High-Intensity Blue Light (450-460 nm) Phototherapy for Pseudomonas aeruginosa-Infected Wounds.

Background: Nosocomial wound infection with Pseudomonas aeruginosa (PA) is a serious complication often responsible for the septic mortality of burn patients. Objective: High-intensity antimicrobial blue light (aBL) treatment may represent an alternative therapy for PA infections and will be investigated in this study. Methods: Antibacterial effects of a light-emitting diode array (450-460 nm; 300 mW/cm2; 15/30 min; 270/540 J/cm2) against PA were determined by suspension assay, biofilm assay, and a human skin wound model and compared with 15-min topically applied 3% citric acid (CA) and wound irrigation solution (Prontosan®; PRT). Results: aBL reduced the bacterial number [2.51-3.56 log10 colony-forming unit (CFU)/mL], whereas PRT or CA treatment achieved a 4.64 or 6.60 log10 CFU/mL reduction in suspension assays. aBL reduced biofilm formation by 60-66%. PRT or CA treatment showed reductions by 25% or 13%. Here, aBL reduced bacterial number in biofilms (1.30-1.64 log10 CFU), but to a lower extend than PRT (2.41 log10 CFU) or CA (2.48 log10 CFU). In the wound skin model, aBL (2.21-2.33 log10 CFU) showed a bacterial reduction of the same magnitude as PRT (2.26 log10 CFU) and CA (2.30 log10 CFU). Conclusions: aBL showed a significant antibacterial efficacy against PA and biofilm formation in a short time. However, a clinical application of aBL in wound therapy requires effective active skin cooling and eye protection, which in turn may limit clinical implementation.

Successful phage-antibiotic therapy of P. aeruginosa implant-associated infection in a Siamese cat.

Antibiotic-resistant pathogens are a growing global issue, leading to untreatable infectious diseases in both humans and animals. Personalized bacteriophage (phage) therapy, the use of specific anti-bacterial viruses, is currently a leading approach to combat antibiotic-resistant infections. The implementation of phage therapy has primarily been focused on humans, almost neglecting the impact of such infections on the health and welfare of companion animals. Pets also have the potential to spread resistant infections to their owners or the veterinary staff through zoonotic transmission. Here, we showcase personalized phage-antibiotic treatment of a cat with a multidrug-resistant Pseudomonas aeruginosa implant-associated infection post-arthrodesis surgery. The treatment encompassed a tailored combination of an anti-P. aeruginosa phage and ceftazidime, precisely matched to the pathogen. The phage was topically applied to the surgical wound while the antibiotic was administered intramuscularly. After two treatment courses spanning 7 and 3 weeks, the surgical wound, which had previously remained open for five months, fully closed. To the best of our knowledge, this is the first case of personalized phage therapy application in felines, which provides further evidence of the effectiveness of this approach. The successful outcome paves the way for personalized phage-antibiotic treatments against persistent infections therapy in veterinary practice.

Cu-MOF loaded chitosan based freeze-dried highly porous dressings with anti-biofilm and pro-angiogenic activities accelerated Pseudomonas aeruginosa infected wounds healing in rats.

Metal-organic frameworks (MOFs)-based therapy opens a new area for antibiotic-drug free infections treatment. In the present study, chitosan membranes (CS) loaded with two concentrations of copper-MOF 10 mg/20 ml (Cu-MOF10/CS) & 20 mg/20 ml (Cu-MOF20/CS) were prepared by a simple lyophilization procedure. FTIR spectra of Cu-MOF10/CS and Cu-MOF20/CS dressings confirmed absence of any undesirable chemical changes after loading Cu-MOF. The SEM images of the synthesized materials (CS, Cu-MOF10/CS & Cu-MOF20/CS) showed interconnected porous structures. Cytocompatibility of the materials was confirmed by fibroblasts cells culturing and the materials were hemocompatible, with blood clotting index <5 %. Cu-MOF20/CS showed comparatively higher effective antibacterial activity against the tested strains; E. coli (149.2 %), P. aeruginosa (165 %) S. aureus (117.8 %) and MRSA (142 %) as compared to Amikacin, CS and Cu-MOF10/CS membranes. Similarly, Cu-MOF20/CS dressing significantly eradicated the biofilms; P. aeruginosa (37 %) and MRSA (52 %) respectively. In full thickness infected wound rat model, on day 23, Cu-MOF10/CS and Cu-MOF20/CS promoted wound healing up to 87.7 % and 82 % respectively. H&E staining of wounded tissues treated with Cu-MOF10/CS & Cu-MOF20/CS demonstrated enhanced neovascularization and re-epithelization along-with reduced inflammation, while trichrome staining exhibited increased collagen deposition. Overall, this study declares Cu-MOFs loaded chitosan dressings a multifunctional platform for the healing of infected wounds.

Lytic bacteriophages induce the secretion of antiviral and proinflammatory cytokines from human respiratory epithelial cells.

Phage therapy is a therapeutic approach to treat multidrug-resistant (MDR) infections that employs lytic bacteriophages (phages) to eliminate bacteria. Despite the abundant evidence for its success as an antimicrobial in Eastern Europe, there is scarce data regarding its effects on the human host. Here, we aimed to understand how lytic phages interact with cells of the airway epithelium, the tissue site that is colonized by bacterial biofilms in numerous chronic respiratory disorders. Using a panel of Pseudomonas aeruginosa phages and human airway epithelial cells (AECs) derived from a person with cystic fibrosis (CF), we determined that interactions between phages and epithelial cells depend on specific phage properties as well as physiochemical features of the microenvironment. Although poor at internalizing phages, the airway epithelium responds to phage exposure by changing its transcriptional profile and secreting antiviral and proinflammatory cytokines that correlate with specific phage families. Overall, our findings indicate that mammalian responses to phages are heterogenous and could potentially alter the way that respiratory local defenses aid in bacterial clearance during phage therapy. Thus, besides phage receptor specificity in a particular bacterial isolate, the criteria to select lytic phages for therapy should be expanded to include mammalian cell responses.

Mesenchymal stem cell-based adjunctive therapy for Pseudomonas aeruginosa-induced keratitis: A proof-of-concept in-vitro study.

PURPOSE: Pseudomonas aeruginosa-induced keratitis is one of the most severe and challenging forms of corneal infection, owing to its associated intense inflammatory reactions leading to corneal necrosis and dense corneal scar with loss of vision. Since mesenchymal stem cells (MSCs) are reported to possess antimicrobial and immunomodulatory properties, they can be tested as an adjuvant treatment along with the antibiotics which are the current standard of care. This study aims to investigate the anti-bacterial and immunomodulatory roles of human bone marrow MSC-derived conditioned medium (MSC-CM) in P. aeruginosa-infected human corneal epithelial cells (HCECs) in vitro. METHODS: The effect of MSC-CM on the growth of clinical isolates of P. aeruginosa was evaluated by colony-forming unit assay. The expression of inflammatory cytokines (IL-6 and TNF-α) and an antimicrobial peptide (Lipocalin 2) in lipopolysaccharide-treated MSCs and HCECs was analyzed through ELISA. Corneal epithelial repair following infection with P. aeruginosa was studied through scratch assay. RESULTS: Compared to control (P. aeruginosa (5*105) incubated in DMEM (1 ml) at 37 °C for 16 h), MSC-CM significantly: i) inhibits the growth of P. aeruginosa (159*109 vs. 104*109 CFU/ml), ii) accelerates corneal epithelial repair following infection with P. aeruginosa (9% vs. 24% closure of the wounded area after 12 h of infection), and iii) downregulates the lipopolysaccharide-induced expression of IL-6, TNF-α and Lipocalin 2 in HCECs. A combination of MSC-CM with an antibiotic, Ciprofloxacin moderately regulated the expression of IL-6, TNF-α, and Lipocalin 2. CONCLUSION: MSC-CM holds promise as an adjunctive therapeutic approach for P. aeruginosa-induced corneal epithelial damage.

Characterization of a new Pseudomonas aeruginosa Queuovirinae bacteriophage.

The ESKAPEE pathogen Pseudomonas aeruginosa is a common cause of chronic wound and cystic fibrosis lung infections, as well as acute burn and nosocomial infections. Many of these infections are recalcitrant to conventional antibiotic therapies due to both traditional antibiotic resistance mechanisms and antimicrobial tolerance. Recent successes with bacteriophage (phage) therapy to treat chronic human P. aeruginosa infections have led to a renewed interest in isolating and characterizing new P. aeruginosa phages. Here, we isolated and characterized a new lytic phage (termed PIP, pili-infecting phage) capable of infecting P. aeruginosa PA14. PIP is a tailed phage with an icosahedral head and flexible tail containing a genome that is 57,462 bp in length. Phylogenetic analysis reveals that PIP belongs to the subfamily Queuovirinae and genus Nipunavirus but is highly divergent in gene content from known Nipunaviruses. By isolating and characterizing a P. aeruginosa strain that spontaneously evolved resistance to PIP, we show that the receptor for PIP is Type IV pili. In summary, we isolated a new P. aeruginosa phage species with a unique genome, thus increasing the diversity of phages known to infect this important human pathogen.IMPORTANCEThe opportunistic pathogen Pseudomonas aeruginosa causes both acute and chronic human infections. These infections are notoriously difficult to treat due to both antibiotic resistance and antibiotic tolerance. The increasing frequency of antibiotic failure in P. aeruginosa infections has led scientists to explore other treatment options, including bacteriophage (phage) therapy. To this end, there has been a significant effort to identify new Pseudomonas phages. Here, we isolated and characterized a bacteriophage (termed PIP, pili-infecting phage) that infects P. aeruginosa PA14. Examination of the PIP genome revealed that this phage represents a new species in the subclass Queuovirinae. The isolation and characterization of spontaneous PA14 mutants that are resistant to PIP infection revealed Type IV pili as the PIP receptor. Ultimately, this study characterizes a new species of Pseudomonas phage, thus enhancing the known diversity of phages that infect this important pathogen.

Bacteriophages for bronchiectasis: treatment of the future?

PURPOSE OF REVIEW: Bronchiectasis is a chronic respiratory disease characterized by dilated airways, persistent sputum production and recurrent infective exacerbations. The microbiology of bronchiectasis includes various potentially pathogenic microorganisms including Pseudomonas aeruginosa which is commonly cultured from patients' sputum. P. aeruginosa is difficult to eradicate and frequently exhibits antimicrobial resistance. Bacteriophage therapy offers a novel and alternative method to treating bronchiectasis and can be used in conjunction with antibiotics to improve patient outcome. RECENT FINDINGS: Thirteen case reports/series to date have successfully used phages to treat infections in bronchiectasis patients, however these studies were constrained to few patients ( n  = 32) and utilized personalized phage preparations and adjunct antibiotics. In these studies, phage therapy was delivered by inhalation, intravenously or orally and was well tolerated in most patients without any unfavourable effects. Favourable clinical or microbiological outcomes were seen following phage therapy in many patients. Longitudinal patient follow-up reported regrowth of bacteria and phage neutralization in some studies. There are five randomized clinical controlled trials ongoing aiming to use phage therapy to treat P. aeruginosa associated respiratory conditions, with limited results available to date. SUMMARY: More research, particularly robust clinical trials, into how phages can clear respiratory infections, interact with resident microbiota, and how bacteria might develop resistance will be important to establish to ensure the success of this promising therapeutic alternative.

Studying Bacteriophage Efficacy Using a Zebrafish Model.

The rise of bacteria resistant to the antibiotics currently in use (multiple drug-resistant, MDR) is a serious problem for patients affected by infections. This situation is even more worrying in the case of chronic bacterial infections, such as those caused by Pseudomonas aeruginosa (Pa), in patients with cystic fibrosis (CF). As an alternative to antibiotic treatments, the use of bacteriophages (phages) to fight bacterial infections has gained increasing interest in the last few years. Phages are viruses that specifically infect and multiply within the bacteria without infecting eukaryotic cells. It is well assumed that phage therapy has a high bacterial specificity, which, unlike antibiotics, should limit the damage to the endogenous microbiome. In addition, phages can kill antibiotic-resistant bacteria and perform self-amplification at the site of the infection.The protocol detailed in this chapter describes how the antimicrobial effect of phages can be studied in vivo in the zebrafish (Danio rerio) model infected with Pa. The same procedure can be applied to test the effectiveness of several different phages killing other bacterial species and for the rapid preclinical testing of phages to be used as personalized medicine.

Identification and impact on Pseudomonas aeruginosa virulence of mutations conferring resistance to a phage cocktail for phage therapy.

IMPORTANCE: In this work, we identified the putative receptors of 16 Pseudomonas phages and evaluated how resistance to phages recognizing different bacterial receptors may affect the virulence. Our findings are relevant for the implementation of phage therapy of Pseudomonas aeruginosa infections, which are difficult to treat with antibiotics. Overall, our results highlight the need to modify natural phages to enlarge the repertoire of receptors exploited by therapeutic phages and suggest that phages using the PAO1-type T4P as receptor may have limited value for the therapy of the cystic fibrosis infection.

[Improving the management of chronic Pseudomonas aeruginosa infection in lower respiratory tract].

Pseudomonas aeruginosa is one of the most important pathogens causing chronic lower respiratory tract infections in patients with chronic lung diseases such as cystic fibrosis, bronchiectasis and chronic obstructive pulmonary disease. The poor prognosis of these diseases has been found to be associated with chronic Pseudomonas aeruginosa infection in lower respiratory tract, which can be a consequence or a cause of the disease progression depending on different circumstances. Optimizing the management of chronic Pseudomonas aeruginosa infection is of great significance to improve the prognosis of these chronic lung diseases. Unlike the therapy of acute pneumonia due to Pseudomonas aeruginosa, the goals of the management for chronic Pseudomonas aeruginosa infection are not only to control infection, but also to reduce symptoms, prevent exacerbations, stop the disease progression and improve the quality of life. In addition to systemic anti-pseudomonas therapy during exacerbations, long-term multiple measures including anti-inflammatory therapy, immunomodulatory therapy,airway clearance techniques, mucoactive therapy, etc. should also be given to the patients with chronic lower respiratory tract infection due to Pseudomonas aeruginosa.

Membrane lipid renovation in Pseudomonas aeruginosa - implications for phage therapy?

Pseudomonas aeruginosa is an important Gram-negative pathogen with intrinsic resistance to many clinically used antibiotics. It is particularly troublesome in nosocomial infections, immunocompromised patients, and individuals with cystic fibrosis. Antimicrobial resistance (AMR) is a huge threat to global health, with a predicted 10 million people dying from resistant infections by 2050. A promising therapy for combatting AMR infections is phage therapy. However, more research is required to investigate mechanisms that may influence the efficacy of phage therapy. An important overlooked aspect is the impact of membrane lipid remodelling on phage binding ability. P. aeruginosa undergoes changes in membrane lipids when it encounters phosphorus stress, an environmental perturbation that is likely to occur during infection. Lipid changes include the substitution of glycerophospholipids with surrogate glycolipids and the over-production of ornithine-containing aminolipids. Given that membrane lipids are known to influence the structure and function of membrane proteins, we propose that changes in the composition of membrane lipids during infection may alter phage binding and subsequent phage infection dynamics. Consideration of such effects needs to be urgently prioritised in order to develop the most effective phage therapy strategies for P. aeruginosa infections.

IL-6-elafin genetically modified macrophages as a lung immunotherapeutic strategy against Pseudomonas aeruginosa infections.

Pseudomonas aeruginosa (P.a) infections are a major public health issue in ventilator-associated pneumoniae, cystic fibrosis, and chronic obstructive pulmonary disease exacerbations. P.a is multidrug resistant, and there is an urgent need to develop new therapeutic approaches. Here, we evaluated the effect of direct pulmonary transplantation of gene-modified (elafin and interleukin [IL]-6) syngeneic macrophages in a mouse model of acute P.a infection. Wild-type (WT) or Elafin-transgenic (eTg) alveolar macrophages (AMs) or bone marrow-derived macrophages (BMDMs) were recovered from bronchoalveolar lavage or generated from WT or eTg mouse bone marrow. Cells were modified with adenovirus IL-6 (Ad-IL-6), characterized in vitro, and transferred by oropharyngeal instillation in the lungs of naive mice. The protective effect was assessed during P.a acute infection (survival studies, mechanistic studies of the inflammatory response). We show that a single bolus of genetically modified syngeneic AMs or BMDMs provided protection in our P.a-induced model. Mechanistically, Elafin-modified AMs had an IL-6-IL-10-IL-4R-IL-22-antimicrobial molecular signature that, in synergy with IL-6, enhanced epithelial cell proliferation and tissue repair in the alveolar unit. We believe that this innovative cell therapy strategy could be of value in acute bacterial infections in the lung.

Risk factors for Pseudomonas aeruginosa colonization in non-cystic fibrosis bronchiectasis and clinical implications.

BACKGROUND: Pseudomonas aeruginosa is one of the commonest bacteria colonizing the airway in patients with non-cystic fibrosis bronchiectasis. Pseudomonas aeruginosa colonization is associated with poor outcomes in patients with bronchiectasis, including rapid decline in lung function, exacerbation frequency and hospitalization. METHODS: A cross-sectional study in Queen Mary Hospital, Hong Kong that included 350 Chinese patients with non-cystic fibrosis bronchiectasis to investigate the risk factors for Pseudomonas aeruginosa colonization and clinical implications on disease outcomes. DISCUSSIONS: Pseudomonas aeruginosa colonization was more commonly found in patients with longer duration of bronchiectasis and those on proton pump inhibitors (PPIs) with adjusted ORs of 1.066 (95% CI = 1.036-1.096, p < 0.001) and 2.815 (95% CI = 1.307-6.064, p = 0.008) respectively. Patients with Pseudomonas aeruginosa colonization have more extensive lung involvement and higher risks of exacerbation requiring hospitalization with adjusted ORs of 2.445 (95% CI = 1.283-4.657, p = 0.007) and 2.745 (95% CI = 1.012-7.449, p = 0.047) respectively. Pseudomonas aeruginosa colonization is more common among patients with longer duration of bronchiectasis and those on PPI. Pseudomonas aeruginosa colonization is associated with more extensive lung involvement and higher risks of exacerbation requiring hospitalization.

Immune Responses to Pseudomonas aeruginosa Biofilm Infections.

Pseudomonas aeruginosa is a key pathogen of chronic infections in the lungs of cystic fibrosis patients and in patients suffering from chronic wounds of diverse etiology. In these infections the bacteria congregate in biofilms and cannot be eradicated by standard antibiotic treatment or host immune responses. The persistent biofilms induce a hyper inflammatory state that results in collateral damage of the adjacent host tissue. The host fails to eradicate the biofilm infection, resulting in hindered remodeling and healing. In the present review we describe our current understanding of innate and adaptive immune responses elicited by P. aeruginosa biofilms in cystic fibrosis lung infections and chronic wounds. This includes the mechanisms that are involved in the activation of the immune responses, as well as the effector functions, the antimicrobial components and the associated tissue destruction. The mechanisms by which the biofilms evade immune responses, and potential treatment targets of the immune response are also discussed.

Impact of positive biphasic pressure during low and high inspiratory efforts in Pseudomonas aeruginosa-induced pneumonia.

BACKGROUND: During pneumonia, normal alveolar areas coexist adjacently with consolidated areas, and high inspiratory efforts may predispose to lung damage. To date, no study has evaluated different degrees of effort during Biphasic positive airway pressure (BIVENT) on lung and diaphragm damage in experimental pneumonia, though largely used in clinical setting. We aimed to evaluate lung damage, genes associated with ventilator-induced lung injury (VILI) and diaphragmatic injury, and blood bacteria in pressure-support ventilation (PSV), BIVENT with low and high inspiratory efforts in experimental pneumonia. MATERIAL AND METHODS: Twenty-eight male Wistar rats (mean ± SD weight, 333±78g) were submitted Pseudomonas aeruginosa-induced pneumonia. After 24-h, animals were ventilated for 1h in: 1) PSV; 2) BIVENT with low (BIVENTLow-Effort); and 3) BIVENT with high inspiratory effort (BIVENTHigh-Effort). BIVENT was set at Phigh to achieve VT = 6 ml/kg and Plow at 5 cmH2O (n = 7/group). High- and low-effort conditions were obtained through anaesthetic infusion modulation based on neuromuscular drive (P0.1). Lung mechanics, histological damage score, blood bacteria, and expression of genes related to VILI in lung tissue, and inflammation in diaphragm tissue. RESULTS: Transpulmonary peak pressure and histological damage score were higher in BIVENTHigh-Effort compared to BIVENTLow-Effort and PSV [16.1 ± 1.9cmH2O vs 12.8 ± 1.5cmH2O and 12.5 ± 1.6cmH2O, p = 0.015, and p = 0.010; median (interquartile range) 11 (9-13) vs 7 (6-9) and 7 (6-9), p = 0.021, and p = 0.029, respectively]. BIVENTHigh-Effort increased interleukin-6 expression compared to BIVENTLow-Effort (p = 0.035) as well as expressions of cytokine-induced neutrophil chemoattractant-1, amphiregulin, and type III procollagen compared to PSV (p = 0.001, p = 0.001, p = 0.004, respectively). Tumour necrosis factor-α expression in diaphragm tissue and blood bacteria were higher in BIVENTHigh-Effort than BIVENTLow-Effort (p = 0.002, p = 0.009, respectively). CONCLUSION: BIVENT requires careful control of inspiratory effort to avoid lung and diaphragm damage, as well as blood bacteria. P0.1 might be considered a helpful parameter to optimize inspiratory effort.

Bacteriophage therapy for infections in CF.

Pseudomonas aeruginosa and Staphylococcus aureus are bacterial pathogens frequently associated with pulmonary complications and disease progression in cystic fibrosis (CF). However, these bacteria increasingly show resistance to antibiotics, necessitating novel management strategies. One possibility is bacteriophage (phages; bacteria-specific viruses) therapy, where lytic phages are administered to kill target bacterial pathogens. Recent publications of case reports of phage therapy to treat antibiotic-resistant lung infections in CF have garnered significant attention. These cases exemplify the renewed interest in phage therapy, an older concept that is being newly updated to include rigorous collection and analysis of patient data to assess clinical benefit, which will inform the development of clinical trials. As outcomes of these trials become public, the results will valuable gauge the potential usefulness of phage therapy to address the rise in antibiotic-resistant bacterial infections. In addition, we highlight the further need for basic research to accurately predict the different responses of target bacterial pathogens when phages are administered alone, sequentially, or as mixtures (cocktails), and whether within-cocktail interactions among phages hold consequences for the efficacy of phage therapy in patient treatment.

Rescue from Pseudomonas aeruginosa Airway Infection via Stem Cell Transplantation.

Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which lead to impaired ion transport in epithelial cells. Although lung failure due to chronic infection is the major comorbidity in individuals with cystic fibrosis, the role of CFTR in non-epithelial cells has not been definitively resolved. Given the important role of host defense cells, we evaluated the Cftr deficiency in pulmonary immune cells by hematopoietic stem cell transplantation in cystic fibrosis mice. We transplanted healthy bone marrow stem cells and could reveal a stable chimerism of wild-type cells in peripheral blood. The outcome of stem cell transplantation and the impact of healthy immune cells were evaluated in acute Pseudomonas aeruginosa airway infection. In this study, mice transplanted with wild-type cells displayed better survival, lower lung bacterial numbers, and a milder disease course. This improved physiology of infected mice correlated with successful intrapulmonary engraftment of graft-derived alveolar macrophages, as seen by immunofluorescence microscopy and flow cytometry of graft-specific leucocyte surface marker CD45 and macrophage marker CD68. Given the beneficial effect of hematopoietic stem cell transplantation and stable engraftment of monocyte-derived CD68-positive macrophages, we conclude that replacement of mutant Cftr macrophages attenuates airway infection in cystic fibrosis mice.

High-Voltage, Pulsed Electric Fields Eliminate Pseudomonas aeruginosa Stable Infection in a Mouse Burn Model.

Objective: The incidence of severe infectious complications after burn injury increases mortality by 40%. However, traditional approaches for managing burn infections are not always effective. High-voltage, pulsed electric field (PEF) treatment shortly after a burn injury has demonstrated an antimicrobial effect in vivo; however, the working parameters and long-term effects of PEF treatment have not yet been investigated. Approach: Nine sets of PEF parameters were investigated to optimize the applied voltage, pulse duration, and frequency or pulse repetition for disinfection of Pseudomonas aeruginosa infection in a stable mouse burn wound model. The bacterial load after PEF administration was monitored for 3 days through bioluminescence imaging. Histological assessments and inflammation response analyses were performed at 1 and 24 h after the therapy. Results: Among all tested PEF parameters, the best disinfection efficacy of P. aeruginosa infection was achieved with a combination of 500 V, 100 µs, and 200 pulses delivered at 3 Hz through two plate electrodes positioned 1 mm apart for up to 3 days after the injury. Histological examinations revealed fewer inflammatory signs in PEF-treated wounds compared with untreated infected burns. Moreover, the expression levels of multiple inflammatory-related cytokines (interleukin [IL]-1α/ß, IL-6, IL-10, leukemia inhibitory factor [LIF], and tumor necrosis factor-alpha [TNF-α]), chemokines (macrophage inflammatory protein [MIP]-1α/ß and monocyte chemoattractant protein-1 [MCP-1]), and inflammation-related factors (vascular endothelial growth factor [VEGF], macrophage colony-stimulating factor [M-CSF], and granulocyte-macrophage colony-stimulating factor [G-CSF]) were significantly decreased in the infected burn wound after PEF treatment. Innovation: We showed that PEF treatment on infected wounds reduces the P. aeruginosa load and modulates inflammatory responses. Conclusion: The data presented in this study suggest that PEF treatment is a potent candidate for antimicrobial therapy for P. aeruginosa burn infections.

NK cell-derived exosomes improved lung injury in mouse model of Pseudomonas aeruginosa lung infection.

BACKGROUND: Pseudomonas aeruginosa (PA) is one of the most common bacteria that causes lung infection in hospital. The aim of our study is to explore the role and action mechanism of NK cells in lung PA infection. METHODS: In this present study, 2.5 × 108 CFU/mouse PA was injected into murine trachea to make lung PA infection mouse model. Anti-asialo GM1 was used to inhibit NK cell. The percentage of NK cells was ensured by flow cytometry, and the M1- and M2-polarized macrophages were determined by flow cytometry, qRT-PCR, and ELISA assay. Besides, H&E staining was performed to ensure the pathological changes in lung tissues. Transmission electron microscopy and western blot were carried out to identify the exosome. RESULTS: Here, in the mouse model of PA lung infection, NK cell depletion caused M2 polarization of lung macrophage, and exacerbated PA-induced lung injury. Next, our data shown that M2 macrophage polarization was enhanced when the generation of NK cell-derived exosome was blocked in the co-culture system of NK cells and macrophages. Subsequently, we demonstrated that NK cells promoted M1 macrophage polarization both in PA-infected macrophage and the mouse model of PA lung infection, and attenuated lung injury through exosome. CONCLUSION: Overall, our data proved that NK cell may improve PA-induced lung injury through promoting M1 lung macrophage polarization by secreting exosome. Our results provide a new idea for the treatment of PA lung infection.

Assessment of Silver Levels in a Closed-Incision Negative Pressure Therapy Dressing: In Vitro and In Vivo Study.

Objective: In recent years, reticulated open-cell foam-based closed-incision negative pressure therapy (ROCF-ciNPT) has shown effectiveness in management of various postoperative incisions. These dressings consist of a skin interface layer that absorbs fluid from the skin surface and reduces the potential for microbial colonization within the dressing by means of ionic silver. This study examines the ability of silver to reduce the bioburden within the dressing as well as the localized effect due to potential silver mobility. Approach: Ability of silver to reduce bioburden within the ROCF-ciNPT dressing was assessed using Staphylococcus aureus, Pseudomonas aeruginosa, and Candida spp. Furthermore, silver mobility was assessed using an in vitro skin model to study the zone of inhibition along with released silver quantification. Using a porcine model, diffusion of silver into blood and tissue was studied using emission spectrometry and histology. Results: Microbial growth in the ROCF-ciNPT dressing was significantly reduced (∼2.7-4.9 log reduction) compared to a silver-free negative control. No zone of inhibition was observed for microbial colonies for up to 7 days with minimal localized silver release (<5.5 ppm release). In vivo studies demonstrated no measurable concentration (<0.2 µg/g) of silver in the blood, urine, feces, kidney, and liver tissue biopsy. Innovation: This study provides an important insight into silver concentration and mobility within the ROCF-ciNPT dressing, given emerging concerns associated with potential silver cytotoxicity. Conclusion: These results indicate the concentration of silver (0.019% silver by weight) in the ROCF-ciNPT dressings has been adequate to reduce bioburden within the skin interface layer, while severely limiting the amount of silver leaching out.