Impact of Pseudomonas aeruginosa Infection on Patients with Chronic Inflammatory Airway Diseases

Aspartic acid unveils as antibiofilm agent and tobramycin adjuvant against mucoid and small colony variants of Pseudomonas aeruginosa isolates in vitro within cystic fibrosis airway mucus

Antibiotics are central to managing airway infections in cystic fibrosis (CF), yet current treatments often fail due to the presence of Pseudomonas aeruginosa biofilms, settling down the need for seeking therapies targeting biofilms. This study aimed to investigate the antibiofilm activity of aspartic acid and its potential as an adjuvant to tobramycin against P. aeruginosa biofilms formed by mucoid and small colony variant (SCV) tobramycin tolerant strain. We assessed the effect of aspartic acid on both surface-attached and suspended P. aeruginosa biofilms within CF artificial mucus and investigated the synergistic impact of combining it with non-lethal tobramycin concentrations. Our findings showed that aspartic acid inhibited planktonic P. aeruginosa without affecting its viability and prevented biofilm formation by hindering bacterial adhesion or interfering with EPS production, depending on the experimental conditions. In CF mucus, aspartic acid significantly reduced bacterial growth, with the highest inhibition observed when combined with tobramycin, showing notable effects against the mucoid and tolerant SCV strain. Despite these reductions, P. aeruginosa repopulated the mucus within 24 h of stress withdrawal. Additional strategies, including delayed tobramycin application and a second dose of co-application of aspartic acid and tobramycin were explored to address bacterial survival and recovery. Although none of the strategies eradicated P. aeruginosa, the second co-application resulted in slower bacterial recovery rates. In conclusion, this study highlighted aspartic acid as an effective antibiofilm agent and demonstrated for the first time its potential as an adjuvant to tobramycin. The combined use of aspartic acid and tobramycin offers a promising advancement in CF therapeutics, particularly against P. aeruginosa biofilms formed by mucoid and SCV strains, mitigating their antibiotic resistance.

Pseudomonas aeruginosa chronic infections in patients with bronchiectasis: a silent reservoir of carbapenemase-producing epidemic high-risk clones

Objectives

Pseudomonas aeruginosa is one of the major drivers of morbidity and mortality in patients with chronic underlying diseases. Whereas cystic fibrosis (CF) P. aeruginosa strains have been well studied, non-CF bronchiectasis isolates have received less scientific attention.

Methods

We determined the antibiotic susceptibility profiles of a collection of 100 P. aeruginosa isolates recovered from a total of 100 non-CF bronchiectasis patients attending a Catalonian hospital. All carbapenemase-producing isolates were characterized by WGS.

Results

Twelve isolates were classified as MDR (12%) and six were found to be carbapenemase (VIM-2) producers (6%). Of note, two of the VIM-2-producing isolates were carbapenem susceptible due to the presence of inactivating mutations in MexAB-OprM efflux pump components. These isolates exhibited properties of chronic P. aeruginosa isolates, such as mutator or mucoid phenotypes that are associated with persistent infections despite intensive antibiotic therapies. The phylogenetic analysis evidenced that all VIM-2 isolates belonged to the high-risk clone ST235. Core-genome MLST analysis revealed 7-260 allelic differences, arguing against recent transmission but a common source of infection or an ancient interpatient transmission event could not be ruled out.

Conclusions

Altogether, these findings suggest that P. aeruginosa chronic respiratory infections can be an important and silent reservoir of transferable resistance determinants and P. aeruginosa high-risk clones, thus contributing to their increased resistance and worldwide dissemination.

tesG expression as a potential clinical biomarker for chronic Pseudomonas aeruginosa pulmonary biofilm infections

BACKGROUND

Pseudomonas aeruginosa infections in the lungs affect millions of children and adults worldwide. To our knowledge, no clinically validated prognostic biomarkers for chronic pulmonary P. aeruginosa infections exist. Therefore, this study aims to identify potential prognostic markers for chronic P. aeruginosa biofilm lung infections.

METHODS

Here, we screened the expression of 11 P. aeruginosa regulatory genes (tesG, algD, lasR, lasA, lasB, pelB, phzF, rhlA, rsmY, rsmZ, and sagS) to identify associations between clinical status and chronic biofilm infection.

RESULTS

RNA was extracted from 210 sputum samples from patients (n = 70) with chronic P. aeruginosa lung infections (mean age; 29.3-56.2 years; 33 female). Strong biofilm formation was correlated with prolonged hospital stays (212.2 days vs. 44.4 days) and increased mortality (46.2% (18)). Strong biofilm formation is associated with increased tesG expression (P = 0.001), influencing extended intensive care unit (P = 0.002) or hospitalisation stays (P = 0.001), pneumonia risk (P = 0.006), and mortality (P = 0.001). Notably, tesG expression is linked to the modulation of systemic and sputum inflammatory responses and predicts biofilm biomass.

CONCLUSIONS

This study provides the first clinical dataset of tesG expression levels as a predictive biomarker for chronic P. aeruginosa pulmonary infections.

Establishment and characterization of persistent Pseudomonas aeruginosa infections in air-liquid interface cultures of human airway epithelial cells

Bacteria exhibit distinct behaviors in laboratory settings compared to infection environments. The presence of host cells induces changes in bacterial activity, while pathogens trigger immune responses that shape the microenvironment. Studying infection dynamics by microscopy, cytokine screening, and dual RNA sequencing in an air-liquid interface model, we found that prolonged Pseudomonas aeruginosa colonization of airway epithelium led to a pro-inflammatory response, consistent across P. aeruginosa strains, despite differences in the dynamics of this response. Concurrently, P. aeruginosa formed non-attached aggregates on the apical side of the cell layer and upregulated genes involved in biofilm formation and virulence. Notably, there was remarkable resemblance between the P. aeruginosa transcriptional profile in our model and that previously reported upon host cell contact. Developing a platform that replicates host microenvironments is vital not only for gaining deeper insights into the interplay between host and pathogen but also for evaluating therapeutic strategies in conditions that closely mirror clinical environments.

Sputum metagenomics reveals a multidrug resistant Pseudomonas-dominant severe asthma phenotype in an Asian population

BACKGROUND AND OBJECTIVE

While the lung microbiome in severe asthma has been studied, work has employed targeted amplicon-based sequencing approaches without functional assessment with none focused on multi-ethnic Asian populations. Here we investigate the clinical relevance of microbial phenotypes of severe asthma in Asians using metagenomics.

METHODS

Prospective assessment of clinical, radiological, and immunological measures were performed in a multi-ethnic Asian severe asthma cohort (N = 70) recruited across two centres in Singapore. Sputum was subjected to shotgun metagenomic sequencing and patients followed up for a 2-year period. Metagenomic assessment of sputum microbiomes, resistomes and virulomes were related to clinical outcomes.

RESULTS

The lung microbiome in a multi-ethnic Asian cohort with severe asthma demonstrates an increased abundance of Pseudomonas species. Unsupervised clustering of sputum metagenomes identified two patient clusters: C1 (n = 52) characterized by upper airway commensals and C2 (n = 18) dominated by established respiratory pathogens including M. catarrhalis, S. aureus and most significantly P. aeruginosa. C2 patients demonstrated a significantly increased exacerbation frequency on 2-year follow up and an antimicrobial resistome characterized by multidrug resistance. Virulomes appear indistinguishable between severe asthmatics with or without co-existing bronchiectasis, and C2 patients exhibit increased gene expression related to biofilm formation, effector delivery systems and microbial motility. Independent comparison of the C2 cluster to a non-asthmatic bronchiectasis cohort demonstrates analogous airway microbial virulence patterns.

CONCLUSION

Sputum metagenomics demonstrates a multidrug-resistant Pseudomonas-dominant severe asthma phenotype in Asians, characterized by poor clinical outcome including increased exacerbations which is independent of co-existing bronchiectasis.

Critical functions and key interactions mediated by the RNase E scaffolding domain in Pseudomonas aeruginosa

The RNA degradosome is a bacterial multi-protein complex mediating mRNA processing and degradation. In Pseudomonadota, this complex assembles on the C-terminal domain (CTD) of RNase E through short linear motifs (SLiMs) that determine its composition and functionality. In the human pathogen Pseudomonas aeruginosa, the RNase E CTD exhibits limited similarity to that of model organisms, impeding our understanding of RNA metabolic processes in this bacterium. Our study systematically maps the interactions mediated by the P. aeruginosa RNase E CTD and highlights its critical role in transcript regulation and cellular functions. We identified the SLiMs crucial for membrane attachment, RNA binding and complex clustering, as well as for direct binding to the core components PNPase and RhlB. Transcriptome analyses of RNase E CTD mutants revealed altered expression of genes involved in quorum sensing, type III secretion, and amino acid metabolism. Additionally, we show that the mutants are impaired in cold adaptation, pH response, and virulence in an infection model. Overall, this work establishes the essential role of the RNA degradosome in driving bacterial adaptability and pathogenicity.

Isolation and characterization of new lytic bacteriophage PSA-KC1 against Pseudomonas aeruginosa isolates from cystic fibrosis patients

A novel lytic bacteriophage, PSA-KC1, was isolated from wastewater. In this study, the whole genome of the bacteriophage PSA-KC1 was analyzed, and its lytic properties were assessed. PSA-KC1 has a linear double-stranded DNA genome with a total length of 43,237 base pairs and a GC content of 53.6%. In total, 65 genes were predicted, 46 of which were assigned functions as structural proteins involved in genome replication, packaging or phage lysis. PSA-KC1 belongs to the genus Septimatrevirus under the Caudoviricetes class. The aim of this study was to investigate the efficacy of the lytic bacteriophage PSA-KC1 and compare it with that of the Pyophage phage cocktail on 25 multi drug resistant (MDR) Pseudomonas aeruginosa strains isolated from sputum samples of cystic fibrosis patients. Seventeen of these strains were susceptible (68%) to the PSA-KC1 lytic phage we isolated, whereas eight clinical strains were resistant. However, 22 (88%) of the P. aeruginosa strains were susceptible to the Pyophage cocktail, and three (12%) were resistant to the Phage cocktail. At the end of our study, a new lytic phage active against multidrug-resistant P. aeruginosa strains from CF patients was isolated, and its genome was characterized. Since the PSA-KC1 phage does not contain virulence factors, toxins or integrase genes, it can be expected to be a therapeutic candidate with the potential to be used safely in phage therapy.

Altitudinal influence on survival mechanisms, nutritional composition, and antimicrobial activity of Moringa Peregrina in the summer climate of Fujairah, UAE

Extreme environments significantly impact the metabolic profiles of plants, leading to variations in chemical composition and bioactivity. This study investigates the effects of altitude, plant part age, and light exposure on the chemical composition and antimicrobial properties of Moringa peregrina. Based on our results, mineral contents were plant location dependent; while dry matter, ash, total digestible nutrients (TDN), fibre, protein, and tannins, were greater in the samples from the mountain. Vitamin E was more concentrated in the wadi. Vitamin A, selenium, phenols, and heavy metals were undetectable in both environments. Antimicrobial assays revealed stronger activity in mountain samples than the other locations. Age-dependent analyses showed that nitrogen, protein, ash, and electrolyte leakage were higher in young plant parts, whereas chlorophyll a and b levels were elevated in mature leaves and younger branches, particularly in lower elevations. Interestingly, young leaves from mountain regions had higher chlorophyll concentrations compared to mature leaves, contrasting with trends at other elevations. Photosynthetic photon flux density (PPFD) measurements were also highest in the mountain region. These findings suggest that M. peregrina employs diverse metabolic adaptations for survival in challenging environments, potentially offering socioeconomic value to indigenous communities through its bioactive properties.

Intracellular Pseudomonas aeruginosa persist and evade antibiotic treatment in a wound infection model

Persistent bacterial infections evade host immunity and resist antibiotic treatments through various mechanisms that are difficult to evaluate in a living host. Pseudomonas aeruginosa is a main cause of chronic infections in patients with cystic fibrosis (CF) and wounds. Here, by immersing wounded zebrafish embryos in a suspension of P. aeruginosa isolates from CF patients, we established a model of persistent infection that mimics a murine chronic skin infection model. Live and electron microscopy revealed persisting aggregated P. aeruginosa inside zebrafish cells, including macrophages, at unprecedented resolution. Persistent P. aeruginosa exhibited adaptive resistance to several antibiotics, host cell permeable drugs being the most efficient. Moreover, persistent bacteria could be partly re-sensitized to antibiotics upon addition of anti-biofilm molecules that dispersed the bacterial aggregates in vivo. Collectively, this study demonstrates that an intracellular location protects persistent P. aeruginosa in vivo in wounded zebrafish embryos from host innate immunity and antibiotics, and provides new insights into efficient treatments against chronic infections.

Inflammation-induced loss of CFTR-expressing airway ionocytes in non-eosinophilic asthma

BACKGROUND AND OBJECTIVE

Severe asthma is a heterogeneous disease with subtype classification according to dominant airway infiltrates, including eosinophilic (Type 2 high), or non-eosinophilic asthma. Non-eosinophilic asthma is further divided into paucigranulocytic or neutrophilic asthma characterized by elevated neutrophils, and mixed Type 1 and Type 17 cytokines in the airways. Severe non-eosinophilic asthma has few effective treatments and many patients do not qualify for biologic therapies. The cystic fibrosis transmembrane conductance regulator (CFTR) is dysregulated in multiple respiratory diseases including cystic fibrosis and chronic obstructive pulmonary disease and has proven a valuable therapeutic target. We hypothesized that the CFTR may also play a role in non-eosinophilic asthma.

METHODS

Patient-derived human bronchial epithelial cells (hBECs) were isolated and differentiated at the air-liquid interface. Single cell RNA-sequencing (scRNAseq) was used to identify epithelial cell subtypes and transcriptional activity. Ion transport was investigated with Ussing chambers and immunofluorescent quantification of ionocyte abundance in human airway epithelial cells and murine models of asthma.

RESULTS

We identified that hBECs from patients with non-eosinophilic asthma had reduced CFTR function, and did not differentiate into CFTR-expressing ionocytes compared to those from eosinophilic asthma or healthy donors. Similarly, ionocytes were also diminished in the airways of a murine model of neutrophilic-dominant but not eosinophilic asthma. Treatment of hBECs from healthy donors with a neutrophilic asthma-like inflammatory cytokine mixture led to a reduction in ionocytes.

CONCLUSION

Inflammation-induced loss of CFTR-expressing ionocytes in airway cells from non-eosinophilic asthma may represent a key feature of disease pathogenesis and a novel drug target.

Mechanistic Insights into Succinic Acid as an Adjuvant for Ciprofloxacin in Treating Pseudomonas aeruginosa Growing Within Cystic Fibrosis Airway Mucus

Pseudomonas aeruginosa is a major cause of chronic respiratory infections in patients with cystic fibrosis (CF), with biofilm formation contributing to its persistence and antibiotic resistance. This study aimed to gain insights into the mechanistic action of succinic acid as a ciprofloxacin adjuvant against clinically relevant CF isolates, including small colony variants and mucoid strains, and a ciprofloxacin-resistant strain grown within CF dense mucus. Time-kill assays in artificial CF mucus, along with planktonic and surface-attached biofilm experiments, were used to assess the activity of succinic acid alone and in combination with sublethal ciprofloxacin concentrations. Succinic acid demonstrated an adjuvant effect of ciprofloxacin against P. aeruginosa grown within CF mucus at pH levels below pKa1 during the early bacterial growth stages. In examining planktonic growth and biofilms under these conditions, we found that succinic acid demonstrated strong antibacterial and antibiofilm properties. Conversely, succinic acid activity decreased at later growth stages, though it enhanced the ciprofloxacin effect, especially against mucoid biofilms. Moreover, we noted that, in dense CF mucus, succinic acid activity was attenuated compared to a non-CF environment, indicating diffusion challenges. These findings underscore the potential of succinic acid as a therapeutic adjuvant for improving antibiotic treatment outcomes and overcoming biofilm-associated resistance in CF.

Bioaerosol emission and exposure risk from a wastewater treatment plant in winter and spring

The potential health risks posed by bioaerosols containing pathogens originating from wastewater treatment plants (WWTPs) have gaining intensive attention. This study designated sampling locations within a WWTP situated in Xi'an, a major city in northwest China. The airborne bacterial concentration, taxonomic composition, and the associated health risks were analyzed in the aeration tanks with bottom microporous aeration system. The Anaerobic-Anoxic-Oxic (AAO) tank emitted significantly higher culturable bacteria (1.58×104 CFU m-3 in spring, 6.69×103 CFU m-3 in winter) compared to Double-ditch (DE) oxidation ditch and aerated grit chamber (AGC) chamber, aligning with 16S rDNA quantification results. The bacterial concentrations are higher in spring than that in winter, with the AAO tank posing the highest exposure risk during the spring season. The dominant genera in the air samples include Cutibacterium, Lawsonella, Acinetobacter, Pseudomonas, and Aeromonas. Among the identified genus, 139 bacterial genera were identified as potential human pathogens like Neisseria, Moraxella, Haemophilus, Escherichia-Shigella and Streptococcus. These pathogens further elevate exposure risks from WWTP bioaerosols. This study provides relevant information on the seasonal health risk variations tied to bioaerosol emissions from diverse aeration tanks with bottom microporous aeration system in the mega city of northwest China, emphasizing the imperative to enhance the management and control measures for bioaerosols originating from the AAO tank.

A Multifaceted Exploration of Status Asthmaticus: A Retrospective Analysis in a Romanian Hospital

Background: Status asthmaticus is a severe, life-threatening asthma exacerbation requiring urgent medical intervention. This study aims to examine its epidemiology in Timis County, Romania, over 11 years. Methods: A retrospective analysis was conducted using hospital records from 2013 to 2023, focusing on demographic, geospatial, and temporal distributions. Network analysis of the recorded comorbidities was used to identify phenotypic clusters among patients. Results: Females and older adults were disproportionately affected. Several triggers and geospatial patterns were identified. Five phenotypic clusters were determined: two in the T2-high endotype, two in T2-low, and a mixed one. Conclusions: The findings highlight the need for personalized asthma management strategies and public healthcare interventions in Timiș County, addressing specific demographic and geospatial factors. This study also provides a valuable reference for similar regions.

Therapeutic Interventions for Pseudomonas Infections in Cystic Fibrosis Patients: A Review of Phase IV Trials

Pseudomonas aeruginosa (Pa) poses a significant threat to individuals with cystic fibrosis (CF), as this bacterium is highly adaptable and resistant to antibiotics. While early-stage Pa infections can often be eradicated with aggressive antibiotic therapy, chronic infections are nearly impossible to eliminate and require treatments that focus on long-term bacterial suppression. Without such suppression, these persistent infections can severely damage the lungs, leading to serious complications and a reduced life expectancy for CF patients. Evidence for a specific treatment regimen for managing Pa infections in CF patients remains limited. This narrative review provides a detailed analysis of antimicrobial therapies assessed in completed phase IV trials, focusing on their safety and efficacy, especially with prolonged use. Key antibiotics, including tobramycin, colistin, meropenem, aztreonam, ceftolozane/tazobactam, ciprofloxacin, and azithromycin, are discussed, emphasizing their use, side effects, and delivery methods. Inhaled antibiotics are preferred for their targeted action and minimal side effects, while systemic antibiotics offer potency but carry risks like nephrotoxicity. The review also explores emerging treatments, such as phage therapy and antibiofilm agents, which show promise in managing chronic infections. Nonetheless, further research is necessary to enhance the safety and effectiveness of existing therapies while investigating new approaches for better long-term outcomes.

Flagellar motility and the mucus environment influence aggregation mediated antibiotic tolerance of Pseudomonas aeruginosa in chronic lung infection

Pseudomonas aeruginosa frequently causes chronic lung infection in individuals with muco-obstructive airway diseases (MADs). Chronic P. aeruginosa infections are difficult to treat, primarily owing to antibiotic treatment failure, which is often observed in the absence of antimicrobial resistance. In MADs, P. aeruginosa forms biofilm-like aggregates within the luminal mucus. While the contribution of mucin hyperconcentration towards antibiotic tolerance has been described, the mechanism for mucin driven antibiotic tolerance and the influence of aggregates have not been fully elucidated. In this study, we investigated the contribution of flagellar motility towards aggregate formation as it relates to the diseased mucus environment. We found that loss of flagellar motility resulted in increased P. aeruginosa aggregation and tolerance to multiple classes of antibiotics. Further, we observed differential roles in antimicrobial tolerance of the motAB and motCD stators, which power the flagellum. Additionally, we found that control of fliC expression was important for aggregate formation and antibiotic tolerance as a strain constitutively expressing fliC was unable to form aggregates and was highly susceptible to treatment. Lastly, we demonstrate that neutrophil elastase, an abundant immune mediator and biomarker of chronic lung infection, promotes aggregation and antibiotic tolerance by impairing flagellar motility. Collectively, these results highlight the key role of flagellar motility in aggregate formation and antibiotic tolerance and deepens our understanding of how the MADs lung environment promotes antibiotic tolerance of P. aeruginosa.

Contribution of Pseudomonas aeruginosa - mediated club cell necroptosis to the bias of type 17 inflammation and steroid insensitivity in asthma

INTRODUCTION

Opportunistic pathogen infection is one of the important inducements for asthma exacerbation. Pseudomonas aeruginosa (PA) is a kind of dominant pathogenic bacteria in the respiratory tract that is associated with severe asthma, but the underlying mechanisms still remains unclear.

OBJECTIVES

To examine the role of PA infection in the bias of the inflammatory endotype in asthma and its effect on the sensitivity to steroid therapy.

METHODS

An adjusted HDM (House Dust Mite) -induced asthma model with PA inoculation in the airway was utilized to mimic the process of opportunistic PA infection in asthma, focusing on the interaction between bacteria and epithelium. Dexamethasone administration in vivo was used to test the sensitivity to steroid therapy.

RESULTS

It was uncovered that PA could promote the loss of club cells in the necroptosis pattern through cellular CYP450 activation, leading to an imbalance of inflammatory response and steroid insensitivity. Club cell loss results in the activation of cellular E-cadherin/β-catenin axis in the rest of club cells for goblet metaplasia and mucus hypersecretion, as well as epithelial damage and GR downregulation for steroid resistance. For clinical applications, the necroptosis inhibitor Nec-1 can effectively relieve the pathological symptoms of asthma in vivo. Meanwhile, CCSP administration in the airway can regulate the pulmonary inflammation and restore the steroid sensitivity in asthma.

CONCLUSION

These experiments provide a novel mechanism of concurrent PA infection in asthma through club cell necroptosis and the pathological consequences. Nec-1 treatment and CCSP supplementation may be possible therapeutic strategies for asthma treatment.

Phage therapy to treat cystic fibrosis Burkholderia cepacia complex lung infections: perspectives and challenges

Burkholderia cepacia complex is a cause of serious lung infections in people with cystic fibrosis, exhibiting extremely high levels of antimicrobial resistance. These infections are difficult to treat and are associated with high morbidity and mortality. With a notable lack of new antibiotic classes currently in development, exploring alternative antimicrobial strategies for Burkholderia cepacia complex is crucial. One potential alternative seeing renewed interest is the use of bacteriophage (phage) therapy. This review summarises what is currently known about Burkholderia cepacia complex in cystic fibrosis, as well as challenges and insights for using phages to treat Burkholderia cepacia complex lung infections.

Omega-3 long-chain polyunsaturated fatty acids and their bioactive lipids: A strategy to improve resistance to respiratory tract infectious diseases in the elderly?

Age-related changes in organ function, immune dysregulation, and the effects of senescence explain in large part the high prevalence of infections, including respiratory tract infections in older persons. Poor nutritional status in many older persons increases susceptibility to infection and worsens prognosis. Interestingly, there is an association between the amount of saturated fats in the diet and the rate of community-acquired pneumonia. Polyunsaturated fatty acids, particularly omega-3 long chain polyunsaturated fatty acids (ω-3 LC-PUFAs) including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have well-known anti-inflammatory, immunomodulatory, and antimicrobial effects, which may, in theory, be largely induced by PUFAs-derived lipids such as specialized pro-resolving mediators (SPMs). In adults, preliminary results of studies show that ω-3 LC-PUFAs supplementation can lead to SPM generation. SPMs have a crucial role in the resolution of inflammation, a factor relevant to survival from infection independent of the pathogen’s virulence. Moreover, the immune system of older adults appears to be more sensitive to ω-3 PUFAs. This review explores the effects of ω-3 LC-PUFAs, and PUFA bioactive lipid-derived SPMs in respiratory tract infections and the possible relevance of these data to infectious disease outcomes in the older population. The hypothesis that PUFAs have beneficial effects via SPM generation will need to be confirmed by animal experiments and patient-derived data.

A chronic Pseudomonas aeruginosa mouse lung infection modeling the pathophysiology and inflammation of human cystic fibrosis

Investigation of chronic cystic fibrosis (CF) lung infections has been limited by a lack of murine models that reproduce obstructive lung pathology, chronicity of bacterial infections, and complex inflammation in human CF lung pathology. Three different approaches have been used separately to address these limitations, including using transgenic Scnn1b-Tg mice overexpressing a lung epithelial sodium channel to mimic the mucus-rich and hyperinflammatory CF lung environment, using synthetic CF sputum medium (SCFM) in an acute infection to induce bacterial phenotypes consistent with human CF, or using agar beads to promote chronic infections. Here, we combine these three models to establish a chronic Pseudomonas aeruginosa lung infection model using SCFM agar beads and Scnn1b-Tg mice (SCFM-Tg-mice) to recapitulate nutrients, mucus, and inflammation characteristic of the human CF lung environment. Like people with CF, SCFM-Tg-mice failed to clear bacterial infections. Lung function measurements showed that infected SCFM-Tg-mice had decreased inspiratory capacity and compliance, elevated airway resistance, and significantly reduced FVC and FEV0.1. Using spectral flow cytometry and multiplex cytokine arrays we show that, like people with CF, SCFM-Tg-mice developed inflammation characterized by eosinophil infiltration and Th2 lymphocytic cytokine responses. Chronically infected SCFM-Tg-mice developed an exacerbated mix of innate and Th1, Th2, and Th17-mediated inflammation, causing higher lung cellular damage, and elevated numbers of unusual Siglec F+ neutrophils. Thus, SCFM-Tg-mice represents a powerful tool to investigate bacterial pathogenesis and potential treatments for chronic CF lung infections and reveal a potential role for Siglec F+ neutrophils in CF inflammation.

Penicillin-binding protein 3 sequence variations reduce susceptibility of Pseudomonas aeruginosa to β-lactams but inhibit cell division

BACKGROUND

β-lactam antibiotics, which inhibit penicillin-binding protein 3 (PBP3) that is required for cell division, play a key role in treating P. aeruginosa infections. Some sequence variations in PBP3 have been associated with β-lactam resistance but the effects of variations on antibiotic susceptibility and on cell division have not been quantified. Antibiotic efflux can also reduce susceptibility.

OBJECTIVES

To quantify the effects of PBP3 variations on β-lactam susceptibility and cell morphology in P. aeruginosa.

METHODS

Nineteen PBP3 variants were expressed from a plasmid in the reference strain P. aeruginosa PAO1 and genome engineering was used to construct five mutants expressing PBP3 variants from the chromosome. The effects of the variations on β-lactam minimum inhibitory concentration (MIC) and cell morphology were measured.

RESULTS

Some PBP3 variations reduced susceptibility to a variety of β-lactam antibiotics including meropenem, ceftazidime, cefepime and ticarcillin with different variations affecting different antibiotics. None of the tested variations reduced susceptibility to imipenem or piperacillin. Antibiotic susceptibility was further reduced when PBP3 variants were expressed in mutant bacteria overexpressing the MexAB-OprM efflux pump, with some variations conferring clinical levels of resistance. Some PBP3 variations, and sub-MIC levels of β-lactams, reduced bacterial growth rates and inhibited cell division, causing elongated cells.

CONCLUSIONS

PBP3 variations in P. aeruginosa can increase the MIC of multiple β-lactam antibiotics, although not imipenem or piperacillin. PBP3 variations, or the presence of sub-lethal levels of β-lactams, result in elongated cells indicating that variations reduce the activity of PBP3 and may reduce bacterial fitness.

Electrochemical Detection of Pseudomonas aeruginosa Quorum Sensing Molecule (S)-N-Butyryl Homoserine Lactone Using Molecularly Imprinted Polymers

Pseudomonas aeruginosa is a multidrug-resistant Gram-negative bacterium that poses a significant threat to public health, necessitating rapid and on-site detection methods for rapid recognition. The goal of the project is therefore to indirectly detect the presence of P. aeruginosa in environmental water samples targeting one of its quorum-sensing molecules, namely, (S)-N-butyryl homoserine lactone (BHL). To this aim, molecularly imprinted polymers (MIPs) were synthesized via bulk free-radical polymerization using BHL as a template molecule. The obtained MIP particles were immobilized onto screen-printed electrodes (MIP-SPEs), and the BHL rebinding was analyzed via electrochemical impedance spectroscopy (EIS). To study the specificity of the synthesized MIPs, isotherm curves were built after on-point rebinding analysis performed via LC-MS measurements for both MIPs and NIPs (nonimprinted polymers, used as a negative control), obtaining an imprinting factor (IF) of 2.8 (at C f = 0.4 mM). The MIP-SPEs were integrated into an electrochemical biosensor with a linear range of 1 × 101-1 × 103 nM and a limit of detection (LoD) of 31.78 ± 4.08 nM. Selectivity measurements were also performed after choosing specific interferent molecules, such as structural analogs and potential interferents, followed by on-point analysis performed in spiked tap water to prove the sensor's potential to detect the presence of the quorum-sensing molecule in environmentally related real-life samples.

Respiratory tract infections: an update on the complexity of bacterial diversity, therapeutic interventions and breakthroughs

Respiratory tract infections (RTIs) have a significant impact on global health, especially among children and the elderly. The key bacterial pathogens Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, Staphylococcus aureus and non-fermenting Gram Negative bacteria such as Acinetobacter baumannii and Pseudomonas aeruginosa are most commonly associated with RTIs. These bacterial pathogens have evolved a diverse array of resistance mechanisms through horizontal gene transfer, often mediated by mobile genetic elements and environmental acquisition. Treatment failures are primarily due to antimicrobial resistance and inadequate bacterial engagement, which necessitates the development of alternative treatment strategies. To overcome this, our review mainly focuses on different virulence mechanisms and their resulting pathogenicity, highlighting different therapeutic interventions to combat resistance. To prevent the antimicrobial resistance crisis, we also focused on leveraging the application of artificial intelligence and machine learning to manage RTIs. Integrative approaches combining mechanistic insights are crucial for addressing the global challenge of antimicrobial resistance in respiratory infections.

Anti-Biofilm and Anti-Inflammatory Properties of the Truncated Analogs of the Scorpion Venom-Derived Peptide IsCT against Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen in humans and a frequent cause of severe nosocomial infections and fatal infections in immunocompromised individuals. Its ability to form biofilms has been the main driving force behind its resistance to almost all conventional antibiotics, thereby limiting treatment efficacy. In an effort to discover novel therapeutic agents to fight P. aeruginosa-associated biofilm infections, the truncated analogs of scorpion venom-derived peptide IsCT were synthesized and their anti-biofilm properties were examined. Among the investigated peptides, the IsCT-Δ6-8 peptide evidently showed the most potential anti-P. aeruginosa biofilm activity and the effect was not due to bacterial growth inhibition. The IsCT-Δ6-8 peptide also exhibited inhibitory activity against the production of pyocyanin, an important virulence factor of P. aeruginosa. Furthermore, the IsCT-Δ6-8 peptide significantly suppressed the production of inflammatory mediators nitric oxide and interleukin-6 in P. aeruginosa LPS-induced macrophages. Due to its low cytotoxicity to mammalian cells, the IsCT-Δ6-8 peptide emerges as a promising candidate with significant anti-biofilm and anti-inflammatory properties. These findings highlight its potential application in treating P. aeruginosa-related biofilm infections.

Adjuvant-independent airway sensitization and infection mouse models leading to allergic asthma

Asthma is a chronic respiratory disease of global importance. Mouse models of allergic asthma have been instrumental in advancing research and novel therapeutic strategies for patients. The application of relevant allergens and physiological routes of exposure in such models has led to valuable insights into the complexities of asthma onset and development as well as key disease mechanisms. Furthermore, environmental microbial exposures and infections have been shown to play a fundamental part in asthma pathogenesis and alter disease outcome. In this review, we delve into physiological mouse models of allergic asthma and explore literature reports on most significant interplays between microbial infections and asthma development with relevance to human disease.

Beyond antibiotics: Emerging antivirulence strategies to combat Pseudomonas aeruginosa in cystic fibrosis

Pseudomonas aeruginosa is an opportunistic pathogen that poses a significant threat to individuals suffering from cystic fibrosis (CF). The pathogen is highly prevalent in CF individuals and is responsible for chronic infection, resulting in severe tissue damage and poor patient outcome. Prolonged antibiotic administration has led to the emergence of multidrug resistance in P. aeruginosa. In this direction, antivirulence strategies achieving targeted inhibition of bacterial virulence pathways, including quorum sensing, efflux pumps, lectins, and iron chelators, have been explored against CF isolates of P. aeruginosa. Hence, this review article presents a bird's eye view on the pulmonary infections involving P. aeruginosa in CF patients by laying emphasis on factors contributing to bacterial colonization, persistence, and disease progression along with the current line of therapeutics against P. aeruginosa in CF. We further collate scientific literature and discusses various antivirulence strategies that have been tested against P. aeruginosa isolates from CF patients.

Modeling Host-Pathogen Interactions in C. elegans: Lessons Learned from Pseudomonas aeruginosa Infection

Infections, such as that by the multiresistant opportunistic bacterial pathogen Pseudomonas aeruginosa, may pose a serious health risk, especially on vulnerable patient populations. The nematode Caenorhabditis elegans provides a simple organismal model to investigate both pathogenic mechanisms and the emerging role of innate immunity in host protection. Here, we review the virulence and infection strategies of P. aeruginosa and host defenses of C. elegans. We summarize the recognition mechanisms of patterns of pathogenesis, including novel pathogen-associated molecular patterns and surveillance immunity of translation, mitochondria, and lysosome-related organelles. We also review the regulation of antimicrobial and behavioral defenses by the worm's neuroendocrine system. We focus on how discoveries in this rich field align with well-characterized evolutionary conserved protective pathways, as well as on potential crossovers to human pathogenesis and innate immune responses.

Systemic antibiotics for Pseudomonas aeruginosa infection in outpatients with non-hospitalised exacerbations of pre-existing lung diseases: a randomised clinical trial

BACKGROUND

The effect of dual systemic antibiotic therapy against Pseudomonas aeruginosa in patients with pre-existing lung disease is unknown. To assess whether dual systemic antibiotics against P. aeruginosa in outpatients with COPD, non-cystic fibrosis (non-CF) bronchiectasis, or asthma can improve outcomes.

METHODS

Multicenter, randomised, open-label trial conducted at seven respiratory outpatient clinics in Denmark. Outpatients with COPD, non-CF bronchiectasis, or asthma with a current P. aeruginosa-positive lower respiratory tract culture (clinical routine samples obtained based on symptoms of exacerbation not requiring hospitalisation), regardless of prior P. aeruginosa-status, no current need for hospitalisation, and at least two moderate or one hospitalisation-requiring exacerbation within the last year were eligible. Patients were assigned 1:1 to 14 days of dual systemic anti-pseudomonal antibiotics or no antibiotic treatment. Primary outcome was time to prednisolone or antibiotic-requiring exacerbation or death from day 20 to day 365.

RESULTS

The trial was stopped prematurely based in lack of recruitment during the COVID-19 pandemic, this decision was endorsed by the Data and Safety Monitoring Board. Forty-nine outpatients were included in the study. There was a reduction in risk of the primary outcome in the antibiotic group compared to the control group (HR 0.51 (95%CI 0.27-0.96), p = 0.037). The incidence of admissions with exacerbation within one year was 1.1 (95%CI 0.6-1.7) in the dual antibiotic group vs. 2.9 (95%CI 1.3-4.5) in the control group, p = 0.037.

CONCLUSIONS

Use of dual systemic antibiotics for 14 days against P. aeruginosa in outpatients with chronic lung diseases and no judged need for hospitalisation, improved clinical outcomes markedly. The main limitation was the premature closure of the trial.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03262142, registration date 2017-08-25.

Recent trends and challenges to overcome Pseudomonas aeruginosa infections

INTRODUCTION

Pseudomonas aeruginosa (PA) is a Gram-negative bacterium that can cause a wide range of severe infections in immunocompromised patients. The most difficult challenge is due to its ability to rapidly develop multi drug-resistance. New strategies are urgently required to improve the outcome of patients with PA infections. The present patent review highlights the new molecules acting on different targets involved in the antibiotic resistance.

AREA COVERED

This review offers an insight into new potential PA treatment disclosed in patent literature. From a broad search of documents claiming new PA inhibitors, we selected and summarized molecules that showed in vitro and in vivo activity against PA spp. in the period 2020 and 2023. We collected the search results basing on the targets explored.

EXPERT OPINION

This review examined the main patented compounds published in the last three years, with regard to the structural novelty and the identification of innovative targets. The main areas of antibiotic resistance have been explored. The compounds are structurally unrelated to earlier antibiotics, characterized by a medium-high molecular weight and the presence of heterocycle rings. Peptides and antibodies have also been reported as potential alternatives to chemical treatment, hereby expanding the therapeutic possibilities in this field.

A role for the stringent response in ciprofloxacin resistance in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a major cause of nosocomial infections and the leading cause of chronic lung infections in cystic fibrosis and chronic obstructive pulmonary disease patients. Antibiotic treatment remains challenging because P. aeruginosa is resistant to high concentrations of antibiotics and has a remarkable ability to acquire mutations conferring resistance to multiple groups of antimicrobial agents. Here we report that when P. aeruginosa is plated on ciprofloxacin (cipro) plates, the majority of cipro-resistant (ciproR) colonies observed at and after 48 h of incubation carry mutations in genes related to the Stringent Response (SR). Mutations in one of the major SR components, spoT, were present in approximately 40% of the ciproR isolates. Compared to the wild-type strain, most of these isolates had decreased growth rate, longer lag phase and altered intracellular ppGpp content. Also, 75% of all sequenced mutations were insertions and deletions, with short deletions being the most frequently occurring mutation type. We present evidence that most of the observed mutations are induced on the selective plates in a subpopulation of cells that are not instantly killed by cipro. Our results suggests that the SR may be an important contributor to antibiotic resistance acquisition in P. aeruginosa.

Antimicrobial resistance of Pseudomonas aeruginosa: navigating clinical impacts, current resistance trends, and innovations in breaking therapies

Pseudomonas aeruginosa, a Gram-negative bacterium, is recognized for its adaptability and opportunistic nature. It poses a substantial challenge in clinical settings due to its complicated antibiotic resistance mechanisms, biofilm formation, and capacity for persistent infections in both animal and human hosts. Recent studies revealed a potential zoonotic transmission of P. aeruginosa between animals, the environment, and human populations which highlights awareness of this microbe. Implementation of the One Health approach, which underscores the connection between human, animal, and environmental health, we aim to offer a comprehensive perspective on the current landscape of P. aeruginosa management. This review presents innovative strategies designed to counteract P. aeruginosa infections. Traditional antibiotics, while effective in many cases, are increasingly compromised by the development of multidrug-resistant strains. Non-antibiotic avenues, such as quorum sensing inhibition, phage therapy, and nanoparticle-based treatments, are emerging as promising alternatives. However, their clinical application encounters obstacles like cost, side effects, and safety concerns. Effectively addressing P. aeruginosa infections necessitates persistent research efforts, advancements in clinical development, and a comprehension of host-pathogen interactions to deal with this resilient pathogen.

An integrated metabo-lipidomics profile of induced sputum for the identification of novel biomarkers in the differential diagnosis of asthma and COPD

BACKGROUND

Due to their complexity and to the presence of common clinical features, differentiation between asthma and chronic obstructive pulmonary disease (COPD) can be a challenging task, complicated in such cases also by asthma-COPD overlap syndrome. The distinct immune/inflammatory and structural substrates of COPD and asthma are responsible for significant differences in the responses to standard pharmacologic treatments. Therefore, an accurate diagnosis is of central relevance to assure the appropriate therapeutic intervention in order to achieve safe and effective patient care. Induced sputum (IS) accurately mirrors inflammation in the airways, providing a more direct picture of lung cell metabolism in comparison to those specimen that reflect analytes in the systemic circulation.

METHODS

An integrated untargeted metabolomics and lipidomics analysis was performed in IS of asthmatic (n = 15) and COPD (n = 22) patients based on Ultra-High-Pressure Liquid Chromatography-Mass Spectrometry (UHPLC-MS) and UHPLC-tandem MS (UHPLC-MS/MS). Partial Least Squares-Discriminant Analysis (PLS-DA) was applied to resulting dataset. The analysis of main enriched metabolic pathways and the association of the preliminary metabolites/lipids pattern identified to clinical parameters of asthma/COPD differentiation were explored. Multivariate ROC analysis was performed in order to determine the discriminatory power and the reliability of the putative biomarkers for diagnosis between COPD and asthma.

RESULTS

PLS-DA indicated a clear separation between COPD and asthmatic patients. Among the 15 selected candidate biomarkers based on Variable Importance in Projection scores, putrescine showed the highest score. A differential IS bio-signature of 22 metabolites and lipids was found, which showed statistically significant variations between asthma and COPD. Of these 22 compounds, 18 were decreased and 4 increased in COPD compared to asthmatic patients. The IS levels of Phosphatidylethanolamine (PE) (34:1), Phosphatidylglycerol (PG) (18:1;18:2) and spermine were significantly higher in asthmatic subjects compared to COPD.

CONCLUSIONS

This is the first pilot study to analyse the IS metabolomics/lipidomics signatures relevant in discriminating asthma vs COPD. The role of polyamines, of 6-Hydroxykynurenic acid and of D-rhamnose as well as of other important players related to the alteration of glycerophospholipid, aminoacid/biotin and energy metabolism provided the construction of a diagnostic model that, if validated on a larger prospective cohort, might be used to rapidly and accurately discriminate asthma from COPD.

Eco-evolutionary dynamics of experimental Pseudomonas aeruginosa populations under oxidative stress

Within-host environments are likely to present a challenging and stressful environment for opportunistic pathogenic bacteria colonizing from the external environment. How populations of pathogenic bacteria respond to such environmental challenges and how this varies between strains is not well understood. Oxidative stress is one of the defences adopted by the human immune system to confront invading bacteria. In this study, we show that strains of the opportunistic pathogenic bacterium Pseudomonas aeruginosa vary in their eco-evolutionary responses to hydrogen peroxide stress. By quantifying their 24 h growth kinetics across hydrogen peroxide gradients we show that a transmissible epidemic strain isolated from a chronic airway infection of a cystic fibrosis patient, LESB58, is much more susceptible to hydrogen peroxide than either of the reference strains, PA14 or PAO1, with PAO1 showing the lowest susceptibility. Using a 12 day serial passaging experiment combined with a mathematical model, we then show that short-term susceptibility controls the longer-term survival of populations exposed to subinhibitory levels of hydrogen peroxide, but that phenotypic evolutionary responses can delay population extinction. Our model further suggests that hydrogen peroxide driven extinctions are more likely with higher rates of population turnover. Together, these findings suggest that hydrogen peroxide is likely to be an effective defence in host niches where there is high population turnover, which may explain the counter-intuitively high susceptibility of a strain isolated from chronic lung infection, where such ecological dynamics may be slower.

Fibroblast Growth Factor 23 Signaling Does Not Increase Inflammation from Pseudomonas aeruginosa Infection in the Cystic Fibrosis Bronchial Epithelium

Background and Objectives: Chronic inflammation due to Pseudomonas aeruginosa (PA) infection in people with cystic fibrosis (CF) remains a concerning issue in the wake of modulator therapy initiation. Given the perpetuating cycle of colonization, infection, chronic inflammation, and recurrent injury to the lung, there are increases in the risk for mortality in the CF population. We have previously shown that fibroblast growth factor (FGF) 23 can exaggerate transforming growth factor (TGF) beta-mediated bronchial inflammation in CF. Our study aims to shed light on whether FGF23 signaling also plays a role in PA infection of the CF bronchial epithelium. Materials and Methods: CF bronchial epithelial cells were pretreated with FGF23 or inhibitors for FGF receptors (FGFR) and then infected with different PA isolates. After infection, immunoblot analyses were performed on these samples to assess the levels of phosphorylated phospholipase C gamma (PLCγ), total PLCγ, phosphorylated extracellular signal-regulated kinase (ERK), and total ERK. Additionally, the expression of FGFRs and interleukins at the transcript level (RT-qPCR), as well as production of interleukin (IL)-6 and IL-8 at the protein level (ELISA) were determined. Results: Although there were decreases in isoform-specific FGFRs with increases in interleukins at the mRNA level as well as phosphorylated PLCγ and the production of IL-8 protein with PA infection, treatment with FGF23 or FGFR blockade did not alter downstream targets such as IL-6 and IL-8. Conclusions: FGF23 signaling does not seem to modulate the PA-mediated inflammatory response of the CF bronchial epithelium.

Biofilm Dispersal, Reduced Viscoelasticity, and Antibiotic Sensitization via Nitric Oxide-Releasing Biopolymers

Compared to planktonic bacteria, biofilms are notoriously difficult to eradicate due to their inherent protection against the immune response and antimicrobial agents. Inducing biofilm dispersal to improve susceptibility to antibiotics is an attractive therapeutic avenue for eradicating biofilms. Nitric oxide (NO), an endogenous antibacterial agent, has previously been shown to induce biofilm dispersal, but with limited understanding of the effects of NO-release properties. Herein, the antibiofilm effects of five promising NO-releasing biopolymer candidates were studied by assessing dispersal, changes in biofilm viscoelasticity, and increased sensitization to tobramycin after treatment with NO. A threshold level of NO was needed to achieve biofilm dispersal, with longer-releasing systems requiring lower concentrations. The most positively charged NO-release systems (from the presence of primary amines) led to the greatest reduction in viscoelasticity of Pseudomonas aeruginosa biofilms. Co-treatment of tobramycin with the NO-releasing biopolymer greatly decreased the dose of tobramycin required to eradicate tobramycin-susceptible and -resistant biofilms in both cellular and tissue models.

Antibacterial Activity of a Phenylpropanoid from the Root Extract of Carduus leptacanthus Fresen

Background

The emergence and rapid spread of antimicrobial drug-resistance microorganisms exacerbate the treatment of infectious diseases, underscoring the importance of finding new, safe, and effective drugs. In Ethiopia, the roots of Carduus leptacanthus have traditionally been employed to treat microbial infectious diseases The aim of this study was to evaluate the antibacterial activity of the root extract and its primary components against six bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus agalactiae, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia).

Methods

The extraction involved maceration of air-dried and powdered roots of C. leptacanthus with 80% methanol. The compound was isolated from the root extract using silica gel column chromatography and recrystallization in CHCl3/MeOH (9 : 1) and was characterized using ESI-MS and 1D-NMR spectroscopy. Antibacterial activity of the extract was assessed using agar well diffusion and broth microdilution methods.

Results

Syringin, a phenylpropanoid, was isolated and characterized from the extract of C. leptacanthus. The extract showed the most substantial efficacy against S. epidermidis (MIC = 5.33 mg/ml and inhibition zone diameter of 24 mm at 200 mg/m). Syringin also elicited antibacterial activity against S. aureus (MIC = 13.33 mg/ml), S. epidermidis (MIC = 16 mg/ml), and S. agalactiae (MIC = 16 mg/ml). Despite being tested up to a maximum concentration of 16 mg/ml, syringin did not exhibit antibacterial activity against the Gram-negative bacteria (P. aeruginosa, E. coli, and K. pneumonia).

Conclusions

In conclusion, the findings suggest that syringin exhibits partial involvement in the root extract's antibacterial activity, thereby potentially supporting the traditional medicinal use of the plant.

Stability Considerations for Bacteriophages in Liquid Formulations Designed for Nebulization

Pulmonary bacterial infections present a significant health risk to those with chronic respiratory diseases (CRDs) including cystic fibrosis (CF) and chronic-obstructive pulmonary disease (COPD). With the emergence of antimicrobial resistance (AMR), novel therapeutics are desperately needed to combat the emergence of resistant superbugs. Phage therapy is one possible alternative or adjunct to current antibiotics with activity against antimicrobial-resistant pathogens. How phages are administered will depend on the site of infection. For respiratory infections, a number of factors must be considered to deliver active phages to sites deep within the lung. The inhalation of phages via nebulization is a promising method of delivery to distal lung sites; however, it has been shown to result in a loss of phage viability. Although preliminary studies have assessed the use of nebulization for phage therapy both in vitro and in vivo, the factors that determine phage stability during nebulized delivery have yet to be characterized. This review summarizes current findings on the formulation and stability of liquid phage formulations designed for nebulization, providing insights to maximize phage stability and bactericidal activity via this delivery method.

Isolation of Pseudomonas aeruginosa in Stable Chronic Obstructive Pulmonary Disease Patients-Should We Treat It?

Chronic obstructive pulmonary disease (COPD) is one of the most frequent inflammatory diseases of the airways [...].

A novel in vitro model to study prolonged Pseudomonas aeruginosa infection in the cystic fibrosis bronchial epithelium

Pseudomonas aeruginosa (PA) is known to chronically infect airways of people with cystic fibrosis (CF) by early adulthood. PA infections can lead to increased airway inflammation and lung tissue damage, ultimately contributing to decreased lung function and quality of life. Existing models of PA infection in vitro commonly utilize 1-6-hour time courses. However, these relatively early time points may not encompass downstream airway cell signaling in response to the chronic PA infections observed in people with cystic fibrosis. To fill this gap in knowledge, the aim of this study was to establish an in vitro model that allows for PA infection of CF bronchial epithelial cells, cultured at the air liquid interface, for 24 hours. Our model shows with an inoculum of 2 x 102 CFUs of PA for 24 hours pro-inflammatory markers such as interleukin 6 and interleukin 8 are upregulated with little decrease in CF bronchial epithelial cell survival or monolayer confluency. Additionally, immunoblotting for phosphorylated phospholipase C gamma, a well-known downstream protein of fibroblast growth factor receptor signaling, showed significantly elevated levels after 24 hours with PA infection that were not seen at earlier timepoints. Finally, inhibition of phospholipase C shows significant downregulation of interleukin 8. Our data suggest that this newly developed in vitro "prolonged PA infection model" recapitulates the elevated inflammatory markers observed in CF, without compromising cell survival. This extended period of PA growth on CF bronchial epithelial cells will have impact on further studies of cell signaling and microbiological studies that were not possible in previous models using shorter PA exposures.

Modified Dingchuan Decoction treats cough-variant asthma by suppressing lung inflammation and regulating the lung microbiota

ETHNOPHARMACOLOGICAL RELEVANCE

Modified Dingchuan Decoction (MDD) is a Chinese medicine formula containing 11 materials with cough suppression, asthma relief, and anti-inflammatory effects.

AIM OF THE STUDY

This study aimed to evaluate the therapeutic effect of MDD on cough-variant asthma (CVA) and to investigate its mechanism of action.

MATERIALS AND METHODS

The chemical constituents of MDD were analyzed by ultra-performance liquid chromatography-quadrupole/electrostatic field orbitrap high-resolution mass spectrometry (UPLC-Q-Orbitrap HRMS). A guinea pig CVA model was established using an intramuscular injection of ovalbumin (OVA), combined with an intraperitoneal injection of aluminum hydroxide [Al(OH)₃] and nebulized OVA. At the beginning of day 18, the low, medium, and high MDD groups were gavaged with 7.23 g/kg, 14.46 g/kg, and 28.92 g/kg of MDD, respectively, and the positive group was gavaged with 5 mg/kg of prednisone acetate combined with 1 mg/kg of montelukast sodium; the normal and model groups were given an equal volume of distilled water, once a day for 21 days. The cough was induced by 10^-3 mol/L capsaicin solution 1 h after the last administration, and the number of coughs and the latency of coughs were evaluated. Hematoxylin and eosin staining (H&E) was used to observe pathological changes in the lungs and airways. The concentration of inflammatory factors in bronchoalveolar lavage fluid (BALF) was measured by enzyme-linked immunosorbent assay (ELISA). We analyzed the lung microbiota using 16 S ribosomal DNA (16 S rDNA) high-throughput sequencing.

RESULTS

The 38 chemical components were found in MDD, and MDD reduced the number of coughs in guinea pigs with CVA, prolonged cough latency, improved pathological damage to the lungs and airways, regulated inflammatory factor levels in BALF, and modulated the lung microbiota.

CONCLUSIONS

This study demonstrated that treating CVA with MDD may be related to inhibiting lung inflammation and regulating lung microbiota.

TargIDe: a machine-learning workflow for target identification of molecules with antibiofilm activity against Pseudomonas aeruginosa

Bacterial biofilms are a source of infectious human diseases and are heavily linked to antibiotic resistance. Pseudomonas aeruginosa is a multidrug-resistant bacterium widely present and implicated in several hospital-acquired infections. Over the last years, the development of new drugs able to inhibit Pseudomonas aeruginosa by interfering with its ability to form biofilms has become a promising strategy in drug discovery. Identifying molecules able to interfere with biofilm formation is difficult, but further developing these molecules by rationally improving their activity is particularly challenging, as it requires knowledge of the specific protein target that is inhibited. This work describes the development of a machine learning multitechnique consensus workflow to predict the protein targets of molecules with confirmed inhibitory activity against biofilm formation by Pseudomonas aeruginosa. It uses a specialized database containing all the known targets implicated in biofilm formation by Pseudomonas aeruginosa. The experimentally confirmed inhibitors available on ChEMBL, together with chemical descriptors, were used as the input features for a combination of nine different classification models, yielding a consensus method to predict the most likely target of a ligand. The implemented algorithm is freely available at https://github.com/BioSIM-Research-Group/TargIDe under licence GNU General Public Licence (GPL) version 3 and can easily be improved as more data become available.

A 10-year microbiological study of Pseudomonas aeruginosa strains revealed the circulation of populations resistant to both carbapenems and quaternary ammonium compounds

Pseudomonas aeruginosa is one of the leading causes of healthcare-associated infections. For this study, the susceptibility profiles to antipseudomonal antibiotics and a quaternary ammonium compound, didecyldimethylammonium chloride (DDAC), widely used as a disinfectant, were established for 180 selected human and environmental hospital strains isolated between 2011 and 2020. Furthermore, a genomic study determined resistome and clonal putative relatedness for 77 of them. During the ten-year study period, it was estimated that 9.5% of patients' strains were resistant to carbapenems, 11.9% were multidrug-resistant (MDR), and 0.7% were extensively drug-resistant (XDR). Decreased susceptibility (DS) to DDAC was observed for 28.0% of strains, a phenotype significantly associated with MDR/XDR profiles and from hospital environmental samples (p < 0.0001). According to genomic analyses, the P. aeruginosa population unsusceptible to carbapenems and/or to DDAC was diverse but mainly belonged to top ten high-risk clones described worldwide by del Barrio-Tofiño et al. The carbapenem resistance appeared mainly due to the production of the VIM-2 carbapenemase (39.3%) and DS to DDAC mediated by MexAB-OprM pump efflux overexpression. This study highlights the diversity of MDR/XDR populations of P. aeruginosa which are unsusceptible to compounds that are widely used in medicine and hospital disinfection and are probably distributed in hospitals worldwide.

Responses of carbapenemase-producing and non-producing carbapenem-resistant Pseudomonas aeruginosa strains to meropenem revealed by quantitative tandem mass spectrometry proteomics

Pseudomonas aeruginosa is an opportunistic pathogen with increasing incidence of multidrug-resistant strains, including resistance to last-resort antibiotics, such as carbapenems. Resistances are often due to complex interplays of natural and acquired resistance mechanisms that are enhanced by its large regulatory network. This study describes the proteomic responses of two carbapenem-resistant P. aeruginosa strains of high-risk clones ST235 and ST395 to subminimal inhibitory concentrations (sub-MICs) of meropenem by identifying differentially regulated proteins and pathways. Strain CCUG 51971 carries a VIM-4 metallo-β-lactamase or 'classical' carbapenemase; strain CCUG 70744 carries no known acquired carbapenem-resistance genes and exhibits 'non-classical' carbapenem-resistance. Strains were cultivated with different sub-MICs of meropenem and analyzed, using quantitative shotgun proteomics based on tandem mass tag (TMT) isobaric labeling, nano-liquid chromatography tandem-mass spectrometry and complete genome sequences. Exposure of strains to sub-MICs of meropenem resulted in hundreds of differentially regulated proteins, including β-lactamases, proteins associated with transport, peptidoglycan metabolism, cell wall organization, and regulatory proteins. Strain CCUG 51971 showed upregulation of intrinsic β-lactamases and VIM-4 carbapenemase, while CCUG 70744 exhibited a combination of upregulated intrinsic β-lactamases, efflux pumps, penicillin-binding proteins and downregulation of porins. All components of the H1 type VI secretion system were upregulated in strain CCUG 51971. Multiple metabolic pathways were affected in both strains. Sub-MICs of meropenem cause marked changes in the proteomes of carbapenem-resistant strains of P. aeruginosa exhibiting different resistance mechanisms, involving a wide range of proteins, many uncharacterized, which might play a role in the susceptibility of P. aeruginosa to meropenem.

Pseudomonas aeruginosa is oxygen-deprived during infection in cystic fibrosis lungs, reducing the effectiveness of antibiotics

Pseudomonas aeruginosa infects the lungs of patients with cystic fibrosis. Sputum expectorated from the lungs of patients contains low levels of oxygen, indicating that P. aeruginosa may be oxygen-deprived during infection. During in vitro growth under oxygen-limiting conditions, a P. aeruginosa reference strain increases expression of a cytochrome oxidase with a high affinity for oxygen, and of nitrate and nitrite reductases that enable it to use nitrate instead of oxygen during respiration. Here, we quantified transcription of the genes encoding these three enzymes in sputum samples from 18 infected patients, and in bacteria isolated from the sputum samples and grown in aerobic and anaerobic culture. In culture, expression of all three genes was increased by averages of 20- to 500-fold in anaerobically grown bacteria compared with those grown aerobically, although expression levels varied greatly between isolates. Expression of the same genes in sputum was similar to that of the corresponding bacteria in anaerobic culture. The isolated bacteria were less susceptible to tobramycin and ciprofloxacin, two widely used anti-pseudomonal antibiotics, when grown anaerobically than when grown aerobically. Our findings show that P. aeruginosa experiences oxygen starvation during infection in cystic fibrosis, reducing the effectiveness of antibiotic treatment.

Gene-Gene Interactions Reduce Aminoglycoside Susceptibility of Pseudomonas aeruginosa through Efflux Pump-Dependent and -Independent Mechanisms

Pseudomonas aeruginosa causes a wide range of acute and chronic infections. Aminoglycosides are a cornerstone of treatment, but isolates are often resistant. The purpose of this research was to better understand the genetic basis of aminoglycoside resistance in P. aeruginosa. Bioinformatic approaches identified mutations in resistance-associated genes in the clinical isolates of P. aeruginosa. The common mutations were then engineered into the genome of P. aeruginosa reference strain PAO1. Mutations in the elongation factor gene fusA1 caused the biggest reduction in aminoglycoside susceptibility, with mutations in the two-component regulator gene amgS and the efflux pump regulator gene mexZ having less impact. This susceptibility was further reduced by combinations of mutations. Mutations in fusA1, amgS and mexZ all increased the expression of the mexXY efflux pump that is strongly associated with aminoglycoside resistance. Furthermore, the fusA1 amgS mexZ triple mutant had the highest efflux pump gene expression. Engineering fusA1 and amgS mutants lacking this efflux pump showed that fusA1 and amgS also reduce aminoglycoside susceptibility through additional mechanisms. The fusA1 and amgS mutations reduced bacterial growth, showing that these mutations have a fitness cost. Our findings demonstrate the complex interplay between mutations, efflux pump expression and other mechanisms for reducing the susceptibility of P. aeruginosa to aminoglycosides.

The gut microbiome is a significant risk factor for future chronic lung disease

BACKGROUND

The gut-lung axis is generally recognized, but there are few large studies of the gut microbiome and incident respiratory disease in adults.

OBJECTIVE

We sought to investigate the association and predictive capacity of the gut microbiome for incident asthma and chronic obstructive pulmonary disease (COPD).

METHODS

Shallow metagenomic sequencing was performed for stool samples from a prospective, population-based cohort (FINRISK02; N = 7115 adults) with linked national administrative health register-derived classifications for incident asthma and COPD up to 15 years after baseline. Generalized linear models and Cox regressions were used to assess associations of microbial taxa and diversity with disease occurrence. Predictive models were constructed using machine learning with extreme gradient boosting. Models considered taxa abundances individually and in combination with other risk factors, including sex, age, body mass index, and smoking status.

RESULTS

A total of 695 and 392 statistically significant associations were found between baseline taxonomic groups and incident asthma and COPD, respectively. Gradient boosting decision trees of baseline gut microbiome abundance predicted incident asthma and COPD in the validation data sets with mean area under the curves of 0.608 and 0.780, respectively. Cox analysis showed that the baseline gut microbiome achieved higher predictive performance than individual conventional risk factors, with C-indices of 0.623 for asthma and 0.817 for COPD. The integration of the gut microbiome and conventional risk factors further improved prediction capacities.

CONCLUSIONS

The gut microbiome is a significant risk factor for incident asthma and incident COPD and is largely independent of conventional risk factors.

Antimicrobial sensitivity pattern of children with cystic fibrosis in Bangladesh: a lesson from a specialized Sishu (Children) Hospital

Background

Infection control in cystic fibrosis (CF) patients plays a crucial role in improving the survival of patients with CF. Antimicrobial sensitivity patterns in these patient groups in our country are currently lacking. Therefore, the purpose of the study was to evaluate the microbiological cultures and antimicrobial susceptibility pattern of pediatric CF patients.

Method

A total of 50 respiratory samples were prospectively collected from the period between February 2021 and October 2021. Sputum and oropharyngeal swabs were processed for culture and microbiological testing. Sample collection and evaluation were performed according to the Good Laboratory Practice guidelines (GLP). Informed written consent was ensured before participation. Statistical analysis was performed with SPSS v 26.

Result

The median age of the children was 30 months (6–120) months, with a male predominance (66% vs 34%). Single and two organisms were isolated in 72% (n = 36) and 12% (n = 6) of cases, respectively. During the study period, 36% of the patients harbored Pseudomonas aeruginosa, 18% harbored Klebsiella pneumoniae, and both Staphylococcus aureus and Escherichia coli were detected in 16% of cases. Levofloxacin was found to be the most active antibiotic agent with 100% susceptibility. In contrast, nearly all isolates were resistant to amoxicillin, erythromycin and rifampicin.

Conclusion

Levofloxacin is the most effective agent to treat CF patients. Active surveillance of the resistance pattern should always continue to be promoted.

Bacteriophage: A new therapeutic player to combat neutrophilic inflammation in chronic airway diseases

Persistent respiratory bacterial infections are a clinical burden in several chronic inflammatory airway diseases and are often associated with neutrophil infiltration into the lungs. Following recruitment, dysregulated neutrophil effector functions such as increased granule release and formation of neutrophil extracellular traps (NETs) result in damage to airway tissue, contributing to the progression of lung disease. Bacterial pathogens are a major driver of airway neutrophilic inflammation, but traditional management of infections with antibiotic therapy is becoming less effective as rates of antimicrobial resistance rise. Bacteriophages (phages) are now frequently identified as antimicrobial alternatives for antimicrobial resistant (AMR) airway infections. Despite growing recognition of their bactericidal function, less is known about how phages influence activity of neutrophils recruited to sites of bacterial infection in the lungs. In this review, we summarize current in vitro and in vivo findings on the effects of phage therapy on neutrophils and their inflammatory mediators, as well as mechanisms of phage-neutrophil interactions. Understanding these effects provides further validation of their safe use in humans, but also identifies phages as a targeted neutrophil-modulating therapeutic for inflammatory airway conditions.

Infection prevention and control policies in hospitals and prevalence of highly resistant microorganisms: an international comparative study

BACKGROUND

There are differences in infection prevention and control (IPC) policies to prevent transmission of highly resistant microorganisms (HRMO). The aim of this study is to give an overview of the IPC policy of six European hospitals and their HRMO prevalence, to compare the IPC policies of these hospitals with international guidelines, and to investigate the hospitals' adherence to their own IPC policy.

METHODS

The participating hospitals were located in Salzburg (Austria), Vienna (Austria), Kayseri (Turkey), Piraeus (Greece), Rome (Italy) and Rotterdam (The Netherlands). Data were collected via an online survey. Questions were aimed at prevalence rates in the years 2014, 2015, 2016 of carbapenemase-producing Klebsiella pneumoniae (CPK), carbapenemase-producing Pseudomonas aeruginosa (CPPA), vancomycin-resistant Enterococcus faecium (VRE) and hospitals' IPC policies of 2017. Implemented IPC measures (i.e. with a self-reported adherence of > 90%) were counted (26 points maximal).

RESULTS

The self-reported prevalence of CPK per year was low in the Austrian and Dutch hospitals and high in the Turkish and Greek hospitals. CPPA was highly prevalent in the Turkish hospital only, while the prevalence of VRE in four hospitals, except the Austrian hospitals which reported lower prevalence numbers, was more evenly distributed. The Dutch hospital had implemented the most IPC measures (n = 21), the Turkish and Greek hospitals the least (n = 14 and 7, respectively).

CONCLUSION

Hospitals with the highest self-reported prevalence of CPK and CPPA reported the least implemented IPC measures. Also, hospitals with a higher prevalence often reported a lower adherence to own IPC policy.

Effect of Flagellin Pre-Exposure on the Inflammatory and Antifungal Response of Bronchial Epithelial Cells to Fungal Pathogens

Bronchial epithelial cells (BEC) play a crucial role in innate immunity against inhaled fungi. Indeed, in response to microorganisms, BEC synthesize proinflammatory cytokines involved in the recruitment of neutrophils. We have recently shown that BEC exert antifungal activity against Aspergillus fumigatus by inhibiting filament growth. In the present study, we first analyzed the inflammatory and antifungal responses of BEC infected by several fungal species such as Aspergillus spp., Scedosporium apiospermum and Candida albicans, which are frequently isolated from the sputum of people with chronic pulmonary diseases. The airways of these patients, such as people with cystic fibrosis (pwCF), are mainly colonized by P. aeruginosa and secondary by fungal pathogens. We have previously demonstrated that BEC are capable of innate immune memory, allowing them to increase their inflammatory response against A. fumigatus following a previous contact with Pseudomonas aeruginosa flagellin. To identify the impact of bacteria exposure on BEC responses to other fungal infections, we extended the analysis of BEC innate immune memory to Aspergillus spp., Scedosporium apiospermum and Candida albicans infection. Our results show that BEC are able to recognize and respond to Aspergillus spp., S. apiospermum and C. albicans infection and that the modulation of BEC responses by pre-exposure to flagellin varies according to the fungal species encountered. Deepening our knowledge of the innate immune memory of BEC should open new therapeutic avenues to modulate the inflammatory response against polymicrobial infections observed in chronic pulmonary diseases such as CF.