Pseudomonas aeruginosa infection in patients with cystic fibrosis: scientific evidence regarding clinical impact, diagnosis, and treatment

Evaluating the Expression of Efflux Pumps in Pseudomonas aeruginosa in Exposure to Sodium Dodecyl Sulfate, Didecyldimethylammonium Chloride, and Octenidine Dihydrochloride

Emerging resistance of Gram-negative bacteria, including Pseudomonas aeruginosa, to commonly used detergents and disinfectant is encountering us with hazard. Inappropriate use of disinfectants has forced bacteria to gain resistance. The ability of bacteria to extrude substrates from the cellular interior to the external environment has enabled them to persist in exposure to toxic compounds, which is due to existence of transport proteins. Efflux pumps, in Gram-negative bacteria, are proteins responsible for exporting molecules outside of the cell, by crossing the two membranes. In this study, 40 P. aeruginosa strains from hospitals, clinics, and burn center laundries and 40 P. aeruginosa strains from urban laundries were collected. This study evaluated the minimum inhibitory concentration (MIC) level of sodium dodecyl sulfate (SDS), didecyldimethylammonium chloride (DDAC), and octenidine dihydrochloride (Od) in P. aeruginosa strains. The real-time PCR was carried out to evaluate the expression of MexAB-OprM, MexCD-OprJ, and MexXY-OprM efflux system. The obtained results indicated a higher MIC level for SDS, DDAC, and Od in medical laundries. The sub-MIC level of DDAC and Od increased the expression level of MexAB-OprM, MexCD-OprJ, and MexXY-OprM in P. aeruginosa strains, suggesting that efflux pumps contribute to disinfectant resistance in P. aeruginosa.

Pseudomonas aeruginosa in chronic lung disease: untangling the dysregulated host immune response

Pseudomonas aeruginosa is a highly adaptable opportunistic pathogen capable of exploiting barriers and immune defects to cause chronic lung infections in conditions such as cystic fibrosis. In these contexts, host immune responses are ineffective at clearing persistent bacterial infection, instead driving a cycle of inflammatory lung damage. This review outlines key components of the host immune response to chronic P. aeruginosa infection within the lung, beginning with initial pathogen recognition, followed by a robust yet maladaptive innate immune response, and an ineffective adaptive immune response that propagates lung damage while permitting bacterial persistence. Untangling the interplay between host immunity and chronic P. aeruginosa infection will allow for the development and refinement of strategies to modulate immune-associated lung damage and potentiate the immune system to combat chronic infection more effectively.

Surgery for nasal polyposis in cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is a life-shortening, autosomal recessive disease that leads to abnormal electrolyte concentration in exocrine secretions. Secretion stasis in paranasal sinuses determines chronic rhinosinusitis (CRS) and nasal polyposis. Endoscopic sinus surgery is used to open the sinuses and allow medical treatment to work properly.

OBJECTIVES

To determine the effects of sinus surgery alone or in combination with medical treatment (non-surgical) compared to medical treatment (non-surgical) alone on both nasal and pulmonary function in people with CF diagnosed with CRS with nasal polyposis. Further, to evaluate the impact of sinus surgery (with or without medical treatment) on hospitalization rates, use of antibiotics and pulmonary exacerbation rates.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and hand searching of journals and conference abstract books. Date of last search: 4 July 2022. We also searched other databases (Pubmed, Embase, World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), Virtual Health Library and ClinicalTrials.gov). Date of last search: 18 September 2022.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing groups who underwent endoscopic sinus surgery and groups with medical treatment alone.

DATA COLLECTION AND ANALYSIS

The review authors independently selected studies, extracted data, assessed the risk of bias and evaluated the certainty of the evidence using GRADE. They contacted the authors of the included study for additional information.

MAIN RESULTS

We identified 66 publications relating to 50 studies from electronic searches. Only one study fulfilled the inclusion criteria, and only limited information was available. In this study, 28 participants aged 19 to 28 years were randomized in equal numbers to either nasal irrigation alone or nasal irrigation with surgery (endoscopic polypectomy with extended sinusotomy). The certainty of the evidence was very low according to the GRADE approach. We are uncertain whether, compared to medical treatment alone, the addition of surgical intervention improves nasal symptoms, or reduces bacterial colonization, the use of antibiotics and pulmonary exacerbations. We are also uncertain whether the addition of surgery to medical treatment leads to changes in pulmonary function. There was one episode of bleeding during surgery that was corrected during the procedure with no further consequences. The study did not report on survival.

AUTHORS' CONCLUSIONS

Very low-certainty evidence means we are not certain if endoscopic sinus surgery to treat chronic rhinosinusitis with nasal polyposis in cystic fibrosis is effective. Future research should be multicentric to increase the number of participants and increase statistical power. Adequate randomization and allocation concealment are important to guarantee that the groups are similar. Blinding, however, may not be possible in an ethical trial; even without blinding, results can achieve high-level evidence if the outcomes used are objective parameters. Future research should follow participants of all ages for at least 12 months to evaluate the evolution of nasal polyposis, its recurrence and how symptoms may return. We also consider mortality an important outcome to be assessed. Future clinical research should consider the effects of cystic fibrosis transmembrane conductance regulators, a new group of drugs that may affect the development of nasal polyps.

Pseudomonas aeruginosa in children with cerebral palsy: a prospective study

Introduction

Children with cerebral palsy (CP) often present with chronic respiratory symptoms. Pseudomonas aeruginosa (PA), is a known pathogen associated with more severe respiratory disease. Preventive actions to eradicate this bacterium and to improve the respiratory condition of children with CP could be very valuable. Therefore, we assessed the prevalence of PA and its association with respiratory disease.

Methods

Throat swabs were taken in children with CP, aged 0-18 years. Data from patient records were extracted from the electronic medical records. Follow-up of respiratory symptoms was done by the Liverpool respiratory symptom questionnaire (LRSQ) after 3 months.

Results

A throat swab and a completed LRSQ after 3 months were received from 79 children with CP. Twenty-eight patients (35.4%) were found to have at least one positive respiratory culture. Only 4 patients (5.1%) were contaminated with PA. Gram negative bacteria were isolated in 21.5% of the positive throat swabs, S. aureus was found in 13.9%. Most pathogens were found in patients with higher GMFCS score (GMFCS IV and V). Results of the LRSQ showed that 52.1% of these patients reported having 1 cold in the past 3 months.

Discussion

The prevalence of PA in our population of children with CP is low, gram-negative bacteria were most commonly found. The respiratory consequences of being colonized with these bacteria were limited. These results may have been affected by the COVID-19 pandemic. Further research is recommended.

Use of soil actinomycetes for pharmaceutical, food, agricultural, and environmental purposes

In this article, we reviewed the international scientific production of the last years on actinomycetes isolated from soil aiming to report recent advances in using these microorganisms for different applications. The most promising genera, isolation conditions and procedures, pH, temperature, and NaCl tolerance of these bacteria were reported. Based on the content analysis of the articles, most studies have focused on the isolation and taxonomic description of new species of actinomycetes. Regarding the applications, the antimicrobial potential (antibacterial and antifungal) prevailed among the articles, followed by the production of enzymes (cellulases and chitinases, etc.), agricultural uses (plant growth promotion and phytopathogen control), bioremediation (organic and inorganic contaminants), among others. Furthermore, a wide range of growth capacity was verified, including temperatures from 4 to 60 °C (optimum: 28 °C), pH from 3 to 13 (optimum: 7), and NaCl tolerance up to 32% (optimum: 0-1%), which evidence a great tolerance for actinomycetes cultivation. Streptomyces was the genus with the highest incidence among the soil actinomycetes and the most exploited for different uses. Besides, the interest in isolating actinomycetes from soils in extreme environments (Antarctica and deserts, for example) is growing to explore the adaptive capacities of new strains and the secondary metabolites produced by these microorganisms for different industrial interests, especially for pharmaceutical, food, agricultural, and environmental purposes.

Surgery for nasal polyposis in cystic fibrosis

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To determine the effects of sinus surgery alone or in combination with medical treatment (non‐surgical) compared to medical treatment (non‐surgical) alone on both nasal and pulmonary function in people with cystic fibrosis diagnosed with CRS with nasal polyposis. Further, to evaluate the impact of sinus surgery (with or without medical treatment) on hospitalization rates, use of antibiotics and pulmonary exacerbation rates.

Acidic Microenvironment Determines Antibiotic Susceptibility and Biofilm Formation of Pseudomonas aeruginosa

Pseudomonas aeruginosa is the most prevalent bacterial species that contribute to cystic fibrosis (CF) respiratory failure. The impaired function of CF transmembrane conductance regulator leads to abnormal epithelial Cl^-/HCO₃ ^- transport and acidification of airway surface liquid. However, it remains unclear why the CF lung is most commonly infected by Pseudomonas aeruginosa versus other pathogens. We carried out studies to investigate if lower pH helps Pseudomonas aeruginosa adapt and thrive in the CF-like acidic lung environment. Our results revealed that Pseudomonas aeruginosa generally forms more biofilm, induces antibiotic resistance faster in acidic conditions, and can be reversed by returning the acidic environment to physiologically neutral conditions. Pseudomonas aeruginosa appears to be highly adaptive to the CF-like acidic pH environment. By studying the effects of an acidic environment on bacterial response, we may provide a new therapeutic option in preventing chronic Pseudomonas aeruginosa infection and colonization.

New insights about the EptA protein and its correlation with the pmrC gene in polymyxin resistance in Pseudomonas aeruginosa

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Computational biology.

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Bacterial resistance.

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Pseudomonas aeruginosa.

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Gram-negative bacteria.

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Polymyxin.

Nowadays, clinical and scientific interest in antibiotics, as polymyxin, has increased due to the large number of reports of multiresistant Gram-negative bacteria, as Pseudomonas aeruginosa. The aim of this study was to investigate a related group of proteins for resistance to polymyxins, encoded by P. aeruginosa genome, through in silico analysis. The mobilized colistin resistance 1 (MCR₁) protein from Escherichia coli was used for comparison. Similar sequences to the protein MCR₁ in P. aeruginosa were analysed for physicochemical properties. 31 protein isoforms in P. aeruginosa (EptA) were found able to confer resistance to polymyxin showing protein lengths between 551 and 572 amino acids, with molecular mass values between 61.36 - 62. 80 kDa, isoelectric point between 6.10 to 7.17, instability index between 33.76 to 41.87, aliphatic index between 98.67 to 102.63 and the hydropathyindex between - 0.008 to 0.094. These proteins belong to the DUF₁₇₀₅ superfamily with bit-score values between 559.81 and 629.78. A high degree of similarity between EpTAs in P. aeruginosa was observed in relation to other proteins that confer resistance to polymyxins, present in Gram-negative bacteria species of clinical interest. Although, further studies are needed to identify the actual contribution of EptAs in P. aeruginosa species.

2-Alkyl-4-quinolone quorum sensing molecules are biomarkers for culture-independent Pseudomonas aeruginosa burden in adults with cystic fibrosis

Introduction. Pseudomonas aeruginosa produces quorum sensing signalling molecules including 2-alkyl-4-quinolones (AQs), which regulate virulence factor production in the cystic fibrosis (CF) airways.Hypothesis/Gap statement. Culture can lead to condition-dependent artefacts which may limit the potential insights and applications of AQs as minimally-invasive biomarkers of bacterial load.Aim. We aimed to use culture-independent methods to explore the correlations between AQ levels and live P. aeruginosa load in adults with CF.Methodology. Seventy-five sputum samples at clinical stability and 48 paired sputum samples obtained at the beginning and end of IV antibiotics for a pulmonary exacerbation in adults with CF were processed using a viable cell separation technique followed by quantitative P. aeruginosa polymerase chain reaction (qPCR). Live P. aeruginosa qPCR load was compared with the concentrations of three AQs (HHQ, NHQ and HQNO) detected in sputum, plasma and urine.Results. At clinical stability and the beginning of IV antibiotics for pulmonary exacerbation, HHQ, NHQ and HQNO measured in sputum, plasma and urine were consistently positively correlated with live P. aeruginosa qPCR load in sputum, compared to culture. Following systemic antibiotics live P. aeruginosa qPCR load decreased significantly (P<0.001) and was correlated with a reduction in plasma NHQ (plasma: r=0.463, P=0.003).Conclusion. In adults with CF, AQ concentrations correlated more strongly with live P. aeruginosa bacterial load measured by qPCR compared to traditional culture. Prospective studies are required to assess the potential of systemic AQs as biomarkers of P. aeruginosa bacterial burden.

Pseudomonas aeruginosa adapts to octenidine via a combination of efflux and membrane remodelling

Pseudomonas aeruginosa is an opportunistic pathogen capable of stably adapting to the antiseptic octenidine by an unknown mechanism. Here we characterise this adaptation, both in the laboratory and a simulated clinical setting, and identify a novel antiseptic resistance mechanism. In both settings, 2 to 4-fold increase in octenidine tolerance was associated with stable mutations and a specific 12 base pair deletion in a putative Tet-repressor family gene (smvR), associated with a constitutive increase in expression of the Major Facilitator Superfamily (MFS) efflux pump SmvA. Adaptation to higher octenidine concentrations led to additional stable mutations, most frequently in phosphatidylserine synthase pssA and occasionally in phosphatidylglycerophosphate synthase pgsA genes, resulting in octenidine tolerance 16- to 256-fold higher than parental strains. Metabolic changes were consistent with mitigation of oxidative stress and altered plasma membrane composition and order. Mutations in SmvAR and phospholipid synthases enable higher level, synergistic tolerance of octenidine.

Cystic fibrosis microbiome: analysis of nasal middle meatus and sputum in different lung disease stages

BACKGROUND: Culture independent methods of molecular detection of microbiome have shown the polymicrobial nature of respiratory infections in cystic fibrosis, with pathogenic agents undetectable in conventional culture methods. Composition and diversity of the airway microbiome are still poorly understood. METHODOLOGY: This study evaluated the airway microbiome in 31 adult cystic fibrosis patients via the analysis of 16S rRNA se- quences by next generation sequencing. RESULTS: Staphylococcus, Streptococcus and Corynebacterium were the most abundant genera in the middle meatus, and Pseudo- monas, Haemophilus and Prevotella were the most abundant in sputum. In patients with advanced disease (FEV1< 50%), there was an increase in the prevalence of Pseudomonas in both sample types when studied separately. In each patient, in a paired analysis, the sputum and middle meatus showed similar microbiome composition in mild or moderate disease (FEV1≥ 50%). In patients with severe lung disease, the relative abundance of Pseudomonas had a positive correlation in both collection sites. CONCLUSIONS: This is the first Brazilian study to evaluate the airway microbiome in cystic fibrosis patients. Our findings agree with those in the international literature and indicate the role of Pseudomonas in the sputum and middle meatus in patients with advanced disease.

Gene Loss and Acquisition in Lineages of Pseudomonas aeruginosa Evolving in Cystic Fibrosis Patient Airways

Bacterial airway infections, predominantly caused by P. aeruginosa, are a major cause of mortality and morbidity of CF patients. While short insertions and deletions as well as point mutations occurring during infection are well studied, there is a lack of understanding of how gene loss and acquisition play roles in bacterial adaptation to the human airways. Here, we investigated P. aeruginosa within-host evolution with regard to gene loss and acquisition. We show that during long-term infection P. aeruginosa genomes tend to lose genes, in particular, genes related to virulence. This adaptive strategy allows reduction of the genome size and evasion of the host’s immune response. This knowledge is crucial to understand the basic mutational steps that, on the timescale of years, diversify lineages and adds to the identification of bacterial genetic determinants that have implications for CF disease.

Genome analyses have documented that there are differences in gene repertoire between evolutionary distant lineages of the same bacterial species; however, less is known about microevolutionary dynamics of gene loss and acquisition within bacterial lineages as they evolve over years. Here, we analyzed the genomes of 45 Pseudomonas aeruginosa lineages evolving in the lungs of cystic fibrosis (CF) patients to identify genes that are lost or acquired during the first years of infection. On average, lineage genome content changed by 88 genes (range, 0 to 473). Genes were more often lost than acquired, and prophage genes were more variable than bacterial genes. We identified convergent loss or acquisition of the same genes across lineages, suggesting selection for loss and acquisition of certain genes in the host environment. We found that a notable proportion of such genes are associated with virulence; a trait previously shown to be important for adaptation. Furthermore, we also compared the genomes across lineages to show that the within-lineage variable genes (i.e., genes that had been lost or acquired during the infection) often belonged to genomic content not shared across all lineages. In sum, our analysis adds to the knowledge on the pace and drivers of gene loss and acquisition in bacteria evolving over years in a human host environment and provides a basis to further understand how gene loss and acquisition play roles in lineage differentiation and host adaptation.

Pseudomonas aeruginosa Type III Secretion System Virulotypes and Their Association with Clinical Features of Cystic Fibrosis Patients

Purpose

Pseudomonas aeruginosa appears as the main pathogen in cystic fibrosis (CF) involved in recurrent pneumonia and pulmonary exacerbations. The type III secretion system (T3SS) is one of its main determinants of virulence and is associated with poor clinical progression and increased mortality. This study determined the relationship of clinical features of patients with CF and P. aeruginosa T3SS virulotypes.

Materials and Methods

From January 2018 to March 2019, P. aeruginosa were isolated from sputum and/or oropharyngeal swabs. T3SS markers (exoS, exoU, exoT and exoY) were detected by PCR. Clinical severity according to Shwachman-Kulckycki score and spirometry data were associated with T3SS virulotypes.

Results

A total of 49 patients had positive cultures for P. aeruginosa. T3SS virulence-related markers were detected as follows: exoS 97.9% (n=48), exoU 63.2% (n=31), exoT 95.9% (n=47) and exoY 97.9% (n=48). The prevalence of exoS⁺/exoU⁺ virulotype was higher than previously reported in CF settings, being detected in 61.2% of the evaluated isolates, present in 70% of intermittent infections and with a significantly higher frequency in cases of exacerbations. The presence of exoU in chronic infection was not associated with poor clinical results. In chronic infections, the exoS⁺/exoU⁻ virulotype prevailed (77.8%) and was associated to worse clinical results according to the Shwachman-Kulckycki score and spirometric.

Conclusion

Our findings revealed a high prevalence of the atypical exoS⁺/exoU⁺ virulotype among P. aeruginosa isolates from patients with CF, which was associated with intermittent infection and early clinical alterations, while the exoS⁺/exoU⁻ virulotype was associated with chronic infection and worse clinical results. Finally, the presented data highlight the relevance of T3SS virulence markers in the clinical progression and disease severity in CF patients.

Micro-rheological properties of lung homogenates correlate with infection severity in a mouse model of Pseudomonas aeruginosa lung infection

Lung infections caused by Pseudomonas aeruginosa pose a serious threat to patients suffering from, among others, cystic fibrosis, chronic obstructive pulmonary disease, or bronchiectasis, often leading to life-threatening complications. The establishment of a chronic infection is substantially related to communication between bacteria via quorum-sensing networks. In this study, we aimed to assess the role of quorum-sensing signaling molecules of the Pseudomonas quinolone signal (PQS) and to investigate the viscoelastic properties of lung tissue homogenates of PA-infected mice in a prolonged acute murine infection model. Therefore, a murine infection model was successfully established via intra-tracheal infection with alginate-supplemented Pseudomonas aeruginosa NH57388A. Rheological properties of lung homogenates were analyzed with multiple particle tracking (MPT) and quorum-sensing molecules were quantified with LC–MS/MS. Statistical analysis of bacterial load and quorum-sensing molecules showed a strong correlation between these biomarkers in infected lungs. This was accompanied by noticeable changes in the consistency of lung homogenates with increasing infection severity. Furthermore, viscoelastic properties of the lung homogenates strongly correlated with bacterial load and quorum sensing molecules. Considering the strong correlation between the viscoelasticity of lung homogenates and the aforementioned biomarkers, the viscoelastic properties of infected lungs might serve as reliable new biomarker for the evaluation of the severity of P. aeruginosa infections in murine models.

Electrochemical Detection of Pyocyanin as a Biomarker for Pseudomonas aeruginosa: A Focused Review

Pseudomonas aeruginosa (PA) is a pathogen that is recognized for its advanced antibiotic resistance and its association with serious diseases such as ventilator-associated pneumonia and cystic fibrosis. The ability to rapidly detect the presence of pathogenic bacteria in patient samples is crucial for the immediate eradication of the infection. Pyocyanin is one of PA’s virulence factors used to establish infections. Pyocyanin promotes virulence by interfering in numerous cellular functions in host cells due to its redox-activity. Fortunately, the redox-active nature of pyocyanin makes it ideal for detection with simple electrochemical techniques without sample pretreatment or sensor functionalization. The previous decade has seen an increased interest in the electrochemical detection of pyocyanin either as an indicator of the presence of PA in samples or as a tool for quantifying PA virulence. This review provides the first overview of the advances in electrochemical detection of pyocyanin and offers an input regarding the future directions in the field.

Human Single-chain Variable Fragments Neutralize Pseudomonas aeruginosa Quorum Sensing Molecule, 3O-C12-HSL, and Prevent Cells From the HSL-mediated Apoptosis

The quorum sensing (QS) signaling molecule, N-(3-oxododecanoyl)-L-homoserine lactone (3O-C12-HSL), contributes to the pathogenesis of Pseudomonas aeruginosa by regulating expression of the bacterial virulence factors that cause intense inflammation and toxicity in the infected host. As such, the QS molecule is an attractive therapeutic target for direct-acting inhibitors. Several substances, both synthetic and naturally derived products, have shown effectiveness against detrimental 3O-C12-HSL activity. Unfortunately, these compounds are relatively toxic to mammalian cells, which limits their clinical application. In this study, fully human single-chain variable fragments (HuscFvs) that bind to P. aeruginosa haptenic 3O-C12-HSL were generated based on the principle of antibody polyspecificity and molecular mimicry of antigenic molecules. The HuscFvs neutralized 3O-C12-HSL activity and prevented mammalian cells from the HSL-mediated apoptosis, as observed by Annexin V/PI staining assay, sub-G1 arrest population investigation, transmission electron microscopy for ultrastructural morphology of mitochondria, and confocal microscopy for nuclear condensation and DNA fragmentation. Computerized homology modeling and intermolecular docking predicted that the effective HuscFvs interacted with several regions of the bacterially derived ligand that possibly conferred neutralizing activity. The effective HuscFvs should be tested further in vitro on P. aeruginosa phenotypes as well as in vivo as a sole or adjunctive therapeutic agent against P. aeruginosa infections, especially in antibiotic-resistant cases.

Multicentre study of the in vitro activity of ceftolozane/tazobactam and other commonly used antibiotics against Pseudomonas aeruginosa isolates from patients in the UK

Objectives

To evaluate the in vitro activity of ceftolozane/tazobactam and other commonly used antipseudomonal antibiotics against geographically spread Pseudomonas aeruginosa isolates in the UK using disc susceptibility testing.

Methods

The in vitro activity of ceftolozane/tazobactam and nine other commonly used antipseudomonal antibiotics was evaluated. Isolates were collected between January 2015 and April 2018. Susceptibility results were interpreted using EUCAST 2018 criteria.

Results

Overall, 1326 clinical isolates from 14 centres in the UK were tested. The majority of the isolates were collected from non-cystic fibrosis (non-CF) patients (n = 1123, 85.0%). In addition, 199 cystic fibrosis (CF) isolates were collected from 10 centres. Overall susceptibility to ceftolozane/tazobactam was 89.3% (n = 1181), which included 128 CF and 1053 non-CF isolates. The other antibacterial agents with the highest susceptibility were tobramycin (92.4%, n = 1221) and piperacillin/tazobactam (90.7%, n = 1199). Susceptibility to all antibacterial agents was lower for CF isolates. Piperacillin/tazobactam was the most active of the antibacterial agents tested, followed by ceftolozane/tazobactam (70.4% and 64.3%, respectively), and <60% of CF isolates were susceptible to ceftazidime and the carbapenems. The reason for the higher rates of susceptibility to piperacillin/tazobactam and lower susceptibility to ceftazidime compared with other studies is unclear.

Conclusions

The data presented here support the need to investigate the place of ceftolozane/tazobactam as a treatment option in the management of pseudomonal infections, particularly in patients with CF. The results highlight the importance of routine testing of new antibacterial agents and of making the data available to clinicians to make appropriate and informed treatment choices.

Clinical significance of Pseudomonas aeruginosa 2-alkyl-4-quinolone quorum-sensing signal molecules for long-term outcomes in adults with cystic fibrosis

Introduction. Pseudomonas aeruginosa is an important respiratory pathogen in cystic fibrosis (CF), which is associated with an accelerated decline in lung function, frequent pulmonary exacerbations and increased mortality. P. aeruginosa produces intercellular signalling molecules including 2-alkyl-4-quinolones (AQs), which regulate virulence-factor production and biofilm formation in the CF airways. Studies have shown that AQs are detectable in the sputum and plasma of adults with CF and chronic pulmonary P. aeruginosa.Aim. We tested the hypothesis that the presence of six AQs in plasma or sputum obtained from adults with CF was associated with long-term adverse clinical outcomes.Methodology. We analysed clinical data over an 8 year follow period for 90 people with CF who had previously provided samples for AQ analysis at clinical stability. The primary outcome was all cause mortality or lung transplantation. Secondary outcomes were the rate of lung-function decline and the number of intravenous (IV) antibiotic days for pulmonary exacerbations.Results. There was no statistical association between the presence of any of the six measured AQs and the primary outcomes or the secondary outcome of decline in lung function. One of the six AQs was associated with IV antibiotic usage. The presence of 2-nonyl-3-hydroxy-4(1 h)-quinolone (C9-PQS) in sputum was associated with an increase in the number of IV antibiotic days in the follow-up period (Mann-Whitney; P=0.011).Conclusion. Further investigation to confirm the hypothesis that C9-PQS may be associated with increased antibiotic usage for pulmonary exacerbations is warranted as AQ-dependent signalling is a potential future target for anti-virulence therapies.

Effectiveness of Efflux Pump Inhibitors as Biofilm Disruptors and Resistance Breakers in Gram-Negative (ESKAPEE) Bacteria

Antibiotic resistance represents a significant threat to the modern healthcare provision. The ESKAPEE pathogens (Enterococcus faecium., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Escherichia coli), in particular, have proven to be especially challenging to treat, due to their intrinsic and acquired ability to rapidly develop resistance mechanisms in response to environmental threats. The development of biofilm has been characterised as an essential contributing factor towards antimicrobial-resistance and tolerance. Several studies have implicated the involvement of efflux pumps in antibiotic resistance, both directly, via drug extrusion and indirectly, through the formation of biofilm. As a result, the underlying mechanism of these pumps has attracted considerable interest due to the potential of targeting these protein structures and developing novel adjunct therapies. Subsequent investigations have revealed the ability of efflux pump-inhibitors (EPIs) to block drug-extrusion and disrupt biofilm formation, thereby, potentiating antibiotics and reversing resistance of pathogen towards them. This review will discuss the potential of EPIs as a possible solution to antimicrobial resistance, examining different challenges to the design of these compounds, with an emphasis on Gram-negative ESKAPEE pathogens.

Bacterial Type I CRISPR-Cas systems influence inflammasome activation in mammalian host by promoting autophagy

The clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated systems (CRISPR-Cas) systems in prokaryotes function at defending against foreign DNAs, providing adaptive immunity to maintain homeostasis. CRISPR-Cas may also influence immune regulation ability in mammalian cells through alterations of pathogenic extent and nature. Recent research has implied that Type I CRISPR-Cas systems of Pseudomonas aeruginosa strain UCBPP-PA14 impede recognition by Toll-like receptor 4, and decrease pro-inflammatory responses both in vitro and in vivo. However, the molecular mechanism by which CRISPR-Cas systems affect host immunity is largely undemonstrated. Here, we explored whether CRISPR-Cas systems can influence autophagy to alter the activation of inflammasome. Using the wild-type PA14 and total CRISPR-Cas region deletion (∆TCR) mutant strain, we elucidated the role and underlying mechanism of Type I CRISPR-Cas systems in bacterial infection, and showed that CRISPR-Cas systems impacted the release of mitochondrial DNA and induction of autophagy. CRISPR-Cas deficiency led to an increase of mitochondrial DNA release, a decrease in autophagy, an increase of inflammasome activation and, ultimately, an elevation of pro-inflammatory response. Our findings illustrate a new important mechanism by which Type I CRISPR-Cas systems control their virulence potency to evade host defense.

Impact of colonizing organism in the respiratory tract on the incidence, duration, and time between subsequent hospitalizations among patients with cystic fibrosis

BACKGROUND

This study aimed to examine the association between colonizing respiratory tract organism and frequency, duration, and time between subsequent hospitalizations among hospitalized patients with cystic fibrosis (CF).

METHODS

This retrospective cohort study of 312 CF patients from 2 New York City hospitals (2006-2016) examined the effects of colonization with Pseudomonas aeruginosa, methicillin-susceptible Staphylococcus aureus (MSSA) or methicillin-resistant S aureus (MRSA), co-colonization on incidence of hospitalization, time to next hospitalization, and total length of stay (LOS).

RESULTS

Annual rate of subsequent hospitalizations was highest in patients with P aeruginosa: adjusted incidence rate ratios (aIRRs) were 2.75 (95% confidence interval [CI], 1.72-4.41) for P aeruginosa versus MSSA, 2.57 (95% CI, 1.52-4.31) for co-colonization versus MSSA, and 1.77 (95% CI, 1.04-3.01) for P aeruginosa versus MRSA. Time to readmission was shortest for P aeruginosa: aIRRs were 1.75 (95% CI, 1.05-2.94) for MRSA versus P aeruginosa, 1.64 (95% CI, 1.03-2.59) for MSSA versus P aeruginosa, and 1.61 (95% CI, 1.04-2.47) for co-colonization versus P aeruginosa. LOS was longest for P aeruginosa: aIRRs were 3.41 (95% CI, 2.19-5.32) for P aeruginosa versus MSSA, 1.66 (95% CI, 1.01-2.75) for co-colonization versus MSSA, 2.50 (95% CI, 1.58-3.93) for P aeruginosa versus MRSA, and 2.05 (95% CI, 1.32-3.18) for P aeruginosa versus co-colonization.

CONCLUSIONS

CF patients with P aeruginosa alone experienced more hospitalizations, longer LOS, and shorter time to readmission versus patients with S aureus or both organisms.

Inhibition of Pseudomonas aeruginosa biofilm formation and expression of virulence genes by selective epimerization in the peptide Esculentin-1a(1-21)NH2

Pseudomonas aeruginosa is a pathogenic bacterium known to cause serious human infections, especially in immune-compromised patients. This is due to its unique ability to transform from a drug-tolerant planktonic to a more dangerous and treatment-resistant sessile life form, called biofilm. Recently, two derivatives of the frog skin antimicrobial peptide esculentin-1a, i.e. Esc(1-21) and its D-amino acids containing diastereomer Esc(1-21)-1c, were characterized for their powerful anti-Pseudomonal activity against both forms. Prevention of biofilm formation already in its early stages could be even more advantageous for counteracting infections induced by this bacterium. In this work, we studied how the diastereomer Esc(1-21)-1c can inhibit Pseudomonas biofilm formation in comparison to the parent peptide and two clinically-used conventional antibiotics, i.e. colistin and aztreonam, when applied at dosages below the minimal growth inhibitory concentration. Biofilm prevention was correlated to the peptides' ability to inhibit Pseudomonas motility and to reduce the production of virulent metabolites, for example, pyoverdine and rhamnolipids. Furthermore, the molecular mechanism underlying these activities was evaluated by studying the peptides' effect on the expression of key genes involved in the virulence and motility of bacteria, as well as by monitoring the peptides' binding to the bacterial signaling nucleotide ppGpp. Our results demonstrate that the presence of only two D-amino acids in Esc(1-21)-1c is sufficient to downregulate ppGpp-mediated expression of biofilm-associated genes, presumably as a result of higher peptide stability and therefore prolonged interaction with the nucleotide. Overall, these studies should assist efficient design and optimization of new anti-infective agents with multiple pharmacologically beneficial properties.

Quorum Sensing as Antivirulence Target in Cystic Fibrosis Pathogens

Cystic fibrosis (CF) is an autosomal recessive genetic disorder which leads to the secretion of a viscous mucus layer on the respiratory epithelium that facilitates colonization by various bacterial pathogens. The problem of drug resistance has been reported for all the species able to colonize the lung of CF patients, so alternative treatments are urgently needed. In this context, a valid approach is to investigate new natural and synthetic molecules for their ability to counteract alternative pathways, such as virulence regulating quorum sensing (QS). In this review we describe the pathogens most commonly associated with CF lung infections: Staphylococcus aureus, Pseudomonas aeruginosa, species of the Burkholderia cepacia complex and the emerging pathogens Stenotrophomonas maltophilia, Haemophilus influenzae and non-tuberculous Mycobacteria. For each bacterium, the QS system(s) and the molecules targeting the different components of this pathway are described. The amount of investigations published in the last five years clearly indicate the interest and the expectations on antivirulence therapy as an alternative to classical antibiotics.

Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

The Gram-negative opportunistic pathogen Pseudomonas aeruginosa causes severe nosocomial infections. It uses quorum sensing (QS) to regulate and coordinate population-wide group behaviours in the infection process like concerted secretion of virulence factors. One very important signalling network is the Pseudomonas quinolone signal (PQS) QS. With the aim to devise novel and innovative anti-infectives, inhibitors have been designed to address the various potential drug targets present within pqs QS. These range from enzymes within the biosynthesis cascade of the signal molecules PqsABCDE to the receptor of these autoinducers PqsR (MvfR). This review shortly introduces P. aeruginosa and its pathogenicity traits regulated by the pqs system and highlights the published drug discovery efforts providing insights into the compound binding modes if available. Furthermore, suitability of the individual targets for pathoblocker design is discussed.

The maternity ward of a teaching hospital: reconfiguration of maternal-child nursing care

OBJECTIVE

to analyze the strategies used by nurses and nurse professors for a better position in the maternity ward of the teaching hospital of the Universidade Federal do Espírito Santo.

METHOD

this is a social-historical study with a qualitative approach. The primary sources were written documents, such as official letters, memos, ordinances, standards and routines of the hospital; photographic material; and oral testimonies from seven participants. The interviews were performed using a semi-structured questionnaire, with questions regarding the adaptation from a sanatorium to a teaching hospital, the challenges faced, and the strategies adopted by the nursing department.

RESULTS

the results allowed us to understand the close link between the maternity ward and the nursing course of the Universidade Federal do Espírito Santo, which created a differentiated nursing care that integrated training and care with a broader and humanized look.

FINAL CONSIDERATIONS

the actions of the nurses were recognized and gave them professional visibility, influencing a new form of care in the maternity ward.

The Microbial Endocrinology of Pseudomonas aeruginosa: Inflammatory and Immune Perspectives

Pseudomonas aeruginosa is a major pathogen responsible for both acute and chronic infection. Known as a colonising pathogen of the cystic fibrosis (CF) lung, it is implicated in other settings such as bronchiectasis. It has the ability to cause acute disseminated or localised infection particularly in the immunocompromised. Human hormones have been highlighted as potential regulators of bacterial virulence through crosstalk between analogous "quorum sensing" (QS) systems present in the bacteria that respond to mammalian hormones. Pseudomonas aeruginosa is known to utilise interconnected QS systems to coordinate its virulence and evade various aspects of the host immune system activated in response to infection. Several human hormones demonstrate an influence on P. aeruginosa growth and virulence. This inter-kingdom signalling, termed "microbial endocrinology" has important implications for host-microbe interaction during infection and, potentially opens up novel avenues for therapeutic intervention. This phenomenon, supported by the existence of sexual dichotomies in both microbial infection and chronic lung diseases such as CF is potentially explained by sex hormones and their influence on the infective process. This review summarises our current understanding of the microbial endocrinology of P. aeruginosa, including its endogenous QS systems and their intersection with human endocrinology, pathogenesis of infection and the host immune system.

High attainment of optimal nutritional and growth status observed among Greek pediatric cystic fibrosis patients: results from the GreeCF study

BACKGROUND

Pediatric cystic fibrosis (CF) patients suffer high rates of undernutrition, subject to several parameters. We aimed to assess growth and nutritional status of Greek children and adolescents with CF.

METHODS

Eighty-four patients (35 boys) formed the sample. Anthropometrics and FEV1 were measured, growth and weight status were assessed. Body mass index (BMI), arm circumference (MUAC), fat (MUAFA) and muscle (MUAMA) were calculated.

RESULTS

In the total sample, 6.0% of the patients were underweight, 4.8% stunted, 8.3% wasted and 17.9% in nutritional failure, whereas 59.5% attained the ideal BMI for CF. FEV1 positively associated with BMI (B=0.03, p≤0.003), weight (B=0.03, p≤0.003) and MUAMA z-scores (B=0.04, p≤0.005). Meconium ileus negatively associated with FEV1 (B=-14.17, p≤0.003) and stature (B=-0.65, p≤0.043). Pancreatic insufficiency negatively influenced MUAC and MUAFA z-scores (p≤0.05 for both).

CONCLUSIONS

The examined CF patients appear to be thriving. Unlike published research, the participants' sex, gene mutation and acquisition of pathogens did not affect growth.

Brazilian guidelines for the diagnosis and treatment of cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive genetic disorder characterized by dysfunction of the CFTR gene. It is a multisystem disease that most often affects White individuals. In recent decades, various advances in the diagnosis and treatment of CF have drastically changed the scenario, resulting in a significant increase in survival and quality of life. In Brazil, the current neonatal screening program for CF has broad coverage, and most of the Brazilian states have referral centers for the follow-up of individuals with the disease. Previously, CF was limited to the pediatric age group. However, an increase in the number of adult CF patients has been observed, because of the greater number of individuals being diagnosed with atypical forms (with milder phenotypic expression) and because of the increase in life expectancy provided by the new treatments. However, there is still great heterogeneity among the different regions of Brazil in terms of the access of CF patients to diagnostic and therapeutic methods. The objective of these guidelines was to aggregate the main scientific evidence to guide the management of these patients. A group of 18 CF specialists devised 82 relevant clinical questions, divided into five categories: characteristics of a referral center; diagnosis; treatment of respiratory disease; gastrointestinal and nutritional treatment; and other aspects. Various professionals working in the area of CF in Brazil were invited to answer the questions devised by the coordinators. We used the PubMed database to search the available literature based on keywords, in order to find the best answers to these questions.

Evolution of Cost-Free Resistance under Fluctuating Drug Selection in Pseudomonas aeruginosa

Antibiotic resistance is a global problem that greatly impacts human health. How resistance persists, even in the absence of antibiotic treatment, is thus a public health problem of utmost importance. In this study, we explored the antibiotic treatment conditions under which cost-free resistance arises, using experimental evolution of the bacterium Pseudomonas aeruginosa and the quinolone antibiotic ciprofloxacin. We found that intermittent antibiotic treatment led to the evolution of cost-free resistance and demonstrate that compensatory evolution is the mechanism responsible for cost-free resistance. Our results suggest that discontinuous administration of antibiotic may be contributing to the high levels of antibiotic resistance currently found worldwide.

Antibiotic resistance evolves rapidly in response to drug selection, but it can also persist at appreciable levels even after the removal of the antibiotic. This suggests that many resistant strains can both be resistant and have high fitness in the absence of antibiotics. To explore the conditions under which high-fitness, resistant strains evolve and the genetic changes responsible, we used a combination of experimental evolution and whole-genome sequencing to track the acquisition of ciprofloxacin resistance in the opportunistic pathogen Pseudomonas aeruginosa under conditions of constant and fluctuating antibiotic delivery patterns. We found that high-fitness, resistant strains evolved readily under fluctuating but not constant antibiotic conditions and that their evolution was underlain by a trade-off between resistance and fitness. Whole-genome sequencing of evolved isolates revealed that resistance was gained through mutations in known resistance genes and that second-site mutations generally compensated for costs associated with resistance in the fluctuating treatment, leading to the evolution of cost-free resistance. Our results suggest that current therapies involving intermittent administration of antibiotics are contributing to the maintenance of antibiotic resistance at high levels in clinical settings.

IMPORTANCE Antibiotic resistance is a global problem that greatly impacts human health. How resistance persists, even in the absence of antibiotic treatment, is thus a public health problem of utmost importance. In this study, we explored the antibiotic treatment conditions under which cost-free resistance arises, using experimental evolution of the bacterium Pseudomonas aeruginosa and the quinolone antibiotic ciprofloxacin. We found that intermittent antibiotic treatment led to the evolution of cost-free resistance and demonstrate that compensatory evolution is the mechanism responsible for cost-free resistance. Our results suggest that discontinuous administration of antibiotic may be contributing to the high levels of antibiotic resistance currently found worldwide.

Pseudomonas aeruginosa Lifestyle: A Paradigm for Adaptation, Survival, and Persistence

Pseudomonas aeruginosa is an opportunistic pathogen affecting immunocompromised patients. It is known as the leading cause of morbidity and mortality in cystic fibrosis (CF) patients and as one of the leading causes of nosocomial infections. Due to a range of mechanisms for adaptation, survival and resistance to multiple classes of antibiotics, infections by P. aeruginosa strains can be life-threatening and it is emerging worldwide as public health threat. This review highlights the diversity of mechanisms by which P. aeruginosa promotes its survival and persistence in various environments and particularly at different stages of pathogenesis. We will review the importance and complexity of regulatory networks and genotypic-phenotypic variations known as adaptive radiation by which P. aeruginosa adjusts physiological processes for adaptation and survival in response to environmental cues and stresses. Accordingly, we will review the central regulatory role of quorum sensing and signaling systems by nucleotide-based second messengers resulting in different lifestyles of P. aeruginosa. Furthermore, various regulatory proteins will be discussed which form a plethora of controlling systems acting at transcriptional level for timely expression of genes enabling rapid responses to external stimuli and unfavorable conditions. Antibiotic resistance is a natural trait for P. aeruginosa and multiple mechanisms underlying different forms of antibiotic resistance will be discussed here. The importance of each mechanism in conferring resistance to various antipseudomonal antibiotics and their prevalence in clinical strains will be described. The underlying principles for acquiring resistance leading pan-drug resistant strains will be summarized. A future outlook emphasizes the need for collaborative international multidisciplinary efforts to translate current knowledge into strategies to prevent and treat P. aeruginosa infections while reducing the rate of antibiotic resistance and avoiding the spreading of resistant strains.

Use of macrolides in lung diseases: recent literature controversies

OBJECTIVE

To review the mechanisms of action of macrolides in pediatric respiratory diseases and their clinical indications.

SOURCES

Review in the PubMed database, comprising the following terms in English: "macrolide and asthma"; "macrolide and cystic fibrosis"; "macrolide bronchiolitis and viral acute"; "macrolide and bronchiolitis obliterans" and "macrolide and non-CF bronchiectasis".

SUMMARY OF THE FINDINGS

The spectrum of action of macrolides includes production of inflammatory mediators, control of mucus hypersecretion, and modulation of host-defense mechanisms. The potential benefit of macrolide antibiotics has been studied in a variety of lung diseases, such as cystic fibrosis (CF), bronchiectasis, asthma, acute bronchiolitis, and non-CF bronchiectasis. Several studies have evaluated the benefits of macrolides in asthma refractory to therapy, but the results are controversial and indications should be limited to specific phenotypes. In viral bronchiolitis, there is no consistent benefit in acute conditions, although recent data have shown an effect in recurrent wheezing prevention. In patients with CF results are also contradictory, but the consensus states there is a small clinical benefit, especially for patients infected with P. aeruginosa. There was also no positive action of macrolides in patients with post-infectious bronchiolitis obliterans. Children with non-CF bronchiectasis seem to have clear benefits regarding the use of macrolides, which showed clinical advantages in parenchyma protection and lung function.

CONCLUSIONS

The long-term use of macrolides should be limited to highly selected situations, especially in patients with bronchiectasis. Careful evaluation of the benefits and potential damage are tools for their indication in specific groups.

Chronic rhinosinusitis and nasal polyposis in cystic fibrosis: update on diagnosis and treatment

Although cystic fibrosis (CF) is an irreversible genetic disease, advances in treatment have increased the life expectancy of CF patients. Upper airway involvement, which is mainly due to pathological changes in the paranasal sinuses, is prevalent in CF patients, although many are only mildly symptomatic (with few symptoms). The objective of this literature review was to discuss the pathophysiology and current therapeutic management of chronic rhinosinusitis (CRS) in CF patients. The review was based on current evidence, which was classified in accordance with the Oxford Centre for Evidence-Based Medicine criteria. When symptomatic, CRS with nasal polyps can affect quality of life and can lead to pulmonary exacerbations, given that the paranasal sinuses can be colonized with pathogenic bacteria, especially Pseudomonas aeruginosa. Infection with P. aeruginosa plays a crucial role in morbidity and mortality after lung transplantation in CF patients. Although clinical treatment of the upper airways is recommended as initial management, this recommendation is often extrapolated from studies of CRS in the general population. When sinonasal disease is refractory to noninvasive therapy, surgery is indicated. Further studies are needed in order to gain a better understanding of upper airway involvement and improve the management of CRS in CF patients, with the objective of preserving lung function and avoiding unnecessary invasive procedures.