Paving the way for phage therapy using novel drug delivery approaches

Case report: Local bacteriophage therapy for fracture-related infection with polymicrobial multi-resistant bacteria: hydrogel application and postoperative phage analysis through metagenomic sequencing

Fracture-related infections can be challenging, particularly with concomitant severe bone defects and multi-resistant microorganisms. We present a case of a 42-year-old patient with a fracture-related infection following a war injury from a gunshot, resulting in a 12-cm subtrochanteric segmental bone defect and the detection of four different multi-resistant Gram-negative bacteria. Due to antibiotic drug resistance, treatment with bacteriophages was considered. Phage susceptibility testing revealed the activity of a commercially available bacteriophage cocktail (Intesti bacteriophage, Eliava Institute, Tbilisi, Georgia). This phage cocktail was included in a modified two-stage Masquelet technique. During the first intervention, the bone was debrided and samples for microbiological and phage testing were harvested. The indwelling intramedullary rod was removed, and the bone defect was filled with a PMMA spacer loaded with colistin and the bone stabilized with a plate. During the second procedure, the PMMA spacer was removed and a silver-coated angular stable plate was implanted. The bone defect was filled with a fibular autograft and allograft cancellous bone chips. At the end of the procedure, the Intesti bacteriophage cocktail was injected into a DAC hydrogel and this bacteriophage hydrogel composite was then put onto the angular stable plate. Postoperatively the wound fluid was collected over 72 h, and high-throughput metagenomic sequencing was performed. This showed a time-dependent release of the bacteriophages in the wound fluid, with a relatively high concentration after 12 h, decreasing to DNA copies of 0 after 72 h. Furthermore, we have assessed the release of phages from DAC gel and the effect of DAC gel on the phages in vitro. The results showed a stable and rapid release of phages from the DAC gel (~1×103 PFU/mL). The clinical course of the patient showed no relapse of the infection with good bone consolidation of the bone defect after 1 year without the need for any surgical revision. To the best of our knowledge, this is the first case that shows the detection of bacteriophage DNA copies by high-throughput metagenomics sequencing in a patient with a complex fracture-related infection. Successful treatment of this case encourages further investigation of bacteriophage therapy in patients with complex bone and joint infections.

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.

Phage formulations and delivery strategies: Unleashing the potential against antibiotic-resistant bacteria

Bacterial control promoted by bacteriophages (phages) is an attractive tool in the face of the antibiotic crisis triggered by the exacerbated use of these drugs. Despite the growing interest in using these viruses, some gaps still need answers, such as the protection and delivery of phages. Some limitation points involve the degradation of phage proteins by enzymes or inactivation in low-pH environments. In this review, a literature search using keywords related to the field of virus delivery formulations was done to understand the current scenario of using delivery techniques and phage formulations. A total of 2096 raw results were obtained, which resulted in 140 publications after refinement. These studies were analyzed for main application techniques and areas, keywords, and countries. Of the total, 57% of the publications occurred in the last five years, and the encapsulation technique was the most used among the articles analyzed. As excipient agents, lactose, trehalose, mannitol, PEG, and Leucine stand out. The development of phage formulations, protection approaches, their delivery routes, and the knowledge about the best application strategy enables the use of these organisms in several sectors. It can act as a powerful tool against antibiotic-resistant bacteria.

Alginate- and Chitosan-Modified Gelatin Hydrogel Microbeads for Delivery of E. coli Phages

Bacterial infections are among the most significant health problems/concerns worldwide. A very critical concern is the rapidly increasing number of antibiotic-resistant bacteria, which requires much more effective countermeasures. As nature's antibacterial entities, bacteriophages shortly ("phages") are very important alternatives to antibiotics, having many superior features compared with antibiotics. The development of phage-carrying controlled-release formulations is still challenging due to the need to protect their activities in preparation, storage, and use, as well as the need to create more user-friendly forms by considering their application area/site/conditions. Here, we prepared gelatin hydrogel microbeads by a two-step process. Sodium alginate was included for modification within the initial recipes, and these composite microbeads were further coated with chitosan. Their swelling ratio, average diameters, and Zeta potentials were determined, and degradations in HCl were demonstrated. The target bacteria Escherichia coli (E.coli) and its specific phage (T4) were obtained from bacterial culture collections and propagated. Phages were loaded within the microbeads with a simple method. The phage release characteristics were investigated comparatively and were demonstrated here. High release rates were observed from the gelatin microbeads. It was possible to reduce the phage release rate using sodium alginate in the recipe and chitosan coating. Using these gelatin-based microbeads as phage carrier matrices-especially in lyophilized forms-significantly improved the phage stability even at room temperature. It was concluded that phage release from gelatin hydrogel microbeads could be further controlled by alginate and chitosan modifications and that user-friendly lyophilized phage formulations with a much longer shelf life could be produced.

The Medicinal Phage-Regulatory Roadmap for Phage Therapy under EU Pharmaceutical Legislation

Bacteriophage therapy is a promising approach to treating bacterial infections. Research and development of bacteriophage therapy is intensifying due to the increase in antibiotic resistance and the faltering development of new antibiotics. Bacteriophage therapy uses bacteriophages (phages), i.e., prokaryotic viruses, to specifically target and kill pathogenic bacteria. The legal handling of this type of therapy raises several questions. These include whether phage therapeutics belong to a specially regulated class of medicinal products, and which legal framework should be followed with regard to the various technical ways in which phage therapeutics can be manufactured and administered. The article shows to which class of medicinal products phage therapeutics from wild type phages and from genetically modified (designer) phages do or do not belong. Furthermore, the article explains which legal framework is relevant for the manufacture and administration of phage therapeutics, which are manufactured in advance in a uniform, patient-independent manner, and for tailor-made patient-specific phage therapeutics. For the systematically coherent, successful translation of phage therapy, the article considers pharmaceutical law and related legal areas, such as genetic engineering law. Finally, the article shows how the planned legislative revisions of Directive 2001/83/EC and Regulation (EC) No 726/2004 may affect the legal future of phage therapy.

The Next Generation of Drug Delivery: Harnessing the Power of Bacteriophages

The use of biomaterials, such as bacteriophages, as drug delivery vehicles (DDVs) has gained increasing interest in recent years due to their potential to address the limitations of conventional drug delivery systems. Bacteriophages offer several advantages as drug carriers, such as high specificity for targeting bacterial cells, low toxicity, and the ability to be engineered to express specific proteins or peptides for enhanced targeting and drug delivery. In addition, bacteriophages have been shown to reduce the development of antibiotic resistance, which is a major concern in the field of antimicrobial therapy. Many initiatives have been taken to take up various payloads selectively and precisely by surface functionalization of the outside or interior of self-assembling viral protein capsids. Bacteriophages have emerged as a promising platform for the targeted delivery of therapeutic agents, including drugs, genes, and imaging agents. They possess several properties that make them attractive as drug delivery vehicles, including their ability to specifically target bacterial cells, their structural diversity, their ease of genetic manipulation, and their biocompatibility. Despite the potential advantages of using bacteriophages as drug carriers, several challenges and limitations need to be addressed. One of the main challenges is the limited host range of bacteriophages, which restricts their use to specific bacterial strains. However, this can also be considered as an advantage, as it allows for precise and targeted drug delivery to the desired bacterial cells. The use of biomaterials, including bacteriophages, as drug delivery vehicles has shown promising potential to address the limitations of conventional drug delivery systems. Further research is needed to fully understand the potential of these biomaterials and address the challenges and limitations associated with their use.

Nano/microformulations for Bacteriophage Delivery

Encapsulation methodologies allow the protection of bacteriophages for overcoming critical environmental conditions. Moreover, they improve the stability and the controlled delivery of bacteriophages which is of great innovative value in bacteriophage therapy. Here, two different encapsulation methodologies of bacteriophages are described using two biocompatible materials: a lipid cationic mixture and a combination of alginate with the antacid CaCO3. To perform bacteriophage encapsulation is necessary to dispose of a purified and highly concentrated lysate (around 1010 to 1011 pfu/mL) and a specific equipment. Both methodologies have been successfully applied for encapsulating Salmonella bacteriophages with different morphologies. Also, the material employed does not modify the antibacterial action of bacteriophages. Moreover, both technologies can be adapted to any bacteriophage and possibly to any delivery route for bacteriophage therapy.

Engineering pH-sensitive erodible chitosan hydrogel composite containing bacteriophage: An interplay between hydrogel and bacteriophage against Staphylococcus aureus

Encapsulation of phages represents a key approach for improving phage stability and controlling phage delivery dosage. The hydrogel made from positively charged quaternized chitosan (QCS) and multivalent crosslinker, aldehyde-modified poly(xylitol sebacate)-co-poly(ethylene glycol) (APP) was introduced for the first time for drug (phage 44AHJD) delivery. The freeze-thawing (FT) treatment enhanced the porous structure and the stress resistance of native hydrogel with increased compression stress (stiffness) from 10 to 20 kPa. The stiffness of the phage-loaded hydrogel (FTP) was suitable for the proper release of phage particles and polymer chains, both working synergistically against bacterial growth. The FTP followed the Korsmeyer-Peppas model's anomalous diffusion of phage particles at different temperatures (30-45 °C) and pH (6.6-8.5) conditions. FTP was sensitive to pH, which released more phage particles at pH-neutral conditions, while the release under acidic and alkaline conditions was more based on gel degradation. The high biocompatibility of FTP hydrogel at its working concentration of 30 mg mL-1 was demonstrated through a hemolysis ratio of <2 %. Sixty percent of the total encapsulated phages and 6 mg mL-1 of hydrogel debris were released after 10 h of hydrogel submerge treatment, which can fight the growing bacteria and the emergence of phage-resistant bacteria.

Freeze-Drying of Encapsulated Bacteriophage T4 to Obtain Shelf-Stable Dry Preparations for Oral Application

Therapeutic application of bacterial viruses (phage therapy) has in recent years been rediscovered by many scientists, as a method which may potentially replace conventional antibacterial strategies. However, one of the main problems related to phage application is the stability of bacterial viruses. Though many techniques have been used to sustain phage activity, novel tools are needed to allow long-term phage storage and application in versatile forms. In this study, we combined two well-known methods for bacteriophage immobilization. First, encapsulated phages were obtained by means of extrusion-ionic gelation, and then alginate microspheres were dried using the lyophilization process (freeze-drying). To overcome the risk of phage instability upon dehydration, the microspheres were prepared with the addition of 0.3 M mannitol. Bacteriophage-loaded microspheres were stored at room temperature for 30 days and subsequently exposed to simulated gastric fluid (SGF). The survival of encapsulated phages after drying was significantly higher in the presence of mannitol. The highest number of viable bacteriophages exceeding 4.8 log10 pfu/mL in SGF were recovered from encapsulated and freeze-dried microspheres, while phages in lyophilized lysate were completely inactivated. Although the method requires optimization, it may be a promising approach for the immobilization of bacteriophages in terms of practical application.

Alginate-Encapsulated Mycobacteriophage: A Potential Approach for the Management of Intestinal Mycobacterial Disease

Encapsulated medication is a common method of administering therapeutic treatments. As researchers explore alternative therapies, it is likely that encapsulation will remain a feature of these novel treatments, particularly when routes of delivery are considered. For instance, alginate-encapsulation is often favoured where gastric digestion poses an obstacle. When exposed to cations (namely Ca2+), alginate readily forms gels that are resilient to acidic conditions and readily dissociate in response to mid-range pH. This action can be extremely valuable for the encapsulation of phages. The efficient delivery of phages to the intestine is important when considering mycobacteriophage (MP) therapy (or MP prophylaxis) for disseminated mycobacterial infections and chronic gastroenteritis conditions. This study presents the design and in vitro validation of an alginate-encapsulated MP capable of releasing phages in a pH-dependent manner. Ultimately, it is shown that encapsulated phages pretreated with simulated gastric fluid (SGF) are capable of releasing viable phages into simulated intestinal fluid (SIF) and thereby reducing the mycobacterial numbers in spiked SIF by 90%. These findings suggest that alginate encapsulation may be a viable option for therapeutic and prophylactic approaches to the management of intestinal mycobacterial disease, such as Johne's disease.

New advances in the treatments of drug-resistant tuberculosis

INTRODUCTION

TB is associated with high mortality and morbidity among infected individuals and a high transmission rate from person to person. Despite the availability of vaccines and several anti-TB,TB infection continues to increase. Global resistance to TB remains the greatest challenge. There has not been extensive research into a new treatment and management strategy for TB resistance therapy. This review is based on a review of new advances and alternative drugs in the treatment of drug-resistant TB.

AREAS COVERED

New drug-resistant Mycobacterium tuberculosis therapy involves a combination of the latest TB drugs, new anti-TB drugs based on medicinal plant extracts for drug-resistant TB, mycobacteriophage therapy, the CRISPR/Cas9 system, and nanotechnology.

EXPERT OPINION

It is necessary to determine the function of individual gene alterations in drug-resistant TB. A combination of the most recent anti-TB drugs, such as bedaquiline and delamanid, is recommended. Longitudinal studies and animal model experiments with some medicinal plant extracts are required for better results. Nanotechnology has the potential to reduce drug side effects. Useful efficacy of phage therapy and CRISPR-cas9 technology as adjunct therapies for the management of drug-resistant TB.

Phage for drug delivery vehicles

Viruses being the natural carriers of gene have been widely used as drug delivery systems. However, the commonly used eukaryotic viruses such as adenoviruses, retroviruses, and lentiviruses, besides efficiently targeting the cells, can also stimulate immunological response or disrupt tumour suppressor genes leading to cancer. Consequently, there has been an increase interest in the scientific fraternity towards exploring other alternatives, which are safer and equally efficient for drug delivery. Bacteriophages, in this context have been at the forefront as an efficient, reliable, and safer choice. Novel phage dependent technologies led the foundation of peptide libraries and provides way to recognising abilities and targeting of specific ligands. Hybridisation of phage with inorganic complexes could be an appropriate strategy for the construction of carrying bioinorganic carriers. In this chapter, we have tried to cover major advances in the phage species that can be used as drug delivery vehicles.

Recent advancements in nanotechnology-based bacteriophage delivery strategies against bacterial ocular infections

Antibiotic resistance is growing as a critical challenge in a variety of disease conditions including ocular infections leading to disastrous effects on the human eyes. Staphylococcus aureus (S. aureus) mediated ocular infections are very common affecting different parts of the eye viz. vitreous chamber, conjunctiva, cornea, anterior and posterior chambers, tear duct, and eyelids. Blepharitis, dacryocystitis, conjunctivitis, keratitis, endophthalmitis, and orbital cellulitis are some of the commonly known ocular infections caused by S. aureus. Some of these infections are so fatal that they could cause bilateral blindness like panophthalmitis and orbital cellulitis, which is caused by methicillin-resistant S. aureus (MRSA) and vancomycin-resistance S. aureus (VRSA). The treatment of S. aureus infections with known antibiotics is becoming gradually difficult because of the development of resistance against multiple antibiotics. Apart from the different combinations and formulation strategies, bacteriophage therapy is growing as an effective alternative to treat such infections. Although the superiority of bacteriophage therapy is well established, yet physical factors (high temperatures, acidic pH, UV-rays, and ionic strength) and pharmaceutical barriers (poor stability, low in-vivo retention, controlled and targeted delivery, immune system neutralization, etc.) have the greatest influence on the viability of phage virions (also phage proteins). A variety of Nanotechnology based formulations such as polymeric nanoparticles, liposomes, dendrimers, nanoemulsions, and nanofibres have been recently reported to overcome the above-mentioned obstacles. In this review, we have compiled all these recent reports and discussed bacteriophage-based nanoformulations techniques for the successful treatment of ocular infections caused by multidrug-resistant S. aureus and other bacteria.

Phage engineering and phage-assisted CRISPR-Cas delivery to combat multidrug-resistant pathogens

Antibiotic resistance ranks among the top threats to humanity. Due to the frequent use of antibiotics, society is facing a high prevalence of multidrug resistant pathogens, which have managed to evolve mechanisms that help them evade the last line of therapeutics. An alternative to antibiotics could involve the use of bacteriophages (phages), which are the natural predators of bacterial cells. In earlier times, phages were implemented as therapeutic agents for a century but were mainly replaced with antibiotics, and considering the menace of antimicrobial resistance, it might again become of interest due to the increasing threat of antibiotic resistance among pathogens. The current understanding of phage biology and clustered regularly interspaced short palindromic repeats (CRISPR) assisted phage genome engineering techniques have facilitated to generate phage variants with unique therapeutic values. In this review, we briefly explain strategies to engineer bacteriophages. Next, we highlight the literature supporting CRISPR-Cas9-assisted phage engineering for effective and more specific targeting of bacterial pathogens. Lastly, we discuss techniques that either help to increase the fitness, specificity, or lytic ability of bacteriophages to control an infection.

Masquelet technique with radical debridement and alternative fixation in treatment of infected bone nonunion

Background

Infected bone nonunion is the toughest problem in fracture-related infection, leading to high disability and recurrence. The aim of this study was to evaluate the effectiveness of the Masquelet technique with radical debridement and alternative fixation in the management of infected bone nonunion.

Patients and Methods

A retrospective study of prospectively collected data in two trauma centers was performed from 2016 to 2020. Patients diagnosed as infected bone nonunion were included in this study. The initial implant was removed and all patients received a two-stage Masquelet procedure with radical debridement and alternative fixation. The disappearance of inflammatory manifestations and regression of infection indicators (such as interleukin-6 (IL-6), C-reactive protein, white blood cell count) to the normal range were regarded as radical debridement. The alternative fixation depended on local soft tissue conditions. Results were evaluated according to clinical and radiographic assessment and patient satisfaction.

Results

A total of 23 patients were included in our study. Six of them received internal fixation, while the other 17 received external fixation. Of the 23 cases, 21 were successfully reconstructed without infection recurrence, except 2 reinfected cases. Mean full weight bearing time was 6.6 months follow-up post last surgery. Out of the 23, 20 cases had satisfactory functional outcomes without additional bone or soft tissue comorbidities. Discrepancies in leg length and joint stiffness were observed in three cases and marked as unsatisfied results.

Conclusions

Infected bone nonunion can be successfully managed using the Masquelet technique under radical debridement combined with an alternative fixation method.

Enhancing the Stability of Bacteriophages Using Physical, Chemical, and Nano-Based Approaches: A Review

Phages are efficient in diagnosing, treating, and preventing various diseases, and as sensing elements in biosensors. Phage display alone has gained attention over the past decade, especially in pharmaceuticals. Bacteriophages have also found importance in research aiming to fight viruses and in the consequent formulation of antiviral agents and vaccines. All these applications require control over the stability of virions. Phages are considered resistant to various harsh conditions. However, stability-determining parameters are usually the only additional factors in phage-related applications. Phages face instability and activity loss when preserved for extended periods. Sudden environmental changes, including exposure to UV light, temperature, pH, and salt concentration, also lead to a phage titer fall. This review describes various formulations that impart stability to phage stocks, mainly focusing on polymer-based stabilization, encapsulation, lyophilization, and nano-assisted solutions.

Diet-gut microbiota-epigenetics in metabolic diseases: From mechanisms to therapeutics

The prevalence of metabolic diseases, including obesity, dyslipidemia, type 2 diabetes mellitus (T2DM), and non-alcoholic fatty liver disease (NAFLD), is a severe burden in human society owing to the ensuing high morbidity and mortality. Various factors linked to metabolic disorders, particularly environmental factors (such as diet and gut microbiota) and epigenetic modifications, contribute to the progression of metabolic diseases. Dietary components and habits regulate alterations in gut microbiota; in turn, microbiota-derived metabolites, such as short-chain fatty acids (SCFAs), are influenced by diet. Interestingly, diet-derived microbial metabolites appear to produce substrates and enzymatic regulators for epigenetic modifications (such as DNA methylation, histone modifications, and non-coding RNA expression). Epigenetic changes mediated by microbial metabolites participate in metabolic disorders via alterations in intestinal permeability, immune responses, inflammatory reactions, and insulin resistance. In addition, microbial metabolites can trigger inflammatory immune responses and microbiota dysbiosis by directly binding to G-protein-coupled receptors (GPCRs). Hence, diet-gut microbiota-epigenetics may play a role in metabolic diseases. However, their complex relationships with metabolic diseases remain largely unknown and require further investigation. This review aimed to elaborate on the interactions among diet, gut microbiota, and epigenetics to uncover the mechanisms and therapeutics of metabolic diseases.