further research elucidating the anti-QS mechanism of this compound in vivo is warranted.

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Histological, Biomechanical, and Biological Properties of Genipin-Crosslinked Decellularized Peripheral Nerves

International Journal of Molecular Sciences ◽

10.3390/ijms22020674 ◽

2021 ◽

Vol 22 (2) ◽

pp. 674

Author(s):

Óscar Darío García-García ◽

Marwa El Soury ◽

David González-Quevedo ◽

David Sánchez-Porras ◽

Jesús Chato-Astrain ◽

...

Keyword(s):

Ex Vivo ◽

Nerve Repair ◽

Wistar Rat ◽

Biomechanical Properties ◽

Biological Properties ◽

Suitable Alternative ◽

Promising Alternative ◽

Histological Pattern ◽

The Impact

Acellular nerve allografts (ANGs) represent a promising alternative in nerve repair. Our aim is to improve the structural and biomechanical properties of biocompatible Sondell (SD) and Roosens (RS) based ANGs using genipin (GP) as a crosslinker agent ex vivo. The impact of two concentrations of GP (0.10% and 0.25%) on Wistar rat sciatic nerve-derived ANGs was assessed at the histological, biomechanical, and biocompatibility levels. Histology confirmed the differences between SD and RS procedures, but not remarkable changes were induced by GP, which helped to preserve the nerve histological pattern. Tensile test revealed that GP enhanced the biomechanical properties of SD and RS ANGs, being the crosslinked RS ANGs more comparable to the native nerves used as control. The evaluation of the ANGs biocompatibility conducted with adipose-derived mesenchymal stem cells cultured within the ANGs confirmed a high degree of biocompatibility in all ANGs, especially in RS and RS-GP 0.10% ANGs. Finally, this study demonstrates that the use of GP could be an efficient alternative to improve the biomechanical properties of ANGs with a slight impact on the biocompatibility and histological pattern. For these reasons, we hypothesize that our novel crosslinked ANGs could be a suitable alternative for future in vivo preclinical studies.

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