scholarly journals Blocking the alternative sigma factor RpoN reduces virulence ofPseudomonas aeruginosaisolated from cystic fibrosis patients and increases antibiotic sensitivity in a laboratory strain

2018 ◽  
Author(s):  
MG Lloyd ◽  
JL Vossler ◽  
CT Nomura ◽  
JF Moffat
Keyword(s):  
Cystic Fibrosis ◽  
Sigma Factor ◽  
Antimicrobial Agents ◽  
Laboratory Strain ◽  
Infection Model ◽  
Alternative Sigma Factor ◽  
Beta Lactam ◽  
Cis Acting

AbstractMultidrug-resistant organisms (MDROs) are increasing in the health care setting, and there are few antimicrobial agents available to treat infections caused by these bacteria.Pseudomonas aeruginosais an opportunistic pathogen in burn patients and individuals with cystic fibrosis (CF), and a leading cause of nosocomial infections.P. aeruginosais inherently resistant to many antibiotics and can develop or acquire resistance to others, limiting options for treatment.P. aeruginosahas virulence factors that are regulated by sigma factors in response to the tissue microenvironment. The alternative sigma factor, RpoN (σ54), regulates many virulence genes and is linked to antibiotic resistance. Recently, we described a cis-acting peptide, RpoN*, which acts as a “molecular roadblock”, binding RpoN consensus promoters at the −24 site and blocking transcription. RpoN* reduces virulence ofP. aeruginosalaboratory strains bothin vitroandin vivo,but its effects in clinical isolates was not known. We investigated the effects of RpoN* on phenotypically variedP. aeruginosastrains isolated from cystic fibrosis patients. RpoN* expression reduced motility, biofilm formation, and pathogenesis in aP. aeruginosa – C. elegansinfection model. RpoN* expression increased susceptibility to several beta-lactam based antibiotics in the lab strainP. aeruginosaPA19660Xen5. Here, we show that using a cis-acting peptide to block RpoN consensus promoters has potential clinical implications in reducing virulence and enhancing the activity of antibiotics.

scholarly journals In VivoEfficacy of Anuran Trypsin Inhibitory Peptides against Staphylococcal Skin Infection and the Impact of Peptide Cyclization

2015 ◽  
Vol 59 (4) ◽  
pp. 2113-2121 ◽  
Author(s):  
U. Malik ◽  
O. N. Silva ◽  
I. C. M. Fensterseifer ◽  
L. Y. Chan ◽  
R. J. Clark ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Cyclic Peptide ◽  
Sequence Similarity ◽  
Infection Model ◽  
Content Type ◽  
Wide Range ◽  
Inhibitory Activities ◽  
The Impact

ABSTRACTStaphylococcus aureusis a virulent pathogen that is responsible for a wide range of superficial and invasive infections. Its resistance to existing antimicrobial drugs is a global problem, and the development of novel antimicrobial agents is crucial. Antimicrobial peptides from natural resources offer potential as new treatments against staphylococcal infections. In the current study, we have examined the antimicrobial properties of peptides isolated from anuran skin secretions and cyclized synthetic analogues of these peptides. The structures of the peptides were elucidated by nuclear magnetic resonance (NMR) spectroscopy, revealing high structural and sequence similarity with each other and with sunflower trypsin inhibitor 1 (SFTI-1). SFTI-1 is an ultrastable cyclic peptide isolated from sunflower seeds that has subnanomolar trypsin inhibitory activity, and this scaffold offers pharmaceutically relevant characteristics. The five anuran peptides were nonhemolytic and noncytotoxic and had trypsin inhibitory activities similar to that of SFTI-1. They demonstrated weakin vitroinhibitory activities againstS. aureus, but several had strong antibacterial activities againstS. aureusin anin vivomurine wound infection model. pYR, an immunomodulatory peptide fromRana sevosa, was the most potent, with complete bacterial clearance at 3 mg · kg−1. Cyclization of the peptides improved their stability but was associated with a concomitant decrease in antimicrobial activity. In summary, these anuran peptides are promising as novel therapeutic agents for treating infections from a clinically resistant pathogen.

scholarly journals The Mycobacterium tuberculosis Extracytoplasmic-Function Sigma Factor SigL Regulates Polyketide Synthases and Secreted or Membrane Proteins and Is Required for Virulence

2005 ◽  
Vol 187 (20) ◽  
pp. 7062-7071 ◽  
Author(s):  
Mi-Young Hahn ◽  
Sahadevan Raman ◽  
Mauricio Anaya ◽  
Robert N. Husson
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Stress Responses ◽  
Sigma Factor ◽  
Sigma Factors ◽  
Infection Model ◽  
Transcription Start Sites ◽  
Promoter Sequences ◽  
Extracytoplasmic Function Sigma Factor

ABSTRACT Mycobacterium tuberculosis sigL encodes an extracytoplasmic function (ECF) sigma factor and is adjacent to a gene for a membrane protein (Rv0736) that contains a conserved HXXXCXXC sequence. This motif is found in anti-sigma factors that regulate several ECF sigma factors, including those that control oxidative stress responses. In this work, SigL and Rv0736 were found to be cotranscribed, and the intracellular domain of Rv0736 was shown to interact specifically with SigL, suggesting that Rv0736 may encode an anti-sigma factor of SigL. An M. tuberculosis sigL mutant was not more susceptible than the parental strain to several oxidative and nitrosative stresses, and sigL expression was not increased in response to these stresses. In vivo, sigL is expressed from a weak SigL-independent promoter and also from a second SigL-dependent promoter. To identify SigL-regulated genes, sigL was overexpressed and microarray analysis of global transcription was performed. Four small operons, sigL (Rv0735)-Rv0736, mpt53 (Rv2878c)-Rv2877c, pks10 (Rv1660)-pks7 (Rv1661), and Rv1139c-Rv1138c, were among the most highly upregulated genes in the sigL-overexpressing strain. SigL-dependent transcription start sites of these operons were mapped, and the consensus promoter sequences TGAACC in the −35 region and CGTgtc in the −10 region were identified. In vitro, purified SigL specifically initiated transcription from the promoters of sigL, mpt53, and pks10. Additional genes, including four PE_PGRS genes, appear to be regulated indirectly by SigL. In an in vivo murine infection model, the sigL mutant strain showed marked attenuation, indicating that the sigL regulon is important in M. tuberculosis pathogenesis.

A Practical Look at the Clinical Usefulness of the Beta-Lactam/Beta-Lactamase Inhibitor Combinations

1996 ◽  
Vol 30 (10) ◽  
pp. 1130-1140 ◽  
Author(s):  
Susan M. Hart ◽  
Elaine M. Bailey
Keyword(s):  
English Language ◽  
Antimicrobial Agents ◽  
In Vivo Studies ◽  
Patient Specific ◽  
Beta Lactamase ◽  
Beta Lactam ◽  
Intraabdominal Infections ◽  
Lactamase Inhibitor

OBJECTIVE: To aid clinicians in developing an approach to the use of intravenous beta-lactam/beta-lactamase inhibitors on a patient-specific basis. To achieve this, the pharmacology, in vitro activity, and clinical use of the intravenous beta-lactam/beta-lactamase inhibitor combinations in the treatment of selected infections seen in hospitalized patients are discussed. DATA IDENTIFICATION: An English-language literature search using MEDLINE (1987–1995); Index Medicus (1987–1995); program and abstracts of the 32nd (1992), 33rd (1993), 34th (1994), and 35th (1995) Interscience Conference on Antimicrobial Agents and Chemotherapy; bibliographic reviews of review articles; and package inserts. STUDY SELECTION: In vitro and in vivo studies on the pharmacokinetics, microbiology, pharmacology, and clinical effectiveness of ampicillin/sulbactam, ticarcillin/clavulanate, and piperacillin/tazobactam were evaluated. DATA SYNTHESIS: Many properties of the beta-lactam/beta-lactamase inhibitor combinations are similar. Differences in dosing, susceptibilities, and clinical applications are important considerations for clinicians. Potential roles for these agents in the clinical setting include pneumonia, intraabdominal infections, and soft tissue infections. A short discussion on susceptibility data interpretation is also presented. CONCLUSIONS: There are important differences among the available beta-lactam/beta-lactamase inhibitor combinations, such as spectra of activity, which need to be considered in choosing an agent for a patient-specific case. These products can be useful alternatives to conventional two- to three-drug regimens in mixed infections such as foot infections in patients with diabetes and hospital-acquired intraabdominal infections.

scholarly journals Antimicrobial Effects of Ibuprofen Combined with Standard of Care Antimicrobials against Cystic Fibrosis Pathogens

2021 ◽  
Author(s):  
Qingquan Chen ◽  
Marleini Ilanga ◽  
Sabona B Simbassa ◽  
Bhagath Chirra ◽  
Kush N Shah ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Antimicrobial Activity ◽  
Standard Of Care ◽  
Infection Model ◽  
High Dose ◽  
Synergistic Activity ◽  
Drug Resistant ◽  
Anti Inflammatory

Cystic Fibrosis (CF) is a common fatal genetic disease caused by mutations happened to cystic fibrosis transmembrane conductance regulator (CFTR) gene. Lungs of CF patients are often colonized or infected with microorganisms. Drug resistant bacterial infection has been problematic in cystic fibrosis patient. The chronic bacterial infections and concomitant airway inflammation could damage the lung and lead to respiratory failure. Several clinical trials have demonstrated that high-dose ibuprofen reduces the rate of pulmonary function decline in CF patients. This beneficial effect has been attributed to the anti-inflammatory properties of ibuprofen. Previously, we have confirmed that high-dose ibuprofen demonstrated antimicrobial activity against P. aeruginosa in in vitro and in vivo. However, no study has examined the antimicrobial effect of combining ibuprofen with standard-of-care (SoC) antimicrobials. Here, we evaluated possible synergistic activity of combinations of common nonsteroidal anti-inflammatory drugs (NSAIDs), namely, aspirin, naproxen, and ibuprofen, with commonly used antibiotics for CF patients. The drug combinations were screened against different CF clinical isolates. Drugs that demonstrated efficacy in the presence of ibuprofen were further verified synergistic effects between these antimicrobials and NSAIDs. Finally, the survival analysis of an P. aeruginosa murine infection model was used to demonstrate the efficacy of synergistic combination. Our results suggest that combinations of ibuprofen with commonly used antibiotics demonstrate synergistic antimicrobial activity against drug resistant, clinical bacterial strains in in vitro. The efficacy of combination ceftazidime and ibuprofen was demonstrated in in vivo.

scholarly journals Fusidic Acid-Resistant Mutants of Salmonella enterica Serovar Typhimurium with Low Fitness In Vivo Are Defective in RpoS Induction

2003 ◽  
Vol 47 (12) ◽  
pp. 3743-3749 ◽  
Author(s):  
Mirjana Macvanin ◽  
Johanna Björkman ◽  
Sofia Eriksson ◽  
Mikael Rhen ◽  
Dan I. Andersson ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Fusidic Acid ◽  
Salmonella Enterica ◽  
Antimicrobial Agents ◽  
Relative Fitness ◽  
Infection Model ◽  
Macrophage Infection ◽  
Serovar Typhimurium

ABSTRACT Mutants of Salmonella enterica serovar Typhimurium resistant to fusidic acid (Fusr) have mutations in fusA, the gene encoding translation elongation factor G (EF-G). Most Fusr mutants have reduced fitness in vitro and in vivo, in part explained by mutant EF-G slowing the rate of protein synthesis and growth. However, some Fusr mutants with normal rates of protein synthesis still suffer from reduced fitness in vivo. As shown here, Fusr mutants could be similarly ranked in their relative fitness in mouse infection models, in a macrophage infection model, in their relative hypersensitivity to hydrogen peroxide in vivo and in vitro, and in the amount of RpoS production induced upon entry into the stationary phase. We identify a reduced ability to induce production of RpoS (σs) as a defect associated with Fusr strains. Because RpoS is a regulator of the general stress response, and an important virulence factor in Salmonella, an inability to produce RpoS in appropriate amounts can explain the low fitness of Fusr strains in vivo. The unfit Fusr mutants also produce reduced levels of the regulatory molecule ppGpp in response to starvation. Because ppGpp is a positive regulator of RpoS production, we suggest that a possible cause of the reduced levels of RpoS is the reduction in ppGpp production associated with mutant EF-G. The low fitness of Fusr mutants in vivo suggests that drugs that can alter the levels of global regulators of gene expression deserve attention as potential antimicrobial agents.

scholarly journals Synergistic Activity of Berberine with Azithromycin against Pseudomonas Aeruginosa Isolated from Patients with Cystic Fibrosis of Lung In Vitro and In Vivo

2017 ◽  
Vol 42 (4) ◽  
pp. 1657-1669 ◽  
Author(s):  
YongTao Li ◽  
JianRong Huang ◽  
LanJuan Li ◽  
LinSheng Liu
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Lung Infection ◽  
Extracellular Dna ◽  
Pcr Analysis ◽  
Infection Model ◽  
Synergistic Activity ◽  
Time Kill

Background/Aims: Pseudomonas aeruginosa (PA) is one of the major opportunistic pathogens which can cause chronic lung infection of cystic fibrosis (CF). The formation of PA biofilm promotes CF development and restricts the antimicrobial efficacies of current antibiotics. Methods: The antimicrobial effects of azithromycin (AZM) and berberine (BER) alone and in combination were evaluated using microdilution method, checkerboard assay, time-kill test, qRT-PCR analysis and absorption method. The treatments of AZM and/or BER were further evaluated in an animal lung infection model via observing survival rate, bacterial burden and histopathology of lung, the levels of pro-/anti-inflammatory cytokines. Results: AZM-BER were demonstrated to be synergistic against ten clinical PA isolates as well as the standard reference PA ATCC27853, in which PA03 was the most susceptible isolate to AZM-BER with FICI of 0.13 and chosen for subsequent experiments. The synergism of AZM-BER was further confirmed against PA03 in time-kill test and scanning electron microscope (SEM) at their concentrations showing synergism. In PA03, we found that AZM-BER could significantly attenuate productions of a series of virulence factors including alginate, LasA protease, LasB protease, pyoverdin, pyocyanin, chitinase as well as extracellular DNA, and remarkably inhibit the levels of quorum sensing (QS) molecules and the expressions of lasI, lasR, rhlI, rhlR at 1/2×MIC, 1×MIC and 2×MIC. In the infection model, the mice survival were increased markedly, the inflammations of infected lungs were improved greatly along with reduced IL-6, IL-8 and ascended IL-10 at 0.8 mg/kg of AZM combined with 3.2 mg/kg of BER. Conclusion: BER might be a promising synergist to enhance the antimicrobial activity of AZM in vitro and in vivo.

scholarly journals Phenotypic diversification in vivo: Pseudomonas aeruginosa gacS− strains generate small colony variants in vivo that are distinct from in vitro variants

Microbiology ◽  
2010 ◽  
Vol 156 (12) ◽  
pp. 3699-3709 ◽  
Author(s):  
Lisa K. Nelson ◽  
M. Mark Stanton ◽  
Robyn E. A. Elphinstone ◽  
Janessa Helwerda ◽  
Raymond J. Turner ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Phenotypic Variation ◽  
Antimicrobial Agents ◽  
Mucosal Surface ◽  
Infection Model ◽  
Bacterial Survival ◽  
Small Colony Variants ◽  
Small Colony

Pseudomonas aeruginosa has long been known to produce phenotypic variants during chronic mucosal surface infections. These variants are thought to be generated to ensure bacterial survival against the diverse challenges in the mucosal environment. Studies have begun to elucidate the mechanisms by which these variants emerge in vitro; however, too little information exists on phenotypic variation in vivo to draw any links between variants generated in vitro and in vivo. Consequently, in this study, the P. aeruginosa gacS gene, which has previously been linked to the generation of small colony variants (SCVs) in vitro, was studied in an in vivo mucosal surface infection model. More specifically, the rat prostate served as a model mucosal surface to test for the appearance of SCVs in vivo following infections with P. aeruginosa gacS− strains. As in in vitro studies, deletion of the gacS gene led to SCV production in vivo. The appearance of these in vivo SCVs was important for the sustainability of a chronic infection. In the subset of rats in which P. aeruginosa gacS− did not convert to SCVs, clearance of the bacteria took place and healing of the tissue ensued. When comparing the SCVs that arose at the mucosal surface (MS-SCVs) with in vitro SCVs (IV-SCVs) from the same gacS− parent, some differences between the phenotypic variants were observed. Whereas both MS-SCVs and IV-SCVs formed dense biofilms, MS-SCVs exhibited a less diverse resistance profile to antimicrobial agents than IV-SCVs. Additionally, MS-SCVs were better suited to initiate an infection in the rat model than IV-SCVs. Together, these observations suggest that phenotypic variation in vivo can be important for maintenance of infection, and that in vivo variants may differ from in vitro variants generated from the same genetic parent.

scholarly journals Pyocin efficacy in a murine model of Pseudomonas aeruginosa sepsis

2020 ◽  
Author(s):  
Anne Six ◽  
Khedidja Mosbahi ◽  
Madhuri Barge ◽  
Colin Kleanthous ◽  
Thomas Evans ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Murine Model ◽  
Antimicrobial Agents ◽  
Galleria Mellonella ◽  
Bloodstream Infections ◽  
Infection Model ◽  
Antibiotic Resistant ◽  
Naturally Occurring

SynopsisBackgroundBloodstream infections with antibiotic resistant Pseudomonas aeruginosa are common and increasingly difficult to treat. Pyocins are naturally occurring protein antibiotics produced by P. aeruginosa that have potential for human use.ObjectivesTo determine if pyocin treatment is effective in a murine model of sepsis with P. aeruginosa.MethodsRecombinant pyocins S5 and AP41 were purified tested for efficacy in a Galleria mellonella infection model and a murine model of P. aeruginosa sepsis.ResultsBoth pyocins produced no adverse effects when injected alone into mice and showed good in vitro antipseudomonal activity. In an invertebrate model of sepsis using Galleria mellonella, both pyocins significantly prolonged survival. Following injection into mice, both showed extensive distribution into different organs. When administered 5 hours after infection, both pyocins reduced mortality, with pyocin S5 being more effective than AP41.ConclusionsPyocins S5 and AP41 show in vivo biological activity and can improve survival in a murine model of P. aeruginosa infection. They hold promise as novel antimicrobial agents for treatment of multi-drug resistant infections with this microbe.

scholarly journals Genetic dissection of the fermentative and respiratory contributions supporting Vibrio cholerae hypoxic growth

2020 ◽  
Author(s):  
Emilio Bueno ◽  
Brandon Sit ◽  
Matthew K. Waldor ◽  
Felipe Cava
Keyword(s):  
Vibrio Cholerae ◽  
Respiratory Chain ◽  
Antimicrobial Agents ◽  
Infection Model ◽  
Genetic Dissection ◽  
Low Oxygen ◽  
Pathogen Fitness ◽  
Antimicrobial Interventions

ABSTRACTBoth fermentative and respiratory processes contribute to bacterial metabolic adaptations to low oxygen tension (hypoxia). In the absence of O2 as a respiratory electron sink, many bacteria utilize alternative electron acceptors such as nitrate (NO3−). During canonical NO3− respiration, NO3− is reduced in a stepwise manner to N2 by a dedicated set of reductases. Vibrio cholerae, the etiological agent of cholera, only requires a single periplasmic NO3− reductase (NapA) to undergo NO3− respiration, suggesting that the pathogen possesses a non-canonical NO3− respiratory chain. Here, we used complementary transposon-based screens to identify genetic determinants of general hypoxic growth and NO3− respiration in V. cholerae. We found that while the V. cholerae NO3− respiratory chain is primarily composed of homologues of established NO3− respiratory genes, it also includes components previously unlinked to this process, such as the Na+-NADH dehydrogenase Nqr. The ethanol-generating enzyme AdhE was shown to be the principal fermentative branch required during hypoxic growth in V. cholerae. Relative to single adhE or napA mutant strains, a V. cholerae strain lacking both genes exhibited severely impaired hypoxic growth in vitro and in vivo. Our findings reveal the genetic bases for interactions between disparate energy production pathways that support pathogen fitness in shifting conditions. Such metabolic specializations in V. cholerae and other pathogens are potential targets for antimicrobial interventions.IMPORTANCEBacteria reprogram their metabolism in environments with low oxygen levels (hypoxia). Typically, this occurs via regulation of two major, but largely independent, metabolic pathways-fermentation and respiration. Here, we found that the diarrheal pathogen Vibrio cholerae has a respiratory chain for NO3− that consists largely of components found in other NO3− respiratory systems, but also contains several proteins not previously linked to this process. Both AdhE-dependent fermentation and NO3− respiration were required for efficient pathogen growth in both laboratory conditions and in an animal infection model. These observations provide genetic evidence for fermentative-respiratory interactions and identify metabolic vulnerabilities that may be targetable for new antimicrobial agents in V. cholerae and related pathogens.

Sign in / Sign up

Export Citation Format

Share Document