Quality-controlled small-scale production of a well-defined bacteriophage cocktail for use in human clinical trials

Urinary bacteriophage cooperation with bacterial pathogens during human urinary tract infections supports lysogenic phage therapy

Despite much promise in overcoming drug-resistant infections, clinical studies of bacteriophage antibacterial therapy have failed to show durable effectiveness. Although lysogeny plays an important role in bacterial physiology, its significance in diverse microbiomes remains unclear. Here, we tested the following hypotheses: 1) urinary microbiome phage populations switch to a higher relative proportion of temperate phages, and 2) the activity of the phage recombination machinery (integration/excision/transposition) is higher during human urinary tract infections (UTIs) than in non-infected urinary tracts. Using human urine, model organisms, mass spectrometry, gene expression analysis, and the phage phenotype prediction model BACPHLIP, the results corroborated our hypotheses at the functional protein and gene levels. From a human health perspective, these data suggest that temperate phages may facilitate bacterial infections rather than function as protective agents. These findings support the use of lysogenic phages as therapeutic Trojan Horses.

The pharmaceutical quality of freeze-dried tablets containing therapeutic bacteriophages against Pseudomonas aeruginosa and Staphylococcus aureus

The preparation of a solid dosage form containing bacteriophages, which meets pharmaceutical requirements and ensures long-term stability of the phage effect, is significant for implementing phage therapy in practice. A commonly used method for processing phages into a solid form is freeze-drying into a so-called freeze-dried cake; however, to date there have been no studies examining the pharmacopeial parameters of freeze-dried tablets with bacteriophages. In this study, we describe the preparation and properties of freeze-dried tablets containing a cocktail of purified pseudomonal bacteriophage DSM 33593 from the genus Pbunavirus and staphylococcal bacteriophage DSM 33473 from the genus Kayvirus (108 PFU/tablet) as the active ingredient. Maltodextrin was used as a tablet filler, and D-mannitol was used as a cryoprotectant. The tablet preparation process resulted in a decrease in phage titer by no more than 1 log PFU/mL. For Pbunavirus, the titer values in tablet and liquid form were comparable. Kayvirus was more stable in tablet form than in liquid form after six months of storage at 25 °C (a decrease of 1.9 ± 0.8 log PFU/mL and 3.8 ± 0.7 log PFU/mL, respectively). The uniformity of mass of single-dose preparations, uniformity of content of single-dose preparations, and their disintegration complied with pharmacopeial requirements. The uniformity of dosage units of the tablets was maintained over three months. A microscopic examination of the internal part of the tablet revealed a heterogeneous structure, which does not affect the required pharmacopeial properties of the tablets. This study highlights the potential of freeze-dried tablets for long-term preservation of the phage effect at room temperature.

Molecular Epidemiology and In-Depth Characterization of Klebsiella pneumoniae Clinical Isolates from Armenia

The global dissemination of Klebsiella pneumoniae pathotypes with multidrug-resistant (MDR) and hypervirulent traits poses a threat to public health. The situation in Armenia is unclear, and we performed a comprehensive characterisation of 48 clinical isolates of K. pneumoniae, collected from 2018 to 2024. The majority of the isolates (64.58%) were extensively drug-resistant (XDR) and MDR. Genomic analysis of 21 isolates revealed the presence of international high-risk MDR clones (ST395, ST15, and ST307). The ST395 strains were isolated from children and resisted the first-line drugs such as beta-lactams. These isolates harboured a range of virulence determinants, from capsule polysaccharides to siderophores to regulators of the mucoid phenotype. The ST395 strains are enriched by ICEs, plasmids, and prophages, on which antimicrobial resistance (AMR) and virulence genes are located and which may lead to the convergence of MDR and hypervirulent traits. There is a widespread non-specific AMR mechanism among our K. pneumoniae strains. These are mutations in the porin genes, which reduce permeability to antimicrobials, and mutations in the regulators of efflux pumps, which lead to overexpression of drug efflux pumps such as AcrAB. These mechanisms may contribute to the elevated MICs and confer AMR to strains with no specific AMR genes.

Bacteriophages: A Challenge for Antimicrobial Therapy

Phage therapy, which involves the use of bacteriophages (phages) to combat bacterial infections, is emerging as a promising approach to address the escalating threat posed by multidrug-resistant (MDR) bacteria. This brief review examines the historical background and recent advancements in phage research, focusing on their genomics, interactions with host bacteria, and progress in medical and biotechnological applications. Additionally, we expose key aspects of the mechanisms of action, and therapeutic uses of phage considerations in treating MDR bacterial infections are discussed, particularly in the context of infections related to virus-bacteria interactions.

Free DNA partially clarifies discrepancies between qPCR and the conventional phage quantification method

To use phages in a personalized therapy and industrial applications, an accurate quantification is needed. The gold standard method, namely the culture-based double agar overlay (DAO) method, provides an accurate estimate of the number of infectious phages but is laborious and time-intensive. Quantitative polymerase chain reaction (qPCR) can be used as a fast alternative but tends to overestimate the number of infectious phage particles. Here we describe the use of a DNase treatment before quantification of the Staphylococcus aureus phage ISP with qPCR to obtain a more accurate estimate of the number of infectious phage particles. We showed that DNase treatment results in a significant decrease of the concentration when measured with qPCR although for two out of three tested ISP phage stocks, there was still a significant difference with the DAO method. We also showed that the discrepancy between quantification with qPCR and the DAO method is dependent on the storage period of the phage stock, with a larger discrepancy for older stocks. Additionally, we used negative contrast immune electron microscopy to confirm the presence of DNA in the medium of the phage stock and the impact of the DNase treatment on the free DNA.

Evaluation of bacteriophage cocktail on urinary tract infection caused by colistin-resistant Klebsiella pneumoniae in mice model

OBJECTIVE

The colistin-resistant Klebsiella pneumoniae causes complicated urinary tract infections (UTIs). Of them, 73% of strains of K. pneumoniae formed moderate to strong biofilm. Multidrug-resistant (MDR)/Pandrug-resistant (PDR) bacteria causing UTIs are very challenging to conventional antibiotic therapy. However, bacteriophages may be a promising alternative as they easily disrupt the biofilm and act on receptors unrelated to antibiotic resistance mechanisms. This preclinical study evaluated the efficacy of a phage cocktail with different routes and dosages (in quantity and frequency) to eradicate the K. pneumoniae-associated UTI in the mice model.

METHODS

The three lytic phages with the broadest spectrum activity (ΦKpnBHU1, ΦKpnBHU2 and ΦKpnBHU3) were meticulously characterized using SEM and sequencing. The cocktails were administered to mice through urethral, rectal, subcutaneous and oral routes after establishing the UTI with 1 × 108 colony-forming unit/mouse (CFU/mouse) of K. pneumoniae (KpnBHU09) resistant to both the drugs carbapenem and colistin. The efficacy of different routes with varying dosages and frequency of administration was thoroughly optimized.

RESULTS

We observed that two doses of a phage cocktail containing 1 × 105 Plaque-Forming Unit (PFU/mouse) and a single dose of 1 × 109 PFU/mouse per urethra could eradicate KpnBHU09. Intriguingly, the non-invasive administration through oral and rectal routes required higher concentration and many dosages of phages to eliminate KpnBHU09 at any stage of acute UTI. The subcutaneous route was found unsatisfactory in curing the infection.

CONCLUSION

Bacteriophage cocktails administered through transurethral, oral and rectal routes may cure UTIs.

Biological Therapy on Infected Traumatic Wounds: A Case-Control Study

Background:Traumatic wound is a great challenging issue to surgeons, because of large in size, heavily contaminated, infected and unscenic. Infection proceeded to progressive tissue necrosis, septicemia, organ failure or even death. Majority has polymicrobial infections. Bacteriohage therapy will have revolutionized in the treatment of wound. The present study was planned to evaluate the efficacy of topical bacteriophage therapy on large traumatic wounds in comparison with conventional therapy. Methods:The Study conducted from Sept. 2018 to July 2020. Samples between 12- 60 years was taken into study. Customized bacteriophage applied over the wound after serial debridement in case and conventional dressing in control. Fifty four wounded person met the clinical inclusion criteria; 27 in each group. Wound swab and tissue biopsy was taken for bacterial isolation. Isolated specific phage was applied over the wound on alternate day till the wound become sterile and fit for further definitive management. Results: A significant and rapid improvement was observed in wound healing in cases then control group. Average number of day required for complete granulation of wound and attaining sterility was half in cases then control. The hospital stay of the patients on BT was half (20days) than those on CT (40 days). The financial analysis also favours the BT over CT as only 1/third expenditure incurred in BT group as compared to CT Conclusion:Topical Bacteriophage therapy is efficient, effective to clearing the infection in shorter length of time and cost effective for infected traumatic wounds as compared to conventional dressing.

Phage therapy: A primer for orthopaedic trauma surgeons

Phage therapy (PT) continues to attract interest in the fight against fracture-related infection (FRI), particularly for recurring infections that have not been resolved using conventional therapeutic approaches. The journey PT has taken from early clinical application in the pre-antibiotic era to its recent reintroduction to western clinical practice has been accelerated by the increased prevalence of multi-drug resistant (MDR) pathogens in the clinic. This review will present PT's potential as a precise, adaptable, and effective treatment modality, with a focus on patient and phage selection, as well as the various administration protocols currently applied to patients. The challenges for PT, for example the most optimal application technique and dosing, are also discussed and underscore the importance of personalized approaches and the urgent need for more robust clinical evidence. Future perspectives, including phage engineering and innovative delivery systems will be discussed, as they may broaden the applicability of PT to a point where it may become a standard rather than an option of last resort for orthopedic infection management.

A game of resistance: War between bacteria and phages and how phage cocktails can be the solution

While phages hold promise as an antibiotic alternative, they encounter significant challenges in combating bacterial infections, primarily due to the emergence of phage-resistant bacteria. Bacterial defence mechanisms like superinfection exclusion, CRISPR, and restriction-modification systems can hinder phage effectiveness. Innovative strategies, such as combining different phages into cocktails, have been explored to address these challenges. This review delves into these defence mechanisms and their impact at each stage of the infection cycle, their challenges, and the strategies phages have developed to counteract them. Additionally, we examine the role of phage cocktails in the evolving landscape of antibacterial treatments and discuss recent studies that highlight the effectiveness of diverse phage cocktails in targeting essential bacterial receptors and combating resistant strains.

The treatment of Enterococcus faecalis related root canal biofilms with phage therapy

As one of the global concerns, antimicrobial resistance crisis increases the clinical importance of Enterococcus species. Enterococcus faecalis (E. faecalis) specifically penetrates the dentinal tubules and remains prevalent even after endodontic treatment. It has also biofilm forming character as well as the development of resistance to antibiotics. Sodium hypochlorite (NaOCl) is considered the gold standard among antibacterial washing solutions. However, due to its toxic effects, its usage limitations have led to the search for natural, non-toxic alternatives. Phages can be considered an important alternative because of their effects on specific bacteria. The objective of this study was to compare the effect of isolated active vB_Ef1 phage on the removal of E. faecalis biofilm in dentin, together and separately with the chemical irrigation solution NaOCl. As a result of study, the optimal NaOCl solution concentration to be applied with vB_Ef1 phage is 0.5 %, and the use of solution at this value reduces the biofilm mass by 84 %, reaching the highest biofilm mass reduction value. It was found that the combination of phage and NaOCl at appropriate concentrations had the strongest biofilm disruption effect.

Adapting nature's own solution: The effect of rhamnolipid and lytic bacteriophage cocktail on enteric pathogens that proliferate in mucilage

The mucilage event witnessed in the Sea of Marmara in 2021 has emerged as a prominent environmental concern, capturing public attention due to its detrimental effects on ecological, economic, and aesthetic dimensions. Addressing the multifaceted impacts of mucilage demands a nature-centric scientific approach, given its global ramifications spanning economy, public health, international relations, and tourism. Consequently, this study sought to explore alternative approaches for the removal of pathogenic enteric bacteria associated with mucilage occurrences, diverging from conventional methodologies. Specifically, the primary objective was to assess the efficacy of rhamnolipid and a bacteriophage cocktail in mitigating the proliferation of enteric pathogens within mucilaginous environments. During the study, 91 phage isolations were obtained from 45 water samples taken and 10 phages were selected for the broad host range and because of the efficacy tests, a phage cocktail was created with 5 phages. It was found that the mixture of rhamnolipid, phage cocktail and rhamnolipid-phage cocktail reduced bacterial load by 7-9 log10, 9-12 log10 and 9-11 log10 respectively under laboratory conditions. When the study was carried out in seawater, reductions of 4-5 log10, 3 log10 and 4 log10 were achieved. This study has shown that the combined use of rhamnolipid, phage cocktail and rhamnolipid-phage cocktail can be considered as the most effective natural solution proposal for reducing bacterial load, both in laboratory conditions and in sea surface water.

Mini review advantages and limitations of lytic phages compared with chemical antibiotics to combat bacterial infections

The overuse of antibiotics has caused the emergence of antibiotic-resistant strains, such as multidrug-resistant, extensively drug-resistant, and pandrug-resistant bacteria. The treatment of infections caused by such strains has become a formidable challenge. In the post-antibiotic era, phage therapy is an attractive solution for this problem and some successful phase 1 and 2 studies have demonstrated the efficacy and safety of phage therapy over the last decade. It is a form of evolutionary medicine, phages exhibit immunomodulatory and anti-inflammatory properties. However, phage therapy is limited by factors, such as the narrow spectrum of host strains, the special pharmacokinetics and pharmacodynamics in vivo, immune responses, and the development of phage resistance. The aim of this minireview was to compare the potencies of lytic phages and chemical antibiotics to treat bacterial infections. The advantages of phage therapy has fewer side effects, self-replication, evolution, bacterial biofilms eradication, immunomodulatory and anti-inflammatory properties compared with chemical antibiotics. Meanwhile, the disadvantages of phage therapy include the narrow spectrum of available host strains, the special pharmacokinetics and pharmacodynamics in vivo, immune responses, and phage resistance hurdles. Recently, some researchers continue to make efforts to overcome these limitations of phage therapy. Phage therapy will be a welcome addition to the gamut of options available for treating antibiotic-resistant bacterial infections. We focus on the advantages and limitations of phage therapy with the intention of exploiting the advantages and overcoming the limitations.

Mycobacteriophages: therapeutic approach for mycobacterial infections

Tuberculosis (TB) is a significant global health threat, and cases of infection with non-tuberculous mycobacteria (NTM) causing lung disease (NTM-LD) are rising. Bacteriophages and their gene products have garnered interest as potential therapeutic options for bacterial infections. Here, we have compiled information on bacteriophages and their products that can kill Mycobacterium tuberculosis or NTM. We summarize the mechanisms whereby viable phages can access macrophage-resident bacteria and not elicit immune responses, review methodologies of pharmaceutical product development containing mycobacteriophages and their gene products, mainly lysins, in the context of drug regulatory requirements and we discuss industrially relevant methods for producing pharmaceutical products comprising mycobacteriophages, emphasizing delivery of mycobacteriophages to the lungs. We conclude with an outline of some recent case studies on mycobacteriophage therapy.

Pseudomonas aeruginosa Bacteriophages and Their Clinical Applications

Antimicrobial resistance poses a serious risk to contemporary healthcare since it reduces the number of bacterial illnesses that may be treated with antibiotics, particularly for patients with long-term conditions like cystic fibrosis (CF). People with a genetic predisposition to CF often have recurrent bacterial infections in their lungs due to a buildup of sticky mucus, necessitating long-term antibiotic treatment. Pseudomonas aeruginosa infections are a major cause of CF lung illness, and P. aeruginosa airway isolates are frequently resistant to many antibiotics. Bacteriophages (also known as phages), viruses that infect bacteria, are a viable substitute for antimicrobials to treat P. aeruginosa infections in individuals with CF. Here, we reviewed the utilization of P. aeruginosa bacteriophages both in vivo and in vitro, as well as in the treatment of illnesses and diseases, and the outcomes of the latter.

Bacteriophage ISP eliminates Staphylococcus aureus in planktonic phase, but not in the various stages of the biofilm cycle

Metal-implant associated bacterial infections are a major clinical problem due to antibiotic treatment failure. As an alternative, we determined the effects of bacteriophage ISP on clinical isolates of Staphylococcus aureus in various stages of its life cycle in relation to biofilm formation and maturation. ISP effectively eliminated all planktonic phase bacteria, whereas its efficacy was reduced against bacteria attached to the metal implant and bacteria embedded within biofilms. The biofilm architecture hampered the bactericidal effects of ISP, as mechanical disruption of biofilms improved the efficacy of ISP against the bacteria. Phages penetrated the biofilm and interacted with the bacteria throughout the biofilm. However, most of the biofilm-embedded bacteria were phage-tolerant. In agreement, bacteria dispersed from mature biofilms of all clinical isolates, except for LUH15394, tolerated the lytic activity of ISP. Lastly, persisters within mature biofilms tolerated ISP and proliferated in its presence. Based on these findings, we conclude that ISP eliminates planktonic phase Staphylococcus aureus while its efficacy is limited against bacteria attached to the metal implant, embedded within (persister-enriched) biofilms, and dispersed from biofilms.

Personalized bacteriophage therapy outcomes for 100 consecutive cases: a multicentre, multinational, retrospective observational study

In contrast to the many reports of successful real-world cases of personalized bacteriophage therapy (BT), randomized controlled trials of non-personalized bacteriophage products have not produced the expected results. Here we present the outcomes of a retrospective observational analysis of the first 100 consecutive cases of personalized BT of difficult-to-treat infections facilitated by a Belgian consortium in 35 hospitals, 29 cities and 12 countries during the period from 1 January 2008 to 30 April 2022. We assessed how often personalized BT produced a positive clinical outcome (general efficacy) and performed a regression analysis to identify functional relationships. The most common indications were lower respiratory tract, skin and soft tissue, and bone infections, and involved combinations of 26 bacteriophages and 6 defined bacteriophage cocktails, individually selected and sometimes pre-adapted to target the causative bacterial pathogens. Clinical improvement and eradication of the targeted bacteria were reported for 77.2% and 61.3% of infections, respectively. In our dataset of 100 cases, eradication was 70% less probable when no concomitant antibiotics were used (odds ratio = 0.3; 95% confidence interval = 0.127-0.749). In vivo selection of bacteriophage resistance and in vitro bacteriophage-antibiotic synergy were documented in 43.8% (7/16 patients) and 90% (9/10) of evaluated patients, respectively. We observed a combination of antibiotic re-sensitization and reduced virulence in bacteriophage-resistant bacterial isolates that emerged during BT. Bacteriophage immune neutralization was observed in 38.5% (5/13) of screened patients. Fifteen adverse events were reported, including seven non-serious adverse drug reactions suspected to be linked to BT. While our analysis is limited by the uncontrolled nature of these data, it indicates that BT can be effective in combination with antibiotics and can inform the design of future controlled clinical trials. BT100 study, ClinicalTrials.gov registration: NCT05498363 .

Decoding antimicrobial resistance: unraveling molecular mechanisms and targeted strategies

Antimicrobial resistance poses a significant global health threat, necessitating innovative approaches for combatting it. This review explores various mechanisms of antimicrobial resistance observed in various strains of bacteria. We examine various strategies, including antimicrobial peptides (AMPs), novel antimicrobial materials, drug delivery systems, vaccines, antibody therapies, and non-traditional antibiotic treatments. Through a comprehensive literature review, the efficacy and challenges of these strategies are evaluated. Findings reveal the potential of AMPs in combating resistance due to their unique mechanisms and lower propensity for resistance development. Additionally, novel drug delivery systems, such as nanoparticles, show promise in enhancing antibiotic efficacy and overcoming resistance mechanisms. Vaccines and antibody therapies offer preventive measures, although challenges exist in their development. Non-traditional antibiotic treatments, including CRISPR-Cas systems, present alternative approaches to combat resistance. Overall, this review underscores the importance of multifaceted strategies and coordinated global efforts to address antimicrobial resistance effectively.

Characterization of two bacteriophages specific to Acinetobacter baumannii and their effects on catheters biofilm

Multidrug-resistant strains of Acinetobacter baumannii cause major nosocomial infections. Bacteriophages that are specific to the bacterial species and destroy bacteria can be effectively used for treatment. In this study, we characterized lytic bacteriophages specific to A. baumannii strains. We isolated lytic bacteriophages from environmental water samples and then investigated their morphology, host range, growth characteristics, stability, genome analysis, and biofilm destruction on the catheter surface. Our results showed that the efficacy of the phages varied between 32% and 78%, tested on 78 isolates of A. baumannii; 80 phages were isolated, and two lytic bacteriophages, vB_AbaP_HB01 (henceforth called C2 phage) and vB_AbaM_HB02 (henceforth called K3 phage), were selected for characterization. Electron microscopy scans revealed that the C2 and K3 phages were members of the Podoviridae and Myoviridae families, respectively. Whole-genome sequencing revealed that the sequence of the C2 phage is available in the NCBI database (accession number: OP917929.1), and it was found sequence identity with Acinetobacter phage AB1 18%, the K3 phage DNA sequence is closely related to Acinetobacter phage vB_AbaM_phiAbaA1 (94% similarity). The cocktail of C2 and K3 phages demonstrated a promising decrease in the bacterial cell counts of the biofilm after 4 h. Under a scanning electron microscope, the cocktail treatment destructed the biofilm on the catheter. We propose that the phage cocktail could be a strong alternative to antibiotics to control the A. baumannii biofilm in catheter infections.

Stability study in selected conditions and biofilm-reducing activity of phages active against drug-resistant Acinetobacter baumannii

Acinetobacter baumannii is currently a serious threat to human health, especially to people with immunodeficiency as well as patients with prolonged hospital stays and those undergoing invasive medical procedures. The ever-increasing percentage of strains characterized by multidrug resistance to widely used antibiotics and their ability to form biofilms make it difficult to fight infections with traditional antibiotic therapy. In view of the above, phage therapy seems to be extremely attractive. Therefore, phages with good storage stability are recommended for therapeutic purposes. In this work, we present the results of studies on the stability of 12 phages specific for A. baumannii under different conditions (including temperature, different pH values, commercially available disinfectants, essential oils, and surfactants) and in the urine of patients with urinary tract infections (UTIs). Based on our long-term stability studies, the most optimal storage method for the A. baumannii phage turned out to be - 70 °C. In contrast, 60 °C caused a significant decrease in phage activity after 1 h of incubation. The tested phages were the most stable at a pH from 7.0 to 9.0, with the most inactivating pH being strongly acidic. Interestingly, ethanol-based disinfectants caused a significant decrease in phage titers even after 30 s of incubation. Moreover, copper and silver nanoparticle solutions also caused a decrease in phage titers (which was statistically significant, except for the Acba_3 phage incubated in silver solution), but to a much lesser extent than disinfectants. However, bacteriophages incubated for 24 h in essential oils (cinnamon and eucalyptus) can be considered stable.

Exploiting lung adaptation and phage steering to clear pan-resistant Pseudomonas aeruginosa infections in vivo

Pseudomonas aeruginosa is a major nosocomial pathogen that causes severe disease including sepsis. Carbapenem-resistant P. aeruginosa is recognised by the World Health Organisation as a priority 1 pathogen, with urgent need for new therapeutics. As such, there is renewed interest in using bacteriophages as a therapeutic. However, the dynamics of treating pan-resistant P. aeruginosa with phage in vivo are poorly understood. Using a pan-resistant P. aeruginosa in vivo infection model, phage therapy displays strong therapeutic potential, clearing infection from the blood, kidneys, and spleen. Remaining bacteria in the lungs and liver displays phage resistance due to limiting phage adsorption. Yet, resistance to phage results in re-sensitisation to a wide range of antibiotics. In this work, we use phage steering in vivo, pre-exposing a pan resistant P. aeruginosa infection with a phage cocktail to re-sensitise bacteria to antibiotics, clearing the infection from all organs.

Investigation into scalable and efficient enterotoxigenic Escherichia coli bacteriophage production

As the demand for bacteriophage (phage) therapy increases due to antibiotic resistance in microbial pathogens, strategies and methods for increased efficiency, large-scale phage production need to be determined. To date, very little has been published on how to establish scalable production for phages, while achieving and maintaining a high titer in an economical manner. The present work outlines a phage production strategy using an enterotoxigenic Escherichia coli-targeting phage, 'Phage75', and accounts for the following variables: infection load, multiplicity of infection, temperature, media composition, harvest time, and host bacteria. To streamline this process, variables impacting phage propagation were screened through a high-throughput assay monitoring optical density at 600 nm (OD600) to indirectly infer phage production from host cell lysis. Following screening, propagation conditions were translated in a scalable fashion in shake flasks at 0.01 L, 0.1 L, and 1 L. A final, proof-of-concept production was then carried out in a CellMaker bioreactor to represent practical application at an industrial level. Phage titers were obtained in the range of 9.5-10.1 log10 PFU/mL with no significant difference between yields from shake flasks and CellMaker. Overall, this suggests that the methodology for scalable processing is reliable for translating into large-scale phage production.

Nano-emulsion encapsulation for the efficient delivery of bacteriophage therapeutics

Antibiotic resistance has become the major concern for global public health. Phage therapy is being considered as an alternative for antibiotics to treat the multidrug resistant bacterial infections. Bacteriophage therapeutic developments has faced many challenges, including the drug formulations for sustainable phage delivery. The nano-emulsion platform has been described as the best approach to retain phage efficacy, shelf life and stability. Encapsulated phage drugs ensure stable delivery of phages to the target site and integrate in the system. In this review, our main focus is on the nano-emulsion encapsulation of bacteriophages and its effects towards the phage therapeutic development.

Isolation and characterization of a multidrug-resistant Staphylococcus aureus infecting phage and its therapeutic use in mice

In recent years, the emergence of multidrug-resistant bacteria has limited the selection of drugs for treating bacterial infections, reduced clinical efficacy, and increased treatment costs and mortality. It is urgent to find alternative antibiotics. In order to explore a new method for controlling methicillin-resistant Staphylococcus aureus (S. aureus), this study isolated and purified a multidrug-resistant S. aureus broad-spectrum phage JPL-50 from wastewater. JPL-50 belongs to the Siphoviridae family after morphological observation, biological characterization, and transmission electron microscopy (TEM) fragmentation spectrum analysis. It can cleave 84% of tested S. aureus (168/200), in which 100% of tested mastitis-associated strains (48/48) and 72.04% of MRSA strains (67/93) were lysed. In addition, it has an optimal growth temperature of about 30°C, a high activity within a wide pH range (pH 3-10), and an optimal multiplicity of infection of 0.01. The one-step growth curve shows a latent time of 20 min, an explosive time of 80 min. JPL-50 was 16 927 bp in length and was encoded by double-stranded DNA, with no genes associated with bacterial resistance or virulence factors detected. In a therapeutic study, injection of the phage JPL-50 once and for 7 times in 7 days protected 40% and 60% of the mice from fatal S. aureus infection, respectively. More importantly, JPL-50-doxycycline combination could effectively inhibit host S. aureus in vitro and reduce the use of doxycycline within 8 h. In conclusion, the bacteriophage JPL-50 has a wide lysis spectrum, high lysis rate, high tolerance to extreme environments, and moderate in vivo activity, providing ideas for developing multidrug-resistant S. aureus infections.

Propagation, Purification, and Characterization of Bacteriophages for Phage Therapy

Phage therapy is an alternative approach to combat bacterial infections. In this approach, bacteriophages are used as antimicrobial agents due to their properties to infect specific bacterial cells, to propagate inside their hosts, and to lyse host cell to release progeny phages. However, to introduce bacteriophages to clinical or veterinary practice, it is necessary to construct a large library of precisely characterized phages. Therefore, in this chapter, methods for propagation, purification, and microbiological characterization of bacteriophages are presented in the light of their potential use in phage therapy. Isolation of newly discovered bacteriophages from different habitats is also described as it is a preliminary assessment of their efficacy in combating bacterial biofilms and in the treatment of bacterial infections in a simple insect model-Galleria mellonella.

Bacteriophage Production in Compliance with Regulatory Requirements

In this chapter, we discuss production requirements for therapeutic bacteriophage preparations. We review the current regulatory expectancies and focus on pragmatic production processes, implementing relevant controls to ensure the quality, safety, and efficacy of the final products. The information disclosed in this chapter can also serve as a basis for discussions with competent authorities regarding the implementation of expedited bacteriophage product development and licensing pathways, taking into account some peculiarities of bacteriophages (as compared to conventional medicines), such as their specificity for, and co-evolution with, their bacterial hosts. To maximize the potential of bacteriophages as natural controllers of bacterial populations, the implemented regulatory frameworks and manufacturing processes should not only cater to defined bacteriophage products. But, they should also facilitate personalized approaches in which bacteriophages are selected ad hoc and even trained to target the patient's infecting bacterial strain(s), whether or not in combination with other antimicrobials such as antibiotics.

Human Complement Inhibits Myophages against Pseudomonas aeruginosa

Therapeutic bacteriophages (phages) are primarily chosen based on their in vitro bacteriolytic activity. Although anti-phage antibodies are known to inhibit phage infection, the influence of other immune system components is less well known. An important anti-bacterial and anti-viral innate immune system that may interact with phages is the complement system, a cascade of proteases that recognizes and targets invading microorganisms. In this research, we aimed to study the effects of serum components such as complement on the infectivity of different phages targeting Pseudomonas aeruginosa. We used a fluorescence-based assay to monitor the killing of P. aeruginosa by phages of different morphotypes in the presence of human serum. Our results reveal that several myophages are inhibited by serum in a concentration-dependent way, while the activity of four podophages and one siphophage tested in this study is not affected by serum. By using specific nanobodies blocking different components of the complement cascade, we showed that activation of the classical complement pathway is a driver of phage inhibition. To determine the mechanism of inhibition, we produced bioorthogonally labeled fluorescent phages to study their binding by means of microscopy and flow cytometry. We show that phage adsorption is hampered in the presence of active complement. Our results indicate that interactions with complement may affect the in vivo activity of therapeutically administered phages. A better understanding of this phenomenon is essential to optimize the design and application of therapeutic phage cocktails.

Advanced Manufacturing, Formulation and Microencapsulation of Therapeutic Phages

Manufacturing and formulation of stable, high purity, and high dose bacteriophage drug products (DPs) suitable for clinical usage would benefit from improved process monitoring and control of critical process parameters that affect product quality attributes. Chemistry, Manufacturing, and Controls (CMC) for both upstream (USP) and downstream processes (DSP) need mapping of critical process parameters (CPP) and linking these to critical quality attributes (CQA) to ensure quality and consistency of phage drug substance (DS) and DPs development. Single-use technologies are increasingly becoming the go-to manufacturing option with benefits both for phage bioprocess development at the engineering run research stage and for final manufacture of the phage DS. Future phage DPs under clinical development will benefit from implementation of process analytical technologies (PAT) for better process monitoring and control. These are increasingly being used to improve process robustness (to reduce batch-to-batch variability) and productivity (yielding high phage titers). Precise delivery of stable phage DPs that are suitably formulated as liquids, gels, solid-oral dosage forms, and so forth, could significantly enhance efficacy of phage therapy outcomes. Pre-clinical development of phage DPs must include at an early stage of development, considerations for their formulation including their characterization of physiochemical properties (size, charge, etc.), buffer pH and osmolality, compatibility with regulatory approved excipients, storage stability (packaging, temperature, humidity, etc.), ease of application, patient compliance, ease of manufacturability using scalable manufacturing unit operations, cost, and regulatory requirements.

The Potential of Bacteriophage Therapy as an Alternative Treatment Approach for Antibiotic-Resistant Infections

OBJECTIVE

This study aimed to provide a comprehensive overview of the current state of the literature on the therapeutical application of bacteriophages.

METHODS

First, a bibliometric analysis was performed using the database Web of Science to determine annual number of publications and citations. Second, a systematic literature review was conducted on randomized-controlled trials (RCTs) of phage therapy in PubMed.

RESULTS

Over the past decade, the number of publications on bacteriophage therapy increased more than fourfold with 212 articles in 2011 and 739 in 2022. The systematic search in PubMed yielded 7 RCTs eligible for inclusion, reporting on a total of 418 participants. Identified indications in this study included bacterial diarrhea, urinary tract infections, infected burn wounds, chronic otitis, chronic venous leg ulcers, and chronic rhinosinusitis. In three studies, mild to moderate adverse events were reported in 10/195 participants (5.1%). Three of the studies reported a statistically significant difference in outcomes comparing phage therapy with standard of care or placebo.

CONCLUSION

Phage therapy has gained increasing interest over the years. RCTs on different indications suggest the safety of phage therapy; however, reasons why phage therapy is not yet well accepted are limitations in the study designs. For a successful translation into clinical practice researchers and clinicians should learn from the earlier experiences and consider issues such as the quality of phage preparation, sensitivity testing, titer and dosages, as well as access to the infection site and stability for standardized protocols and future trials.

Distribution, inducibility, and characteristics of Latilactobacillus curvatus temperate phages

Aim: Temperate phages are known to heavily impact the growth of their host, be it in a positive way, e.g., when beneficial genes are provided by the phage, or negatively when lysis occurs after prophage induction. This study provides an in-depth look into the distribution and variety of prophages in Latilactobacillus curvatus (L. curvatus). This species is found in a wide variety of ecological niches and is routinely used as a meat starter culture. Methods: Fourty five L. curvatus genomes were screened for prophages. The intact predicted prophages and their chromosomal integration loci were described. Six L. curvatus lysogens were analysed for phage-mediated lysis post induction via UV light and/or mitomycin C. Their lysates were analysed for phage particles via viral DNA sequencing and transmission electron microscopy. Results: Two hundred and six prophage sequences of any completeness were detected within L. curvatus genomes. The 50 as intact predicted prophages show high levels of genetic diversity on an intraspecies level with conserved regions mostly in the replication and head/tail gene clusters. Twelve chromosomal loci, mostly tRNA genes, were identified, where intact L. curvatus phages were integrated. The six analysed L. curvatus lysogens showed strain-dependent lysis in various degrees after induction, yet only four of their lysates appeared to contain fully assembled virions with the siphovirus morphotype. Conclusion: Our data demonstrate that L. curvatus is a (pro)phage-susceptible species, harbouring multiple intact prophages and remnant sequences thereof. This knowledge provides a basis to study phage-host interaction influencing microbial communities in food fermentations.

The Potential of Bacteriophage-Antibiotic Combination Therapy in Treating Infections with Multidrug-Resistant Bacteria

The growing threat of antibiotic resistance is a significant global health challenge that has intensified in recent years. The burden of antibiotic resistance on public health is augmented due to its multifaceted nature, as well as the slow-paced and limited development of new antibiotics. The threat posed by resistance is now existential in phage therapy, which had long been touted as a promising replacement for antibiotics. Consequently, it is imperative to explore the potential of combination therapies involving antibiotics and phages as a feasible alternative for treating infections with multidrug-resistant bacteria. Although either bacteriophage or antibiotics can potentially treat bacterial infections, they are each fraught with resistance. Combination therapies, however, yielded positive outcomes in most cases; nonetheless, a few combinations did not show any benefit. Combination therapies comprising the synergistic activity of phages and antibiotics and combinations of phages with other treatments such as probiotics hold promise in the treatment of drug-resistant bacterial infections.

Stability Considerations for Bacteriophages in Liquid Formulations Designed for Nebulization

Pulmonary bacterial infections present a significant health risk to those with chronic respiratory diseases (CRDs) including cystic fibrosis (CF) and chronic-obstructive pulmonary disease (COPD). With the emergence of antimicrobial resistance (AMR), novel therapeutics are desperately needed to combat the emergence of resistant superbugs. Phage therapy is one possible alternative or adjunct to current antibiotics with activity against antimicrobial-resistant pathogens. How phages are administered will depend on the site of infection. For respiratory infections, a number of factors must be considered to deliver active phages to sites deep within the lung. The inhalation of phages via nebulization is a promising method of delivery to distal lung sites; however, it has been shown to result in a loss of phage viability. Although preliminary studies have assessed the use of nebulization for phage therapy both in vitro and in vivo, the factors that determine phage stability during nebulized delivery have yet to be characterized. This review summarizes current findings on the formulation and stability of liquid phage formulations designed for nebulization, providing insights to maximize phage stability and bactericidal activity via this delivery method.

Phage Therapy for Diabetic Foot Infection: A Case Series

PURPOSE

Infected diabetic foot ulcers can be difficult to treat and, despite appropriate antibiotic therapy, some diabetic foot infections (DFIs) require amputation. Bacteriophages (phages) are viruses that infect and kill bacteria. Phage therapy has been repeatedly used to successfully treat DFIs and other chronic wounds.

METHODS

This article reports the provision of topical adjunctive anti-staphylococcal phage therapy to 10 patients with DFI at high risk of amputation at two UK hospitals as part of clinical care; tolerability and efficacy were clinically assessed.

FINDINGS

The opinion of the experienced clinical teams caring for these patients was that 9 of the 10 patients appeared to benefit from adjunctive phage therapy. No adverse effects were reported by clinicians or patients. In 6 of 10 patients the clinical impression was that phage therapy facilitated clinical resolution of infection and limb salvage. Resolution of soft tissue infection was observed in a 7th patient but unresolved osteomyelitis required amputation. An 8th patient demonstrated eradication of Staphylococcus aureus from a polymicrobial infection and a 9th showed signs of clinical improvement before early cessation of phage therapy due to an unrelated event. One patient, with a weakly susceptible S aureus isolate, had no significant response.

IMPLICATIONS

This report describes the largest application of phage therapy in the United Kingdom to date and the first application of phage therapy for DFI in the United Kingdom and offers subjective hints toward impressive tolerability and efficacy. Phage therapy has the potential to transform the prevention and treatment of DFIs.

Peptidoglycan Endopeptidase from Novel Adaiavirus Bacteriophage Lyses Pseudomonas aeruginosa Strains as Well as Arthrobacter globiformis and A. pascens Bacteria

A novel virus lytic for Pseudomonas aeruginosa has been purified. Its viral particles have a siphoviral morphology with a head 60 nm in diameter and a noncontractile tail 184 nm long. The dsDNA genome consists of 16,449 bp, has cohesive 3' termini, and encodes 28 putative proteins in a single strain. The peptidoglycan endopeptidase encoded by ORF 16 was found to be the lytic enzyme of this virus. The recombinant, purified enzyme was active up to 55 °C in the pH range 6-9 against all tested isolates of P. aeruginosa, but, surprisingly, also against the distant Gram-positive micrococci Arthrobacter globiformis and A. pascens. Both this virus and its endolysin are further candidates for possible treatment against P. aeruginosa and probably also other bacteria.

The effect of phage-antibiotic combination strategy on multidrug-resistant Acinetobacter baumannii biofilms

Acinetobacter baumannii (A. baumannii) is considered a critical human pathogen due to multi-drug resistance and increased infections. As a result of the resistance of A. baumannii biofilms to antimicrobial agents, it is necessary to develop new biofilm control strategies. In the present study, we evaluated the efficacy of two previously isolated bacteriophage C2 phage, K3 phage and phage cocktail (C2 + K3 phage) as a therapeutic agent in combination with antibiotic (colistin) against biofilm of multidrug-resistant A. baumannii strains (n = 24). The effects of phage and antibiotics on mature biofilm were investigated simultaneously and sequentially in 24 and 48 h. The combination protocol was more effective than antibiotics alone in 54.16% of the strains in 24 h. The sequential application was more effective than the simultaneous protocol compared with the 24 h single applications. When the application of antibiotics and phages alone was compared with their combined administration in 48 h. The sequential and simultaneous applications were more effective than single applications in all strains except two. We observed that combination of phage and antibiotics could increase biofilm eradication and provides new insights into the use of bacteriophages and antibiotics in the treatment of biofilm-associated infections caused by antibiotic-resistant bacteria.

Isolation and in vitro characterization of novel S. epidermidis phages for therapeutic applications

S. epidermidis is an important opportunistic pathogen causing chronic prosthetic joint infections associated with biofilm growth. Increased tolerance to antibiotic therapy often requires prolonged treatment or revision surgery. Phage therapy is currently used as compassionate use therapy and continues to be evaluated for its viability as adjunctive therapy to antibiotic treatment or as an alternative treatment for infections caused by S. epidermidis to prevent relapses. In the present study, we report the isolation and in vitro characterization of three novel lytic S. epidermidis phages. Their genome content analysis indicated the absence of antibiotic resistance genes and virulence factors. Detailed investigation of the phage preparation indicated the absence of any prophage-related contamination and demonstrated the importance of selecting appropriate hosts for phage development from the outset. The isolated phages infect a high proportion of clinically relevant S. epidermidis strains and several other coagulase-negative species growing both in planktonic culture and as a biofilm. Clinical strains differing in their biofilm phenotype and antibiotic resistance profile were selected to further identify possible mechanisms behind increased tolerance to isolated phages.

Successful Bacteriophage-Antibiotic Combination Therapy against Multidrug-Resistant Pseudomonas aeruginosa Left Ventricular Assist Device Driveline Infection

There is considerable interest in the use of bacteriophages (phages) to treat Pseudomonas aeruginosa infections associated with left ventricular assist devices (LVADs). These infections are often challenging to manage due to high rates of multidrug resistance and biofilm formation, which could potentially be overcome with the use of phages. We report a case of a 54-year-old man with relapsing multidrug-resistant P. aeruginosa LVAD driveline infection, who was treated with a combination of two lytic antipseudomonal phages administered intravenously and locally. Treatment was combined with LVAD driveline repositioning and systemic antibiotic administration, resulting in a successful outcome with clinical cure and eradication of the targeted bacteria. However, laboratory in vitro models showed that phages alone could not eradicate biofilms but could prevent biofilm formation. Phage-resistant bacterial strains evolved in biofilm models and showed decreased susceptibility to the phages used. Further studies are needed to understand the complexity of phage resistance and the interaction of phages and antibiotics. Our results indicate that the combination of phages, antibiotics, and surgical intervention can have great potential in treating LVAD-associated infections. More than 21 months post-treatment, our patient remains cured of the infection.

A Century of Clinical Use of Phages: A Literature Review

Growing antibiotic resistance and the broken antibiotic market have renewed interest in the use of phages, a century-old therapy that fell into oblivion in the West after two decades of promising results. This literature review with a particular focus on French literature aims to complement current scientific databases with medical and non-medical publications on the clinical use of phages. While several cases of successful treatment with phages have been reported, prospective randomized clinical trials are needed to confirm the efficacy of this therapy.

Coping with the ESKAPE pathogens: Evolving strategies, challenges and future prospects

Globally, the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are the major cause of nosocomial infections. These pathogens are multidrug resistant, and their negative impacts have brought serious health challenges and economic burden on many countries worldwide. Thus, this narrative review exploits different emerging alternative therapeutic strategies including combination antibiotics, antimicrobial peptides ((AMPs), bacteriophage and photodynamic therapies used in the treatment of the ESKAPE pathogens, their merits, limitations, and future prospects. Our findings indicate that ESKAPE pathogens exhibit resistance to drug using different mechanisms including drug inactivation by irreversible enzyme cleavage, drug-binding site alteration, diminution in permeability of drug or drug efflux increment to reduce accumulation of drug as well as biofilms production. However, the scientific community has shown significant interest in using these novel strategies with numerous benefits although they have some limitations including but not limited to instability and toxicity of the therapeutic agents, or the host developing immune response against the therapeutic agents. Thus, comprehension of resistance mechanisms of these pathogens is necessary to further develop or modify these approaches in order to overcome these health challenges including the barriers of bacterial resistance.

Phage Therapy as an Alternative Treatment Modality for Resistant Staphylococcus aureus Infections

The production and use of antibiotics increased significantly after the Second World War due to their effectiveness against bacterial infections. However, bacterial resistance also emerged and has now become an important global issue. Those most in need are typically high-risk and include individuals who experience burns and other wounds, as well as those with pulmonary infections caused by antibiotic-resistant bacteria, such as Pseudomonas aeruginosa, Acinetobacter sp, and Staphylococci. With investment to develop new antibiotics waning, finding and developing alternative therapeutic strategies to tackle this issue is imperative. One option remerging in popularity is bacteriophage (phage) therapy. This review focuses on Staphylococcus aureus and how it has developed resistance to antibiotics. It also discusses the potential of phage therapy in this setting and its appropriateness in high-risk people, such as those with cystic fibrosis, where it typically forms a biofilm.

Monitoring phage-induced lysis of gram-negatives in real time using a fluorescent DNA dye

Bacteriophages (phages) are viruses that specifically attack bacteria. Their use as therapeutics, which constitutes a promising alternative to antibiotics, heavily relies on selecting effective lytic phages against the pathogen of interest. Current selection techniques are laborious and do not allow for direct visualization of phage infection dynamics. Here, we present a method that circumvents these limitations. It can be scaled for high-throughput and permits monitoring of the phage infection in real time via a fluorescence signal readout. This is achieved through the use of a membrane-impermeant nucleic acid dye that stains the DNA of damaged or lysed bacteria and new phage progeny. We have tested the method on Pseudomonas aeruginosa and Klebsiella pneumoniae and show that an increase in fluorescence reflects phage-mediated killing. This is confirmed by other techniques including spot tests, colony plating, flow cytometry and metabolic activity measurements. Furthermore, we illustrate how our method may be used to compare the activity of different phages and to screen the susceptibility of clinical isolates to phage. Altogether, we present a fast, reliable way of selecting phages against Gram-negative bacteria, which may be valuable in optimizing the process of selecting phages for therapeutic use.

A novel virulent Litunavirus phage possesses therapeutic value against multidrug resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is a notable nosocomial pathogen that can cause severe infections in humans and animals. The emergence of multidrug resistant (MDR) P. aeruginosa has motivated the development of phages to treat the infections. In this study, a novel Pseudomonas phage, vB_PaeS_VL1 (VL1), was isolated from urban sewage. Phylogenetic analyses revealed that VL1 is a novel species in the genus Litunavirus of subfamily Migulavirinae. The VL1 is a virulent phage as no genes encoding lysogeny, toxins or antibiotic resistance were identified. The therapeutic potential of phage VL1 was investigated and revealed that approximately 56% (34/60 strains) of MDR P. aeruginosa strains, isolated from companion animal diseases, could be lysed by VL1. In contrast, VL1 did not lyse other Gram-negative and Gram-positive bacteria suggesting its specificity of infection. Phage VL1 demonstrated high efficiency to reduce bacterial load (~ 6 log cell number reduction) and ~ 75% reduction of biofilm in pre-formed biofilms of MDR P. aeruginosa. The result of two of the three MDR P. aeruginosa infected Galleria mellonella larvae showed that VL1 could significantly increase the survival rate of infected larvae. Taken together, phage VL1 has genetic and biological properties that make it a potential candidate for phage therapy against P. aeruginosa infections.

[Viruses for health: Bacteriophages]

Bacteriophages are naturally occurring viruses that specifically target bacteria. They are widely distributed in the environment. The concept of phage therapy is to isolate phages, characterize them, cultivate them and then purify them to treat bacterial infections. There is currently a revival of phage therapy, and its implementation presupposes the availability of active phages of pharmaceutical quality. From a regulatory point of view, the status of phages is not yet clearly defined by the authorities. The availability of phages produced by the pharmaceutical industry and through academic development programs such as the PHAGEinLYON program represents a breakthrough in the development of phage therapy. Prosthetic joint infections and digestive diseases seem to be relevant indications, but preclinical studies and randomized clinical trials are now needed to be done.

The potential of bacteriophage therapy in the treatment of paediatric respiratory infections

The looming antibiotic resistance crisis is forcing clinicians to consider alternative approaches to treating bacterial infections. As the window of use for current antimicrobial agents becomes ever narrower, we consider if looking back will now be the way forward. Conceptually, phage therapy is simple and specific; a targeted treatment to control bacterial overgrowth. In this article we discuss bacteriophage and potential use in future therapy.

Tracking the phage trends: A comprehensive review of applications in therapy and food production

In the present scenario, the challenge of emerging antimicrobial resistance is affecting human health globally. The increasing incidences of multidrug-resistant infections have become harder to treat, causing high morbidity, and mortality, and are posing extensive financial loss. Limited discovery of new antibiotic molecules has further complicated the situation and has forced researchers to think and explore alternatives to antibiotics. This has led to the resurgence of the bacteriophages as an effective alternative as they have a proven history in the Eastern world where lytic bacteriophages have been used since their first implementation over a century ago. To help researchers and clinicians towards strengthening bacteriophages as a more effective, safe, and economical therapeutic alternative, the present review provides an elaborate narrative about the important aspects of bacteriophages. It abridges the prerequisite essential requirements of phage therapy, the role of phage biobank, and the details of immune responses reported while using bacteriophages in the clinical trials/compassionate grounds by examining the up-to-date case reports and their effects on the human gut microbiome. This review also discusses the potential of bacteriophages as a biocontrol agent against food-borne diseases in the food industry and aquaculture, in addition to clinical therapy. It finishes with a discussion of the major challenges, as well as phage therapy and phage-mediated biocontrols future prospects.

Characteristics of a novel temperate bacteriophage against Staphylococcus arlettae (vB_SarS_BM31)

BACKGROUND

Staphylococcus arlettae is a rarely reported coagulase-negative staphylococcus (CoNS) isolated from infected humans and livestock. Observing phage-bacteria interaction could improve the understanding of bacterial pathogenetic mechanisms, providing foundational evidence for phage therapy or phage detection. Herein, we aimed to characterise and annotate a novel bacteriophage, vB_SarS_BM31 (BM31), specific to S. arlettae. This bacteriophage was isolated from a milk sample associated with bovine mastitis and collected in the Sichuan Province, China.

RESULTS

The BM31 genome comprised a linear double-stranded DNA of 42,271 base pair in length with a G + C content of 34.59%. A total of 65 open reading frames (ORFs) were assembled from phage DNA, of which 29 were functionally annotated. These functional genes were divided into four modules: the structural, DNA packing and replication, lysis, and lysogeny modules. Holin (ORF25), lysin (ORF26), and integrase (ORF28) were located closely in the entire BM31 genome and were important for lyse or lysogeny cycle of BM31. The phage was identified as a temperate phage according to whole genome analysis and life cycle assay, with basic biological characteristics such as small burst size, short latency period, and narrow host range, consistent with the characteristics of the family Siphoviridae, subcluster B14 of the Staphylococcus bacteriophage.

CONCLUSIONS

The present isolation and characterisation of BM31 contributes to the Staphylococcus bacteriophage database and provides a theoretical foundation for its potential applications. To the best of our knowledge, BM31 is the only shared and completely reported phage against S. arlettae in the entire public database.

Isolation and Characterization of Lytic Bacteriophages Active against Clinical Strains of E. coli and Development of a Phage Antimicrobial Cocktail

Pathogenic E. coli cause urinary tract, soft tissue and central nervous system infections, sepsis, etc. Lytic bacteriophages can be used to combat such infections. We investigated six lytic E. coli bacteriophages isolated from wastewater. Transmission electron microscopy and whole genome sequencing showed that the isolated bacteriophages are tailed phages of the Caudoviricetes class. One-step growth curves revealed that their latent period of reproduction is 20-30 min, and the average value of the burst size is 117-155. During co-cultivation with various E. coli strains, the phages completely suppressed bacterial host culture growth within the first 4 h at MOIs 10^-7 to 10^-3. The host range lysed by each bacteriophage varied from six to two bacterial strains out of nine used in the study. The cocktail formed from the isolated bacteriophages possessed the ability to completely suppress the growth of all the E. coli strains used in the study within 6 h and maintain its lytic activity for 8 months of storage. All the isolated bacteriophages may be useful in fighting pathogenic E. coli strains and in the development of phage cocktails with a long storage period and high efficiency in the treatment of bacterial infections.

Isolation and Characterization of Lytic Pseudomonas aeruginosa Bacteriophages Isolated from Sewage Samples from Tunisia

Bacteriophages could be a useful adjunct to antibiotics for the treatment of multidrug-resistant Pseudomonas aeruginosa infections. In this study, lytic P. aeruginosa myoviruses PsCh, PsIn, Ps25, and Ps12on-D were isolated from Tunisian sewage samples. Phage Ps12on-D displayed an adsorption time of ~10 min, a short latency period (~10 min), and a large burst size (~115 PFU per infected cell) under standard growth conditions. All phages were active at broad temperature (4 °C to 50 °C) and pH (3.0 to 11.0) ranges and were able to lyse a wide variety of P. aeruginosa strains isolated from clinical and environmental samples worldwide. Illumina sequencing revealed double-stranded DNA genomes ranging from 87,887 and 92,710 bp with high sequence identity to Pseudomonas phage PAK_P1. All four phages based on sequence analysis were assigned to the Pakpunavirus genus. The presented characterization and preclinical assessment are part of an effort to establish phage therapy treatment as an alternative strategy for the management of multidrug-resistant P. aeruginosa infections in Tunisia.

Bacteriophage-antibiotic combination therapy against extensively drug-resistant Pseudomonas aeruginosa infection to allow liver transplantation in a toddler

Post-operative bacterial infections are a leading cause of mortality and morbidity after ongoing liver transplantation. Bacteria causing these infections in the hospital setting can exhibit high degrees of resistance to multiple types of antibiotics, which leads to major therapeutic hurdles. Alternate ways of treating these antibiotic-resistant infections are thus urgently needed. Phage therapy is one of them and consists in using selected bacteriophage viruses - viruses who specifically prey on bacteria, naturally found in various environmental samples - as bactericidal agents in replacement or in combination with antibiotics. The use of phage therapy raises various research questions to further characterize what determines therapeutic success or failure. In this work, we report the story of a toddler who suffered from extensively drug-resistant Pseudomonas aeruginosa sepsis after liver transplantation. He was treated by a bacteriophage-antibiotic intravenous combination therapy for 86 days. This salvage therapy was well tolerated, without antibody-mediated phage neutralization. It was associated with objective clinical and microbiological improvement, eventually allowing for liver retransplantation and complete resolution of all infections. Clear in vitro phage-antibiotic synergies were observed. The occurrence of bacterial phage resistance did not result in therapeutic failure, possibly due to phage-induced virulence tradeoffs, which we investigated in different experimental models.