WS19.3 Virulence of serial Pseudomonas aeruginosa isolates grown under aerobic and anaerobic conditions using the Galleria mellonella infection model

ABSTRACT Pseudomonas aeruginosa, one of the most common pathogens in hospital-acquired infections, is tightly controlled by a multilayered regulatory network, including the quorum sensing system (QS), the type VI secretion system (T6SS), and resistance to host immunity. We found that the P. aeruginosa 3880 (PA3880) gene, which encodes an unknown protein, acts as a regulator of anaerobic metabolism in response to oxidative stress and virulence in P. aeruginosa. More than 30 PA3880 homologs were found in other bacterial genomes, indicating that PA3880 is widely distributed in the Bacteria kingdom as a highly conserved gene. Deletion of the PA3880 gene changed the expression levels of more than 700 genes, including a group of virulence genes, under both aerobic and anaerobic conditions. To further study the mechanisms of PA3880-mediated regulation in virulence, we utilized a bacterial two-hybrid assay and found that the PA3880 protein interacted directly with QS regulator MvfR and anaerobic regulator Anr. Loss of the PA3880 protein significantly blunted the pathogenicity of P. aeruginosa, resulting in increased host survival, decreased bacterial burdens, reduced inflammatory responses, and fewer lung injuries in challenged mice hosts. Mechanistically, we found that Cys44 was a critical site for the full function of PA3880 in influencing alveolar macrophage phagocytosis and bacterial clearance. We also found that AnvM directly interacted with host receptors Toll-like receptor 2 (TLR2) and TLR5, which might lead to activation of the host immune response. Hence, we gave the name AnvM (anaerobic and virulence modulator) to the PA3880 protein. This characterization of AnvM could help to uncover new targets and strategies to treat P. aeruginosa infections. IMPORTANCE Infections by Pseudomonas aeruginosa, one of the most frequently isolated human pathogens, can create huge financial burdens. However, knowledge of the molecular mechanisms involved in the pathogenesis of P. aeruginosa remains elusive. We identified AnvM as a novel regulator of virulence in P. aeruginosa. Deletion of anvM altered the expression levels of more than 700 genes under aerobic and anaerobic conditions, including quorum sensing system genes and oxidative stress resistance genes. AnvM directly interacted with MvfR and Anr, thus regulating their downstream genes. More importantly, AnvM directly bound to TLR2 and TLR5, which turn on the host immune response. These findings provide insights into the significance of AnvM homologs in pathogenic bacteria and suggest a potential drug target against bacterial infection.

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The Effects of Differential Protease Secretion by Pseudomonas aeruginosa under Aerobic and Anaerobic Conditions In Vitro.

10.1164/ajrccm-conference.2009.179.1_meetingabstracts.a1772 ◽

2009 ◽

Author(s):

S Cosgrove ◽

N Guyot ◽

CM Greene ◽

NG McElvaney

Keyword(s):

Pseudomonas Aeruginosa ◽

Anaerobic Conditions ◽

Protease Secretion ◽

Aerobic And Anaerobic ◽

Aerobic And Anaerobic Conditions

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Antimicrobial Activity of Fosfomycin-Tobramycin Combination against Pseudomonas aeruginosa Isolates Assessed by Time-Kill Assays and Mutant Prevention Concentrations

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00822-15 ◽

2015 ◽

Vol 59 (10) ◽

pp. 6039-6045 ◽

Cited By ~ 18

Author(s):

María Díez-Aguilar ◽

María Isabel Morosini ◽

Ana P. Tedim ◽

Irene Rodríguez ◽

Zerrin Aktaş ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Wild Type ◽

Anaerobic Conditions ◽

Mutant Selection ◽

Content Type ◽

Mutant Prevention Concentration ◽

Fosfomycin Resistance ◽

Time Kill ◽

Aerobic And Anaerobic ◽

Aerobic And Anaerobic Conditions

ABSTRACTThe antibacterial activity of fosfomycin-tobramycin combination was studied by time-kill assay in eightPseudomonas aeruginosaclinical isolates belonging to the fosfomycin wild-type population (MIC = 64 μg/ml) but with different tobramycin susceptibilities (MIC range, 1 to 64 μg/ml). The mutant prevention concentration (MPC) and mutant selection window (MSW) were determined in five of these strains (tobramycin MIC range, 1 to 64 μg/ml) in aerobic and anaerobic conditions simulating environments that are present in biofilm-mediated infections. Fosfomycin-tobramycin was synergistic and bactericidal for the isolates with mutations in themexZrepressor gene, with a tobramycin MIC of 4 μg/ml. This effect was not observed in strains displaying tobramycin MICs of 1 to 2 μg/ml due to the strong bactericidal effect of tobramycin alone. Fosfomycin presented higher MPC values (range, 2,048 to >2,048 μg/ml) in aerobic and anaerobic conditions than did tobramycin (range, 16 to 256 μg/ml). Interestingly, the association rendered narrow or even null MSWs in the two conditions. However, for isolates with high-level tobramycin resistance that harbored aminoglycoside nucleotidyltransferases, time-kill assays showed no synergy, with wide MSWs in the two environments.glpTgene mutations responsible for fosfomycin resistance inP. aeruginosawere determined in fosfomycin-susceptible wild-type strains and mutant derivatives recovered from MPC studies. All mutant derivatives had changes in the GlpT amino acid sequence, which resulted in a truncated permease responsible for fosfomycin resistance. These results suggest that fosfomycin-tobramycin can be an alternative for infections due toP. aeruginosasince it has demonstrated synergistic and bactericidal activity in susceptible isolates and those with low-level tobramycin resistance. It also prevents the emergence of resistant mutants in either aerobic or anaerobic environments.

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Antibacterial Action of Nitric Oxide-Releasing Chitosan Oligosaccharides against Pseudomonas aeruginosa under Aerobic and Anaerobic Conditions

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01208-15 ◽

2015 ◽

Vol 59 (10) ◽

pp. 6506-6513 ◽

Cited By ~ 28

Author(s):

Katelyn P. Reighard ◽

Mark H. Schoenfisch

Keyword(s):

Nitric Oxide ◽

Pseudomonas Aeruginosa ◽

Anaerobic Conditions ◽

No Donor ◽

Bacterial Killing ◽

Content Type ◽

Bacterial Physiology ◽

Chitosan Oligosaccharides ◽

Aerobic And Anaerobic ◽

Aerobic And Anaerobic Conditions

ABSTRACTChitosan oligosaccharides were modified withN-diazeniumdiolates to yield biocompatible nitric oxide (NO) donor scaffolds. The minimum bactericidal concentrations and MICs of the NO donors againstPseudomonas aeruginosawere compared under aerobic and anaerobic conditions. Differential antibacterial activities were primarily the result of NO scavenging by oxygen under aerobic environments and not changes in bacterial physiology. Bacterial killing was also tested against nonmucoid and mucoid biofilms and compared to that of tobramycin. Smaller NO payloads were required to eradicateP. aeruginosabiofilms under anaerobic versus aerobic conditions. Under oxygen-free environments, the NO treatment was 10-fold more effective at killing biofilms than tobramycin. These results demonstrate the potential utility of NO-releasing chitosan oligosaccharides under both aerobic and anaerobic environments.

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Impairment of Pseudomonas aeruginosa Biofilm Resistance to Antibiotics by Combining the Drugs with a New Quorum-Sensing Inhibitor

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02533-15 ◽

2015 ◽

Vol 60 (3) ◽

pp. 1676-1686 ◽

Cited By ~ 42

Author(s):

Aurelie Furiga ◽

Barbora Lajoie ◽

Salome El Hage ◽

Genevieve Baziard ◽

Christine Roques

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Homoserine Lactone ◽

Regulatory Genes ◽

Antibiofilm Activity ◽

Anaerobic Conditions ◽

Content Type ◽

Biofilm Development ◽

Aerobic And Anaerobic ◽

Aerobic And Anaerobic Conditions

Pseudomonas aeruginosaplays an important role in chronic lung infections among patients with cystic fibrosis (CF) through its ability to form antibiotic-resistant biofilms. InP. aeruginosa, biofilm development and the production of several virulence factors are mainly regulated by therhlandlasquorum-sensing (QS) systems, which are controlled by twoN-acyl-homoserine lactone signal molecules. In a previous study, we discovered an original QS inhibitor,N-(2-pyrimidyl)butanamide, called C11, based on the structure of C4-homoserine lactone, and found that it is able to significantly inhibitP. aeruginosabiofilm formation. However, recent data indicate thatP. aeruginosagrows under anaerobic conditions and forms biofilms in the lungs of CF patients that are denser and more robust than those formed under aerobic conditions. Our confocal microscopy observations ofP. aeruginosabiofilms developed under aerobic and anaerobic conditions confirmed that the biofilms formed under these two conditions have radically different architectures. C11 showed significant dose-dependent antibiofilm activity on biofilms grown under both aerobic and anaerobic conditions, with a greater inhibitory effect being seen under conditions of anaerobiosis. Gene expression analyses performed by quantitative reverse transcriptase PCR showed that C11 led to the significant downregulation ofrhlQS regulatory genes but also to the downregulation of bothlasQS regulatory genes and QS system-regulated virulence genes,rhlAandlasB. Furthermore, the activity of C11 in combination with antibiotics againstP. aeruginosabiofilms was tested, and synergistic antibiofilm activity between C11 and ciprofloxacin, tobramycin, and colistin was obtained under both aerobic and anaerobic conditions. This study demonstrates that C11 may increase the efficacy of treatments forP. aeruginosainfections by increasing the susceptibility of biofilms to antibiotics and by attenuating the pathogenicity of the bacterium.

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