Mitigation of evolved bacterial resistance to phage therapy

The virulent bacteriophage Henu8 as an antimicrobial synergist against Escherichia coli

As the overuse of antibiotics has not yet been strictly limited in urban areas, drug-resistant Escherichia coli has become a fatal pressure for bacteremia treatment. Considering the outstanding performance of bacteriophages in vitro, bacteriophages may serve as an alternative to heal chronic refractory infections. In this study, a 49,890 bp double-stranded circular DNA phage, Henu8, was isolated and was able to lyse the group of E. coli strains tested in this study. Prominent biological characterization revealed that the highly adsorbed bacteriophage Henu8 could form a fully transparent plaque with a narrow translucent halo. The optimal multiplicity of infection of the bacteriophage Henu8 was 0.01, with a burst size of 275 PFU/cell. Genomic analysis revealed a G + C content of 44.17% Henu8, in which 65 open reading frames were located, which could be assigned as a new species in the genus Hanrivervirus of the subfamily Tempevirinae. The effective antibacterial ability and the obvious biofilm destruction and inhibition capability of phage Henu8 were observed. The time-killing assay demonstrated the synergetic potential of Henu8 with antibiotics in vitro for E. coli eradication. Henu8 has profound medicinal potential in a mouse bacteremia model. These studies indicate that Henu8 is a novel bacteriophage with therapeutic potential alone or in combination with antibiotics for clinical treatment.IMPORTANCEThe findings described in this study constitute concrete evidence that it is possible to significantly synergize the antimicrobial activity of bacteriophages and antibiotics. We showed that the newly isolated potent bacteriophage Henu8 lyses Escherichia coli rapidly but tends to produce resistant bacteria. The bacteriophage Henu8 has synergistic antimicrobial effects with several antibiotics and is not susceptible to developing resistance. These results provide further evidence that bacterial resistance to phages arises, possibly at an adaptive cost to sensitivity to antibiotics. Therefore, the findings of this study are important for increasing the potential of phages for clinical applications and developing new approaches to improve their therapeutic efficacy against bacterial drug resistance.

Personalized inhaled bacteriophage therapy for treatment of multidrug-resistant Pseudomonas aeruginosa in cystic fibrosis

Bacteriophage (phage) therapy, which uses lytic viruses as antimicrobials, is a potential strategy to address the antimicrobial resistance crisis. Cystic fibrosis, a disease complicated by recurrent Pseudomonas aeruginosa pulmonary infections, is an example of the clinical impact of antimicrobial resistance. Here, using a personalized phage therapy strategy that selects phages for a predicted evolutionary trade-off, nine adults with cystic fibrosis (eight women and one man) of median age 32 (range 22-46) years were treated with phages on a compassionate basis because their clinical course was complicated by multidrug-resistant or pan-drug-resistant Pseudomonas that was refractory to prior courses of standard antibiotics. The individuals received a nebulized cocktail or single-phage therapy without adverse events. Five to 18 days after phage therapy, sputum Pseudomonas decreased by a median of 104 CFU ml-1, or a mean difference of 102 CFU ml-1 (P = 0.006, two-way analysis of variance with Dunnett's multiple-comparisons test), without altering sputum microbiome, and an analysis of sputum Pseudomonas showed evidence of trade-offs that decreased antibiotic resistance or bacterial virulence. In addition, an improvement of 6% (median) and 8% (mean) predicted FEV1 was observed 21-35 days after phage therapy (P = 0.004, Wilcoxon signed-rank t-test), which may reflect the combined effects of decreased bacterial sputum density and phage-driven trade-offs. These results show that a personalized, nebulized phage therapy trade-off strategy may affect clinical and microbiologic endpoints, which must be evaluated in larger clinical trials.

Two virulent Vibrio campbellii phages with potential for phage therapy in aquaculture

BACKGROUND

As aquaculture continues to expand globally, diseases caused by Vibrio species are becoming increasingly prevalent. Vibriosis encompasses a range of infections, which can lead to symptoms such as skin lesions, hemorrhaging, and high mortality rates in fish and shellfish, especially in high-density farming systems, resulting in significant economic losses. Simultaneously, the extensive use of antibiotics has fostered the emergence of antibiotic-resistant bacteria, exacerbated disease outbreaks, and complicated control measures. Phage therapy, which leverages bacteriophages as natural antibacterial agents, offers a promising eco-friendly alternative to the antibiotics used in aquaculture. This study aimed to evaluate the potential of two vibriophages for phage therapy in aquaculture.

RESULTS

Two virulent vibriophages, vB_VcaP_R24D and vB_VcaP_R25D, were isolated from aquaculture wastewater from seafood markets using Vibrio campbellii LMG 11216T as the host strain. The two vibriophages were identified based on their morphology, infection dynamics, host range, genomic features, lytic activity, and environmental stability. Both phages belong to the podovirus morphotype and exhibit a lytic life cycle characterised by a short latent period (< 10 min). Genomic analyses confirmed the absence of lysogenic genes, virulence factors, and antibiotic-resistance genes, thereby ensuring genetic safety. Additionally, both phages demonstrated high stability over a broad range of temperatures (4-45 °C) and pH (3-10). Lytic curve analyses further indicated a robust lytic efficiency during the logarithmic growth phase of the vibriophages.

CONCLUSIONS

These biological and genomic characteristics highlight the potential of vB_VcaP_R24D and vB_VcaP_R25D as effective biocontrol agents for mitigating vibriosis in aquaculture. Although this study demonstrates their narrow host range, the possibility of phage infection in other untested hosts cannot be entirely excluded. Furthermore, the findings offer valuable insights for future research on phage-host interactions and the development of phage cocktails to improve disease management in aquaculture systems.

Sphae: an automated toolkit for predicting phage therapy candidates from sequencing data

Motivation

Phage therapy offers a viable alternative for bacterial infections amid rising antimicrobial resistance. Its success relies on selecting safe and effective phage candidates that require comprehensive genomic screening to identify potential risks. However, this process is often labor intensive and time-consuming, hindering rapid clinical deployment.

Results

We developed Sphae, an automated bioinformatics pipeline designed to streamline the therapeutic potential of a phage in under 10 minutes. Using Snakemake workflow manager, Sphae integrates tools for quality control, assembly, genome assessment, and annotation tailored specifically for phage biology. Sphae automates the detection of key genomic markers, including virulence factors, antimicrobial resistance genes, and lysogeny indicators such as integrase, recombinase, and transposase, which could preclude therapeutic use. Among the 65 phage sequences analyzed, 28 showed therapeutic potential, 8 failed due to low sequencing depth, 22 contained prophage or virulent markers, and 23 had multiple phage genomes. This workflow produces a report to assess phage safety and therapy suitability quickly. Sphae is scalable and portable, facilitating efficient deployment across most high-performance computing and cloud platforms, accelerating the genomic evaluation process.

Availability and implementation

Sphae source code is freely available at https://github.com/linsalrob/sphae, with installation supported on Conda, PyPi, Docker containers.

Evolution takes multiple paths to evolvability when facing environmental change

Life at all scales is surprisingly effective at exploiting new opportunities, as demonstrated by the rapid emergence of antimicrobial resistance and novel pathogens. How populations acquire this level of evolvability and the various ways it aids survival are major open questions with direct implications for human health. Here, we use digital evolution to show that changing environments facilitate the simultaneous evolution of high mutation rates and a distribution of mutational effects skewed toward beneficial phenotypes. The evolved mutational neighborhoods allow rapid adaptation to previously encountered environments, whereas higher mutation rates aid adaptation to completely new environmental conditions. By precisely tracking evolving lineages and the phenotypes of their mutants, we show that evolving populations localize on phenotypic boundaries between distinct regions of genotype space. Our results demonstrate how evolution shapes multiple determinants of evolvability concurrently, fine-tuning a population's adaptive responses to unpredictable or recurrent environmental shifts.

Alhagi maurorum extract in combination with lytic phage cocktails: a promising therapeutic approach against biofilms of multi-drug resistant P. mirabilis

Antimicrobial resistance (AMR) poses a significant global threat to public health systems, rendering antibiotics ineffective in treating infectious diseases. Combined use of bio compounds, including bacteriophages and plant extracts, is an attractive approach to controlling antibiotic resistance. In this study, the combination of phage cocktail (Isf-Pm1 and Isf-Pm2) and Alhagi maurorum crude extract (AME) was investigated in controlling biofilm-forming multi-drug resistant P. mirabilis isolates, in vitro and a phantom bladder model. The combination of AME and phage cocktails demonstrated no significant disparity in its ability to inhibit quorum sensing (QS) when compared to the individual control of AME alone. Following treatment with the combination of phage cocktail and AME at a 125 μg/mL concentration, the MDR P. mirabilis biofilm biomass was notably reduced by 73% compared to the control (P< 0.0001). The anti-biofilm effect was confirmed by Scanning Electron Microscopy (SEM). Moreover, in a bladder phantom model, there was a considerable decrease in encrustation levels compared to the control. The combined treatment resulted in a 1.85 logarithmic reduction in bacterial adhesion to Vero cells compared to the control. The real-time PCR results indicated significant downregulation of QS- and adhesion-related gens. The phage therapy, combined with AME, holds promising potential in reducing biofilm formation.

phage therapy candidates from Sphae: An automated toolkit for predicting sequencing data

Motivation

Phage therapy is a viable alternative for treating bacterial infections amidst the escalating threat of antimicrobial resistance. However, the therapeutic success of phage therapy depends on selecting safe and effective phage candidates. While experimental methods focus on isolating phages and determining their lifecycle and host range, comprehensive genomic screening is critical to identify markers that indicate potential risks, such as toxins, antimicrobial resistance, or temperate lifecycle traits. These analyses are often labor-intensive and time-consuming, limiting the rapid deployment of phage in clinical settings.

Results

We developed Sphae, an automated bioinformatics pipeline designed to streamline therapeutic potential of a phage in under ten minutes. Using Snakemake workflow manager, Sphae integrates tools for quality control, assembly, genome assessment, and annotation tailored specifically for phage biology. Sphae automates the detection of key genomic markers, including virulence factors, antimicrobial resistance genes, and lysogeny indicators like integrase, recombinase, and transposase, which could preclude therapeutic use. Benchmarked on 65 phage sequences, 28 phage samples showed therapeutic potential, 8 failed during assembly due to low sequencing depth, 22 samples included prophage or virulent markers, and the remaining 23 samples included multiple phage genomes per sample. This workflow outputs a comprehensive report, enabling rapid assessment of phage safety and suitability for phage therapy under these criteria. Sphae is scalable, portable, facilitating efficient deployment across most high-performance computing (HPC) and cloud platforms, expediting the genomic evaluation process.

Availability

Sphae is source code and freely available at https://github.com/linsalrob/sphae, with installation supported on Conda, PyPi, Docker containers.

A Klebsiella-phage cocktail to broaden the host range and delay bacteriophage resistance both in vitro and in vivo

Bacteriophages (phages), viruses capable of infecting and lysing bacteria, are a promising alternative for treating infections from hypervirulent, antibiotic-resistant pathogens like Klebsiella pneumoniae, though narrow host range and phage resistance remain challenges. In this study, the hypervirulent K. pneumoniae NTUH-K2044 was used to purify phage ΦK2044, while two ΦK2044-resistant strains were used to purify two further phages: ΦKR1, and ΦKR8 from hospital sewage. A detailed characterization showed that ΦK2044 specifically killed KL1 capsule-type K. pneumoniae, while ΦKR1 and ΦKR8 targeted 13 different capsular serotypes. The phage cocktail (ΦK2044 + ΦKR1 + ΦKR8) effectively killed K. pneumoniae in biofilms, pre-treatment biofilm formation, and delayed phage-resistance. The phage cocktail improved 7-day survival in Galleria mellonella and mouse models and showed therapeutic potential in a catheter biofilm model. In summary, this proof-of-principle phage cocktail has a broad host range, including hypervirulent and highly drug-resistant K. pneumoniae, and serves as a promising starting point for optimizing phage therapy.

Rapid design of bacteriophage cocktails to suppress the burden and virulence of gut-resident carbapenem-resistant Klebsiella pneumoniae

Antibiotic use can lead to the expansion of multi-drug-resistant pathobionts within the gut microbiome that can cause life-threatening infections. Selective alternatives to conventional antibiotics are in dire need. Here, we describe a Klebsiella PhageBank for the tailored design of bacteriophage cocktails to treat multi-drug-resistant Klebsiella pneumoniae. Using a transposon library in carbapenem-resistant K. pneumoniae, we identify host factors required for phage infection in major Klebsiella phage families. Leveraging the diversity of the PhageBank, we formulate phage combinations that eliminate K. pneumoniae with minimal phage resistance. Optimized cocktails selectively suppress the burden of K. pneumoniae in the mouse gut and drive the loss of key virulence factors that act as phage receptors. Phage-mediated diversification of bacterial populations in the gut leads to co-evolution of phage variants with higher virulence and broader host range. Altogether, the Klebsiella PhageBank charts a roadmap for phage therapy against a critical multidrug-resistant human pathogen.

Variable fitness effects of bacteriophage resistance mutations in Escherichia coli: implications for phage therapy

Bacteria exposed to bactericidal treatment, such as antibiotics or bacteriophages (phages), often develop resistance. While phage therapy is proposed as a solution to the antibiotic resistance crisis, the bacterial resistance emerging during phage therapy remains poorly characterized. In this study, we examined a large population of phage-resistant extra-intestinal pathogenic Escherichia coli 536 clones that emerged from both in vitro (non-limited liquid medium) and in vivo (murine pneumonia) conditions. Genome sequencing uncovered a convergent mutational pattern in phage resistance mechanisms under both conditions, particularly targeting two cell-wall components, the K15 capsule and the lipopolysaccharide (LPS). This suggests that their identification in vivo could be predicted from in vitro assays. Phage-resistant clones exhibited a wide range of fitness according to in vitro tests, growth rate, and resistance to amoeba grazing, which could not distinguish between the K15 capsule and LPS mutants. In contrast, K15 capsule mutants retained virulence comparable to the wild-type strain, whereas LPS mutants showed significant attenuation in the murine pneumonia model. Additionally, we observed that resistance to the therapeutic phage through a nonspecific mechanism, such as capsule overproduction, did not systematically lead to co-resistance to other phages that were initially capable or incapable of infecting the wild-type strain. Our findings highlight the importance of incorporating a diverse range of phages in the design of therapeutic cocktails to target potential future phage-resistant clones effectively.

IMPORTANCE

This study isolated more than 50 phage-resistant mutants from both in vitro and in vivo conditions, exposing an extra-intestinal pathogenic Escherichia coli strain to a single virulent phage. The characterization of these clones revealed several key findings: (1) mutations occurring during phage treatment affect the same pathways as those identified in vitro; (2) the resistance mechanisms are associated with the modification of two cell-wall components, with one involving receptor deletion (phage-specific mechanism) and the other, less frequent, involving receptor masking (phage-nonspecific mechanism); (3) an in vivo virulence assay demonstrated that the absence of the receptor abolishes virulence while masking the receptor preserves it; and (4) clones with a resistance mechanism nonspecific to a particular phage can remain susceptible to other phages. This supports the idea of incorporating diverse phages into therapeutic cocktails designed to collectively target both wild-type and phage-resistant strains, including those with resistance mechanisms nonspecific to a phage.

Strategies and mechanisms targeting Enterococcus faecalis biofilms associated with endodontic infections: a comprehensive review

Enterococcus faecalis is one of the main microorganisms that infects root canals, ranking among the most prevalent microorganisms associated with endodontic treatment failure. Given its pervasive presence in persistent endodontic infections, the successful elimination of Enterococcus faecalis is crucial for effective endodontic treatment and retreatment. Furthermore, Enterococcus faecalis can form biofilms - defense structures that microbes use to fight environmental threats. These biofilms confer resistance against host immune system attacks and antibiotic interventions. Consequently, the presence of biofilms poses a significant challenge in the complete eradication of Enterococcus faecalis and its associated disease. In response, numerous scholars have discovered promising outcomes in addressing Enterococcus faecalis biofilms within root canals and undertaken endeavors to explore more efficacious approaches in combating these biofilms. This study provides a comprehensive review of strategies and mechanisms for the removal of Enterococcus faecalis biofilms.

Characterization and therapeutic potential of MRABP9, a novel lytic bacteriophage infecting multidrug-resistant Acinetobacter baumannii clinical strains

Acinetobacter baumannii is one of the most important pathogens of healthcare-associated infections. The rising prevalence of multidrug-resistant A. baumannii (MRAB) strains and biofilm formation impact the outcome of conventional treatment. Phage-related therapy is a promising strategy to tame troublesome multidrug-resistant bacteria. Here, we isolated and evaluated a highly efficient lytic phage called MRABP9 from hospital sewage. The phage was a novel species within the genus Friunavirus and exhibited lytic activity against 2 other identified MRAB strains. Genomic analysis revealed it was a safe virulent phage and a pectate lyase domain was identified within its tail spike protein. MRABP9 showed potent bactericidal and anti-biofilm activity against MRAB, significantly delaying the time point of bacterial regrowth in vitro. Phage administration could rescue the mice from acute lethal MRAB infection. Considering its features, MRABP9 has the potential as an efficient candidate for prophylactic and therapeutic use against acute infections caused by MRAB strains.

Host immunity involvement in the outcome of phage therapy against hypervirulent Klebsiella pneumoniae infections

Highly encapsulated hypervirulent Klebsiella pneumoniae (hvKp) causes severe infections. Bacteriophage therapy, an antibiotic alternative, effectively treats bacterial infections. Phage φFK1979 encoding polysaccharide depolymerases can target and disarm the capsule of hvKp FK1979, showing promise against FK1979 infection. Resistant strains induced by φFK1979 are possibly eliminated by host immunity and new phage phiR3 targeting them. We constructed varied immunocompromised FK1979 infection mouse models to assess the therapy efficacy of φFK1979 alone or in combination with phiR3. Survival rates, bacterial loads, histopathology, inflammation, and immune cell distribution of mice were studied. Prompt and adequate administration of φFK1979, rather than phiR3, significantly improved survival rates in mice with different immune statuses. However, immunocompromised mice showed lower efficacy due to reduced tolerance to low-virulence φFK1979-resistant bacteria compared to immunocompetent mice. Adding phiR3 sequentially greatly enhanced therapy efficacy for them, leading to increased survival rates and notable improvements in pathology and inflammation. Immunocompetent mice exhibited the most favorable response to φFK1979 monotherapy, as their immune system cleared φFK1979-resistant bacteria while avoiding a robust response to phiR3 combating φFK1979-resistant bacteria. This study revealed host immunity involvement in the outcome of phage therapy against infections and introduced, for the first time, personalized phage therapy strategies for hvKp-infected mice with varying immune statuses.IMPORTANCEHypervirulent Klebsiella pneumoniae (hvKp), with high capsular polysaccharide production, can cause severe invasive infections. Capsule-targeting phage poses the potential to fight against hvKp. We previously elucidated that the capsule-targeting phage induces resistance in hvKp, while phage-resistant strains exhibit sensitivity to host innate immunity and new phages targeting them. This indicated that phage-resistant strains can be eliminated by the immune system in immunocompetent patients, whereas they may require treatment with phages targeting resistant bacteria in immunocompromised patients. HvKp can infect individuals with varying immune statuses, including both immunocompetent and immunocompromised/deficient patients. This study, for the first time, developed personalized phage therapy strategies for hvKp-infected mice with different immune statuses, optimizing phage therapy against hvKp infections. This research is expected to provide a theoretical foundation and novel insights for clinical phage therapy against hvKp infections, offering significant societal benefits and clinical value.

Isolation, characterization and application of noble bacteriophages targeting potato common scab pathogen Streptomyces stelliscabiei

Bacteriophages have emerged as promising alternatives to pesticides for controlling bacterial pathogens in crops. Among these pathogens, Streptomyces stelliscabiei (syn. S. stelliscabiei) is a primary causative agent of potato common scab (PCS), resulting in substantial global economic losses. The traditional management methods for PCS face numerous challenges, highlighting the need for effective and environmentally friendly control strategies. In this study, we successfully isolated three novel bacteriophages, namely Psst1, Psst2, and Psst4, which exhibited a broad host range encompassing seven S. stelliscabiei strains. Morphological analysis revealed their distinct features, including an icosahedral head and a non-contractile tail. These phages demonstrated stability across a broad range of temperatures (20-50°C), pH (pH 3-11), and UV exposure time (80 min). Genome sequencing revealed double-stranded DNA phage with open reading frames encoding genes for phage structure, DNA packaging and replication, host lysis and other essential functions. These phages lacked genes for antibiotic resistance, virulence, and toxicity. Average nucleotide identity, phylogenetic, and comparative genomic analyses classified the three phages as members of the Rimavirus genus, with Psst1 and Psst2 representing novel species. All three phages efficiently lysed S. stelliscabiei in the liquid medium and alleviated scab symptom development and reduced pathogen abundance on potato slices. Furthermore, phage treatments of radish seedlings alleviated the growth inhibition caused by S. stelliscabiei with no disease symptoms. In soil potted experiments, phages significantly reduced disease incidence by 40%. This decrease is attributed to a reduction in pathogen density and the selection of S. stelliscabiei strains with reduced virulence and slower growth rates in natural environments. Our study is the first to report the isolation of three novel phages that infect S. stelliscabiei as a host bacterium. These phages exhibit a broad host range, and demonstrate stability under a variety of environmental conditions. Additionally, they demonstrate biocontrol efficacy against bacterial infections in potato slices, radish seedlings, and potted experiments, underscoring their significant potential as biocontrol agents for the effective management of PCS.

Controlling of foodborne pathogen biofilms on stainless steel by bacteriophages: A systematic review and meta-analysis

This study investigates the potential of using bacteriophages to control foodborne pathogen biofilms on stainless steel surfaces in the food industry. Biofilm-forming bacteria can attach to stainless steel surfaces, rendering them difficult to eradicate even after a thorough cleaning and sanitizing procedures. Bacteriophages have been proposed as a possible solution, as they can penetrate biofilms and destroy bacterial cells within, reducing the number of viable bacteria and preventing the growth and spread of biofilms. This systematic review and meta-analysis evaluates the potential of bacteriophages against different biofilm-forming foodborne bacteria, including Cronobacter sakazakii, Escherichia coli, Staphylococcus aureus, Pseudomonas fluorescens, Pseudomonas aeruginosa and Listeria monocytogenes. Bacteriophage treatment generally causes a significant average reduction of 38 % in biofilm formation of foodborne pathogens on stainless steel. Subgroup analyses revealed that phages are more efficient in long-duration treatment. Also, applying a cocktail of phages is 1.26-fold more effective than applying individual phages. Phages at concentrations exceeding 107 PFU/ml are significantly more efficacious in eradicating bacteria within a biofilm. The antibacterial phage activity decreases substantially by 3.54-fold when applied at 4 °C compared to temperatures above 25 °C. This analysis suggests that bacteriophages can be a promising solution for controlling biofilms in the food industry.

Phage Therapy for Respiratory Infections: Opportunities and Challenges

We are entering the post-antibiotic era. Antimicrobial resistance (AMR) is a critical problem in chronic lung infections resulting in progressive respiratory failure and increased mortality. In the absence of emerging novel antibiotics to counter AMR infections, bacteriophages (phages), viruses that infect bacteria, have become a promising option for chronic respiratory infections. However, while personalized phage therapy is associated with improved outcomes in individual cases, clinical trials demonstrating treatment efficacy are lacking, limiting the therapeutic potential of this approach for respiratory infections. In this review, we address the current state of phage therapy for managing chronic respiratory diseases. We then discuss how phage therapy may address major microbiologic obstacles which hinder disease resolution of chronic lung infections with current antibiotic-based treatment practices. Finally, we highlight the challenges that must be addressed for successful phage therapy clinical trials. Through this discussion, we hope to expand on the potential of phages as an adjuvant therapy in chronic lung infections, as well as the microbiologic challenges that need to be addressed for phage therapy to expand beyond personalized salvage therapy.

Nucleus-forming jumbophage PhiKZ therapeutically outcompetes non-nucleus-forming jumbophage Callisto

With the recent resurgence of phage therapy in modern medicine, jumbophages are currently under the spotlight due to their numerous advantages as anti-infective agents. However, most significant discoveries to date have primarily focused on nucleus-forming jumbophages, not their non-nucleus-forming counterparts. In this study, we compare the biological characteristics exhibited by two genetically diverse jumbophages: 1) the well-studied nucleus-forming jumbophage, PhiKZ; and 2) the newly discovered non-nucleus-forming jumbophage, Callisto. Single-cell infection studies further show that Callisto possesses different replication machinery, resulting in a delay in phage maturation compared to that of PhiKZ. The therapeutic potency of both phages was examined in vitro and in vivo, demonstrating that PhiKZ holds certain superior characteristics over Callisto. This research sheds light on the importance of the subcellular infection machinery and the organized progeny maturation process, which could potentially provide valuable insight in the future development of jumbophage-based therapeutics.

Thinking Phage Innovations Through Evolution and Ecology

In this article, we conduct an interdisciplinary review of the potential of phage-based applications in light of current knowledge about phage evolution and ecology. Gaining an improved understanding of phages' ecology and evolutionary dynamics is crucial for recognizing both the benefits and limits of their usage, as well as potential negative downstream effects across different ecological milieus. As a reference, the history of the industrialization of antibiotics and the rise of antimicrobial resistance act as a reminder of the deep entanglement of both the evolvability capacities of micro-organisms and the history of human societies. Based on evolutionary biological parameters, we show that (1) virulent bacteriophages are best candidates for biocontrol, (2) best cocktails harbor complementary bacteriophages preventing bacterial cross-resistance, and (3) cure can also be considered with steer of bacterial bacteriophage-resistance evolution toward loss of virulence factor and/or increase in antibiotic susceptibility. A detailed review of what is known about the role of phages in vine cultivation and wine production finally serves as an example to show how it is important to consider site-specific rather than one-size-fits-all responses.

Addressing the Research and Development Gaps in Modern Phage Therapy

Antimicrobial resistance is on the rise globally, prompting increased research and development (R&D) of phage therapy as a strategy to address difficult-to-treat bacterial infections. We review the current state of phage therapy research, including major operational, epistemic, and biological challenges for phage R&D, and discuss some new approaches to developing the technology motivated by recent breakthroughs such as artificial intelligence and synthetic phage production. In addition, we contextualize these R&D challenges and opportunities in light of the ongoing predicament of commercial antimicrobial innovation and current public-private efforts to reinvigorate the pipeline of antimicrobial drug discovery. We conclude with reflections on the potential for new phage therapies to be readily accessible across all income contexts to better ensure broad patient access, and consider possible alternatives to current public and public-private solutions for phage therapy and production.

Optimized preparation pipeline for emergency phage therapy against Pseudomonas aeruginosa at Yale University

Bacteriophage therapy is one potential strategy to treat antimicrobial resistant or persistent bacterial infections, and the year 2021 marked the centennial of Felix d'Hérelle's first publication on the clinical applications of phages. At the Center for Phage Biology & Therapy at Yale University, a preparatory modular approach has been established to offer safe and potent phages for single-patient investigational new drug applications while recognizing the time constraints imposed by infection(s). This study provides a practical walkthrough of the pipeline with an Autographiviridae phage targeting Pseudomonas aeruginosa (phage vB_PaeA_SB, abbreviated to ΦSB). Notably, a thorough phage characterization and the evolutionary selection pressure exerted on bacteria by phages, analogous to antibiotics, are incorporated into the pipeline.

Engineering and Bio/Nanotechnological Applications of Virus Particles

Virus particles (VPs) are naturally evolved nanomachines. Their outstanding molecular structures, physical and chemical properties, and biological activities make them potentially useful for many biomedical or technological applications. Natural VPs such as virions or capsids must, however, be modified by genetic and/or chemical engineering in order to become adequate for many specific uses. We present first a general overview of the methods used for obtaining virions and viral capsids, and of genetic and chemical engineering approaches to suitably modify VPs. In the second part of the chapter, we present an updated overview on current or developing applications of engineered VPs as tools, materials, reagents, or nanodevices in biomedicine, biotechnology, or nanotechnology.

Overcoming Bacteriophage Resistance in Phage Therapy

Antibiotic resistance among pathogenic bacteria is one of the most severe global challenges. It is predicted that over ten million lives will be lost annually by 2050. Phage therapy is a promising alternative to antibiotics. However, the ease of development of phage resistance during therapy is a concern. This review focuses on the possible ways to overcome phage resistance in phage therapy.

Antibiotic Resistance: Do We Need Only Cutting-Edge Methods, or Can New Visions Such as One Health Be More Useful for Learning from Nature?

Antibiotic resistance is an increasing global problem for public health, and focusing on biofilms has provided further insights into resistance evolution in bacteria. Resistance is innate in many bacterial species, and many antibiotics are derived from natural molecules of soil microorganisms. Is it possible that nature can help control AMR diffusion? In this review, an analysis of resistance mechanisms is summarized, and an excursus of the different approaches to challenging resistance spread based on natural processes is presented as "lessons from Nature". On the "host side", immunotherapy strategies for bacterial infections have a long history before antibiotics, but continuous new inputs through biotechnology advances are enlarging their applications, efficacy, and safety. Antimicrobial peptides and monoclonal antibodies are considered for controlling antibiotic resistance. Understanding the biology of natural predators is providing new, effective, and safe ways to combat resistant bacteria. As natural enemies, bacteriophages were used to treat severe infections before the discovery of antibiotics, marginalized during the antibiotic era, and revitalized upon the diffusion of multi-resistance. Finally, sociopolitical aspects such as education, global action, and climate change are also considered as important tools for tackling antibiotic resistance from the One Health perspective.

Decolonization of asymptomatic carriage of multi-drug resistant bacteria by bacteriophages?

Antimicrobial resistance is a major threat to human and animal health and accounted for up to 4.5 million deaths worldwide in 2019. Asymptomatic colonization of the digestive tract by multidrug resistant (multi-resistant) bacteria such as extended-spectrum beta-lactamase-, or carbapenemase- producing Enterobacterales is (i) a risk factor for infection by these multi-resistant bacteria, (ii) a risk factor of dissemination of these multi-resistant bacteria among patients and in the community, and (iii) allows the exchange of resistance genes between bacteria. Hence, decolonization or reduction of the gastrointestinal tract colonization of these multi-resistant bacteria needs to be urgently explored. Developing new non-antibiotic strategies to limit or eradicate multi-resistant bacteria carriage without globally disrupting the microbiota is considered a priority to fight against antibiotic resistance. Probiotics or Fecal Microbiota Transplantation are alternative strategies to antibiotics that have been considered to decolonize intestinal tract from MDR bacteria but there is currently no evidence demonstrating their efficacy. Lytic bacteriophages are viruses that kill bacteria and therefore could be considered as a promising strategy to combat antibiotic resistance. Successful decolonization by bacteriophages has already been observed clinically. Here, we discuss the current alternative strategies considered to decolonize the digestive tract of multidrug resistant bacteria, briefly describing probiotics and fecal microbiota transplantation approaches, and then detail the in vivo and in vitro studies using bacteriophages, while discussing their limits regarding the animal models used, the characteristics of phages used and their activity in regards of the gut anatomy.

Developing Phage Therapy That Overcomes the Evolution of Bacterial Resistance

The global rise of antibiotic resistance in bacterial pathogens and the waning efficacy of antibiotics urge consideration of alternative antimicrobial strategies. Phage therapy is a classic approach where bacteriophages (bacteria-specific viruses) are used against bacterial infections, with many recent successes in personalized medicine treatment of intractable infections. However, a perpetual challenge for developing generalized phage therapy is the expectation that viruses will exert selection for target bacteria to deploy defenses against virus attack, causing evolution of phage resistance during patient treatment. Here we review the two main complementary strategies for mitigating bacterial resistance in phage therapy: minimizing the ability for bacterial populations to evolve phage resistance and driving (steering) evolution of phage-resistant bacteria toward clinically favorable outcomes. We discuss future research directions that might further address the phage-resistance problem, to foster widespread development and deployment of therapeutic phage strategies that outsmart evolved bacterial resistance in clinical settings.

Genetic Engineering and Biosynthesis Technology: Keys to Unlocking the Chains of Phage Therapy

Phages possess the ability to selectively eliminate pathogenic bacteria by recognizing bacterial surface receptors. Since their discovery, phages have been recognized for their potent bactericidal properties, making them a promising alternative to antibiotics in the context of rising antibiotic resistance. However, the rapid emergence of phage-resistant strains (generally involving temperature phage) and the limited host range of most phage strains have hindered their antibacterial efficacy, impeding their full potential. In recent years, advancements in genetic engineering and biosynthesis technology have facilitated the precise engineering of phages, thereby unleashing their potential as a novel source of antibacterial agents. In this review, we present a comprehensive overview of the diverse strategies employed for phage genetic engineering, as well as discuss their benefits and drawbacks in terms of bactericidal effect.

Epitopes in the capsular polysaccharide and the porin OmpK36 receptors are required for bacteriophage infection of Klebsiella pneumoniae

To kill bacteria, bacteriophages (phages) must first bind to a receptor, triggering the release of the phage DNA into the bacterial cell. Many bacteria secrete polysaccharides that had been thought to shield bacterial cells from phage attack. We use a comprehensive genetic screen to distinguish that the capsule is not a shield but is instead a primary receptor enabling phage predation. Screening of a transposon library to select phage-resistant Klebsiella shows that the first receptor-binding event docks to saccharide epitopes in the capsule. We discover a second step of receptor binding, dictated by specific epitopes in an outer membrane protein. This additional and necessary event precedes phage DNA release to establish a productive infection. That such discrete epitopes dictate two essential binding events for phages has profound implications for understanding the evolution of phage resistance and what dictates host range, two issues critically important to translating knowledge of phage biology into phage therapies.

Translating phage therapy into the clinic: Recent accomplishments but continuing challenges

Phage therapy is a medical form of biological control of bacterial infections, one that uses naturally occurring viruses, called bacteriophages or phages, as antibacterial agents. Pioneered over 100 years ago, phage therapy nonetheless is currently experiencing a resurgence in interest, with growing numbers of clinical case studies being published. This renewed enthusiasm is due in large part to phage therapy holding promise for providing safe and effective cures for bacterial infections that traditional antibiotics acting alone have been unable to clear. This Essay introduces basic phage biology, provides an outline of the long history of phage therapy, highlights some advantages of using phages as antibacterial agents, and provides an overview of recent phage therapy clinical successes. Although phage therapy has clear clinical potential, it faces biological, regulatory, and economic challenges to its further implementation and more mainstream acceptance.

The future of evolutionary medicine: sparking innovation in biomedicine and public health

Evolutionary medicine - i.e. the application of insights from evolution and ecology to biomedicine - has tremendous untapped potential to spark transformational innovation in biomedical research, clinical care and public health. Fundamentally, a systematic mapping across the full diversity of life is required to identify animal model systems for disease vulnerability, resistance, and counter-resistance that could lead to novel clinical treatments. Evolutionary dynamics should guide novel therapeutic approaches that target the development of treatment resistance in cancers (e.g., via adaptive or extinction therapy) and antimicrobial resistance (e.g., via innovations in chemistry, antimicrobial usage, and phage therapy). With respect to public health, the insight that many modern human pathologies (e.g., obesity) result from mismatches between the ecologies in which we evolved and our modern environments has important implications for disease prevention. Life-history evolution can also shed important light on patterns of disease burden, for example in reproductive health. Experience during the COVID-19 (SARS-CoV-2) pandemic has underlined the critical role of evolutionary dynamics (e.g., with respect to virulence and transmissibility) in predicting and managing this and future pandemics, and in using evolutionary principles to understand and address aspects of human behavior that impede biomedical innovation and public health (e.g., unhealthy behaviors and vaccine hesitancy). In conclusion, greater interdisciplinary collaboration is vital to systematically leverage the insight-generating power of evolutionary medicine to better understand, prevent, and treat existing and emerging threats to human, animal, and planetary health.

The role of the animal host in the management of bacteriophage resistance during phage therapy

Multi-drug-resistant bacteria are associated with significantly higher morbidity and mortality. The possibilities for discovering new antibiotics are limited, but phage therapy - the use of bacteriophages (viruses infecting bacteria) to cure infections - is now being investigated as an alternative or complementary treatment to antibiotics. However, one of the major limitations of this approach lies in the antagonistic coevolution between bacteria and bacteriophages, which determines the ultimate success or failure of phage therapy. Here, we review the possible influence of the animal host on phage resistance and its consequences for the efficacy of phage therapy. We also discuss the value of in vitro assays for anticipating the dynamics of phage resistance observed in vivo.

Resistance-resistant antibacterial treatment strategies

Antibiotic resistance is a major danger to public health that threatens to claim the lives of millions of people per year within the next few decades. Years of necessary administration and excessive application of antibiotics have selected for strains that are resistant to many of our currently available treatments. Due to the high costs and difficulty of developing new antibiotics, the emergence of resistant bacteria is outpacing the introduction of new drugs to fight them. To overcome this problem, many researchers are focusing on developing antibacterial therapeutic strategies that are "resistance-resistant"-regimens that slow or stall resistance development in the targeted pathogens. In this mini review, we outline major examples of novel resistance-resistant therapeutic strategies. We discuss the use of compounds that reduce mutagenesis and thereby decrease the likelihood of resistance emergence. Then, we examine the effectiveness of antibiotic cycling and evolutionary steering, in which a bacterial population is forced by one antibiotic toward susceptibility to another antibiotic. We also consider combination therapies that aim to sabotage defensive mechanisms and eliminate potentially resistant pathogens by combining two antibiotics or combining an antibiotic with other therapeutics, such as antibodies or phages. Finally, we highlight promising future directions in this field, including the potential of applying machine learning and personalized medicine to fight antibiotic resistance emergence and out-maneuver adaptive pathogens.

Ecology and Evolutionary Biology of Hindering Phage Therapy: The Phage Tolerance vs. Phage Resistance of Bacterial Biofilms

As with antibiotics, we can differentiate various acquired mechanisms of bacteria-mediated inhibition of the action of bacterial viruses (phages or bacteriophages) into ones of tolerance vs. resistance. These also, respectively, may be distinguished as physiological insensitivities (or protections) vs. resistance mutations, phenotypic resistance vs. genotypic resistance, temporary vs. more permanent mechanisms, and ecologically vs. also near-term evolutionarily motivated functions. These phenomena can result from multiple distinct molecular mechanisms, many of which for bacterial tolerance of phages are associated with bacterial biofilms (as is also the case for the bacterial tolerance of antibiotics). The resulting inhibitions are relevant from an applied perspective because of their potential to thwart phage-based treatments of bacterial infections, i.e., phage therapies, as well as their potential to interfere more generally with approaches to the phage-based biological control of bacterial biofilms. In other words, given the generally low toxicity of properly chosen therapeutic phages, it is a combination of phage tolerance and phage resistance, as displayed by targeted bacteria, that seems to represent the greatest impediments to phage therapy's success. Here I explore general concepts of bacterial tolerance of vs. bacterial resistance to phages, particularly as they may be considered in association with bacterial biofilms.

The dynamic interplay of bacteriophage, bacteria and the mammalian host during phage therapy

For decades, biomedically centered studies of bacteria have focused on mechanistic drivers of disease in their mammalian hosts. Likewise, molecular studies of bacteriophage have centered on understanding mechanisms by which bacteriophage exploit the intracellular environment of their bacterial hosts. These binary interactions - bacteriophage infect bacteria and bacteria infect eukaryotic hosts - have remained largely separate lines of inquiry. However, recent evidence demonstrates how tripartite interactions between bacteriophage, bacteria and the eukaryotic host shape the dynamics and fate of each component. In this perspective, we provide an overview of different ways in which bacteriophage ecology modulates bacterial infections along a spectrum of positive to negative impacts on a mammalian host. We also examine how coevolutionary processes over longer timescales may change the valence of these interactions. We argue that anticipating both ecological and evolutionary dynamics is key to understand and control tripartite interactions and ultimately to the success or failure of phage therapy.

Phage therapy: From biological mechanisms to future directions

Increasing antimicrobial resistance rates have revitalized bacteriophage (phage) research, the natural predators of bacteria discovered over 100 years ago. In order to use phages therapeutically, they should (1) preferably be lytic, (2) kill the bacterial host efficiently, and (3) be fully characterized to exclude side effects. Developing therapeutic phages takes a coordinated effort of multiple stakeholders. Herein, we review the state of the art in phage therapy, covering biological mechanisms, clinical applications, remaining challenges, and future directions involving naturally occurring and genetically modified or synthetic phages.

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.

Bacteriophage Effectively Rescues Pneumonia Caused by Prevalent Multidrug-Resistant Klebsiella pneumoniae in the Early Stage

Pneumonia caused by multidrug-resistant (MDR) Klebsiella pneumoniae of sequence types ST11 and ST383 have highlighted the necessity for new therapies against these prevalent pathogens. Bacteriophages (phages) may be used as alternatives or complements to antibiotics for treating MDR bacteria because they show potential efficacy in mouse models and even individual clinical cases, and they also cause fewer side effects, such as microbiota-imbalance-induced diseases. In the present study, we screened two phages, pKp11 and pKp383, that targeted ST11 and ST383 MDR K. pneumoniae isolates collected from patients with pneumonia, and they exhibited a broad host range, high lytic activity, and high environmental adaptability. Both phages pKp11 and pKp383 provided an effective treatment for the early stage of pneumonia in a murine infection model without promoting obvious side effects, and cocktails consisting of the two phages were more effective for reducing bacterial loads, inflammation, and pathogenic injuries. Our findings support the application of phages as new medications for refractory ST11 and ST383 K. pneumoniae infections and emphasize the potential of enhancing phage therapy modalities through phage screening. These data provided important resources for assessing and optimizing phage therapies for MDR ST11 and ST383 infection treatment. However, substantial amounts of further work are needed before phage therapy can be translated to human therapeutics. IMPORTANCE K. pneumoniae is recognized as the most common pathogen of hospital- and community-acquired pneumonia across the world. The strains of ST11 and ST383 are frequently reported in patients with pneumonia. However, the efficacy of antibiotics toward K. pneumoniae is decreasing dramatically. As a new approach to combat MDR bacteria, phages have exhibited positive clinical effects and efficacy as synergetic or alternative strategies to antibiotics. Thus, we screened two phages that targeted ST11 and ST383 MDR K. pneumoniae, and they exhibited a broad host range, high lytic activity, and high environmental adaptability. Both phages provided an effective treatment for the early stage of pneumonia in mice, and cocktails consisting of the two phages were more effective in reducing bacterial loads, inflammation, and pathogenic injuries. Although these data suggest that phages are effective alternatives or complements to antibiotics, more research is needed before they can be translated into therapeutics for humans.

Super Shedding in Enteric Pathogens: A Review

Super shedding occurs when a small number of individuals from a given host population shed high levels of a pathogen. Beyond this general definition, various interpretations of the shedding patterns have been proposed to identify super shedders, leading to the description of the super shedding phenomenon in a wide range of pathogens, in particular enteric pathogens, which are of considerable interest. Several underlying mechanisms may explain this observation, including factors related to the environment, the gut microbiota, the pathogen itself (i.e., genetic polymorphism), and the host (including immune factors). Moreover, data suggest that the interplay of these parameters, in particular at the host-pathogen-gut microbiota interface, is of crucial importance for the determination of the super shedding phenotype in enteric pathogens. As a phenomenon playing an important role in the epidemics of enteric diseases, the evidence of super shedding has highlighted the need to develop various control strategies.

Development and application of CRISPR-based genetic tools in Bacillus species and Bacillus phages

Recently, the clustered regularly interspaced short palindromic repeats (CRISPR) system has been developed into a precise and efficient genome editing tool. Since its discovery as an adaptive immune system in prokaryotes, it has been applied in many different research fields including biotechnology and medical sciences. The high demand for rapid, highly efficient and versatile genetic tools to thrive in bacteria-based cell factories accelerates this process. This review mainly focuses on significant advancements of the CRISPR system in Bacillus subtilis, including the achievements in gene editing, and on problems still remaining. Next, we comprehensively summarize this genetic tool's up-to-date development and utilization in other Bacillus species, including B. licheniformis, B. methanolicus, B. anthracis, B. cereus, B. smithii and B. thuringiensis. Furthermore, we describe the current application of CRISPR tools in phages to increase Bacillus hosts' resistance to virulent phages and phage genetic modification. Finally, we suggest potential strategies to further improve this advanced technique and provide insights into future directions of CRISPR technologies for rendering Bacillus species cell factories more effective and more powerful.

A Phage Foundry Framework to Systematically Develop Viral Countermeasures to Combat Antibiotic-Resistant Bacterial Pathogens

At its current rate, the rise of antimicrobial-resistant (AMR) infections is predicted to paralyze our industries and healthcare facilities while becoming the leading global cause of loss of human life. With limited new antibiotics on the horizon, we need to invest in alternative solutions. Bacteriophages (phages)-viruses targeting bacteria-offer a powerful alternative approach to tackle bacterial infections. Despite recent advances in using phages to treat recalcitrant AMR infections, the field lacks systematic development of phage therapies scalable to different applications. We propose a Phage Foundry framework to establish metrics for phage characterization and to fill the knowledge and technological gaps in phage therapeutics. Coordinated investment in AMR surveillance, sampling, characterization, and data sharing procedures will enable rational exploitation of phages for treatments. A fully realized Phage Foundry will enhance the sharing of knowledge, technology, and viral reagents in an equitable manner and will accelerate the biobased economy.