Pseudomonas aeruginosa community-acquired pneumonia following soil ingestion: A case report

BACKGROUND

Pseudomonas aeruginosa (P. aeruginosa) is an uncommon etiological agent in community-acquired pneumonia (CAP), typically associated with nosocomial or healthcare-associated infections, particularly in patients with underlying structural lung abnormalities or immunosuppression. P. aeruginosa is a ubiquitous gram-negative rod, widely distributed in the environment. However, CAP due to P. aeruginosa following soil ingestion is exceedingly rare.

CASE PRESENTATION

We present the case of a previously healthy 31-year-old patient, a middle school teacher, who developed CAP due to P. aeruginosa after ingesting garden soil for three consecutive days. The patient was admitted with symptoms including fever, chest pain, vomiting, and diarrhea. Chest computed tomography (CT) revealed two suspicious lesions in the left lower lobe, with one lesion exhibiting cavitation. Microbiological culture of bronchoalveolar lavage fluid (BALF) and stool confirmed the presence of P. aeruginosa infection. Subsequent antimicrobial susceptibility testing revealed that the P. aeruginosa isolate was pan-sensitive. Following 13 days of targeted antimicrobial therapy, the patient's symptoms and laboratory markers of infection improved significantly. A follow-up CT scan one month later demonstrated substantial resolution of the left lower lobe lesions, and the patient remained asymptomatic.

CONCLUSIONS

This case, along with a review of related literature, suggests that geophagy may be a potential risk factor for P. aeruginosa infection. It underscores the importance of avoiding the consumption of unprocessed soil, which may be contaminated with pathogenic organisms.

A comprehensive review of emerging 3D-printing materials against bacterial biofilm growth on the surface of healthcare settings

A significant burden on the healthcare system, microbial contamination of biomedical surfaces can result in hospital-acquired illnesses. Bacteria, viruses, and fungi may live on surfaces for days or months and spread to patients and medical personnel. This article describes the 3D printing technologies, such as fused deposition modeling, bioprinting, binder jetting/inkjet, poly-jet, electron beam manufacturing, stereolithography, selective laser sintering, and laminated object manufacturing used for manufacturing the healthcare setting's surface to reduce bacterial contamination with exploring anti-biofilm activity against different bacterial species responsible for infections, based on the critical evaluation of published reports. This strategy has immense potential to become an upcoming approach for advancing the coating concept on the material's surface in healthcare settings. Our literature evaluation identifies beneficial 3D printing materials and associated technologies against microorganisms' growth, mainly bacteria involved in implant-based infection, emphasizing the development of anti-biofilm 3D-printed surfaces. Additionally, the authors have identified a few key areas where research and development are critically required to advance 3D-printing technology in healthcare settings.

Niclosamide as a potential antivirulence agent disrupting quorum sensing in Pseudomonas aeruginosa: A molecular and in silico approach

Pseudomonas aeruginosa is a formidable pathogen linked to various challenging infections. Quorum sensing (QS) plays a pivotal role in regulating the virulence factors of P. aeruginosa. Targeting QS represents a promising strategy for mitigating P. aeruginosa virulence. This study explores the potential of niclosamide (NIC) as an antivirulence agent, emphasizing its effects on biofilm formation, pigment production, and its molecular interaction with the QS regulator, LasR. A comprehensive methodology was employed, encompassing in-silico, molecular, and in vitro analyses to assess the antivirulence properties of NIC. Sub-inhibitory concentrations of NIC (64 μg/ml) were evaluated for their capacity to inhibit biofilm formation and pigment production in P. aeruginosa. NIC resulted in a 45.4 % reduction in biofilm formation, a 48.8 % decrease in pyocyanin production, and a 41.3 % reduction in rhamnolipid production. Furthermore, NIC displayed a dose-dependent antagonistic effect on LasR, with an IC50 of 5.82 ± 0.17 μM, without any noted agonistic activity. Molecular modeling and molecular dynamics (MD) simulations indicated that NIC interacts with LasR, hindering its dimerization and destabilizing its structure. These findings were corroborated by sedimentation velocity experiments and thermal shift assays. NIC shows considerable promise as an antivirulence agent against P. aeruginosa by disrupting the LasR-mediated QS system. Through its interaction with LasR, NIC inhibits biofilm formation and diminishes the production of critical virulence factors, making P. aeruginosa less virulent and more vulnerable to conventional antibiotics and immune responses.

Treatment of lung diseases via nanoparticles and nanorobots: Are these viable alternatives to overcome current treatments?

Challenges

Respiratory diseases remain challenging to treat, with current efforts primarily focused on managing symptoms rather than maintaining overall lung health. Traditional treatment methods, such as oral or parenteral administration of antiviral, antibacterial, and anti-inflammatory drugs, face limitations. These include difficulty in delivering therapeutic agents to pathogens residing deep in the airways and the risk of severe side effects due to high systemic drug concentrations. The growing threat of drug-resistant pathogens further complicates infection management.

Advancements

The lung's large surface area offers an attractive target for inhalation-based drug delivery. Nanoparticles (NP) enable uniform and sustained drug distribution across the alveolar network, overcoming challenges posed by complex lung anatomy. Recent breakthroughs in nanorobots (NR) have demonstrated precise navigation through biological environments, delivering therapies directly to affected lung areas with enhanced accuracy. Nanotechnology has also shown promise in treating lung cancer, with nanoparticles engineered to overcome biological barriers, improve drug solubility, and enable controlled drug release.

Future scope

This review explores the progress of NP and NR in addressing challenges in pulmonary drug delivery. These innovations allow targeted delivery of nucleic acids, drugs, or peptides to the pulmonary epithelium with unprecedented accuracy, offering significant potential for improving therapeutic effectiveness in respiratory disorders.

Impact of Pseudomonas aeruginosa carriage on intensive care unit-acquired pneumonia: a European multicentre prospective cohort study

OBJECTIVES

Pseudomonas aeruginosa (PA) is a common causative pathogen of pneumonia acquired in the intensive care unit (ICU). The aim of this study was to determine the incidence of PA ICU pneumonia (PAIP) and to quantify its independent association with PA colonization at different body sites.

METHODS

Adult patients on mechanical ventilation at ICU admission were prospectively enrolled across 30 European ICUs. PA colonization in the perianal area and in the lower respiratory tract was assessed within 72 hours after ICU admission and twice weekly until ICU discharge. PAIP development was evaluated daily. Competing risk models with colonization as a time-varying exposure and ICU death and discharge as competing events were fitted and adjusted for confounders to investigate the association between PA carriage and PAIP.

RESULTS

A total of 1971 subjects were enrolled. The colonization prevalence with PA in the first 72 hours of ICU admission was 10.4% (179 perianal and 51 respiratory), whereas the acquisition incidence during the ICU stay was 7.0% (158 perianal and 47 respiratory). Of the 43 (1.8%) patients who developed PAIP, 11 (25.6%) were PA colonized on admission and 9 (20.9%) acquired colonization before PAIP onset. Both perianal (adjusted subdistribution hazard ratio, 4.4; 95% CI, 1.7-11.6) and respiratory colonization (adjusted subdistribution hazard ratio: 4.6, 95% CI, 1.9-11.1) were independently associated with PAIP development.

DISCUSSION

PAIP incidence was higher in PA colonized vs. non-colonized patients. Colonization of both the rectum and of the respiratory tract was associated with development of PAIP. The increased risk of PA colonization for subsequent infection provides an opportunity for targeted preventive interventions.

Risk factors for detection of Pseudomonas aeruginosa in clinical samples upon hospital admission

BACKGROUND/INTRODUCTION

Antipseudomonal antibiotics are frequently used in patients admitted to hospitals. Many of these substances are classified as a reserve or watch status by the WHO. Inappropriate risk assessment of invasive detection of P. aeruginosa (PAE) can be a reason for overuse of antipseudomonal antibiotics. Therefore it is important to define relevant and specific risk factors for invasive PAE detection.

OBJECTIVE

The objective of this study was to identify risk factors for invasive detection of PAE in patients upon hospital admission.

METHODS

All patients 18 years of age and older with a detection of PAE and/or Enterobacterales in clinical samples taken within 48 h of admission to one of the hospitals of Charité Universitätsmedizin Berlin between 2015 and 2020 were included into this retrospective cohort study.

RESULTS

Overall, we included a total of 27,710 patients. In 3,764 (13.6%) patients PAE was detected in clinical samples taken within 48 h after admission. The most frequently detected Enterobacterales was E. coli in 14.142 (51%) patients followed by Klebsiella spp. in 4.432 (16%) patients. Multivariable regression analysis identified that prior colonisation with a multi drug resistant PAE or detection of a PAE in clinical samples during a previous hospitalisation increased the risk for invasive detection of PAE (OR 39.41; 95% CI 28.54-54.39) and OR 7.87 (95% CI 6.60-9.38) respectively. Admission to a specialised ward for patients with cystic fibrosis was associated with an increased risk (OR 26.99; 95% CI 20.48-35.54). Presence of chronic pulmonary disease (OR 2.05; 95% CI 1.85-2.26), hemiplegia (OR 2.16; 95% CI 1.90-2.45) and male gender (OR 1.60; 95% CI 1.46-1.75) were associated with a modest increase in risk for presence of PAE.

CONCLUSION

Patients with a prior detection of P. aeruginosa or admission to a cystic fibrosis ward had the highest risk for invasive detection of P. aeruginosa. Adherence to specific risk scores based on local risk factors could help to optimize prescription of anti-pseudomonal antibiotics that categorized as reserve and watch.

Distribution and Molecular Characterization of Antibiotic-Resistant Pseudomonas aeruginosa in Hospital Settings of Sulaymaniyah, Iraq

Pseudomonas aeruginosa is a significant pathogen in hospital settings, notorious for its role in hospital-acquired infections and its ability to develop resistance to multiple antibiotics. This study investigates the prevalence, distribution, and antibiotic resistance gene profiles of P. aeruginosa in seven hospitals in Sulaymaniyah City. A total of 300 samples were collected from various hospital surfaces including mops, sinks, medical equipment, beds, desks, and floors. Using bacteriological, biochemical, and molecular methods, 66 isolates were confirmed as Pseudomonas species, with 26 identified as P. aeruginosa. Antibiotic susceptibility testing revealed resistance rates of 23.3% to streptomycin, 13.6% to tobramycin, 22.7% to moxifloxacin, 21.2% to levofloxacin, and 22.7% to norfloxacin. Furthermore, the antibiotic resistance gene detection showed the presence of the bla CTX-M, bla SHV, qnrB, and bla ACC-1 genes among the isolates. The study highlights a 22% contamination rate of hospital surfaces with Pseudomonas species, emphasizing the urgent need for enhanced infection control measures and targeted antimicrobial stewardship to manage and reduce the spread of multidrug-resistant P. aeruginosa.

Multidrug Resistant Pseudomonas aeruginosa in Clinical Settings: A Review of Resistance Mechanisms and Treatment Strategies

Pseudomonas aeruginosa is causing increasing concern among clinicians due to its high mortality and resistance rates. This bacterium is responsible for various infections, especially in hospital settings, affecting some of the most vulnerable patients. Pseudomonas aeruginosa has developed resistance through multiple mechanisms, making treatment challenging. Diagnostic techniques are evolving, with rapid testing systems providing results within 4-6 h. New antimicrobial agents are continuously being developed, offering potential solutions to these complex clinical decisions. This article provides a review of the epidemiology, at-risk populations, resistance mechanisms, and diagnostic and treatment options for Pseudomonas aeruginosa.

Community-Acquired Pneumonia in the Immunocompromised Patients: An Observational Study from a Single Center, TURKEY

Purpose

Immunocompromised hosts are underrepresented in clinical trials. The goal of the study to search for the unmet needs in the management of CAP in immunocompromised hosts.

Patients and Methods

An observational study was conducted with CAP patients documented immunocompromise or those aged over 65 who have at least one chronic visceral disease. We clinically assessed the eligible patients at the time of the presentation with a follow-up assessment on day three of admission. The data were statistically analyzed to assess the impact of variables on mortality.

Results

During a 15-month study period, 140 CAP patients were observed. The overall 30-day mortality rate was 17.8%. The mortality rate was significantly higher in patients with sputum cultures positive for Pseudomonas aeruginosa, or two bacteria (p=0.049). Tachypnea was a stronger predictor of mortality. Failure to achieve a treatment response within three days of treatment identified the population with the worst outcomes. Less than half of such patients survived past one month.

Conclusion

Dynamic response assessment emerged as potentially the strongest predictor of outcomes in CAP of susceptible hosts. We propose that immunocompromised CAP patients who fail to respond early to treatment face extremely high rates of mortality, identifying an unmet need.

The Clinical Application Value of a Novel Chip in the Detection of Pathogens in Adult Pneumonia: A Multi-Centre Prospective Study in China

Purpose

The detection of pathogenic microorganisms plays a significant role in the diagnosis and management of pneumonia that are responsible for a substantial number of deaths worldwide. However, conventional microbiological tests (CMT) have low accuracy and are time-consuming. In this study, we aim to evaluate the clinical value of Chips for Complicated Infection Detection (CCID) in detecting pneumonia pathogens.

Patients and Methods

This study was conducted at nine hospitals in China from January 2021 to September 2022. Respiratory samples from adult pneumonia patients were collected from each patient. CMT and CCID were performed in parallel to identify the pathogens.

Results

A total of 245 patients were included, with 73% being elderly. CCID identified pathogenic microbes in 78.0% of patients and conventional microbiological tests (CMT) in 57.1% of the patients (p<0.001). The overall positive and negative percent agreements between CCID and CMT for pathogen detection were 90.07% and 38.46%, respectively. 38.8% of patients were diagnosed with mixed infections with at least two pathogens by CCID. Bacterial infections identified by CCID accounted for 60.0% of 245 patients, with the top 3 being Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterococcus faecium, respectively. K. pneumoniae was the most common pathogen in elderly patients, with a significantly higher prevalence compared to non-elderly patients (p = 0.0011). Among the 197 patients who had used antibiotics before sample collection, the positive rate of CCID was significantly higher than that of CMT (p < 0.001).

Conclusion

This study indicates that compared to CMT, this novel chip has significant advantages in detecting pathogens in pneumonia patients, especially in the elderly.

Synthetic Biology-Driven Microbial Therapeutics for Disease Treatment

The human microbiome, consisting of microorganisms that coexist symbiotically with the body, impacts health from birth. Alterations in gut microbiota driven by factors such as diet and medication can contribute to diseases beyond the gut. Synthetic biology has paved the way for engineered microbial therapeutics, presenting promising treatments for a variety of conditions. Using genetically encoded biosensors and dynamic regulatory tools, engineered microbes can produce and deliver therapeutic agents, detect biomarkers, and manage diseases. This review organizes engineered microbial therapeutics by disease type, emphasizing innovative strategies and recent advancements. The scope of diseases includes gastrointestinal disorders, cancers, metabolic diseases, infections, and other ailments. Synthetic biology facilitates precise targeting and regulation, improving the efficacy and safety of these therapies. With promising results in animal models, engineered microbial therapeutics provide a novel alternative to traditional treatments, heralding a transformative era in diagnostics and treatment for numerous diseases.

The angiotensin-(1-7)/MasR axis improves pneumonia caused by Pseudomonas aeruginosa: Extending the therapeutic window for antibiotic therapy

Pseudomonas aeruginosa is a frequent cause of antimicrobial-resistant hospital-acquired pneumonia, especially in critically ill patients. Inflammation triggered by P. aeruginosa infection is necessary for bacterial clearance but must be spatially and temporally regulated to prevent further tissue damage and bacterial dissemination. Emerging data have shed light on the pro-resolving actions of angiotensin-(1-7) [Ang-(1-7)] signaling through the G protein-coupled receptor Mas (MasR) during infections. Herein, we investigated the role of the Ang-(1-7)/Mas axis in pneumonia caused by P. aeruginosa by using genetic and pharmacological approach and found that Mas receptor-deficient animals developed a more severe form of pneumonia showing higher neutrophilic infiltration into the airways, bacterial load, cytokines, and chemokines production and more severe pulmonary damage. Conversely, treatment of pseudomonas-infected mice with Ang-(1-7) was able to decrease neutrophilic infiltration in airways and lungs, local and systemic levels of pro-inflammatory cytokines and chemokines, and increase the efferocytosis rates, mitigating lung damage/dysfunction caused by infection. Notably, the therapeutic association of Ang-(1-7) with antibiotics improved the survival rates of mice subjected to lethal inoculum of P. aeruginosa, extending the therapeutic window for imipenem. Mechanistically, Ang-(1-7) increased phagocytosis of bacteria by neutrophils and macrophages to accelerate pathogen clearance. Altogether, harnessing the Ang-(1-7) pathway during infection is a potential strategy for the development of host-directed therapies to promote mechanisms of resistance and resilience to pneumonia.

The RNA from Pseudomonas aeruginosa Reduces Neutrophil Responses Favoring Bacterial Survival

INTRODUCTION

Epithelial and endothelial cells modulate innate immune responses in the lung, including the arrival of neutrophils (PMN), which are crucial cells for the antibacterial host defense. Cells are exposed to prokaryotic RNA (pRNA) during bacterial infections and different pRNA may promote or attenuate the inflammatory response on different immune cells. Pseudomonas aeruginosa (PAE) can cause severe pneumonia and has several immune-evading mechanisms. The aim of this study was to determine the effects of the RNA from PAE (RNAPAE) on lung epithelial, endothelial cells, and PMN, and its impact on bacterial elimination.

METHODS

Purified total RNAPAE was used as a stimulus on a human lung epithelial cell line (Calu-6), human microvascular endothelial cell line HMEC-1 and isolated healthy human PMN. Activation and cytokine secretion were evaluated. In addition, PMN elimination of live ECO or PAE was determined in the presence of RNAPAE.

RESULTS

We found that RNAPAE either induced a pro-inflammatory response on Calu-6 and HMEC-1 or PMN. Pre-stimulation of PMN with RNAPAE diminished activation and chemotaxis induced by live bacteria. Moreover, we found that RNAPAE reduced phagocytosis of live ECO. Finally, we also found that non-degraded fragments of small RNA (<200 bp) were responsible for the PMN microbicidal attenuation during PAE elimination.

CONCLUSION

Our results indicated that short fragments of RNAPAE diminished the immune response of PMN favoring bacterial survival.

Defining the functional properties of cyclopropane fatty acid synthase from Pseudomonas aeruginosa PAO1

Cyclopropane fatty acid synthases (CFAS) catalyze the conversion of unsaturated fatty acids to cyclopropane fatty acids (CFAs) within bacterial membranes. This modification alters the biophysical properties of membranes and has been correlated with virulence in several human pathogens. Despite the central role played by CFAS enzymes in regulating bacterial stress responses, the mechanistic properties of the CFAS enzyme family and the consequences of CFA biosynthesis remain largely uncharacterized in most bacteria. We report the first characterization of the CFAS enzyme from Pseudomonas aeruginosa (PA), an opportunistic human pathogen with complex membrane biology that is frequently associated with antimicrobial resistance and high tolerance to various external stressors. We demonstrate that CFAs are produced by a single enzyme in PA and that cfas gene expression is upregulated during the transition to stationary phase and in response to oxidative stress. Analysis of PA lipid extracts reveal a massive increase in CFA production as PA cells enter stationary phase and help define the optimal membrane composition for in vitro assays. The purified PA-CFAS enzyme forms a stable homodimer and preferentially modifies phosphatidylglycerol lipid substrates and membranes with a higher content of unsaturated acyl chains. Bioinformatic analysis across bacterial phyla shows highly divergent amino acid sequences within the lipid-binding domain of CFAS enzymes, perhaps suggesting distinct membrane-binding properties among different orthologs. This work lays an important foundation for further characterization of CFAS in P. aeruginosa and for examining the functional differences between CFAS enzymes from different bacteria.

Characterization of bacterial diversity in rhizospheric soils, irrigation water, and lettuce crops in municipalities near the Bogotá river, Colombia

The use of wastewater in agricultural practices poses a potential risk for the spread of foodborne diseases. Therefore, this study aimed to characterize the bacterial biodiversity in rhizospheric soil, irrigation water, and lettuce crops in three municipalities adjacent to the Bogotá River, Colombia. Samples were collected in Mosquera, Funza, and Cota municipalities, including rhizospheric soil, lettuce leaves, and irrigation water. The total DNA extraction was performed to analyze bacterial diversity through high-throughput sequencing of the 16S ribosomal RNA genes, utilizing the Illumina HiSeq 2500 PE 300 sequencing platform. A total of 198 genera from the rhizospheric soil were detected including a higher abundance of zOTUs such as Bacillus, Streptomyces, and clinically relevant genera such as Mycobacterium and Pseudomonas. In lettuce, the detection of 26 genera of endophytic bacteria showed to Proteobacteria and Firmicutes as the predominant phyla, with Staphylococcus and Bacillus as the most abundant genera. Notably, Funza's crops exhibited the highest abundance of endophytes, approximately 50 %, compared to Cota (20 %). Furthermore, the most abundant bacterial genera in the irrigation water were Flavobacterium and Pseudomonas. The most prevalent Enterobacteriaceae were Serratia, Enterobacter, Citrobacter, Klebsiella, Yersinia, Shigella, Escherichia, and Erwinia. The Bacillus genus was highly enriched in both rhizospheric soils and lettuce crops, indicating its significant contribution as the main endophytic bacterium.

Phage Therapy in a Burn Patient Colonized with Extensively Drug-Resistant Pseudomonas aeruginosa Responsible for Relapsing Ventilator-Associated Pneumonia and Bacteriemia

Pseudomonas aeruginosa is one of the main causes of healthcare-associated infection in Europe that increases patient morbidity and mortality. Multi-resistant pathogens are a major public health issue in burn centers. Mortality increases when the initial antibiotic treatment is inappropriate, especially if the patient is infected with P. aeruginosa strains that are resistant to many antibiotics. Phage therapy is an emerging option to treat severe P. aeruginosa infections. It involves using natural viruses called bacteriophages, which have the ability to infect, replicate, and, theoretically, destroy the P. aeruginosa population in an infected patient. We report here the case of a severely burned patient who experienced relapsing ventilator-associated pneumonia associated with skin graft infection and bacteremia due to extensively drug-resistant P. aeruginosa. The patient was successfully treated with personalized nebulized and intravenous phage therapy in combination with immunostimulation (interferon-γ) and last-resort antimicrobial therapy (imipenem-relebactam).

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.

Neutrophils and galectin-3 defend mice from lethal bacterial infection and humans from acute respiratory failure

Respiratory infection by Pseudomonas aeruginosa, common in hospitalized immunocompromised and immunocompetent ventilated patients, can be life-threatening because of antibiotic resistance. This raises the question of whether the host's immune system can be educated to combat this bacterium. Here we show that prior exposure to a single low dose of lipopolysaccharide (LPS) protects mice from a lethal infection by P. aeruginosa. LPS exposure trained the innate immune system by promoting expansion of neutrophil and interstitial macrophage populations distinguishable from other immune cells with enrichment of gene sets for phagocytosis- and cell-killing-associated genes. The cell-killing gene set in the neutrophil population uniquely expressed Lgals3, which encodes the multifunctional antibacterial protein, galectin-3. Intravital imaging for bacterial phagocytosis, assessment of bacterial killing and neutrophil-associated galectin-3 protein levels together with use of galectin-3-deficient mice collectively highlight neutrophils and galectin-3 as central players in LPS-mediated protection. Patients with acute respiratory failure revealed significantly higher galectin-3 levels in endotracheal aspirates (ETAs) of survivors compared to non-survivors, galectin-3 levels strongly correlating with a neutrophil signature in the ETAs and a prognostically favorable hypoinflammatory plasma biomarker subphenotype. Taken together, our study provides impetus for harnessing the potential of galectin-3-expressing neutrophils to protect from lethal infections and respiratory failure.

Development of a sensor for disulfide bond formation in diverse bacteria

In bacteria, disulfide bonds contribute to the folding and stability of proteins important for processes in the cellular envelope. In Escherichia coli, disulfide bond formation is catalyzed by DsbA and DsbB enzymes. DsbA is a periplasmic protein that catalyzes disulfide bond formation in substrate proteins, while DsbB is an inner membrane protein that transfers electrons from DsbA to quinones, thereby regenerating the DsbA active state. Actinobacteria including mycobacteria use an alternative enzyme named VKOR, which performs the same function as DsbB. Disulfide bond formation enzymes, DsbA and DsbB/VKOR, represent novel drug targets because their inhibition could simultaneously affect the folding of several cell envelope proteins including virulence factors, proteins involved in outer membrane biogenesis, cell division, and antibiotic resistance. We have previously developed a cell-based and target-based assay to identify molecules that inhibit the DsbB and VKOR in pathogenic bacteria, using E. coli cells expressing a periplasmic β-Galactosidase sensor (β-Galdbs), which is only active when disulfide bond formation is inhibited. Here, we report the construction of plasmids that allows fine-tuning of the expression of the β-Galdbs sensor and can be mobilized into other gram-negative organisms. As an example, when expressed in Pseudomonas aeruginosa UCBPP-PA14, which harbors two DsbB homologs, β-Galdbs behaves similarly as in E. coli, and the biosensor responds to the inhibition of the two DsbB proteins. Thus, these β-Galdbs reporter plasmids provide a basis to identify novel inhibitors of DsbA and DsbB/VKOR in multidrug-resistant gram-negative pathogens and to further study oxidative protein folding in diverse gram-negative bacteria.

IMPORTANCE

Disulfide bonds contribute to the folding and stability of proteins in the bacterial cell envelope. Disulfide bond-forming enzymes represent new drug targets against multidrug-resistant bacteria because inactivation of this process would simultaneously affect several proteins in the cell envelope, including virulence factors, toxins, proteins involved in outer membrane biogenesis, cell division, and antibiotic resistance. Identifying the enzymes involved in disulfide bond formation in gram-negative pathogens as well as their inhibitors can contribute to the much-needed antibacterial innovation. In this work, we developed sensors of disulfide bond formation for gram-negative bacteria. These tools will enable the study of disulfide bond formation and the identification of inhibitors for this crucial process in diverse gram-negative pathogens.

The Pseudomonas aeruginosa lectin LecB modulates intracellular reactive oxygen species production in human neutrophils

Pseudomonas aeruginosa is a Gram-negative bacterium and an opportunistic pathogen ubiquitously present throughout nature. LecB, a fucose-, and mannose-binding lectin, is a prominent virulence factor of P. aeruginosa, which can be expressed on the bacterial surface but also be secreted. However, the LecB interaction with human immune cells remains to be characterized. Neutrophils comprise the first line of defense against infections and their production of reactive oxygen species (ROS) and release of extracellular traps (NETs) are critical antimicrobial mechanisms. When profiling the neutrophil glycome we found several glycoconjugates on granule and plasma membranes that could potentially act as LecB receptors. In line with this, we here show that soluble LecB can activate primed neutrophils to produce high levels of intracellular ROS (icROS), an effect that was inhibited by methyl fucoside. On the other hand, soluble LecB inhibits P. aeruginosa-induced icROS production. In support of that, during phagocytosis of wild-type and LecB-deficient P. aeruginosa, bacteria with LecB induced less icROS production as compared with bacteria lacking the lectin. Hence, LecB can either induce or inhibit icROS production in neutrophils depending on the circumstances, demonstrating a novel and potential role for LecB as an immunomodulator of neutrophil functional responses.

Respiratory culture growth and 3-years lung health outcomes in children with bronchopulmonary dysplasia and tracheostomies

BACKGROUND

While bacteria identification on respiratory cultures is associated with poor short-term outcomes in children with bronchopulmonary dysplasia (BPD) and tracheostomies, the influence on longer-term respiratory support needs remains unknown.

OBJECTIVE

To determine if respiratory culture growth of pathogenic organisms is associated with ongoing need for respiratory support, decannulation, and death at 3 years posttracheostomy placement in children with BPD and tracheostomies.

METHODS

This single center, retrospective cohort study included infants and children with BPD and tracheostomies placed 2010-2018 and ≥1 respiratory culture obtained in 36 months posttracheostomy. Primary predictor was any pathogen identified on respiratory culture. Additional predictors were any Pseudomonas aeruginosa and chronic P. aeruginosa identification. Outcomes included continued use of respiratory support (e.g., oxygen, positive pressure), decannulation, and death at 3 years posttracheostomy. We used Poisson regression models to examine the relationship between respiratory organisms and outcomes, controlling for patient-level covariates and within-patient clustering.

RESULTS

Among 170 children, 59.4% had a pathogen identified, 28.8% ever had P. aeruginosa, and 3.5% had chronic P. aeruginosa. At 3 years, 33.1% of alive children required ongoing respiratory support and 24.8% achieved decannulation; 18.9% were deceased. In adjusted analysis, any pathogen and P. aeruginosa were not associated with ongoing respiratory support or mortality. However, P. aeruginosa was associated with decreased decannulation probability (adjusted risk ratio 0.48, 95% CI 0.23-0.98). Chronic P. aeruginosa was associated with lower survival probability.

CONCLUSION

Our findings suggest that respiratory pathogens including P. aeruginosa may not promote long-term respiratory dysfunction, but identification of P. aeruginosa may delay decannulation.

Deciphering microbial communities and their unique metabolic repertoire across rock-soil-plant continuum in the Dayoukeng fumarolic geothermal field of the Tatun Volcano Group

High temperature and sulfur concentrations in geothermal sulfur fumaroles host unique microbial ecosystems with niche-specific metabolic diversity and physiological functions. In this study, the microbial communities and their functionalities associated with the Dayoukeng geothermal field and the rock-soil-plant continuum were investigated to underpin the microbial modulation at different distances from the fumaroles source. At the phylum level, Bacteroidota, Planctomycetota, Armatimonadota, and Patescibacteria were abundant in plant samples; Elusimicrobiota and Desulfobacterota were in the rock samples while Nitrospirota, Micrarchaeota, and Deinococcota were dominant in the soil samples. Acidophilic thermophiles were enriched in samples within close proximity to the fumaroles, primarily at a distance of 1 m. The sulfur and iron-oxidizing acidophilic bacterial genera such as Acidothiobacillus and Sulfobacillus were abundant in the rock samples. The thermoacidophilic archaeon Acidianus and acidophilic bacteria Acidiphilium were abundant in the soil samples. Additionally, Thermosporothrix and Acidothermus were found abundant in the plant samples. The results of the functional annotation indicated that dark sulfur oxidation, iron oxidation, and hydrogen oxidation pathways were abundant in the soil samples up to 1 m from the fumaroles, while methanogenic and fermentation pathways were more prevalent in the soil samples located 10 m from the fumaroles. Interestingly, the results of this study indicated a higher microbial richness and abundance of acidophilic communities in the soils and plants compared to the rocks of the DYK fumarolic geothermal field.

Regulatory T cells in lung disease and transplantation

Pulmonary disease can refer to the disease of the lung itself or the pulmonary manifestations of systemic diseases, which are often connected to the malfunction of the immune system. Regulatory T (Treg) cells have been shown to be important in maintaining immune homeostasis and preventing inflammatory damage, including lung diseases. Given the increasing amount of evidence linking Treg cells to various pulmonary conditions, Treg cells might serve as a therapeutic strategy for the treatment of lung diseases and potentially promote lung transplant tolerance. The most potent and well-defined Treg cells are Foxp3-expressing CD4+ Treg cells, which contribute to the prevention of autoimmune lung diseases and the promotion of lung transplant rejection. The protective mechanisms of Treg cells in lung disease and transplantation involve multiple immune suppression mechanisms. This review summarizes the development, phenotype and function of CD4+Foxp3+ Treg cells. Then, we focus on the therapeutic potential of Treg cells in preventing lung disease and limiting lung transplant rejection. Furthermore, we discussed the possibility of Treg cell utilization in clinical applications. This will provide an overview of current research advances in Treg cells and their relevant application in clinics.

Changes in the prevalence of pathogens causing hospital-acquired bacterial pneumonia and the impact of their antimicrobial resistance patterns on clinical outcomes: A propensity-score-matched study

BACKGROUND

This study aimed to evaluate changes in the prevalence of pathogens causing hospital-acquired bacterial pneumonia (HABP) and their antimicrobial resistance patterns in recent years, and to identify risk factors for 28-day all-cause mortality (ACM) in patients with HABP.

METHODS

A propensity-score-matched study was performed by randomly allocating patients with ventilator-associated and non-ventilator-associated bacterial pneumonia admitted to two university hospitals between 2011 and 2021.

RESULTS

In total, 17,250 patients with HABP were enrolled. The annual incidence of Staphylococcus aureus HABP decreased during the study period, while that of Klebsiella pneumoniae HABP increased significantly each year. Over the same period, the resistance rate of S. aureus to methicillin decreased from 88.4% to 64.4%, while the non-susceptibility rate of K. pneumoniae to carbapenems increased from 0% to 38%. HABP caused by A. baumannii [adjusted odds ratio (aOR) 1.50, 95% confidence interval (CI) 1.25-1.79], K. pneumoniae (aOR 1.28, 95% CI 1.16-1.40) and Stenotrophomonas maltophilia (aOR 1.32, 95% CI 1.05-1.66) was a risk factor for 28-day ACM. Patients with HABP caused by methicillin-resistant S. aureus and carbapenem-non-susceptible A. baumannii or K. pneumoniae had a significantly lower probability of survival. HABP with preceding coronavirus disease 2019 (COVID-19) was associated with high 28-day ACM (aOR 5.40, 955 CI 3.03-9.64) and high incidence of bacteraemic pneumonia (aOR 40.55, 95% CI 5.26-312.79).

CONCLUSIONS

This study showed shifting trends in HABP-causing pathogens in terms of annual incidence and resistance rates to major therapeutic antimicrobial agents. HABP-causing bacterial pathogens, their antimicrobial resistance phenotypes, and preceding COVID-19 were significantly associated with progression of HABP to bloodstream infection and 28-day ACM in infected patients.

In Vitro Persistence Level Reflects In Vivo Antibiotic Survival of Natural Pseudomonas aeruginosa Isolates in a Murine Lung Infection Model

Clinicians are increasingly confronted with the limitations of antibiotics to clear bacterial infections in patients. It has long been assumed that only antibiotic resistance plays a pivotal role in this phenomenon. Indeed, the worldwide emergence of antibiotic resistance is considered one of the major health threats of the 21st century. However, the presence of persister cells also has a significant influence on treatment outcomes. These antibiotic-tolerant cells are present in every bacterial population and are the result of the phenotypic switching of normal, antibiotic-sensitive cells. Persister cells complicate current antibiotic therapies and contribute to the development of resistance. In the past, extensive research has been performed to investigate persistence in laboratory settings; however, antibiotic tolerance under conditions that mimic the clinical setting remain poorly understood. In this study, we optimized a mouse model for lung infections with the opportunistic pathogen Pseudomonas aeruginosa. In this model, mice are intratracheally infected with P. aeruginosa embedded in seaweed alginate beads and subsequently treated with tobramycin via nasal droplets. A diverse panel of 18 P. aeruginosa strains originating from environmental, human, and animal clinical sources was selected to assess survival in the animal model. Survival levels were positively correlated with the survival levels determined via time-kill assays, a common method to study persistence in the laboratory. We showed that survival levels are comparable and thus that the classical persister assays are indicative of antibiotic tolerance in a clinical setting. The optimized animal model also enables us to test potential antipersister therapies and study persistence in relevant settings. IMPORTANCE The importance of targeting persister cells in antibiotic therapies is becoming more evident, as these antibiotic-tolerant cells underlie relapsing infections and resistance development. Here, we studied persistence in a clinically relevant pathogen, Pseudomonas aeruginosa. It is one of the six ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, P. aeruginosa, and Enterobacter spp.), which are considered major health threats. P. aeruginosa is mostly known to cause chronic lung infections in cystic fibrosis patients. We mimicked these lung infections in a mouse model to study persistence under more clinical conditions. It was shown that the survival levels of natural P. aeruginosa isolates in this model are positively correlated with the survival levels measured in classical persistence assays in vitro. These results not only validate the use of our current techniques to study persistence but also open opportunities to study new persistence mechanisms or evaluate new antipersister strategies in vivo.

Baicalin ameliorates multidrug-resistant Pseudomonas aeruginosa induced pulmonary inflammation in rat via arginine biosynthesis

Multidrug-resistance (MDR) Pseudomonas aeruginosa (P. aeruginosa) is a lethal gram-negative pathogen causing hospital-acquired and ventilator-associated pneumonia, which is difficult to treat. Our previous studies confirmed that baicalin, an essential bioactive component in Scutellaria baicalensis Georgi, exhibited anti-inflammatory effects in an acute pneumonia rat model induced by MDR P. aeruginosa. However, this effect of baicalin in constrast its low bioavailability, and its mechanism of action is still unknown. Thus, this study investigated whether the therapeutic effects of baicalin against MDR P. aeruginosa acute pneumonia are owing to the regulation of gut microbiota and their metabolites using pyrosequencing of the 16S rRNA genes in rat feces and metabolomics. As a result, baicalin attenuated the inflammation by acting directly on neutrophils and regulated the production of the inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-10. The mechanisms were through down-regulation of TLR4 and inhibition of NF-κB. Furthermore, pyrosequencing of the 16S rRNA genes in rat feces revealed that baicalin regulated the composition of gut microbial communities. At the genus level, baicalin efficiently increased the abundance of Ligilactobacillus, Lactobacillus and Bacteroides, but decreased the abundance of Muribaculaceae and Alistipes. Further, arginine biosynthesis was analyzed as the core pathway regulated by baicalin via combination with predicting gut microbiota function and targeted metabolomics. In conclusion, this study has demonstrated that baicalin relieved inflammatory injury in acute pneumonia rat induced by MDR P. aeruginosa via arginine biosynthesis associated with gut microbiota. Baicalin could be a promising and effective adjunctive therapy for lung inflammation caused by MDR P. aeruginosa infection.

Association between combination antibiotic therapy as opposed as monotherapy and outcomes of ICU patients with Pseudomonas aeruginosa ventilator-associated pneumonia: an ancillary study of the iDIAPASON trial

BACKGROUND

The optimal treatment duration and the nature of regimen of antibiotics (monotherapy or combination therapy) for Pseudomonas aeruginosa ventilator‑associated pneumonia (PA-VAP) remain debated. The aim of this study was to evaluate whether a combination antibiotic therapy is superior to a monotherapy in patients with PA-VAP in terms of reduction in recurrence and death, based on the 186 patients included in the iDIAPASON trial, a multicenter, randomized controlled trial comparing 8 versus 15 days of antibiotic therapy for PA-VAP.

METHODS

Patients with PA-VAP randomized in the iDIAPASON trial (short-duration-8 days vs. long-duration-15 days) and who received appropriate antibiotic therapy were eligible in the present study. The main objective is to compare mortality at day 90 according to the antibiotic therapy received by the patient: monotherapy versus combination therapy. The primary outcome was the mortality rate at day 90. The primary outcome was compared between groups using a Chi-square test. Time from appropriate antibiotic therapy to death in ICU or to censure at day 90 was represented using Kaplan-Meier survival curves and compared between groups using a Log-rank test.

RESULTS

A total of 169 patients were included in the analysis. The median duration of appropriate antibiotic therapy was 14 days. At day 90, among 37 patients (21.9%) who died, 17 received monotherapy and 20 received a combination therapy (P = 0.180). Monotherapy and combination antibiotic therapy were similar for the recurrence rate of VAP, the number of extra pulmonary infections, or the acquisition of multidrug-resistant (MDR) bacteria during the ICU stay. Patients in combination therapy were exposed to mechanical ventilation for 28 ± 12 days, as compared with 23 ± 11 days for those receiving monotherapy (P = 0.0243). Results remain similar after adjustment for randomization arm of iDIAPASON trial and SOFA score at ICU admission.

CONCLUSIONS

Except longer durations of antibiotic therapy and mechanical ventilation, potentially related to increased difficulty in achieving clinical cure, the patients in the combination therapy group had similar outcomes to those in the monotherapy group.

TRIAL REGISTRATION

NCT02634411 , Registered 15 December 2015.

7-Ethoxycoumarin rescued Caenorhabditis elegans from infection of COPD derived clinical isolate Pseudomonas aeruginosa through virulence and biofilm inhibition via targeting Rhl and Pqs quorum sensing systems

Pseudomonas aeruginosa is an ambidextrous Gram-negative contagium with density convoluted network defined quorum sensing, which enables the persistent survival within the host environment, contributing to various lung related diseases including Chronic Obstructive Pulmonary Disease (COPD). It is clear that P. aeruginosa is a powerful, exquisite pathogen that has adopted a variety of virulence properties through quorum sensing (QS) regulated phenomenon and that it dominates both in the development and exacerbations of COPD. Interestingly, 7-Ethoxycoumarin (7-EC), a compound that adequately mimics QS signaling molecule of P. aeruginosa, was introduced as part of the process of developing novel ways to treat the severe exacerbations. The results showed that, introduction of 7-EC significantly decreased exopolysaccharide-mediated biofilm development of strains isolated from COPD sputum, as evidenced by SEM analysis. Furthermore, 7-EC was able to modulate a variety of virulence factors and motility without subjecting planktonic cells to any selection pressure. Bacterial invasion assay revealed the potential activity of the 7-EC in preventing the active entry to A549 cells without causing any damage to the cells and found functionally active in protecting the C. elegans from P. aeruginosa infection and being non-toxic to the worms. Docking analysis was further proved that 7-EC to be the potential anti-QS compound competing specifically with Rhl and Pqs Systems. Therefore, 7-EC in the utilisation against the P. aeruginosa based infections, may open an avenue for the futuristic mechanistic study in chronic respiratory diseases and a initiator for the development of non-antibiotic based antibacterial therapy.

A Fatal Case of Pseudomonas aeruginosa Community-Acquired Pneumonia in an Immunocompetent Patient: Clinical and Molecular Characterization and Literature Review

Rare cases of Pseudomonas aeruginosa community-acquired pneumonia (PA-CAP) were reported in non-immunocompromised patients. We describe a case of Pseudomonas aeruginosa (PA) necrotizing cavitary CAP with a fatal outcome in a 53-year-old man previously infected with SARS-CoV-2, who was admitted for dyspnea, fever, cough, hemoptysis, acute respiratory failure and a right upper lobe opacification. Six hours after admission, despite effective antibiotic therapy, he experienced multi-organ failure and died. Autopsy confirmed necrotizing pneumonia with alveolar hemorrhage. Blood and bronchoalveolar lavage cultures were positive for PA serotype O:9 belonging to ST1184. The strain shares the same virulence factor profile with reference genome PA01. With the aim to better investigate the clinical and molecular characteristics of PA-CAP, we considered the literature of the last 13 years concerning this topic. The prevalence of hospitalized PA-CAP is about 4% and has a mortality rate of 33-66%. Smoking, alcohol abuse and contaminated fluid exposure were the recognized risk factors; most cases presented the same symptoms described above and needed intensive care. Co-infection of PA-influenza A is described, which is possibly caused by influenza-inducing respiratory epithelial cell dysfunction: the same pathophysiological mechanism could be assumed with SARS-CoV-2 infection. Considering the high rate of fatal outcomes, additional studies are needed to identify sources of infections and new risk factors, along with genetic and immunological features. Current CAP guidelines should be revised in light of these results.

The RIPK3 Scaffold Regulates Lung Inflammation During Pseudomonas Aeruginosa Pneumonia

RIPK3 (receptor-interacting protein kinase 3) activity triggers cell death via necroptosis, whereas scaffold function supports protein binding and cytokine production. To determine if RIPK3 kinase or scaffold domains mediate pathology during Pseudomonas aeruginosa infection, control mice and those with deletion or mutation of RIPK3 and associated signaling partners were subjected to Pseudomonas pneumonia and followed for survival or killed for biologic assays. Murine immune cells were studied in vitro for Pseudomonas-induced cytokine production and cell death, and RIPK3 binding interactions were blocked with the viral inhibitor M45. Human tissue effects were assayed by infecting airway epithelial cells with Pseudomonas and measuring cytokine production after siRNA inhibition of RIPK3. Deletion of RIPK3 reduced inflammation and decreased animal mortality after Pseudomonas pneumonia. RIPK3 kinase inactivation did neither. In cell culture, RIPK3 was dispensable for cell killing by Pseudomonas and instead drove cytokine production that required the RIPK3 scaffold domain but not kinase activity. Blocking the RIP homotypic interaction motif (RHIM) with M45 reduced the inflammatory response to infection in vitro. Similarly, siRNA knockdown of RIPK3 decreased infection-triggered inflammation in human airway epithelial cells. Thus, the RIPK3 scaffold drives deleterious pulmonary inflammation and mortality in a relevant clinical model of Pseudomonas pneumonia. This process is distinct from kinase-mediated necroptosis, requiring only the RIPK3 RHIM. Inhibition of RHIM signaling is a potential strategy to reduce lung inflammation during infection.

An Isolate of Streptococcus mitis Displayed In Vitro Antimicrobial Activity and Deleterious Effect in a Preclinical Model of Lung Infection

Microbiota studies have dramatically increased over these last two decades, and the repertoire of microorganisms with potential health benefits has been considerably enlarged. The development of next generation probiotics from new bacterial candidates is a long-term strategy that may be more efficient and rapid with discriminative in vitro tests. Streptococcus strains have received attention regarding their antimicrobial potential against pathogens of the upper and, more recently, the lower respiratory tracts. Pathogenic bacterial strains, such as non-typable Haemophilus influenzae (NTHi), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus), are commonly associated with acute and chronic respiratory diseases, and it could be interesting to fight against pathogens with probiotics. In this study, we show that a Streptococcus mitis (S. mitis) EM-371 strain, isolated from the buccal cavity of a human newborn and previously selected for promising anti-inflammatory effects, displayed in vitro antimicrobial activity against NTHi, P. aeruginosa or S. aureus. However, the anti-pathogenic in vitro activity was not sufficient to predict an efficient protective effect in a preclinical model. Two weeks of treatment with S. mitis EM-371 did not protect against, and even exacerbated, NTHi lung infection.

Profiles of oral microbiome associated with nasogastric tube feeding

Background

Dysbiosis of oral microbiome causes chronic diseases including dental caries and periodontitis, which frequently affect older patient populations. Severely disabled individuals with impaired swallowing functions may require nutritional supply via nasogastric (NG) tubes, further impacting their oral condition and possibly microbial composition. However, little is known about the effect of NG tube on oral microbes and its potential ramification.

Methods

By using 16S rRNA amplicon sequencing, we characterized the tongue microbiome of 27 patients fed with NG tubes and 26 others fed orally.

Results

The microbial compositions of NG-tube and oral-feeding patients were substantially different, with more Gram-negative aerobes enriched in the presence of NG tube. Specifically, NG-tube patients presented more opportunistic pathogens like Pseudomonas and Corynebacterium associated with pneumonia and lower levels of commensal Streptococcus and Veillonella. Co-occurrence analysis further showed an inverse relationship between commensal and pathogenic species.

Conclusion

We present a systematic, high-throughput profiling of oral microbiome with regard to long-term NG tube feeding among the older patient population.

Gut to lung translocation and antibiotic mediated selection shape the dynamics of Pseudomonas aeruginosa in an ICU patient

Bacteria have the potential to translocate between sites in the human body, but the dynamics and consequences of within-host bacterial migration remain poorly understood. Here we investigate the link between gut and lung Pseudomonas aeruginosa populations in an intensively sampled ICU patient using a combination of genomics, isolate phenotyping, host immunity profiling, and clinical data. Crucially, we show that lung colonization in the ICU was driven by the translocation of P. aeruginosa from the gut. Meropenem treatment for a suspected urinary tract infection selected for elevated resistance in both the gut and lung. However, resistance was driven by parallel evolution in the gut and lung coupled with organ specific selective pressures, and translocation had only a minor impact on AMR. These findings suggest that reducing intestinal colonization of Pseudomonas may be an effective way to prevent lung infections in critically ill patients.

Gearing up for battle: Harnessing adaptive T cell immunity against gram-negative pneumonia

Pneumonia is one of the leading causes of morbidity and mortality worldwide and Gram-negative bacteria are a major cause of severe pneumonia. Despite advances in diagnosis and treatment, the rise of multidrug-resistant organisms and hypervirulent strains demonstrates that there will continue to be challenges with traditional treatment strategies using antibiotics. Hence, an alternative approach is to focus on the disease tolerance components that mediate immune resistance and enhance tissue resilience. Adaptive immunity plays a pivotal role in modulating these processes, thus affecting the incidence and severity of pneumonia. In this review, we focus on the adaptive T cell responses to pneumonia induced by Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. We highlight key factors in these responses that have potential for therapeutic targeting, as well as the gaps in current knowledge to be focused on in future work.

Duration of Gram-negative antibiotic therapy in patients with pneumonia prior to and after the implementation of MRSA nasal swabs, an antimicrobial stewardship tool

BACKGROUND

The implementation of MRSA PCR nasal swabs has been shown to decrease the use of anti-MRSA therapies through faster antibiotic de-escalation in patients with pneumonia. While this benefit has been shown exclusively in Gram-positive therapy, swab results may lead to additional antibiotic de-escalation discussions early on, potentially providing reduced durations or de-escalations of Gram-negative therapy as well.

OBJECTIVES

To determine if early de-escalation discussions prompted by MRSA swab results lead to shorter durations of Gram-negative antibiotic therapy.

METHODS

A retrospective chart review was conducted to compare pneumonia duration of Gram-negative therapy pre- and post-implementation of MRSA nasal swabs. Time to de-escalation, time to conversion to enteral therapy and cost were also compared between the groups.

RESULTS

Data were collected for 240 patients overall, 120 in each group. The median duration of Gram-negative therapy was 154.0 h in the post-implementation group and 176.4 h in the pre-implementation group (P = 0.002). There was no significant difference in time to de-escalation (52.7 versus 54.9 h; P = 0.351) or time to transition from IV to enteral therapy (53.0 versus 57.3 h; P = 0.289). The median cost of Gram-negative regimens per patient was less expensive in the post-implementation group ($31.36 versus $45.90; P = 0.002).

CONCLUSIONS

MRSA nasal swabs as an antimicrobial stewardship tool were associated with a reduced overall duration of Gram-negative therapy and Gram-negative antibiotic regimen cost. This introduces an additional benefit of MRSA nasal swabs and further incentivizes their use as an antimicrobial stewardship tool.

Angiopteris cochinchinensis de Vriese Ameliorates LPS-Induced Acute Lung Injury via Src Inhibition

Growing demand for treatment options against acute lung injury (ALI) emphasizes studies on plant extracts harboring anti-inflammatory effects. According to GC-MS analysis, Angiopteris cochinchinensis de Vriese consists of various flavonoids with anti-inflammatory activities. Thus, in this study, the anti-inflammatory effects of an extract of Angiopteris cochinchinensis de Vriese (Ac-EE) were assessed using RAW264.6 murine macrophages and a lipopolysaccharide (LPS)-induced ALI model. Ac-EE reduced the nitric oxide production in murine macrophages increased by LPS induction. Moreover, protective effects of Ac-EE on lung tissue were demonstrated by shrinkage of edema and lung injury. Reduced neutrophil infiltration and formation of hyaline membranes were also detected in lung tissues after H&E staining. Semiquantitative RT-PCR, quantitative real-time PCR, and ELISA showed that Ac-EE inhibits the production of proinflammatory mediators, including iNOS and COX-2, and cytokines, such as TNF-α, IL-1β, and IL-6. An Ac-EE-mediated anti-inflammatory response was derived from inhibiting the NF-κB signaling pathway, which was evaluated by luciferase reporter assay and Western blotting analysis. A cellular thermal shift assay revealed that the prime target of Ac-EE in alleviating inflammation was Src. With its direct binding with Src, Angiopteris cochinchinensis de Vriese significantly mitigates lung injury, showing possibilities of its potential as an effective botanical drug.

Potential Synergistic Antibiotic Combinations against Fluoroquinolone-Resistant Pseudomonas aeruginosa

The rise in multiple-drug-resistant (MDR) phenotypes in Gram-negative pathogens is a major public health crisis. Pseudomonas aeruginosa is one of the leading causes of nosocomial infections in clinics. Treatment options for P. aeruginosa have become increasingly difficult due tdo its remarkable capacity to resist multiple antibiotics. The presence of intrinsic resistance factors and the ability to quickly adapt to antibiotic monotherapy warrant us to look for alternative strategies like combinatorial antibiotic therapy. Here, we report the frequency of P. aeruginosa multidrug-resistant and extensively drug-resistance (XDR) phenotypes in a super-specialty tertiary care hospital in north India. Approximately 60 percent of all isolated P. aeruginosa strains displayed the MDR phenotype. We found highest antibiotic resistance frequency in the emergency department (EMR), as 20 percent of isolates were resistant to 15 antipseudomonal antibiotics. Presence of plasmids with quinolone-resistance determinants were major drivers for resistance against fluoroquinolone. Additionally, we explored the possible combinatorial therapeutic options with four antipseudomonal antibiotics—colistin, ciprofloxacin, tobramycin, and meropenem. We uncovered an association between different antibiotic interactions. Our data show that the combination of colistin and ciprofloxacin could be an effective combinatorial regimen to treat infections caused by MDR and XDR P. aeruginosa.

Bacterial Biofilm Formation on Nano-Copper Added PLA Suited for 3D Printed Face Masks

The COVID-19 Pandemic leads to an increased worldwide demand for personal protection equipment in the medical field, such as face masks. New approaches to satisfy this demand have been developed, and one example is the use of 3D printing face masks. The reusable 3D printed mask may also have a positive effect on the environment due to decreased littering. However, the microbial load on the 3D printed objects is often disregarded. Here we analyze the biofilm formation of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli on suspected antimicrobial Plactive™ PLA 3D printing filaments and non-antimicrobial Giantarm™ PLA. To characterize the biofilm-forming potential scanning electron microscopy (SEM), Confocal scanning electron microscopy (CLSM) and colony-forming unit assays (CFU) were performed. Attached cells could be observed on all tested 3D printing materials. Gram-negative strains P. aeruginosa and E. coli reveal a strong uniform growth independent of the tested 3D filament (for P. aeruginosa even with stressed induced growth reaction by Plactive™). Only Gram-positive S. aureus shows strong growth reduction on Plactive™. These results suggest that the postulated antimicrobial Plactive™ PLA does not affect Gram-negative bacteria species. These results indicate that reusable masks, while better for our environment, may pose another health risk.

Ceftazidime/Avibactam versus Polymyxin B in the Challenge of Carbapenem-Resistant Pseudomonas aeruginosa Infection

Purpose

Ceftazidime/avibactam (CAZ/AVI) monotherapy and polymyxin B-based combination therapy are currently two treatment options for patients with carbapenem-resistant Pseudomonas aeruginosa (CRPA) infection; however, few studies have contrasted the relative efficacy of the two antibiotic regimens. The purpose of this study was to compare the effectiveness of CAZ/AVI and polymyxin B against CRPA infection and analyze the independent predictors of 30-day mortality or survival.

Patients and Methods

This single-center retrospective observational study included patients with CRPA infection treated with CAZ/AVI or polymyxin B between January 2018 and December 2020. The primary outcomes were the 14-day and 30-day mortality. The secondary outcomes were in-hospital mortality and bacterial clearance. Baseline characteristics and outcomes were compared between the two groups, and COX regression analysis was used to identify predictors of 30-day mortality.

Results

A total of 136 patients with CRPA infection were enrolled, including 51 patients in the CAZ/AVI group and 85 patients in the polymyxin B group. The 14-day mortality (5.9% vs 27.1%, p=0.002), 30-day mortality (13.7% vs 47.1%, p<0.001) and in-hospital mortality (29.4% vs 60.0%, p=0.001) in the CAZ/AVI group were significantly lower than the polymyxin B group. The bacterial clearance rate (45.1% vs 12.9%, p<0.001) in the CAZ/AVI group were higher than in the polymyxin B group. After adjustment by propensity score matching, the CAV/AVI group still had lower 30-day mortality (14.3% vs 42.9%, p=0.018) and higher bacterial clearance rate (42.9% vs 14.3%, p=0.018) than the polymyxin B group. The multivariate COX analysis showed that the age was identified as independent predictor of 30-day mortality while CAZ/AVI therapy and central venous catheterization emerged as independent predictors of 30-day survival.

Conclusion

CAZ/AVI therapy was superior to polymyxin B therapy for patients with CRPA infection, and provided significant survival benefits, but further larger studies were needed to substantiate our findings.

Pseudomonas aeruginosa Pneumonia: Evolution of Antimicrobial Resistance and Implications for Therapy

Pseudomonas aeruginosa (PA), a non-lactose-fermenting gram-negative bacillus, is a common cause of nosocomial infections in critically ill or debilitated patients, particularly ventilator-associated pneumonia (VAP), and infections of urinary tract, intra-abdominal, wounds, skin/soft tissue, and bloodstream. PA rarely affects healthy individuals, but may cause serious infections in patients with chronic structural lung disease, comorbidities, advanced age, impaired immune defenses, or with medical devices (e.g., urinary or intravascular catheters, foreign bodies). Treatment of pseudomonal infections is difficult, as PA is intrinsically resistant to multiple antimicrobials, and may acquire new resistance determinants even while on antimicrobial therapy. Mortality associated with pseudomonal VAP or bacteremias is high (> 35%) and optimal therapy is controversial. Over the past three decades, antimicrobial resistance (AMR) among PA has escalated globally, via dissemination of several international multidrug resistant "epidemic" clones. We discuss the importance of PA as a cause of pneumonia including health care-associated pneumonia, hospital-acquired pneumonia, VAP, the emergence of AMR to this pathogen, and approaches to therapy (both empirical and definitive).

The Epidemiology and Pathogenesis and Treatment of Pseudomonas aeruginosa Infections: An Update

Pseudomonas aeruginosa is a Gram-negative bacterial pathogen that is a common cause of nosocomial infections, particularly pneumonia, infection in immunocompromised hosts, and in those with structural lung disease such as cystic fibrosis. Epidemiological studies have identified increasing trends of antimicrobial resistance, including multi-drug resistant (MDR) isolates in recent years. P. aeruginosa has several virulence mechanisms that increase its ability to cause severe infections, such as secreted toxins, quorum sensing and biofilm formation. Management of P. aeruginosa infections focuses on prevention when possible, obtaining cultures, and prompt initiation of antimicrobial therapy, occasionally with combination therapy depending on the clinical scenario to ensure activity against P. aeruginosa. Newer anti-pseudomonal antibiotics are available and are increasingly being used in the management of MDR P. aeruginosa.

Clinical and bacterial characteristics of Pseudomonas aeruginosa affecting the outcome of patients with bacteraemic pneumonia

Few studies have assessed the clinical and bacterial characteristics of Pseudomonas aeruginosa (PA) bacteraemic pneumonia (BP) episodes. This study analysed all non-duplicate PA-BP episodes from a tertiary hospital in 2013-2017. Epidemiology, clinical data, antimicrobial therapy and outcomes were recorded. Whole-genome sequencing was performed on PA blood isolates. The impact on early and late overall mortality of host, antimicrobial treatment and pathogen factors was assessed by multivariate logistic regression analysis. Of 55 PA-BP episodes, 32 (58.2%) were caused by extensively drug-resistant (XDR) PA. ST175 (32.7%) and ST235 (25.5%) were the most frequent high-risk clones. β-Lactamases/carbapenemases were detected in 29 isolates, including bla_VIM-2 (27.2%) and bla_GES type (25.5%) [bla_GES-5 (20.0%), bla_GES-1 (3.6%) and bla_GES-20 (1.8%)]. The most prevalent O-antigen serotypes were O4 (34.5%) and O11 (30.9%). Overall, an extensive virulome was identified in all isolates. Early mortality (56.4%) was independently associated with severe neutropenia (aOR = 4.64, 95% CI 1.11-19.33; P = 0.035) and inappropriate empirical antimicrobial therapy (aOR = 5.71, 95% CI 1.41-22.98; P = 0.014). Additionally, late mortality (67.3%) was influenced by septic shock (aOR = 8.85, 95% CI 2.00-39.16; P = 0.004) and XDR phenotype (aOR = 5.46, 95% CI 1.25-23.85; P = 0.024). Moreover, specific genetic backgrounds [ST235, bla_GES, gyrA (T83I), parC (S87L), exoU and O11 serotype] showed significant differences in patient outcomes. Our results confirm the high mortality associated with PA-BP. Besides relevant clinical characteristics and inappropriate empirical therapy, bacteria-specific genetics factors, such as XDR phenotype, adversely affect the outcome of PA-BP.

Effectiveness of empirical anti-pseudomonal antibiotics for recurrent COPD exacerbation: a multicenter retrospective cohort study

Although frequent chronic obstructive pulmonary disease (COPD) exacerbation has been associated with the isolation of Pseudomonas aeruginosa (PA) in sputum cultures, it remains unknown whether the empirical use of anti-pseudomonal antibiotics can improve outcomes in patients with frequent COPD exacerbations. This multicenter retrospective cohort study evaluated whether the empirical use of anti-pseudomonal antibiotics improves the length of the hospital stay in patients with recurrent COPD exacerbation (≥ 2 admissions from April 1, 2008 to July 31, 2020). For statistical analysis, a log-linked Gamma model was used. Parameters were estimated using a generalized estimating equation model with an exchangeable correlation structure accounting for repeated observations from a single patient. Covariates included age, body mass index, home oxygen therapy use, respiratory rate, heart rate, oxygen use on admission, mental status, systemic steroid use, activities of daily living, and the number of recurrences. Hospital-specific effects were specified as fixed effects. In total, 344 patients and 965 observations of recurrent COPD exacerbations were selected. Anti-pseudomonal antibiotics were used in 173 patients (18%). The estimated change in the length of the hospital stay between anti-pseudomonal and non-anti-pseudomonal antibiotics groups was 0.039 days [95% confidence interval; - 0.083, 0.162]. Anti-pseudomonal antibiotics could not shorten the length of the hospital stay.

Definitive and Indeterminate Pseudomonas aeruginosa Infection in Adults with Community-acquired Pneumonia: A Prospective Observational Study

Rationale: Pneumonia due to Pseudomonas aeruginosa (PA) is associated with high mortality and requires antipseudomonal treatment. Because PA can colonize the respiratory tract, the diagnosis of pathogenic PA involvement is challenging.

Objectives: To determine the prevalence of definitive and indeterminate PA infection in community-acquired pneumonia, to describe the clinical and microbiological profiles, and to estimate the burden of unnecessary antipseudomonal drug prescriptions.

Methods: We prospectively enrolled 2,701 patients with community-acquired pneumonia. Using stringent criteria for diagnosing PA pneumonia, we generated the following three groups: 1) definitive PA, 2) indeterminate PA, and 3) non-PA pneumonia.

Results: The prevalence of definitive PA pneumonia was 0.9% (n = 25), and that of indeterminate PA pneumonia was 4.9% (n = 131). Considerable clinical differences were observed among the groups. Patients with definitive PA pneumonia were more likely to have a history of tuberculosis and chronic obstructive pulmonary disease/bronchiectasis and had a higher 30-day mortality (28%) than patients with non-PA pneumonia. Patients with indeterminate PA pneumonia were more likely to have comorbidities than patients with non-PA pneumonia. More than half of the patients with indeterminate PA and 25% of the patients with non-PA pneumonia were treated with an antipseudomonal drug. No patients with definitive PA pneumonia had multidrug resistance.

Conclusions: In this population, the prevalence of community-acquired pneumonia due to PA was low. The clinical features and 30-day mortality rates of patients with indeterminate PA pneumonia were different from those of patients with definitive PA pneumonia. Most of the prescribed antipseudomonal drugs for patients with community-acquired pneumonia were potentially unnecessary.

The Role of Host Cell DNA Methylation in the Immune Response to Bacterial Infection

Host cells undergo complex transcriptional reprogramming upon infection. Epigenetic changes play a key role in the immune response to bacteria, among which DNA modifications that include methylation have received much attention in recent years. The extent of DNA methylation is well known to regulate gene expression. Whilst historically DNA methylation was considered to be a stable epigenetic modification, accumulating evidence indicates that DNA methylation patterns can be altered rapidly upon exposure of cells to changing environments and pathogens. Furthermore, the action of proteins regulating DNA methylation, particularly DNA methyltransferases and ten-eleven translocation methylcytosine dioxygenases, may be modulated, at least in part, by bacteria. This review discusses the principles of DNA methylation, and recent insights about the regulation of host DNA methylation during bacterial infection.

Pseudomonas aeruginosa necrotizing bronchopneumonia

Extremely low birth weight (ELBW) infants are at particularly high risk for infection due to an immature immune system, invasive procedures such as endotracheal intubation, intravascular catheterization, and other factors. Neonatal infections in this population are associated with a high mortality, poor growth, and neurodevelopmental outcomes. Pseudomonas aeruginosa (P. aeruginosa) infection is an uncommon but potentially devastating cause of pneumonia and sepsis in the ELBW population. P. aeruginosa is an important cause of healthcare-associated infections (HAI) or nosocomial infections. P. aeruginosa can perceive unfavorable environmental changes and orchestrate adaptations by developing plasmid-mediated and adaptive resistance to antibiotics. We describe an ELBW infant born at 26 weeks’ gestation who succumbed at 13 days of life to P. aeruginosa infection. Some of the factors related to the pathogenesis and multidrug resistance are described.

Priming with intranasal lactobacilli prevents Pseudomonas aeruginosa acute pneumonia in mice

Background

Increasing resistance to antibiotics of Pseudomonas aeruginosa leads to therapeutic deadlock and alternative therapies are needed. We aimed to evaluate the effects of Lactobacillus clinical isolates in vivo, through intranasal administration on a murine model of Pseudomonas aeruginosa pneumonia.

Results

We screened in vitro 50 pulmonary clinical isolates of Lactobacillus for their ability to decrease the synthesis of two QS dependent-virulence factors (elastase and pyocyanin) produced by Pseudomonas aeruginosa strain PAO1.

Two blends of three Lactobacillus isolates were then tested in vivo: one with highly effective anti-PAO1 virulence factors properties (blend named L.rff for L. rhamnosus, two L. fermentum strains), and the second with no properties (blend named L.psb, for L. paracasei, L. salivarius and L. brevis). Each blend was administered intranasally to mice 18 h prior to PAO1 pulmonary infection. Animal survival, bacterial loads, cytological analysis, and cytokines secretion in the lungs were evaluated at 6 or 24 h post infection with PAO1.

Intranasal priming with both lactobacilli blends significantly improved 7-day mice survival from 12% for the control PAO1 group to 71 and 100% for the two groups receiving L.rff and L.psb respectively. No mortality was observed for both control groups receiving either L.rff or L.psb. Additionally, the PAO1 lung clearance was significantly enhanced at 24 h. A 2-log and 4-log reduction was observed in the L.rff + PAO1 and L.psb + PAO1 groups respectively, compared to the control PAO1 group. Significant reductions in neutrophil recruitment and proinflammatory cytokine and chemokine secretion were observed after lactobacilli administration compared to saline solution, whereas IL-10 production was increased.

Conclusions

These results demonstrate that intranasal priming with lactobacilli acts as a prophylaxis, and avoids fatal complications caused by Pseudomonas aeruginosa pneumonia in mice. These results were independent of in vitro anti-Pseudomonas aeruginosa activity on QS-dependent virulence factors. Further experiments are required to identify the immune mechanism before initiating clinical trials.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02254-7.

Clinical Features and Antimicrobial Susceptibility of Pseudomonas aeruginosa and Acinetobacter baumannii Complex Isolates in Intensive Care Patients with Chronic Obstructive Pulmonary Disease and Community-Acquired Pneumonia in Taiwan

Purpose

Little is known about the features and implications of Pseudomonas aeruginosa (PA) and Acinetobacter baumannii complex (ABC) isolates discovered in patients with chronic obstructive pulmonary disease (COPD) and community-acquired pneumonia (CAP) requiring invasive mechanical ventilation and admission to an intensive care unit. Thus, our study aimed to investigate the clinical characteristics and antimicrobial susceptibilities of PA and ABC isolates cultured from endotracheal aspirates (EAs) in such population.

Patients and Methods

In this retrospective, cross-sectional study, clinical data from medical records were reviewed and collected for analysis.

Results

Of the 262 participants, 17.2% (45/262), 11.5% (30/262), and 27.1% (71/262) had PA, ABC, and any of the two isolates discovered from EA cultures, respectively. Patients with PA isolates were associated with poorer lung function (the Global Initiative for Chronic Obstructive Lung Disease (GOLD) III+IV versus GOLD I+II, odds ratio (OR)=2.39, p= 0.022) and a lower body mass index (per increase of 1 kg/m2, OR= 0.93, p= 0.106) while the former was an independent predictor. Moreover, both subjects with ABC isolates and those with any of these two microorganisms were independently associated with a lower serum albumin level (per increase of 1 g/dL, OR= 0.44, p=0.009 and OR= 0.59, p=0.023, respectively). Participants with PA isolates were more likely to have failed weaning (62.2% versus 44.7%, p= 0.048) and death (28.9% versus 12.4%, p= 0.010) than those without PA isolates. The majority of the PA and ABC isolates were susceptible and resistant to all the tested antimicrobials, respectively, except that tigecycline had a reliable activity against ABC.

Conclusion

Our findings provide important information to help intensivists make better treatment decisions in critically ill patients with COPD and CAP.

Role of CD44 in increasing the potency of mesenchymal stem cell extracellular vesicles by hyaluronic acid in severe pneumonia

Background

Although promising, clinical translation of human mesenchymal stem or stromal cell-derived extracellular vesicles (MSC EV) for acute lung injury is potentially limited by significant production costs. The current study was performed to determine whether pretreatment of MSC EV with high molecular weight hyaluronic acid (HMW HA) would increase the therapeutic potency of MSC EV in severe bacterial pneumonia.

Methods

In vitro experiments were performed to determine the binding affinity of HMW HA to MSC EV and its uptake by human monocytes, and whether HMW HA primed MSC EV would increase bacterial phagocytosis by the monocytes. In addition, the role of CD44 receptor on MSC EV in the therapeutic effects of HMW HA primed MSC EV were investigated. In Pseudomonas aeruginosa (PA) pneumonia in mice, MSC EV primed with or without HMW HA were instilled intravenously 4 h after injury. After 24 h, the bronchoalveolar lavage fluid, blood, and lungs were analyzed for levels of bacteria, inflammation, MSC EV trafficking, and lung pathology.

Results

MSC EV bound preferentially to HMW HA at a molecular weight of 1.0 MDa compared with HA with a molecular weight of 40 KDa or 1.5 MDa. HMW HA primed MSC EV further increased MSC EV uptake and bacterial phagocytosis by monocytes compared to treatment with MSC EV alone. In PA pneumonia in mice, instillation of HMW HA primed MSC EV further reduced inflammation and decreased the bacterial load by enhancing the trafficking of MSC EV to the injured alveolus. CD44 siRNA pretreatment of MSC EV prior to incubation with HMW HA eliminated its trafficking to the alveolus and therapeutic effects.

Conclusions

HMW HA primed MSC EV significantly increased the potency of MSC EV in PA pneumonia in part by enhancing the trafficking of MSC EV to the sites of inflammation via the CD44 receptor on MSC EV which was associated with increased antimicrobial activity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02329-2.