Global trends and hotspots of phage therapy for bacterial infection: A bibliometric visualized analysis from 2001 to 2021

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.

Exploring the Bacteriophage Frontier: A Bibliometric Analysis of Clinical Trials Between 1965 and 2024

In recent years, the rise of antibiotic-resistant bacteria has posed a severe threat to global public health, necessitating innovative and alternative approaches to combat this escalating crisis. Bacteriophages, viruses that infect and replicate within bacteria, have emerged as promising candidates for therapeutic intervention against antibiotic-resistant pathogens. This study delves into the intricate landscape of bacteriophage research, unraveling the trends and impact of research in the field. The analysis considers the chronological evolution of research, identifying key contributors, collaborative networks, and thematic trends that have shaped the trajectory of this rapidly growing field. Out of 101717 search results in the PubMed database, 163 clinical trials were identified, revealing a dynamic landscape of research activity between 1965 and 2024. The annual scientific publication analysis unveiled fluctuations in the number of publications, indicating an overall increasing trend. Notably, 2011 emerged as a peak year, signifying heightened activity in bacteriophage research. Employing Lotka's law, the authors' productivity analysis illustrated an inherent imbalance in author contributions, with a majority contributing to a single clinical trial. Co-authorship analysis highlighted leading collaborators. Co-occurrence analysis of keywords unveiled thematic clusters, providing insights into the diverse aspects of bacteriophage research. A word cloud emphasized significant terms, while a thematic map categorized themes into various developmental stages. Antimicrobial Agents, Chemotherapy, and Poultry Science were the most relevant journals based on the number of publications. The analysis of countries' contributions revealed the United States as a leading contributor, with Switzerland and China following suit. Collaboration patterns suggested predominantly independent research, with potential for increased international partnerships in certain regions. Additionally, temporal analysis of authors, institutions, sources, and countries revealed productivity patterns, historical context, and research shifts. By scrutinizing a vast array of scientific literature, this investigation aims to provide a panoramic view of how the scientific community has explored the potential of bacteriophages in the context of antibiotic resistance.

Bacteriophages: Status quo and emerging trends toward one health approach

The alarming rise in antimicrobial resistance (AMR) among the drug-resistant pathogens has been attributed to the ESKAPEE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa, Enterobacter sp., and Escherichia coli). Recently, these AMR microbes have become difficult to treat, as they have rendered the existing therapeutics ineffective. Thus, there is an urgent need for effective alternatives to lessen or eliminate the current infections and limit the spread of emerging diseases under the "One Health" framework. Bacteriophages (phages) are naturally occurring biological resources with extraordinary potential for biomedical, agriculture/food safety, environmental protection, and energy production. Specific unique properties of phages, such as their bactericidal activity, host specificity, potency, and biocompatibility, make them desirable candidates in therapeutics. The recent biotechnological advancement has broadened the repertoire of phage applications in nanoscience, material science, physical chemistry, and soft-matter research. Herein, we present a comprehensive review, coupling the substantial aspects of phages with their applicability status and emerging opportunities in several interdependent areas under one health concept. Consolidating the recent state-of-the-art studies that integrate human, animal, plant, and environment health, the following points have been highlighted: (i) The biomedical and pharmacological advantages of phages and their antimicrobial derivatives with particular emphasis on in-vivo and clinical studies. (ii) The remarkable potential of phages to be altered, improved, and applied for drug delivery, biosensors, biomedical imaging, tissue engineering, energy, and catalysis. (iii) Resurgence of phages in biocontrol of plant, food, and animal-borne pathogens. (iv) Commercialization of phage-based products, current challenges, and perspectives.

The untapped potential of phage model systems as therapeutic agents

With the emergence of widespread antibiotic resistance, phages are an appealing alternative to antibiotics in the fight against multidrug-resistant bacteria. Over the past few years, many phages have been isolated from various environments to treat bacterial pathogens. While isolating novel phages for treatment has had some success for compassionate use, developing novel phages into a general therapeutic will require considerable time and financial resource investments. These investments may be less significant for well-established phage model systems. The knowledge acquired from decades of research on their structure, life cycle, and evolution ensures safe application and efficient handling. However, one major downside of the established phage model systems is their inability to infect pathogenic bacteria. This problem is not insurmountable; phage host range can be extended through genetic engineering or evolution experiments. In the future, breeding model phages to infect pathogens could provide a new avenue to develop phage therapeutic agents.

Droplet-based methodology for investigating bacterial population dynamics in response to phage exposure

An alarming rise in antimicrobial resistance worldwide has spurred efforts into the search for alternatives to antibiotic treatments. The use of bacteriophages, bacterial viruses harmless to humans, represents a promising approach with potential to treat bacterial infections (phage therapy). Recent advances in microscopy-based single-cell techniques have allowed researchers to develop new quantitative methodologies for assessing the interactions between bacteria and phages, especially the ability of phages to eradicate bacterial pathogen populations and to modulate growth of both commensal and pathogen populations. Here we combine droplet microfluidics with fluorescence time-lapse microscopy to characterize the growth and lysis dynamics of the bacterium Escherichia coli confined in droplets when challenged with phage. We investigated phages that promote lysis of infected E. coli cells, specifically, a phage species with DNA genome, T7 (Escherichia virus T7) and two phage species with RNA genomes, MS2 (Emesvirus zinderi) and Qβ (Qubevirus durum). Our microfluidic trapping device generated and immobilized picoliter-sized droplets, enabling stable imaging of bacterial growth and lysis in a temperature-controlled setup. Temporal information on bacterial population size was recorded for up to 25 h, allowing us to determine growth rates of bacterial populations and helping us uncover the extent and speed of phage infection. In the long-term, the development of novel microfluidic single-cell and population-level approaches will expedite research towards fundamental understanding of the genetic and molecular basis of rapid phage-induced lysis and eco-evolutionary aspects of bacteria-phage dynamics, and ultimately help identify key factors influencing the success of phage therapy.

Pharmacokinetic and Pharmacodynamic Obstacles for Phage Therapy From the Perspective of Clinical Practice

Bacteriophages present unique features that enable targeted killing of bacteria, including strains resistant to many antibiotics. However, phage pharmacokinetics and pharmacodynamics constitute much more complex and challenging aspects for researchers than those attributable to antibiotics. This is because phages are not just chemical substances, but also biological nanostructures built of different proteins and genetic material that replicate within their bacterial hosts and may induce immune responses acting as simple antigens. Here, we present a few examples of how primary general assumptions on phage pharmacokinetics and pharmacodynamics are verified by current preclinical and clinical observations, leading to conclusions that may not be obvious at first but are of significant value for the final success of phage therapy in humans.

Characterization of phage vB_EcoS-EE09 infecting E. coli DSM613 Isolated from Wastewater Treatment Plant Effluent and Comparative Proteomics of the Infected and Non-Infected Host

Phages influence microbial communities, can be applied in phage therapy, or may serve as bioindicators, e.g., in (waste)water management. We here characterized the Escherichia phage vB_EcoS-EE09 isolated from an urban wastewater treatment plant effluent. Phage vB_EcoS-EE09 belongs to the genus Dhillonvirus, class Caudoviricetes. It has an icosahedral capsid with a long non-contractile tail and a dsDNA genome with an approximate size of 44 kb and a 54.6% GC content. Phage vB_EcoS-EE09 infected 12 out of the 17 E. coli strains tested. We identified 16 structural phage proteins, including the major capsid protein, in cell-free lysates by protein mass spectrometry. Comparative proteomics of protein extracts of infected E. coli cells revealed that proteins involved in amino acid and protein metabolism were more abundant in infected compared to non-infected cells. Among the proteins involved in the stress response, 74% were less abundant in the infected cultures compared to the non-infected controls, with six proteins showing significant less abundance. Repressing the expression of these proteins may be a phage strategy to evade host defense mechanisms. Our results contribute to diversifying phage collections, identifying structural proteins to enable better reliability in annotating taxonomically related phage genomes, and understanding phage-host interactions at the protein level.

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.

Enterococcal Phages: Food and Health Applications

Enterococcus is a diverse genus of Gram-positive bacteria belonging to the lactic acid bacteria (LAB) group. It is found in many environments, including the human gut and fermented foods. This microbial genus is at a crossroad between its beneficial effects and the concerns regarding its safety. It plays an important role in the production of fermented foods, and some strains have even been proposed as probiotics. However, they have been identified as responsible for the accumulation of toxic compounds-biogenic amines-in foods, and over the last 20 years, they have emerged as important hospital-acquired pathogens through the acquisition of antimicrobial resistance (AMR). In food, there is a need for targeted measures to prevent their growth without disturbing other LAB members that participate in the fermentation process. Furthermore, the increase in AMR has resulted in the need for the development of new therapeutic options to treat AMR enterococcal infections. Bacteriophages have re-emerged in recent years as a precision tool for the control of bacterial populations, including the treatment of AMR microorganism infections, being a promising weapon as new antimicrobials. In this review, we focus on the problems caused by Enterococcus faecium and Enterococcus faecalis in food and health and on the recent advances in the discovery and applications of enterococcus-infecting bacteriophages against these bacteria, with special attention paid to applications against AMR enterococci.

Current Clinical Landscape and Global Potential of Bacteriophage Therapy

In response to the global spread of antimicrobial resistance, there is an increased demand for novel and innovative antimicrobials. Bacteriophages have been known for their potential clinical utility in lysing bacteria for almost a century. Social pressures and the concomitant introduction of antibiotics in the mid-1900s hindered the widespread adoption of these naturally occurring bactericides. Recently, however, phage therapy has re-emerged as a promising strategy for combatting antimicrobial resistance. A unique mechanism of action and cost-effective production promotes phages as an ideal solution for addressing antibiotic-resistant bacterial infections, particularly in lower- and middle-income countries. As the number of phage-related research labs worldwide continues to grow, it will be increasingly important to encourage the expansion of well-developed clinical trials, the standardization of the production and storage of phage cocktails, and the advancement of international collaboration. In this review, we discuss the history, benefits, and limitations of bacteriophage research and its current role in the setting of addressing antimicrobial resistance with a specific focus on active clinical trials and case reports of phage therapy administration.