scholarly journals Inactivation of the Glycoside Hydrolase NagZ Attenuates Antipseudomonal β-Lactam Resistance in Pseudomonas aeruginosa

2009 ◽  
Vol 53 (6) ◽  
pp. 2274-2282 ◽  
Author(s):  
Azizah Asgarali ◽  
Keith A. Stubbs ◽  
Antonio Oliver ◽  
David J. Vocadlo ◽  
Brian L. Mark
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Glycoside Hydrolase ◽  
Null Mutant ◽  
Gram Negative ◽  
Molecule Inhibitor ◽  
Clinical Resistance ◽  
Gram Negative Organisms ◽  
Null Mutants ◽  
Selection Of

ABSTRACT The overproduction of chromosomal AmpC β-lactamase poses a serious challenge to the successful treatment of Pseudomonas aeruginosa infections with β-lactam antibiotics. The induction of ampC expression by β-lactams is mediated by the disruption of peptidoglycan (PG) recycling and the accumulation of cytosolic 1,6-anhydro-N-acetylmuramyl peptides, catabolites of PG recycling that are generated by an N-acetyl-β-d-glucosaminidase encoded by nagZ (PA3005). In the absence of β-lactams, ampC expression is repressed by three AmpD amidases encoded by ampD, ampDh2, and ampDh3, which act to degrade these 1,6-anhydro-N-acetylmuramyl peptide inducer molecules. The inactivation of ampD genes results in the stepwise upregulation of ampC expression and clinical resistance to antipseudomonal β-lactams due to the accumulation of the ampC inducer anhydromuropeptides. To examine the role of NagZ on AmpC-mediated β-lactam resistance in P. aeruginosa, we inactivated nagZ in P. aeruginosa PAO1 and in an isogenic triple ampD null mutant. We show that the inactivation of nagZ represses both the intrinsic β-lactam resistance (up to 4-fold) and the high antipseudomonal β-lactam resistance (up to 16-fold) that is associated with the loss of AmpD activity. We also demonstrate that AmpC-mediated resistance to antipseudomonal β-lactams can be attenuated in PAO1 and in a series of ampD null mutants using a selective small-molecule inhibitor of NagZ. Our results suggest that the blockage of NagZ activity could provide a strategy to enhance the efficacies of β-lactams against P. aeruginosa and other gram-negative organisms that encode inducible chromosomal ampC and to counteract the hyperinduction of ampC that occurs from the selection of ampD null mutations during β-lactam therapy.

scholarly journals MexAB-OprM Efflux Pump Interaction with the Peptidoglycan of Escherichia coli and Pseudomonas aeruginosa

2021 ◽  
Vol 22 (10) ◽  
pp. 5328
Author(s):  
Miao Ma ◽  
Margaux Lustig ◽  
Michèle Salem ◽  
Dominique Mengin-Lecreulx ◽  
Gilles Phan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Cell Division ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Efflux Pump ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Active Efflux

One of the major families of membrane proteins found in prokaryote genome corresponds to the transporters. Among them, the resistance-nodulation-cell division (RND) transporters are highly studied, as being responsible for one of the most problematic mechanisms used by bacteria to resist to antibiotics, i.e., the active efflux of drugs. In Gram-negative bacteria, these proteins are inserted in the inner membrane and form a tripartite assembly with an outer membrane factor and a periplasmic linker in order to cross the two membranes to expulse molecules outside of the cell. A lot of information has been collected to understand the functional mechanism of these pumps, especially with AcrAB-TolC from Escherichia coli, but one missing piece from all the suggested models is the role of peptidoglycan in the assembly. Here, by pull-down experiments with purified peptidoglycans, we precise the MexAB-OprM interaction with the peptidoglycan from Escherichia coli and Pseudomonas aeruginosa, highlighting a role of the peptidoglycan in stabilizing the MexA-OprM complex and also differences between the two Gram-negative bacteria peptidoglycans.

scholarly journals The extraction of cell walls of Pseudomonas aeruginosa with aqueous phenol. The insoluble residue and material from the aqueous layers

1967 ◽  
Vol 105 (2) ◽  
pp. 759-765 ◽  
Author(s):  
K. Clarke ◽  
G. W. Gray ◽  
D. A. Reaveley
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cell Wall ◽  
Cell Walls ◽  
Lipid A ◽  
Diaminopimelic Acid ◽  
Insoluble Residue ◽  
Muramic Acid ◽  
Gram Negative ◽  
Gram Negative Organisms ◽  
Residue Fraction

1. The insoluble residue and material present in the aqueous layers resulting from treatment of cell walls of Pseudomonas aeruginosa with aqueous phenol were examined. 2. The products (fractions AqI and AqII) isolated from the aqueous layers from the first and second extractions respectively account for approx. 25% and 12% of the cell wall and consist of both lipopolysaccharide and muropeptide. 3. The lipid part of the lipopolysaccharide is qualitatively similar to the corresponding material (lipid A) from other Gram-negative organisms, as is the polysaccharide part. 4. The insoluble residue (fraction R) contains sacculi, which also occur in fraction AqII. On hydrolysis, the sacculi yield glucosamine, muramic acid, alanine, glutamic acid and 2,6-diaminopimelic acid, together with small amounts of lysine, and they are therefore similar to the murein sacculi of other Gram-negative organisms. Fraction R also contains substantial amounts of protein, which differs from that obtained from the phenol layer. 5. The possible association or aggregation of lipopolysaccharide, murein and murein sacculi is discussed.

Frequency of Bacteriological Organism in Patients with Thoracic Empyema

2021 ◽  
Vol 15 (6) ◽  
pp. 1914-1916
Author(s):  
Muhammad Umer Salim ◽  
Syed Mohammad Umair Dilawar ◽  
Syed Tabish Rehman
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Gram Negative ◽  
Thoracic Empyema ◽  
Staph Aureus ◽  
Culture Test ◽  
Test Study ◽  
Bacterial Organism ◽  
Gram Negative Organisms

Objective: To examine the frequency of bacteriological organism present in pleural fluid, in patients positive with thoracic empyema, assessed on the basis of pus culture test. Study Design: Cross-sectional study Place and Duration: Inpatient Department, Chest Medicine Ward 12, JPMC, Karachi, Pakistan for six months duration from 11 February 2019 to 10 August 2019. Methodology: One hundred and thirty nine patients diagnosed with Thoracic Empyema were included in this study. All patients included in the study shall undergo Pus Culture Test prior to identify the presence or absence of bacterial organism. Those with positive bacterial findings (mainly Staph Aureus and gram negative organisms) were further assessed for stratification with reference to their possible variable affecters. Results: There were 107 males and 32 females (%M: F ratio 77:23), with Empyema Thoracic, aged between 25-55 years and having a mean age of 36.28 year (± SD 8.206), were studied. The Pus Culture Test rate was 100% whereas duration of empyema was of average 18.38 days (± S.D 11.16). One hundred and four patients (74.82%) were carrying investigated bacteria which were staph. Aureus in 17 (12.50%) patients. GRAM NEGATIVE ORGANISMS in 87 (62.58%) patients. Echerea Coli in 12 (8.3%) patients, Pseudomonas. Aeruginosa in 46 (33.33%) patients, Klebseilla in 17(12.50%) patients, Enterococcus Species in 12 (8.3%) patients. While remaining thirty five patients (25.17%) were found to have other bacteria, including Streptococcus, Proteus Mirabillis and Acinobacter, responsible for Empyema. Conclusion: It is concluded that 74.82% patients had bacteria and among them 62.58% patients had gram negative organism. Pseudomonas Aeruginosa was the most common organism followed by Klebseilla and staph. Aureus. Keywords: Empyema, Thoracic, Pleural Effusion, Thoracentesis, Thoracostomy

LYSOZYME SENSITIVITY OF THE CELL WALL OF PSEUDO-MONAS AERUGINOSA: FURTHER EVIDENCE FOR THE ROLE OF THE NON-PEPTIDOGLYCAN COMPONENTS IN CELL WALL RIGIDITY

1966 ◽  
Vol 12 (1) ◽  
pp. 105-108 ◽  
Author(s):  
K. Jane Carson ◽  
R. G. Eagon
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cell Wall ◽  
Electron Micrographs ◽  
Cell Walls ◽  
Gram Negative Bacteria ◽  
Normal Cells ◽  
Thin Sections ◽  
Gram Negative ◽  
Cell Wall Rigidity

Electron micrographs of thin sections of normal cells of Pseudomonas aeruginosa showed the cell walls to be convoluted and to be composed of two distinct layers. Electron micrographs of thin sections of lysozyme-treated cells of P. aeruginosa showed (a) that the cell walls lost much of their convoluted nature; (b) that the layers of the cell walls became diffuse and less distinct; and (c) that the cell walls became separated from the protoplasts over extensive cellular areas. These results suggest that the peptidoglycan component of the unaltered cell walls of P. aeruginosa is sensitive to lysozyme. Furthermore, it appears that the peptidoglycan component is not solely responsible for the rigidity of the cell walls of Gram-negative bacteria.

scholarly journals The role of hospital environment in transmissions of multidrug-resistant gram-negative organisms

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Po Ying Chia ◽  
Sharmila Sengupta ◽  
Anjanna Kukreja ◽  
Sasheela S.L. Ponnampalavanar ◽  
Oon Tek Ng ◽  
...  
Keyword(s):  
Multidrug Resistant ◽  
Hospital Environment ◽  
Gram Negative ◽  
Gram Negative Organisms

scholarly journals Overproduction of CcmG and CcmFHRc Fully Suppresses the c-Type Cytochrome Biogenesis Defect of Rhodobacter capsulatus CcmI-Null Mutants

2005 ◽  
Vol 187 (12) ◽  
pp. 4245-4256 ◽  
Author(s):  
Carsten Sanders ◽  
Meenal Deshmukh ◽  
Doniel Astor ◽  
Robert G. Kranz ◽  
Fevzi Daldal
Keyword(s):  
Rhodobacter Capsulatus ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Essential Components ◽  
Heme Ligation ◽  
Null Mutants

ABSTRACT Gram-negative bacteria like Rhodobacter capsulatus use intertwined pathways to carry out the posttranslational maturation of c-type cytochromes (Cyts). This periplasmic process requires at least 10 essential components for apo-Cyt c chaperoning, thio-oxidoreduction, and the delivery of heme and its covalent ligation. One of these components, CcmI (also called CycH), is thought to act as an apo-Cyt c chaperone. In R. capsulatus, CcmI-null mutants are unable to produce c-type Cyts and thus sustain photosynthetic (Ps) growth. Previously, we have shown that overproduction of the putative heme ligation components CcmF and CcmHRc (also called Ccl1 and Ccl2) can partially bypass the function of CcmI on minimal, but not on enriched, media. Here, we demonstrate that either additional overproduction of CcmG (also called HelX) or hyperproduction of CcmF-CcmHRc is needed to completely overcome the role of CcmI during the biogenesis of c-type Cyts on both minimal and enriched media. These findings indicate that, in the absence of CcmI, interactions between the heme ligation and thioreduction pathways become restricted for sufficient Cyt c production. We therefore suggest that CcmI, along with its apo-Cyt chaperoning function, is also critical for the efficacy of holo-Cyt c formation, possibly via its close interactions with other components performing the final heme ligation steps during Cyt c biogenesis.

Molybdenum Binding by Pseudomonas aeruginosa

1986 ◽  
Vol 39 (8) ◽  
pp. 1205 ◽  
Author(s):  
S Stojkovski ◽  
RJ Magee ◽  
J Liesegang
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Uronic Acid ◽  
Extracellular Polysaccharide ◽  
Uronic Acids ◽  
Negative Bacterium ◽  
Molybdenum Complex ◽  
Gram Negative ◽  
Pseudomonas Aeruginosa Pao1 ◽  
Polysaccharide Layer

The uptake of molybdenum by certain bacteria hinders its role as a trace metal in the micronutrients for plant growth. The binding of molybdenum by the Gram-negative bacterium Pseudomonas aeruginosa, PAO1, has been investigated. A molybdenum complex of uronic acid, which forms in the extracellular polysaccharide layer (slime), was isolated and characterized by a variety of techniques. Comparisons with 'mimic' compounds of uronic acids suggest that Pseudomonas aeruginosa, PAO1, produces a binuclear, di-oxo-bridged magnesium salt MgMo2O4(C6H8O7)2.5H2O; this indicates the important role of uronic acids in metallic uptake by bacteria.

scholarly journals Azithromycin in Pseudomonas aeruginosa Biofilms: Bactericidal Activity and Selection of nfxB Mutants

2009 ◽  
Vol 53 (4) ◽  
pp. 1552-1560 ◽  
Author(s):  
Xavier Mulet ◽  
María D. Maciá ◽  
Ana Mena ◽  
Carlos Juan ◽  
José L. Pérez ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Bactericidal Activity ◽  
Cross Resistance ◽  
Resistance Development ◽  
Viable Cells ◽  
Knockout Mutants ◽  
Lung Infections ◽  
Selection Of

ABSTRACT Azithromycin (AZM) has shown promising results in the treatment of Pseudomonas aeruginosa chronic lung infections such as those occurring in cystic fibrosis (CF) patients. We evaluated the effect of hypermutation and alginate hyperproduction on the bactericidal activity and resistance development to AZM in P. aeruginosa biofilms. Strains PAO1, its mucA mutant (PAOMA), and their respective mutS-deficient hypermutable derivatives (PAOMS and PAOMSA) were used. Biofilms were incubated with several AZM concentrations for 1, 2, 4, or 7 days, and the numbers of viable cells were determined. During the first 2 days, AZM showed bactericidal activity for all the strains, but in extended AZM incubation for strain PAOMS and especially strain PAOMSA, a marked increased in the number of viable cells was observed, particularly at 4 μg/ml. Biofilms formed by the lineages recovered from the 7-day experiments showed enhanced AZM resistance. Furthermore, most of the independent lineages studied, including those obtained from biofilms treated with AZM concentrations as low as 0.5 μg/ml, showed MexCD-OprJ hyperexpression and mutations in nfxB. The role of nfxB mutation in AZM resistance was further confirmed through the characterization of nfxB and mexD knockout mutants. Results from this work show that, although AZM exhibits bactericidal activity against P. aeruginosa biofilms, resistant mutants are readily selected and that, furthermore, they frequently show cross-resistance to other unrelated antipseudomonal agents such as ciprofloxacin or cefepime but hypersusceptibility to others such as imipenem or tobramycin. Therefore, these results should help guide the selection of appropriate antipseudomonal therapies in CF patients under AZM maintenance treatment.

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