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Wound infections are the main cause of sepsis in patients with burns and increase burn-related morbidity and mortality. Bacteriophages, natural bacterial viruses, are being considered as an alternative therapy to treat infections caused by multidrug-resistant bacteria. We aimed to compare the efficacy and tolerability of a cocktail of lytic anti-Pseudomonas aeruginosa bacteriophages with standard of care for patients with burns. In this randomised phase 1/2 trial, patients with a confirmed burn wound infection were recruited from nine burn centres in hospitals in France and Belgium. Patients were eligible if they were aged 18 years or older and had a burn wound clinically infected with P aeruginosa. Eligible participants were randomly assigned (1:1) by use of an interactive web response system to a cocktail of 12 natural lytic anti-P aeruginosa bacteriophages (PP1131; 1 × 106 plaque-forming units [PFU] per mL) or standard of care (1% sulfadiazine silver emulsion cream), both given as a daily topical treatment for 7 days, with 14 days of follow-up. Masking of treatment from clinicians was not possible because of the appearance of the two treatments (standard of care a thick cream, PP1131 a clear liquid applied via a dressing), but assignments were masked from microbiologists who analysed the samples and patients (treatment applied while patients were under general anaesthetic). The primary endpoint was median time to sustained reduction in bacterial burden by at least two quadrants via a four-quadrant method, assessed by use of daily swabs in all participants with a microbiologically documented infection at day 0 who were given at least one sulfadiazine silver or phage dressing (modified intention-to-treat population). Safety was assessed in all participants who received at least one dressing according to protocol. Ancillary studies were done in the per-protocol population (all PP1131 participants who completed 7 days of treatment) to assess the reasons for success or failure of phage therapy. This trial is registered with the European Clinical Trials database, number 2014-000714-65, and ClinicalTrials.gov, number NCT02116010, and is now closed. Between July 22, 2015, and Jan 2, 2017, across two recruitment periods spanning 13 months, 27 patients were recruited and randomly assigned to receive phage therapy (n=13) or standard of care (n=14). One patient in the standard of care group was not exposed to treatment, giving a safety population of 26 patients (PP1131 n=13, standard of care n=13), and one patient in the PP1131 group did not have an infection at day 0, giving an efficacy population of 25 patients (PP1131 n=12, standard of care n=13). The trial was stopped on Jan 2, 2017, because of the insufficient efficacy of PP1131. The primary endpoint was reached in a median of 144 h (95% CI 48–not reached) in the PP1131 group versus a median of 47 h (23–122) in the standard of care group (hazard ratio 0·29, 95% CI 0·10–0·79; p=0·018). In the PP1131 group, six (50%) of 12 analysable participants had a maximal bacterial burden versus two (15%) of 13 in the standard of care group. PP1131 titre decreased after manufacturing and participants were given a lower concentration of phages than expected (1 × 102 PFU/mL per daily dose). In the PP1131 group, three (23%) of 13 analysable participants had adverse events versus seven (54%) of 13 in the standard of care group. One participant in each group died after follow-up and the deaths were determined to not be related to treatment. The ancillary study showed that the bacteria isolated from patients with failed PP1131 treatment were resistant to low phage doses. At very low concentrations, PP1131 decreased bacterial burden in burn wounds at a slower pace than standard of care. Further studies using increased phage concentrations and phagograms in a larger sample of participants are warranted. European Commission: Framework Programme 7.

Despite aggressive antibiotic therapy, bronchopulmonary colonization by Pseudomonas aeruginosa causes persistent morbidity and mortality in cystic fibrosis (CF). Chronic P. aeruginosa infection in the CF lung is associated with structured, antibiotic-tolerant bacterial aggregates known as biofilms. We have demonstrated the effects of non-bactericidal, low-dose nitric oxide (NO), a signaling molecule that induces biofilm dispersal, as a novel adjunctive therapy for P. aeruginosa biofilm infection in CF in an ex vivo model and a proof-of-concept double-blind clinical trial. Submicromolar NO concentrations alone caused disruption of biofilms within ex vivo CF sputum and a statistically significant decrease in ex vivo biofilm tolerance to tobramycin and tobramycin combined with ceftazidime. In the 12-patient randomized clinical trial, 10 ppm NO inhalation caused significant reduction in P. aeruginosa biofilm aggregates compared with placebo across 7 days of treatment. Our results suggest a benefit of using low-dose NO as adjunctive therapy to enhance the efficacy of antibiotics used to treat acute P. aeruginosa exacerbations in CF. Strategies to induce the disruption of biofilms have the potential to overcome biofilm-associated antibiotic tolerance in CF and other biofilm-related diseases. This paper reports the first example of targeted anti-biofilm therapy in human disease. We have demonstrated that using low-dose nitric oxide as a non-bactericidal signaling molecule to induce biofilm dispersal may be useful as a novel adjunctive therapy to treat chronic pseudomonal biofilm infection in cystic fibrosis.

Abstract Rationale To identify pathogens that require different treatments in community-acquired pneumonia (CAP), we propose an acronym, “PES” (P  seudomonas aeruginosa, E  nterobacteriaceae extended-spectrum β-lactamase–positive, and methicillin-resistant S  taphylococcus aureus). Objectives To compare the clinical characteristics and outcomes between patients with CAP caused by PES versus other pathogens, and to identify the risk factors associated with infection caused by PES. Methods We conducted an observational prospective study evaluating only immunocompetent patients with CAP and an established etiological diagnosis. We included patients from nursing homes. We computed a score to identify patients at risk of PES pathogens. Measurement and Main Results: Of the 4,549 patients evaluated, we analyzed 1,597 who presented an etiological diagnosis. Pneumonia caused by PES was identified in 94 (6%) patients, with 108 PES pathogens isolated (n = 72 P. aeruginosa, n = 15 E  nterobacteriaceae extended-spectrum β-lactamase positive, and n = 21 methicillin-resistant S  taphylococcus aureus). These patients were older (P = 0.001), had received prior antibiotic treatment more frequently (P < 0.001), and frequently presented with acute renal failure (P = 0.004). PES pathogens were independently associated with increased risk of 30-day mortality (adjusted odds ratio = 2.51; 95% confidence interval = 1.20–5.25; P = 0.015). The area under the curve for the score we computed was 0.759 (95% confidence interval, 0.713–0.806; P < 0.001). Conclusions PES pathogens are responsible for a small proportion of CAP, resulting in high mortality. These pathogens require a different antibiotic treatment, and identification of specific risk factors could help to identify these microbial etiologies.

Cystic fibrosis is a monogenetic disease complicated by recurrent bacterial lung infections that require chronic antibiotics. Pseudomonas aeruginosa is an increasingly antibiotic-resistant pathogen associated with cystic fibrosis morbidity and mortality. Here, we describe the development of a three-phage cocktail (BX004-A) designed to target a wide range of P. aeruginosa strains. We evaluated BX004-A in Part 1 of a first-in-human double-blind placebo-controlled phase 1b/2a clinical trial, which included nine adult cystic fibrosis patients chronically infected with P. aeruginosa (NCT05010577). BX004-A met the primary endpoints of safety and tolerability. Exploratory endpoints included pharmacokinetics and Pseudomonas aeruginosa sputum density reduction. Efficient phage delivery to the lower respiratory tract was observed, and a potential reduction in P. aeruginosa sputum burden was noted in the phage arm. However, due to the study’s small sample size, definitive conclusions regarding efficacy are limited. These data pave the way toward further development of novel phage-based therapeutics in antibiotic-resistant pulmonary bacterial infections. In a randomized, placebo-controlled trial, an inhaled phage cocktail was well tolerated in adults with cystic fibrosis and chronic Pseudomonas aeruginosa infection, with evidence of lung delivery and signs of bacterial reduction.

Background The delivery of antipseudomonal antibiotics by inhalation to Pseudomonas aeruginosa-infected subjects with non-cystic fibrosis (CF) bronchiectasis is a logical extension of treatment strategies successfully developed in CF bronchiectasis. Dual release ciprofloxacin for inhalation (DRCFI) contains liposomal ciprofloxacin, formulated to optimise airway antibiotic delivery. Methods Phase II, 24-week Australian/New Zealand multicentre, randomised, double-blind, placebo-controlled trial in 42 adult bronchiectasis subjects with ≥2 pulmonary exacerbations in the prior 12 months and ciprofloxacin-sensitive P aeruginosa at screening. Subjects received DRCFI or placebo in three treatment cycles of 28 days on/28 days off. The primary outcome was change in sputum P aeruginosa bacterial density to the end of treatment cycle 1 (day 28), analysed by modified intention to treat (mITT). Key secondary outcomes included safety and time to first pulmonary exacerbation—after reaching the pulmonary exacerbation endpoint subjects discontinued study drug although remained in the study. Results DRCFI resulted in a mean (SD) 4.2 (3.7) log10 CFU/g reduction in P aeruginosa bacterial density at day 28 (vs −0.08 (3.8) with placebo, p=0.002). DRCFI treatment delayed time to first pulmonary exacerbation (median 134 vs 58 days, p=0.057 mITT, p=0.046 per protocol). DRCFI was well tolerated with a similar incidence of systemic adverse events to the placebo group, but fewer pulmonary adverse events. Conclusions Once-daily inhaled DRCFI demonstrated potent antipseudomonal microbiological efficacy in adults with non-CF bronchiectasis and ciprofloxacin-sensitive P aeruginosa. In this modest-sized phase II study, DRCFI was also well tolerated and delayed time to first pulmonary exacerbation in the per protocol population.

Background The effect of dual systemic antibiotic therapy against Pseudomonas aeruginosa in patients with pre-existing lung disease is unknown. To assess whether dual systemic antibiotics against P. aeruginosa in outpatients with COPD, non-cystic fibrosis (non-CF) bronchiectasis, or asthma can improve outcomes. Methods Multicenter, randomised, open-label trial conducted at seven respiratory outpatient clinics in Denmark. Outpatients with COPD, non-CF bronchiectasis, or asthma with a current P. aeruginosa -positive lower respiratory tract culture (clinical routine samples obtained based on symptoms of exacerbation not requiring hospitalisation), regardless of prior P. aeruginosa- status, no current need for hospitalisation, and at least two moderate or one hospitalisation-requiring exacerbation within the last year were eligible. Patients were assigned 1:1 to 14 days of dual systemic anti-pseudomonal antibiotics or no antibiotic treatment. Primary outcome was time to prednisolone or antibiotic-requiring exacerbation or death from day 20 to day 365. Results The trial was stopped prematurely based in lack of recruitment during the COVID-19 pandemic, this decision was endorsed by the Data and Safety Monitoring Board. Forty-nine outpatients were included in the study. There was a reduction in risk of the primary outcome in the antibiotic group compared to the control group (HR 0.51 (95%CI 0.27–0.96), p  = 0.037). The incidence of admissions with exacerbation within one year was 1.1 (95%CI 0.6–1.7) in the dual antibiotic group vs. 2.9 (95%CI 1.3–4.5) in the control group, p  = 0.037. Conclusions Use of dual systemic antibiotics for 14 days against P. aeruginosa in outpatients with chronic lung diseases and no judged need for hospitalisation, improved clinical outcomes markedly. The main limitation was the premature closure of the trial. Trial Registration ClinicalTrials.gov, NCT03262142, registration date 2017–08-25.

With the rising development of bacterial resistance the search for new medical treatments beyond conventional antimicrobials has become a key aim of public health research. Possible innovative strategies include the inhibition of bacterial virulence. However, consideration must be given to the evolutionary and environmental consequences of such new interventions. Virulence and cooperative social behaviour of the bacterium Pseudomonas aeruginosa rely on the quorum-sensing (QS) controlled production of extracellular products (public goods). Hence QS is an attractive target for anti-virulence interventions. During colonization, non-cooperating (and hence less virulent) P. aeruginosa QS-mutants, benefiting from public goods provided by wild type isolates, naturally increase in frequency providing a relative protection from invasive infection. We hypothesized that inhibition of QS-mediated gene expression removes this growth advantage and selection of less virulent QS-mutants, and maintains the predominance of more virulent QS-wild type bacteria. We addressed this possibility in a placebo-controlled trial investigating the anti-QS properties of azithromycin, a macrolide antibiotic devoid of bactericidal activity on P. aeruginosa, but interfering with QS, in intubated patients colonized by P. aeruginosa. In the absence of azithromycin, non-cooperating (and hence less virulent) lasR (QS)-mutants increased in frequency over time. Azithromycin significantly reduced QS-gene expression measured directly in tracheal aspirates. Concomitantly the advantage of lasR-mutants was lost and virulent wild-type isolates predominated during azithromycin treatment. We confirmed these results in vitro with fitness and invasion experiments. Azithromycin reduced growth rate of the wild-type, but not of the lasR-mutant. Furthermore, the lasR-mutant efficiently invaded wild-type populations in the absence, but not in the presence of azithromycin. These in vivo and in vitro results demonstrate that anti-virulence interventions based on QS-blockade diminish natural selection towards reduced virulence and therefore may increase the prevalence of more virulent genotypes in the Hospital environment. More generally, the impact of intervention on the evolution of virulence of pathogenic bacteria should be assessed.

Background. A predominantly T-helper type 2 (Th2) immune response is critical in the prognosis of pulmonary Pseudomonas aeruginosa infection. But the mucosal and systemic immune responses can be influenced by the intestinal microbiota. Methods. We assessed the effect of microbiota compositional changes induced by a diet enriched in 5% acidic oligosaccharides derived from pectin (pAOS) on the immune response and outcome of chronic pulmonary P. aeruginosa infection in mice. Results. pAOS promoted Th1 polarization by increasing interferon γ release, upregulating t-bet gene expression, decreasing interleukin 4 secretion, and downregulating gata3 gene expression. pAOS also sustained the release of keratinocyte chemoattractant, recruited polynuclear leukocytes and macrophages, stimulated M1 macrophage activation and interleukin 10 release, and decreased tumor necrosis factor α release in the lung. These effects led to increased bacterial clearance after the first and second P. aeruginosa infections. pAOS modified the intestinal microbiota by stimulating the growth of species involved in immunity development, such as Bifidobacterium species, Sutturella wadsworthia, and Clostridium cluster XIVa organisms, and at the same time increased the production of butyrate and propionate. Conclusion. These results suggest that pAOS may have beneficial effects by limiting the number and severity of pulmonary exacerbations in patients chronically infected with P. aeruginosa, such as individuals with cystic fibrosis.

Purpose Anti-virulence strategies have not been evaluated for the prevention of bacterial infections. Prolonged colonization of intubated patients with Pseudomonas aeruginosa isolates producing high-levels of the quorum sensing (QS)-regulated virulence factor rhamnolipids has been associated with ventilator-associated pneumonia (VAP). In this pathogen, azithromycin reduces QS-regulated virulence. We aimed to assess whether azithromycin could prevent VAP in patients colonized by rhamnolipids producing isolates. Methods In a randomized, double-blind, multicenter trial, intubated colonized patients received either 300 mg/day azithromycin or placebo. Primary endpoint was the occurrence of P. aeruginosa VAP. We further identified those patients persistently colonized by isolates producing high-levels of rhamnolipids and therefore at the highest risk to develop VAP linked to this QS-dependent virulence factor. Results Ninety-two patients were enrolled; 43 azithromycin-treated and 42 placebo patients were eligible for the per-protocol analysis. In the per-protocol population, the occurrence of P. aeruginosa VAP was reduced in the azithromycin group but without reaching statistical significance (4.7 vs. 14.3 % VAP, p  = 0.156). QS-dependent virulence of colonizing isolates was similarly low in both study groups, and only five patients in each arm were persistently colonized by high-level rhamnolipids producing isolates. In this high-risk subgroup, the incidence of VAP was reduced fivefold in azithromycin versus placebo patients (1/5 vs. 5/5 VAP, p  = 0.048). Conclusions There was a trend towards reduced incidence of VAP in colonized azithromycin-treated patients . In addition, azithromycin significantly prevented VAP in those patients at high risk of rhamnolipid-dependent VAP, suggesting that virulence inhibition is a promising anti-microbial strategy.

The objective of this study is to evaluate the antimicrobial activity and healing-promoting effect of topical photodynamic therapy (ALA-PDT) on chronic skin ulcers infected with Pseudomonas aeruginosa (PA). A total of 26 patients with chronic skin ulcers in lower limbs infected with PA were enrolled. The surface areas of the ulcers were treated with either δ-aminolevulinic acid (ALA)-mediated PDT (20 % ALA solution, 1.5 h incubation, 630 nm red light, 80 J/cm 2 ) or red light alone, both once a week for two weeks. Before treatment, the wound areas and the bacteria levels in these two groups were comparable ( p  > 0.05). Results indicated that the bacteria levels in the skin ulcers of the light only group of 24 h post-treatment (3.4 × 10 7  ± 7.1 × 10 7  CFU/cm 2 ) and pre-treatment (5.5 × 10 7  ± 1.6 × 10 8  CFU/cm 2 ) were not significantly different. In contrast, the bacteria levels on the surfaces of the ulcers in the PDT group of 24 h post-treatment (6.3 × 10 5  ± 1.7 × 10 6  CFU/cm 2 ) and pre-treatment (8.9 × 10 7  ± 1.7 × 10 8  CFU/cm 2 ) were significantly different ( p  < 0.01). At seven days post treatment, the mean ulcer area in the red light group was reduced from 11.85 ± 6.83 to 7.8 ± 4.9 cm 2 ( p  < 0.01), that of PDT group from 12.72 ± 8.58 to 3.4 ± 3.4 cm 2 ( p  < 0.01). Better healing was seen in PDT group ( p  < 0.01). In conclusion, ALA-PDT is a potential modality to control PA infection and promote healing of chronic skin ulcers in lower limbs.