The effects of different doses of inhaled bacteriophage therapy for Pseudomonas aeruginosa pulmonary infections in mice

CTC-177, a novel drug-Fc conjugate, shows promise as an immunoprophylactic agent against multidrug-resistant Gram-negative bacterial infections

Background

The widespread emergence of antibiotic resistance including MDR in Gram-negative bacterial pathogens poses a critical challenge to the current antimicrobial armamentarium.

Objectives

To create a novel drug-Fc conjugate (DFC) that can be delivered at sustained and prolonged levels while simultaneously activating the host immune response to combat MDR Gram-negative infections.

Methods

The Cloudbreak™ platform was used to develop DFCs consisting of a targeting moiety (TM) (a polymyxin-derived dimer) attached via a non-cleavable linker to an effector moiety (EM) (the Fc domain of human IgG1). In vitro activities of the DFCs were assessed by MIC testing. Neutropenic mouse models of thigh infection, septicaemia and pneumonia were used to evaluate in vivo efficacy. Pharmacokinetics were evaluated in mice and cynomolgus monkeys.

Results

A single prophylactic dose of our lead DFC, CTC-177, resulted in significantly decreased bacterial burdens and reduced inflammation comparable to daily treatment with colistin in septicaemia and pneumonia mouse models. Furthermore, CTC-177 prophylaxis was able to restore colistin efficacy in colistin-resistant septicaemia, reducing bacterial burdens beyond the limit of detection. Finally, CTC-177 displayed a long terminal half-life of over 24 and 65 h in mice and cynomolgus monkeys, respectively.

Conclusions

These data support the continued development of Cloudbreak™ DFCs as broad-spectrum prophylactic agents against Gram-negative infections.

In vivo efficacy of phage cocktails against carbapenem resistance Acinetobacter baumannii in the rat pneumonia model

Acinetobacter baumannii, an opportunistic pathogen, poses a significant threat in intensive care units, leading to severe nosocomial infections. The rise of multi-drug-resistant strains, particularly carbapenem-resistant A. baumannii, has created formidable challenges for effective treatment. Given the prolonged development cycle and high costs associated with antibiotics, phages have garnered clinical attention as an alternative for combating infections caused by drug-resistant bacteria. However, the utilization of phage therapy encounters notable challenges, including the narrow host spectrum, where each phage targets a limited subset of bacteria, increasing the risk of phage resistance development. Additionally, uncertainties in immune system dynamics during treatment hinder tailoring symptomatic interventions based on patient-specific states. In this study, we isolated two A. baumannii phages from wastewater and conducted a comprehensive assessment of their potential applications. This evaluation included sequencing analysis, genome classification, pH and temperature stability assessments, and in vitro bacterial inhibition assays. Further investigations involved analyzing histological and cytokine alterations in rats undergoing phage cocktail treatment for pneumonia. The therapeutic efficacy of the phages was validated, and transcriptomic studies of rat lung tissue during phage treatment revealed crucial changes in the immune system. The findings from our study underscore the potential of phages for future development as a treatment strategy and offer compelling evidence regarding immune system dynamics throughout the treatment process.IMPORTANCEDue to the growing problem of multi-drug-resistant bacteria, the use of phages is being considered as an alternative to antibiotics, and the genetic safety and application stability of phages determine the potential of phage application. The absence of drug resistance genes and virulence genes in the phage genome can ensure the safety of phage application, and the fact that phage can remain active in a wide range of temperatures and pH is also necessary for application. In addition, the effect evaluation of preclinical studies is especially important for clinical application. By simulating the immune response situation during the treatment process through mammalian models, the changes in animal immunity can be observed, and the effect of phage therapy can be further evaluated. Our study provides compelling evidence that phages hold promise for further development as therapeutic agents for Acinetobacter baumannii infections.

Bacteriophages isolated from mouse feces attenuates pneumonia mice caused by Pseudomonas aeruginosa

BACKGROUND

Most of the current bacteriophages (phages) are mostly isolated from environments. However, phages isolated from feces might be more specific to the bacteria that are harmful to the host. Meanwhile, some phages from the environment might affect non-pathogenic bacteria for the host.

METHODS

Here, bacteriophages isolated from mouse feces were intratracheally (IT) or intravenously (IV) administered in pneumonia mice caused by Pseudomonas aeruginosa at 2 hours post-intratracheal bacterial administration. As such, the mice with phage treatment, using either IT or IV administration, demonstrated less severe pneumonia as indicated by mortality, serum cytokines, bacteremia, bacterial abundance in bronchoalveolar lavage fluid (BALF), and neutrophil extracellular traps (NETs) in lung tissue (immunofluorescence of neutrophil elastase and myeloperoxidase).

RESULTS

Interestingly, the abundance of phages in BALF from the IT and IV injections was similar, supporting a flexible route of phage administration. With the incubation of bacteria with neutrophils, the presence of bacteriophages significantly improved bactericidal activity, but not NETs formation, with the elevated supernatant IL-6 and TNF-α, but not IL-1β. In conclusion, our findings suggest that bacteriophages against Pseudomonas aeruginosa can be discovered from feces of the host.

CONCLUSIONS

The phages attenuate pneumonia partly through an enhanced neutrophil bactericidal activity, but not via inducing NETs formation. The isolation of phages from the infected hosts themselves might be practically useful for future treatment. More studies are warranted.

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.

Phage-antibiotic combinations to control Pseudomonas aeruginosa-Candida two-species biofilms

Phage-antibiotic combinations to treat bacterial infections are gaining increased attention due to the synergistic effects often observed when applying both components together. Most studies however focus on a single pathogen, although in many clinical cases multiple species are present at the site of infection. The aim of this study was to investigate the anti-biofilm activity of phage-antibiotic/antifungal combinations on single- and dual-species biofilms formed by P. aeruginosa and the fungal pathogen Candida albicans. The Pseudomonas phage Motto in combination with ciprofloxacin had significant anti-biofilm activity. We then compared biofilms formed by P. aeruginosa alone with the dual-species biofilms formed by bacteria and C. albicans. Here, we found that the phage together with the antifungal fluconazole was active against 6-h-old dual-species biofilms but showed only negligible activity against 24-h-old biofilms. This study lays the first foundation for potential therapeutic approaches to treat co-infections caused by bacteria and fungi using phage-antibiotic combinations.

Optimizing in vitro phage-ciprofloxacin combination formulation for respiratory therapy of multi-drug resistant Pseudomonas aeruginosa infections

Respiratory infection caused by multi-drug resistant (MDR) Pseudomonas aeruginosa is challenging to treat. In this study, we investigate the optimal dose of anti-pseudomonas phage PEV31 (103, 105, and 108 PFU/mL) combined with ciprofloxacin (ranging from 1/8× MIC to 8× MIC) to treat the MDR P. aeruginosa strain FADD1-PA001 using time-kill studies. We determined the impact of phage growth kinetics in the presence of ciprofloxacin through one-step growth analysis. Single treatments with either phage PEV31 or ciprofloxacin (except at 8× MIC) showed limited bactericidal efficiency, with bacterial regrowth observed at 48 h. The most effective treatments were PEV31 at multiplicity of infection (MOI) of 0.1 and 100 combined with ciprofloxacin at concentrations above 1× MIC, resulting in a >4 log10 reduction in bacterial counts. While the burst size of phage PEV31 was decreased with increasing ciprofloxacin concentration, robust antimicrobial effects were still maintained in the combination treatment. Aerosol samples collected from vibrating mesh nebulization of the combination formulation at phage MOI of 100 with 2× MIC effectively inhibited bacterial density. In summary, our combination treatments eradicated in vitro bacterial growth and sustained antimicrobial effects for 48 h. These results indicated the potential application of nebulization-based strategies for the combination treatment against MDR lung infections.

Characterization, antibacterial, and cytotoxic activities of silver nanoparticles using the whole biofilm layer as a macromolecule in biosynthesis

Recently, multi-drug resistant (MDR) bacteria are responsible for a large number of infectious diseases that can be life-threatening. Globally, new approaches are targeted to solve this essential issue. This study aims to discover novel antibiotic alternatives by using the whole components of the biofilm layer as a macromolecule to synthesize silver nanoparticles (AgNPs) as a promising agent against MDR. In particular, the biosynthesized biofilm-AgNPs were characterized using UV-Vis spectroscopy, electron microscopes, Energy Dispersive X-ray (EDX), zeta sizer and potential while their effect on bacterial strains and normal cell lines was identified. Accordingly, biofilm-AgNPs have a lavender-colored solution, spherical shape, with a size range of 20-60 nm. Notably, they have inhibitory effects when used on various bacterial strains with concentrations ranging between 12.5 and 25 µg/mL. In addition, they have an effective synergistic effect when combined with phage ZCSE9 to inhibit and kill Salmonella enterica with a concentration of 3.1 µg/mL. In conclusion, this work presents a novel biosynthesis preparation of AgNPs using biofilm for antibacterial purposes to reduce the possible toxicity by reducing the MICs using phage ZCSE9.

Characterization and genomic analysis of novel bacteriophage NK20 to revert colistin resistance and combat pandrug-resistant Klebsiella pneumoniae in a rat respiratory infection model

AIM

We investigated the therapeutic capacity of the isolated Klebsiella bacteriophage NK20 against pandrug-resistant strains. Moreover, we assessed the impact of resistance development on the overall therapeutic outcome both in vitro and in vivo.

MAIN METHODS

The pandrug-resistant K. pneumoniae Kp20 is used as a host strain for the isolation of bacteriophages using sewage samples. Spot assay was then used to compare the spectra of the isolated phages, while kinetic and genomic analysis of the phage with the broadest spectrum was assessed. Antibacterial potential of the phage was assessed using turbidimetric assay and MIC with and without colistin. Finally, the therapeutic efficacy was evaluated in vivo using a rat respiratory infection model.

KEY FINDINGS

The isolated lytic bacteriophage (NK20) showed a relatively broad spectrum and an acceptable genomic profile. In vitro antibacterial assay revealed bacterial resistance development after 12 h. Colistin inhibited bacterial regrowth and reduced pandrug-resistant strains' colistin MICs. Despite the isolation of resistant clones, intranasal administration of NK20 significantly (p < 0.05) reduced the bacterial load in both the pulmonary and blood compartments and rescued 100 % of challenged rats. Histological and immunological analysis of treated animals' lung tissue revealed less inflammation and lower TNF-α and caspase-3 expression.

SIGNIFICANCE

NK20 is a promising candidate that rescued rats from untreatable, pan-drug-resistant K. pneumoniae Kp20. Moreover, it steers the evolution of resistant mutants with higher sensitivity to colistin and less virulence, opening the door for using phages as sensitizing and anti-virulence entities rather than direct killer.

Phage therapy in a lung transplant recipient with cystic fibrosis infected with multidrug-resistant Burkholderia multivorans

BACKGROUND

There is increased interest in bacteriophage (phage) therapy to treat infections caused by antibiotic-resistant bacteria. A lung transplant recipient with cystic fibrosis and Burkholderia multivorans infection was treated with inhaled phage therapy for 7 days before she died.

METHODS

Phages were given via nebulization through the mechanical ventilation circuit. Remnant respiratory specimens and serum were collected. We quantified phage and bacterial deoxyribonucleic acid (DNA) using quantitative polymerase chain reaction, and tested phage neutralization in the presence of patient serum. We performed whole genome sequencing and antibiotic and phage susceptibility testing on 15 B. multivorans isolates. Finally, we extracted lipopolysaccharide (LPS) from two isolates and visualized their LPS using gel electrophoresis.

RESULTS

Phage therapy was temporally followed by a temporary improvement in leukocytosis and hemodynamics, followed by worsening leukocytosis on day 5, deterioration on day 7, and death on day 8. We detected phage DNA in respiratory samples after 6 days of nebulized phage therapy. Bacterial DNA in respiratory samples decreased over time, and no serum neutralization was detected. Isolates collected between 2001 and 2020 were closely related but differed in their antibiotic and phage susceptibility profiles. Early isolates were not susceptible to the phage used for therapy, while later isolates, including two isolates collected during phage therapy, were susceptible. Susceptibility to the phage used for therapy was correlated with differences in O-antigen profiles of an early versus a late isolate.

CONCLUSIONS

This case of clinical failure of nebulized phage therapy highlights the limitations, unknowns, and challenges of phage therapy for resistant infections.

To bead or not to bead: A review of Pseudomonas aeruginosa lung infection models for cystic fibrosis

Cystic fibrosis (CF) lung disease is characterised by recurring bacterial infections resulting in inflammation, lung damage and ultimately respiratory failure. Pseudomonas aeruginosa is considered one of the most important lung pathogens in those with cystic fibrosis. While multiple cystic fibrosis animal models have been developed, many fail to mirror the cystic fibrosis lung disease of humans, including the colonisation by opportunistic environmental pathogens. Delivering bacteria to the lungs of animals in different forms is a way to model cystic fibrosis bacterial lung infections and disease. This review presents an overview of previous models, and factors to consider when generating a new P. aeruginosa lung infection model. The future development and application of lung infection models that more accurately reflect human cystic fibrosis lung disease has the potential to assist in understanding the pathophysiology of cystic fibrosis lung disease and for developing treatments.

Phage therapy for pulmonary infections: lessons from clinical experiences and key considerations

Lower respiratory tract infections lead to significant morbidity and mortality. They are increasingly caused by multidrug-resistant pathogens, notably in individuals with cystic fibrosis, hospital-acquired pneumonia and lung transplantation. The use of bacteriophages (phages) to treat bacterial infections is gaining growing attention, with numerous published cases of compassionate treatment over the last few years. Although the use of phages appears safe, the lack of standardisation, the significant heterogeneity of published studies and the paucity of robust efficacy data, alongside regulatory hurdles arising from the existing pharmaceutical legislation, are just some of the challenges phage therapy has to overcome. In this review, we discuss the lessons learned from recent clinical experiences of phage therapy for the treatment of pulmonary infections. We review the key aspects, opportunities and challenges of phage therapy regarding formulations and administration routes, interactions with antibiotics and the immune system, and phage resistance. Building upon the current knowledge base, future pre-clinical studies using emerging technologies and carefully designed clinical trials are expected to enhance our understanding and explore the therapeutic potential of phage therapy.

Novel antimicrobial agents for combating antibiotic-resistant bacteria

Antibiotic therapy has become increasingly ineffective against bacterial infections due to the rise of resistance. In particular, ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) have caused life-threatening infections in humans and represent a major global health threat due to a high degree of antibiotic resistance. To respond to this urgent call, novel strategies are urgently needed, such as bacteriophages (or phages), phage-encoded enzymes, immunomodulators and monoclonal antibodies. This review critically analyses these promising antimicrobial therapies for the treatment of multidrug-resistant bacterial infections. Recent advances in these novel therapeutic strategies are discussed, focusing on preclinical and clinical investigations, as well as combinatorial approaches. In this 'Bad Bugs, No Drugs' era, novel therapeutic strategies can play a key role in treating deadly infections and help extend the lifetime of antibiotics.

Further Considerations on How to Improve Phage Therapy Experimentation, Practice, and Reporting: Pharmacodynamics Perspectives

Phage therapy uses bacterial viruses (bacteriophages) to infect and kill targeted pathogens. Approximately one decade ago, I started publishing on how possibly to improve upon phage therapy experimentation, practice, and reporting. Here, I gather and expand upon some of those suggestions. The issues emphasized are (1) that using ratios of antibacterial agents to bacteria is not how dosing is accomplished in the real world, (2) that it can be helpful to not ignore Poisson distributions as a means of either anticipating or characterizing phage therapy success, and (3) how to calculate a concept of 'inundative phage densities.' Together, these are issues of phage therapy pharmacodynamics, meaning they are ways of thinking about the potential for phage therapy treatments to be efficacious mostly independent of the details of delivery of phages to targeted bacteria. Much emphasis is placed on working with Poisson distributions to better align phage therapy with other antimicrobial treatments.

Phage–Antibiotic Therapy as a Promising Strategy to Combat Multidrug-Resistant Infections and to Enhance Antimicrobial Efficiency

Infections caused by multidrug-resistant (MDR) bacteria have highlighted the importance of the development of new antimicrobial agents. While bacteriophages (phages) are widely studied as alternative agents to antibiotics, combined treatments using phages and antibiotics have exhibited Phage–Antibiotic Synergy (PAS), in which antibiotics promote phage replication and extraordinary antimicrobial efficacy with reduced development of bacterial resistance. This review paper on the current progress of phage–antibiotic therapy includes aspects of the mechanisms of PAS and the therapeutic performance of PAS in combating multidrug-resistant bacterial infections. The choice of phages and antibiotics, the administration time and sequence, and the concentrations of the two agents impact the bacterial inhibitory effects to different extents.