Efficacy of bacteriophage therapy against gut-derived sepsis caused by Pseudomonas aeruginosa in mice

Role of phage therapy in acute gastroenteritis

The gut ecosystem, comprising the gut microbiota and its interactions, plays a crucial role in human health and disease. This complex ecosystem involves a diverse array of microorganisms such as viruses, fungi, and bacteria, collectively known as the gut microbiota. These microorganisms contribute to various functions, including nutrient metabolism and immune modulation, thereby impacting human health. Dysbiosis, or an imbalance in the gut microbiota, has been associated with the pathogenesis of several diseases, ranging from intestinal disorders such as inflammatory bowel disease to extra-intestinal conditions such as metabolic and neurological disorders. The implications of dysbiosis in the gut ecosystem are far-reaching, affecting not only gastrointestinal health but also contributing to the development and progression of conditions such as autoimmune gastritis and gastric cancer. Furthermore, the burden of antimicrobial use and subsequent side effects, including antibiotic resistance, poses additional challenges in managing gastrointestinal diseases. In light of these complexities, investigating the role of bacteriophages as regulators of the gut ecosystem and their potential clinical applications presents a promising opportunity to tackle antibiotic resistance and fight infectious diseases.

Efficacy of Bacteriophages in Wound Healing: An Updated Review

We have attempted to summarize the efficacy of bacteriophage therapy, highlighting the recent advances and phage delivery methods in different clinical trials and animal studies for wound-associated infections. Bacteriophage therapy is the lyse of bacteria by bacteriophages at the site of invasion. As bacteria become more resistant to antibiotics, discovering an alternative is more important than ever, and bacteriophage therapy has yielded promising outcomes. A clear knowledge of the bacteriophage, microbiota, and human host and their interaction is necessary to implement bacteriophage treatment on a large scale. Much technological advancement and regulatory guidelines increased the credibility of phage therapy (PT). Still, the challenges include the development of efficient bacteriophage screening methods, phage therapy strategies for biofilms, and the quality and safety of phage preparations. However, much consideration is to be taken in designing a novel therapeutic approach for antibiotic-resistant infections by using phages, phage lytic proteins, bioengineered phages, or antibiotics in combination.

Pharmacokinetics and pharmacodynamics of bacteriophage therapy: a review with a focus on multidrug-resistant Gram-negative bacterial infections

SUMMARYDespite the early recognition of their therapeutic potential and the current escalation of multidrug-resistant (MDR) pathogens, the adoption of bacteriophages into mainstream clinical practice is hindered by unfamiliarity with their basic pharmacokinetic (PK) and pharmacodynamic (PD) properties, among others. Given the self-replicative nature of bacteriophages in the presence of host bacteria, the adsorption rate, and the clearance by the host's immunity, their PK/PD characteristics cannot be estimated by conventional approaches, and thus, the introduction of new considerations is required. Furthermore, the multitude of different bacteriophage types, preparations, and treatment schedules impedes drawing general conclusions on their in vivo PK/PD features. Additionally, the drawback of acquired bacteriophage resistance of MDR pathogens with clinical and environmental implications should be taken into consideration. Here, we provide an overview of the current state of the field of PK and PD of bacteriophage therapy with a focus on its application against MDR Gram-negative infections, highlighting the potential knowledge gaps and the challenges in translation from the bench to the bedside. After reviewing the in vitro PKs and PDs of bacteriophages against the four major MDR Gram-negative pathogens, Klebsiella pneumoniae, Acinetobacter baumannii complex, Pseudomonas aeruginosa, and Escherichia coli, specific data on in vivo PKs (tissue distribution, route of administration, and basic PK parameters in animals and humans) and PDs (survival and reduction of bacterial burden in relation to the route of administration, timing of therapy, dosing regimens, and resistance) are summarized. Currently available data merit close scrutiny, and optimization of bacteriophage therapy in the context of a better understanding of the underlying PK/PD principles is urgent to improve its therapeutic effect and to minimize the occurrence of bacteriophage resistance.

Emerging roles of bacteriophage-based therapeutics in combating antibiotic resistance

Amid the growing challenge of antibiotic resistance on a global scale, there has been a notable resurgence in bacteriophage-based treatments, signaling a shift in our approach to managing infections. Bacteriophages (BPs), bacterial predators of nature, present a promising alternative for tackling infections caused by antibiotic-resistant pathogens. This review delves into the intricate relationship between bacteriophages and resistant bacteria, exploring various treatment strategies. Drawing upon both preclinical and clinical studies, the review highlights the effectiveness of bacteriophage therapy, particularly when integrated synergistically with conventional antibiotics. It discusses various treatment approaches for systemic and localized infections, demonstrating the adaptability of bacteriophage therapy across different clinical scenarios. Furthermore, the formulation and delivery of bacteriophages shed light on the various methods used to encapsulate and administer them effectively. It also acknowledges the challenge of bacterial resistance to bacteriophages and the ongoing efforts to overcome this hurdle. In addition, this review highlights the importance of the bacteriophage sensitivity profile (phagogram), which helps tailor treatment regimens to individual patients and specific pathogens. By surpassing the limitations of traditional antibiotics, bacteriophage-based therapies offer a personalized and potent solution against antibiotic resistance, promising to reshape the future of infectious disease management.

Porous Microspheres as Pathogen Traps for Sepsis Therapy: Capturing Active Pathogens and Alleviating Inflammatory Reactions

Sepsis is a systemic inflammatory response syndrome caused by pathogen infection, while the current antibiotics mainly utilized in clinical practice to combat infection result in the release of pathogen-associated molecular patterns (PAMPs) in the body. Herein, we provide an innovative strategy for controlling sepsis, namely, capturing active pathogens by means of extracorporeal blood purification. Carbon nanotubes (CNTs) were modified with dimethyldiallylammonium chloride (DDA) through γ-ray irradiation-induced graft polymerization to confer a positive charge. Then, CNT-DDAs are blended with polyurethane (PU) to prepare porous microspheres using the electro-spraying method. The obtained microspheres with a pore diameter of 2 μm served as pathogen traps and are termed as PU-CNT-DDA microspheres. Even at a high flow rate of 50 mL·min-1, the capture efficiencies of the PU-CNT-DDAs for Escherichia coli and Staphylococcus aureus remained 94.7% and 98.8%, respectively. This approach circumvents pathogen lysis and mortality, significantly curtails the release of PAMPs, and hampers the production of pro-inflammatory cytokines. Therefore, hemoperfusion using porous PU-CNT-DDAs as pathogen traps to capture active pathogens and alleviate inflammation opens a new route for sepsis therapy.

Antibiotic action and resistance: updated review of mechanisms, spread, influencing factors, and alternative approaches for combating resistance

Antibiotics represent a frequently employed therapeutic modality for the management of bacterial infections across diverse domains, including human health, agriculture, livestock breeding, and fish farming. The efficacy of antibiotics relies on four distinct mechanisms of action, which are discussed in detail in this review, along with accompanying diagrammatic illustrations. Despite their effectiveness, antibiotic resistance has emerged as a significant challenge to treating bacterial infections. Bacteria have developed defense mechanisms against antibiotics, rendering them ineffective. This review delves into the specific mechanisms that bacteria have developed to resist antibiotics, with the help of diagrammatic illustrations. Antibiotic resistance can spread among bacteria through various routes, resulting in previously susceptible bacteria becoming antibiotic-resistant. Multiple factors contribute to the worsening crisis of antibiotic resistance, including human misuse of antibiotics. This review also emphasizes alternative solutions proposed to mitigate the exacerbation of antibiotic resistance.

Characteristics of Lactococcus petauri GB97 lysate isolated from porcine feces and its in vitro and in vivo effects on inflammation, intestinal barrier function, and gut microbiota composition in mice

IMPORTANCE

Weaning is a crucial step in piglet management to improve pork production. During the weaning phase, disruption of epithelial barrier function and intestinal inflammation can lead to decreased absorption of nutrients and diarrhea. Therefore, maintaining a healthy intestine, epithelial barrier function, and gut microbiota composition in this crucial phase is strategic for optimal weaning in pigs. We isolated a lysate of Lactococcus petauri GB97 (LPL97) from healthy porcine feces and evaluated its anti-inflammatory activities, barrier integrity, and gut microbial changes in LPS-induced murine macrophages and DSS-induced colitis mice. We found that LPL97 regulated the immune response by downregulating the TLR4/NF-κB/MAPK signaling pathway both in vitro and in vivo. Furthermore, LPL97 alleviated the disruption of intestinal epithelial integrity and gut microbiota dysbiosis in colitis mice. This study indicates that LPL97 has the potential to be developed as an alternative feed additive to antibiotics for the swine industry.

Isolation of a bacteriophage targeting Pseudomonas aeruginosa and exhibits a promising in vivo efficacy

Pseudomonas aeruginosa is an important pathogen that causes serious infections. Bacterial biofilms are highly resistant and render bacterial treatment very difficult, therefore necessitates alternative antibacterial strategies. Phage therapy has been recently regarded as a potential therapeutic option for treatment of bacterial infections. In the current study, a novel podovirus vB_PaeP_PS28 has been isolated from sewage with higher lytic activity against P. aeruginosa. Isolated phage exhibits a short latent period, large burst size and higher stability over a wide range of temperatures and pH. The genome of vB_PaeP_PS28 consists of 72,283 bp circular double-stranded DNA, with G + C content of 54.75%. The phage genome contains 94 open reading frames (ORFs); 32 for known functional proteins and 62 for hypothetical proteins and no tRNA genes. The phage vB_PaeP_PS28 effectively inhibited the growth of P. aeruginosa planktonic cells and displayed a higher biofilm degrading capability. Moreover, therapeutic efficacy of isolated phage was evaluated in vivo using mice infection model. Interestingly, survival of mice infected with P. aeruginosa was significantly enhanced upon treatment with vB_PaeP_PS28. Furthermore, the bacterial load in liver and kidney isolated from mice infected with P. aeruginosa and treated with phage markedly decreased as compared with phage-untreated P. aeruginosa-infected mice. These findings support the efficacy of isolated phage vB_PaeP_PS28 in reducing P. aeruginosa colonization and pathogenesis in host. Importantly, the isolated phage vB_PaeP_PS28 could be applied alone or as combination therapy with other lytic phages as phage cocktail therapy or with antibiotics to limit infections caused by P. aeruginosa.

Characterization of Temperate LPS-Binding Bordetella avium Phages That Lack Superinfection Immunity

Bordetella avium causes a highly infectious upper respiratory tract disease in turkeys and other poultry with high economic losses. Considering the antimicrobial resistance crisis, bacteriophages (phages) may be an alternative approach for treating bacterial infections such as bordetellosis. Here, we describe seven B. avium phages, isolated from drinking water and feces from chicken and turkey farms. They showed strong bacteriolytic activity with a broad host range and used lipopolysaccharides (LPS) as a host receptor for their adsorption. All phages are myoviruses based on their structure observed by transmission electron microscopy. Genome sequence analyses revealed genome assembly sizes ranging from 39,087 to 43,144 bp. Their permutated genomes were organized colinearly, with a conserved module order, and were packed according to a predicted headful packing strategy. Notably, they contained genes encoding putative markers of lysogeny, indicative of temperate phages, despite their lytic phenotype. Further investigation revealed that the phages could indeed undergo a lysogenic life cycle with varying frequency. However, the lysogenic bacteria were still susceptible to superinfection with the same phages. This lack of stable superinfection immunity after lysogenization appears to be a characteristic feature of B. avium phages, which is favorable in terms of a potential therapeutic use of phages for the treatment of avian bordetellosis. IMPORTANCE To maintain the effectiveness of antibiotics over the long term, alternatives to treat infectious diseases are urgently needed. Therefore, phages have recently come back into focus as they can specifically infect and lyse bacteria and are naturally occurring. However, there is little information on phages that can infect pathogenic bacteria from animals, such as the causative agent of bordetellosis of poultry, B. avium. Therefore, in this study, B. avium phages were isolated and comprehensively characterized, including whole-genome analysis. Although phenotypically the phages were thought to undergo a lytic cycle, we demonstrated that they undergo a lysogenic phase, but that infection does not confer stable host superinfection immunity. These findings provide important information that could be relevant for potential biocontrol of avian bordetellosis by using phage therapy.

Bacteriophages in Infectious Diseases and Beyond-A Narrative Review

The discovery of antibiotics has revolutionized medicine and has changed medical practice, enabling successful fighting of infection. However, quickly after the start of the antibiotic era, therapeutics for infectious diseases started having limitations due to the development of antimicrobial resistance. Since the antibiotic pipeline has largely slowed down, with few new compounds being produced in the last decades and with most of them belonging to already-existing classes, the discovery of new ways to treat pathogens that are resistant to antibiotics is becoming an urgent need. To that end, bacteriophages (phages), which are already used in some countries in agriculture, aquaculture, food safety, and wastewater plant treatments, could be also used in clinical practice against bacterial pathogens. Their discovery one century ago was followed by some clinical studies that showed optimistic results that were limited, however, by some notable obstacles. However, the rise of antibiotics during the next decades left phage research in an inactive status. In the last decades, new studies on phages have shown encouraging results in animals. Hence, further studies in humans are needed to confirm their potential for effective and safe treatment in cases where there are few or no other viable therapeutic options. This study reviews the biology and applications of phages for medical and non-medical uses in a narrative manner.

Bacteriophage-based techniques for elucidating the function of zebrafish gut microbiota

Bacteriophages (or phages) are unique viruses that can specifically infect bacteria. Since their discovery by Twort and d'Herelle, phages with bacterial specificity have played important roles in microbial regulation. The intestinal microbiota and host health are intimately linked with nutrient, metabolism, development, and immunity aspects. However, the mechanism of interactions between the composition of the microbiota and their functions in maintaining host health still needs to be further explored. To address the lack of methodology and functions of intestinal microbiota in the host, we first proposed that, with the regulations of special intestinal microbiota and applications of germ-free (GF) zebrafish model, phages would be used to infect and reduce/eliminate the defined gut bacteria in the conventionally raised (CR) zebrafish and compared with the GF zebrafish colonized with defined bacterial strains. Thus, this review highlighted the background and roles of phages and their functional characteristics, and we also summarized the phage-specific infection of target microorganisms, methods to improve the phage specificity, and their regulation within the zebrafish model and gut microbial functional study. Moreover, the primary protocol of phage therapy to control the intestinal microbiota in zebrafish models from larvae to adults was recommended including phage screening from natural sources, identification of host ranges, and experimental design in the animal. A well understanding of the interaction and mechanism between phages and gut bacteria in the host can potentially provide powerful strategies or techniques for preventing bacteria-related human diseases by precisely regulating in vitro and in vivo, which will provide novel insights for phages' application and combined research in the future. KEY POINTS: • Zebrafish models for clarifying the microbial and phages' functions were discussed • Phages infect host bacteria with exquisite specificity and efficacy • Phages can reduce/eliminate the defined gut bacteria to clarify their function.

BACTERIOPHAGE M13 MODULATES THE SEPSIS-RELATED INFLAMMATORY RESPONSES AND ORGAN DAMAGE IN A CLP MODEL

ABSTRACT

Background: Sepsis is a life-threatening disorder that leads to the induction of inflammatory responses and organ failure. Phage therapy is a new approach to controlling infections resistant to common treatments, including sepsis. Several studies have shown the effect of lytic bacteriophages on infection control by reducing the bacterial load. The present study deals with lysogenic bacteriophage M13 on the inflammatory responses caused by cecal ligation and puncture (CLP)-induced sepsis in a mouse model. Methods Bacteriophage M13 harvested from ER2738, titrated, and confirmed by transmission electron microscopy analysis. In vitro toxicity and immunomodulatory effect of bacteriophage M13 were assessed on splenocytes by measurement of cell viability and the production level of cytokines, nitric oxide, and reactive oxygen species. For in vivo experiments, 8-weeks-old male C57BL/6 mice were randomly divided into the following three groups: CLP + NS (treated with normal saline), CLP + M13 (treated with an intraperitoneal injection of 10 9 PFU/mL of bacteriophage M13), and sham + NS (induced surgery but without ligation and puncture, treated with NS). The mice were killed at different time points after surgery (6, 24, 48, and 72, n = 10 for each time point of each group). The kidney, liver, and lungs were harvested for histopathological analysis, and blood was obtained for cytokine and liver enzyme assay. The spleen was used to assess the bacterial load using colony-forming unit assay. The rectal temperature and survival were evaluated during the study. Results According to the in vitro results, 10 9 PFU/mL of bacteriophage M13 was not toxic and did not affect the level of cytokine, nitric oxide, and reactive oxygen species production by splenocytes, but it reduced the inflammatory response of splenocytes in responses to LPS. In vivo studies indicated that the amount of proinflammatory cytokines, liver enzymes, bacterial load, and organ failure were decreased in the CLP + M13 group compared with CLP + NS, whereas the survival rate was increased. Conclusions These experiments demonstrated that bacteriophage M13 could lessen the consequences related to sepsis in CLP mice and can be considered a therapeutic approach in sepsis.

The Mechanism of Important Components in Canine Fecal Microbiota Transplantation

Fecal microbiota transplantation (FMT) is a potential treatment for many intestinal diseases. In dogs, FMT has been shown to have positive regulation effects in treating Clostridioides difficile infection (CDI), inflammatory bowel disease (IBD), canine parvovirus (CPV) enteritis, acute diarrhea (AD), and acute hemorrhagic diarrhea syndrome (AHDS). FMT involves transplanting the functional components of a donor's feces into the gastrointestinal tract of the recipient. The effective components of FMT not only include commensal bacteria, but also include viruses, fungi, bacterial metabolites, and immunoglobulin A (IgA) from the donor feces. By affecting microbiota and regulating host immunity, these components can help the recipient to restore their microbial community, improve their intestinal barrier, and induce anti-inflammation in their intestines, thereby affecting the development of diseases. In addition to the above components, mucin proteins and intestinal epithelial cells (IECs) may be functional ingredients in FMT as well. In addition to the abovementioned indications, FMT is also thought to be useful in treating some other diseases in dogs. Consequently, when preparing FMT fecal material, it is important to preserve the functional components involved. Meanwhile, appropriate fecal material delivery methods should be chosen according to the mechanisms these components act by in FMT.

Phage-resistant Pseudomonas aeruginosa against a novel lytic phage JJ01 exhibits hypersensitivity to colistin and reduces biofilm production

Pseudomonas aeruginosa, a major cause of nosocomial infections, has been categorized by World Health Organization as a critical pathogen urgently in need of effective therapies. Bacteriophages or phages, which are viruses that specifically kill bacteria, have been considered as alternative agents for the treatment of bacterial infections. Here, we discovered a lytic phage targeting P. aeruginosa, designated as JJ01, which was classified as a member of the Myoviridae family due to the presence of an icosahedral capsid and a contractile tail under TEM. Phage JJ01 requires at least 10 min for 90% of its particles to be adsorbed to the host cells and has a latent period of 30 min inside the host cell for its replication. JJ01 has a relatively large burst size, which releases approximately 109 particles/cell at the end of its lytic life cycle. The phage can withstand a wide range of pH values (3–10) and temperatures (4–60°C). Genome analysis showed that JJ01 possesses a complete genome of 66,346 base pairs with 55.7% of GC content, phylogenetically belonging to the genus Pbunavirus. Genome annotation further revealed that the genome encodes 92 open reading frames (ORFs) with 38 functionally predictable genes, and it contains neither tRNA nor toxin genes, such as drug-resistant or lysogenic-associated genes. Phage JJ01 is highly effective in suppressing bacterial cell growth for 12 h and eradicating biofilms established by the bacteria. Even though JJ01-resistant bacteria have emerged, the ability of phage resistance comes with the expense of the bacterial fitness cost. Some resistant strains were found to produce less biofilm and grow slower than the wild-type strain. Among the resistant isolates, the resistant strain W10 which notably loses its physiological fitness becomes eight times more susceptible to colistin and has its cell membrane compromised, compared to the wild type. Altogether, our data revealed the potential of phage JJ01 as a candidate for phage therapy against P. aeruginosa and further supports that even though the use of phages would subsequently lead to the emergence of phage-resistant bacteria, an evolutionary trade-off would make them more sensitive to antibiotics.

Membrane lipid renovation in Pseudomonas aeruginosa - implications for phage therapy?

Pseudomonas aeruginosa is an important Gram-negative pathogen with intrinsic resistance to many clinically used antibiotics. It is particularly troublesome in nosocomial infections, immunocompromised patients, and individuals with cystic fibrosis. Antimicrobial resistance (AMR) is a huge threat to global health, with a predicted 10 million people dying from resistant infections by 2050. A promising therapy for combatting AMR infections is phage therapy. However, more research is required to investigate mechanisms that may influence the efficacy of phage therapy. An important overlooked aspect is the impact of membrane lipid remodelling on phage binding ability. P. aeruginosa undergoes changes in membrane lipids when it encounters phosphorus stress, an environmental perturbation that is likely to occur during infection. Lipid changes include the substitution of glycerophospholipids with surrogate glycolipids and the over-production of ornithine-containing aminolipids. Given that membrane lipids are known to influence the structure and function of membrane proteins, we propose that changes in the composition of membrane lipids during infection may alter phage binding and subsequent phage infection dynamics. Consideration of such effects needs to be urgently prioritised in order to develop the most effective phage therapy strategies for P. aeruginosa infections.

Targeted suppression of human IBD-associated gut microbiota commensals by phage consortia for treatment of intestinal inflammation

Human gut commensals are increasingly suggested to impact non-communicable diseases, such as inflammatory bowel diseases (IBD), yet their targeted suppression remains a daunting unmet challenge. In four geographically distinct IBD cohorts (n = 537), we identify a clade of Klebsiella pneumoniae (Kp) strains, featuring a unique antibiotics resistance and mobilome signature, to be strongly associated with disease exacerbation and severity. Transfer of clinical IBD-associated Kp strains into colitis-prone, germ-free, and colonized mice enhances intestinal inflammation. Stepwise generation of a lytic five-phage combination, targeting sensitive and resistant IBD-associated Kp clade members through distinct mechanisms, enables effective Kp suppression in colitis-prone mice, driving an attenuated inflammation and disease severity. Proof-of-concept assessment of Kp-targeting phages in an artificial human gut and in healthy volunteers demonstrates gastric acid-dependent phage resilience, safety, and viability in the lower gut. Collectively, we demonstrate the feasibility of orally administered combination phage therapy in avoiding resistance, while effectively inhibiting non-communicable disease-contributing pathobionts.

Diversity of Pseudomonas aeruginosa Temperate Phages

Modern sequencing technologies have provided insight into the genetic diversity of numerous species, including the human pathogen Pseudomonas aeruginosa. Bacterial genomes often harbor bacteriophage genomes (prophages), which can account for upwards of 20% of the genome. Prior studies have found P. aeruginosa prophages that contribute to their host's pathogenicity and fitness. These advantages come in many different forms, including the production of toxins, promotion of biofilm formation, and displacement of other P. aeruginosa strains. While several different genera and species of P. aeruginosa prophages have been studied, there has not been a comprehensive study of the overall diversity of P. aeruginosa-infecting prophages. Here, we present the results of just such an analysis. A total of 6,852 high-confidence prophages were identified from 5,383 P. aeruginosa genomes from strains isolated from the human body and other environments. In total, 3,201 unique prophage sequences were identified. While 53.1% of these prophage sequences displayed sequence similarity to publicly available phage genomes, novel and highly mosaic prophages were discovered. Among these prophages, there is extensive diversity, including diversity within the functionally conserved integrase and C repressor coding regions, two genes responsible for prophage entering and persisting through the lysogenic life cycle. Analysis of integrase, C repressor, and terminase coding regions revealed extensive reassortment among P. aeruginosa prophages. This catalog of P. aeruginosa prophages provides a resource for future studies into the evolution of the species. IMPORTANCE Prophages play a critical role in the evolution of their host species and can also contribute to the virulence and fitness of pathogenic species. Here, we conducted a comprehensive investigation of prophage sequences from 5,383 publicly available Pseudomonas aeruginosa genomes from human as well as environmental isolates. We identified a diverse population of prophages, including tailed phages, inoviruses, and microviruses; 46.9% of the prophage sequences found share no significant sequence similarity with characterized phages, representing a vast array of novel P. aeruginosa-infecting phages. Our investigation into these prophages found substantial evidence of reassortment. In producing this, the first catalog of P. aeruginosa prophages, we uncovered both novel prophages as well as genetic content that have yet to be explored.

A Bacteriophage Cocktail Significantly Reduces Listeria Monocytogenes without Deleterious Impact on the Commensal Gut Microbiota under Simulated Gastrointestinal Conditions

In this study, we examined the effect of a bacteriophage cocktail (tentatively designated as the Foodborne Outbreak Pill (FOP)) on the levels of Listeria monocytogenes in simulated small intestine, large intestine, and Caco-2 model systems. We found that FOP survival during simulated passage of the upper gastrointestinal was dependent on stomach pH, and that FOP robustly inhibited L. monocytogenes levels with effectiveness comparable to antibiotic treatment (ampicillin) under simulated ilium and colon conditions. The FOP did not inhibit the commensal bacteria, whereas ampicillin treatment led to dysbiosis-like conditions. The FOP was also more effective than an antibiotic in protecting Caco-2 cells from adhesion and invasion by L. monocytogenes (5-log reduction vs. 1-log reduction) while not triggering an inflammatory response. Our data suggested that the FOP may provide a robust protection against L. monocytogenes should the bacterium enter the human gastrointestinal tract (e.g., by consumption of contaminated food), without deleterious impact on the commensal bacteria.

Deploying Viruses against Phytobacteria: Potential Use of Phage Cocktails as a Multifaceted Approach to Combat Resistant Bacterial Plant Pathogens

Plants in nature are under the persistent intimidation of severe microbial diseases, threatening a sustainable food production system. Plant-bacterial pathogens are a major concern in the contemporary era, resulting in reduced plant growth and productivity. Plant antibiotics and chemical-based bactericides have been extensively used to evade plant bacterial diseases. To counteract this pressure, bacteria have evolved an array of resistance mechanisms, including innate and adaptive immune systems. The emergence of resistant bacteria and detrimental consequences of antimicrobial compounds on the environment and human health, accentuates the development of an alternative disease evacuation strategy. The phage cocktail therapy is a multidimensional approach effectively employed for the biocontrol of diverse resistant bacterial infections without affecting the fauna and flora. Phages engage a diverse set of counter defense strategies to undermine wide-ranging anti-phage defense mechanisms of bacterial pathogens. Microbial ecology, evolution, and dynamics of the interactions between phage and plant-bacterial pathogens lead to the engineering of robust phage cocktail therapeutics for the mitigation of devastating phytobacterial diseases. In this review, we highlight the concrete and fundamental determinants in the development and application of phage cocktails and their underlying mechanism, combating resistant plant-bacterial pathogens. Additionally, we provide recent advances in the use of phage cocktail therapy against phytobacteria for the biocontrol of devastating plant diseases.

Prospects of Inhaled Phage Therapy for Combatting Pulmonary Infections

With respiratory infections accounting for significant morbidity and mortality, the issue of antibiotic resistance has added to the gravity of the situation. Treatment of pulmonary infections (bacterial pneumonia, cystic fibrosis-associated bacterial infections, tuberculosis) is more challenging with the involvement of multi-drug resistant bacterial strains, which act as etiological agents. Furthermore, with the dearth of new antibiotics available and old antibiotics losing efficacy, it is prudent to switch to non-antibiotic approaches to fight this battle. Phage therapy represents one such approach that has proven effective against a range of bacterial pathogens including drug resistant strains. Inhaled phage therapy encompasses the use of stable phage preparations given via aerosol delivery. This therapy can be used as an adjunct treatment option in both prophylactic and therapeutic modes. In the present review, we first highlight the role and action of phages against pulmonary pathogens, followed by delineating the different methods of delivery of inhaled phage therapy with evidence of success. The review aims to focus on recent advances and developments in improving the final success and outcome of pulmonary phage therapy. It details the use of electrospray for targeted delivery, advances in nebulization techniques, individualized controlled inhalation with software control, and liposome-encapsulated nebulized phages to take pulmonary phage delivery to the next level. The review expands knowledge on the pulmonary delivery of phages and the advances that have been made for improved outcomes in the treatment of respiratory infections.

Phage therapeutics: from promises to practices and prospectives

The rise in multi-drug resistant bacteria and the inability to develop novel antibacterial agents limits our arsenal against infectious diseases. Antibiotic resistance is a global issue requiring an immediate solution, including the development of new antibiotic molecules and other alternative modes of therapy. This article highlights the mechanism of bacteriophage treatment that makes it a real solution for multidrug-resistant infectious diseases. Several case reports identified phage therapy as a potential solution to the emerging challenge of multi-drug resistance. Bacteriophages, unlike antibiotics, have special features, such as host specificity and do not impact other commensals. A new outlook has also arisen with recent advancements in the understanding of phage immunobiology, where phages are repurposed against both bacterial and viral infections. Thus, the potential possibility of phages in COVID-19 patients with secondary bacterial infections has been briefly elucidated. However, significant obstacles that need to be addressed are to design better clinical studies that may contribute to the widespread use of bacteriophage therapy against multi-drug resistant pathogens. In conclusion, antibacterial agents can be used with bacteriophages, i.e. bacteriophage-antibiotic combination therapy, or they can be administered alone in cases when antibiotics are ineffective.Key points• AMR, a consequence of antibiotic generated menace globally, has led to the resurgence of phage therapy as an effective and sustainable solution without any side effects and high specificity against refractory MDR bacterial infections.• Bacteriophages have fewer adverse reactions and can thus be used as monotherapy as well as in conjunction with antibiotics.• In the context of the COVID-19 pandemic, phage therapy may be a viable option.

Antibiotic resistance in agriculture: Perspectives on upcoming strategies to overcome upsurge in resistance

Antibiotic resistance is a massive problem rising constantly and spreading rapidly since the past decade. The major underlying mechanism responsible for this problem is an overuse or severe misuse of antibiotics. Regardless of this emerging global threat, antibiotics are still being widely used, not only for treatment of human infections, but also to a great extent in agriculture, livestock and animal husbandry. If the current scenario persists, we might enter into a post-antibiotic era where drugs might not be able to treat even the simplest of infections. This review discusses the current status of antibiotic utilization and molecular basis of antibiotic resistance mechanisms acquired by bacteria, along with the modes of transmittance of the resultant resistant genes into human pathogens through their cycling among different ecosystems. The main focus of the article is to provide an insight into the different molecular and other strategies currently being studied worldwide for their use as an alternate to antibiotics with an overall aim to overcome or minimize the global problem of antibiotic resistance.

Intestinal Bacteriophage Therapy: Looking for Optimal Efficacy

Several human intestinal microbiota studies suggest that bacteriophages, viruses infecting bacteria, play a role in gut homeostasis. Currently, bacteriophages are considered a tool to precisely engineer the intestinal microbiota, but they have also attracted considerable attention as a possible solution to fight against bacterial pathogens resistant to antibiotics. These two applications necessitate bacteriophages to reach and kill their bacterial target within the gut environment. Unfortunately, exploitable clinical data in this field are scarce. Here, we review the administration of bacteriophages to target intestinal bacteria in mammalian experimental models. While bacteriophage amplification in the gut was often confirmed, we found that in most studies, it had no significant impact on the load of the targeted bacteria. In particular, we observed that the outcome of bacteriophage treatments is linked to the behavior of the target bacteria toward each animal model. Treatment efficacy ranges from poor in asymptomatic intestinal carriage to high in intestinal disease. This broad range of efficacy underlines the difficulties to reach a consensus on the impact of bacteriophages in the gut and calls for deeper investigations of key parameters that influence the success of such interventions before launching clinical trials.

Microbiome and cancer

The human microbiome constitutes a complex multikingdom community that symbiotically interacts with the host across multiple body sites. Host-microbiome interactions impact multiple physiological processes and a variety of multifactorial disease conditions. In the past decade, microbiome communities have been suggested to influence the development, progression, metastasis formation, and treatment response of multiple cancer types. While causal evidence of microbial impacts on cancer biology is only beginning to be unraveled, enhanced molecular understanding of such cancer-modulating interactions and impacts on cancer treatment are considered of major scientific importance and clinical relevance. In this review, we describe the molecular pathogenic mechanisms shared throughout microbial niches that contribute to the initiation and progression of cancer. We highlight advances, limitations, challenges, and prospects in understanding how the microbiome may causally impact cancer and its treatment responsiveness, and how microorganisms or their secreted bioactive metabolites may be potentially harnessed and targeted as precision cancer therapeutics.

The human oral virome: Shedding light on the dark matter

Mediators of the initiation, development, and recurrence of periodontitis include the oral microbiome embedded in subgingival plaque and the host immune response to a dysbiosis within this dynamic and complex microbial community. Although mediators have been studied extensively, researchers in the field have been unable to fully ascribe certain clinical presentations of periodontitis to their nature. Emergence of high-throughput sequencing technologies has resulted in better characterization of the microbial oral dysbiosis that extends beyond the extensively studied putative bacterial periodontopathogens to a shift in the oral virome composition during disease conditions. Although the biological dark matter inserted by retroviruses was once believed to be nonfunctional, research has revealed that it encodes historical viral-eukaryotic interactions and influences host development. The objective of this review is to evaluate the proposed association of herpesviruses to the etiology and pathogenesis of periodontal disease and survey the highly abundant prokaryotic viruses to delineate their potential roles in biofilm dynamics, as well as their interactions with putative bacterial periodontopathogens and eukaryotic cells. The findings suggest that potential novel periodontal therapies targeting or utilizing the oral virome can alleviate certain clinical presentations of periodontitis. Perhaps it is time to embrace the viral dark matter within the periodontal environment to fully comprehend the pathogenesis and systemic implications of periodontitis.

Pharmacokinetics and Pharmacodynamics of a Novel Virulent Klebsiella Phage Kp_Pokalde_002 in a Mouse Model

Phage therapy is one of the most promising alternatives to antibiotics as we face global antibiotic resistance crisis. However, the pharmacokinetics (PK) and pharmacodynamics (PD) of phage therapy are largely unknown. In the present study, we aimed to evaluate the PK/PD of a locally isolated virulent novel øKp_Pokalde_002 (Podoviridae, C1 morphotype) that infects carbapenem-resistant Klebsiella pneumoniae (Kp56) using oral and intraperitoneal (IP) route in a mouse model. The result showed that the øKp_Pokalde_002 rapidly distributed into the systemic circulation within an hour via both oral and IP routes. A higher concentration of phage in plasma was found after 4 h (2.3 x 10⁵ PFU/ml) and 8 h (7.3 x 10⁴ PFU/ml) of administration through IP and oral route, respectively. The phage titer significantly decreased in the blood and other tissues, liver, kidneys, and spleen after 24 h and completely cleared after 72 h of administration. In the Kp56 infection model, the bacterial count significantly decreased in the blood and other organs by 4-7 log₁₀ CFU/ml after 24 h of øKp_Pokalde_002 administration. Elimination half-life of øKp_Pokalde_002 was relatively shorter in the presence of host-bacteria Kp56 compared to phage only, suggesting rapid clearance of phage in the presence of susceptible host. Further, administration of the øKp_Pokalde_002 alone in healthy mice (via IP or oral) did not stimulate pro-inflammatory cytokines (TNF-α and IL-6). Also, treatment with øKp_Pokalde_002 resulted in a significant reduction of pro-inflammatory cytokines (TNF-α and IL-6) caused by bacterial infection, thereby reducing the tissue inflammation. In conclusion, the øKp_Pokalde_002 possess good PK/PD properties and can be considered as a potent therapeutic candidate for future phage therapy in carbapenem-resistant K. pneumoniae infections.

The Efficacy of Phage Therapy in a Murine Model of Pseudomonas aeruginosa Pneumonia and Sepsis

The emergence of multi-drug resistant Pseudomonas aeruginosa necessitates the search for treatment options other than antibiotic use. The use of bacteriophages is currently being considered as an alternative to antibiotics for the treatment of bacterial infections. A number of bacteriophages were introduced to treat pneumonia in past reports. However, there are still lack of knowledge regarding the dosages, application time, mechanism and safety of phage therapy against P. aeruginosa pneumonia. We used the bacteriophage KPP10 against P. aeruginosa strain D4-induced pneumonia mouse models and observed their outcomes in comparison to control models. We found that the nasal inhalation of highly concentrated KPP10 (MOI = 80) significantly improved survival rate in pneumonia models (P < 0.01). The number of viable bacteria in both lungs and in serum were significantly decreased (P < 0.01) in phage-treated mice in comparison to the control mice. Pathological examination showed that phage-treated group had significantly reduced bleeding, inflammatory cell infiltration, and mucus secretion in lung interstitium. We also measured inflammatory cytokine levels in the serum and lung homogenates of mice. In phage-treated models, serum TNFα, IL-1β, and IFN-γ levels were significantly lower (P < 0.05, P < 0.01, and P < 0.05, respectively) than those in the control models. In the lung homogenate, the mean IL-1β level in phage-treated models was significantly lower (P < 0.05) than that of the control group. We confirmed the presence of phage in blood and lungs, and evaluated the safety of bacteriophage use in living models since bacteriophage mediated bacterial lysis arise concern of endotoxic shock. The study results suggest that phage therapy can potentially be used in treating lung infections caused by Pseudomonas aeruginosa.

Novel therapeutic interventions towards improved management of septic arthritis

Septic arthritis (SA) represents a medical emergency that needs immediate diagnosis and urgent treatment. Despite aggressive treatment and rapid diagnosis of the causative agent, the mortality and lifelong disability, associated with septic arthritis remain high as close to 11%. Moreover, with the rise in drug resistance, the rates of failure of conventional antibiotic therapy have also increased. Among the etiological agents frequently isolated from cases of septic arthritis, Staphylococcus aureus emerges as a dominating pathogen, and to worsen, the rise in methicillin-resistant S. aureus (MRSA) isolates in bone and joint infections is worrisome. MRSA associated cases of septic arthritis exhibit higher mortality, longer hospital stay, and higher treatment failure with poorer clinical outcomes as compared to cases caused by the sensitive strain i.e methicillin-sensitive S. aureus (MSSA).

In addition to this, equal or even greater damage is imposed by the exacerbated immune response mounted by the patient’s body in a futile attempt to eradicate the bacteria. The antibiotic therapy may not be sufficient enough to control the progression of damage to the joint involved thus, adding to higher mortality and disability rates despite the prompt and timely start of treatment. This situation implies that efforts and focus towards studying/understanding new strategies for improved management of sepsis arthritis is prudent and worth exploring.

The review article aims to give a complete insight into the new therapeutic approaches studied by workers lately in this field. To the best of our knowledge studies highlighting the novel therapeutic strategies against septic arthritis are limited in the literature, although articles on pathogenic mechanism and choice of antibiotics for therapy, current treatment algorithms followed have been discussed by workers in the past. The present study presents and discusses the new alternative approaches, their mechanism of action, proof of concept, and work done so far towards their clinical success. This will surely help to enlighten the researchers with comprehensive knowledge of the new interventions that can be used as an adjunct therapy along with conventional treatment protocol for improved success rates.

Clinical Pharmacology of Bacteriophage Therapy: A Focus on Multidrug-Resistant Pseudomonas aeruginosa Infections

Pseudomonas aeruginosa is one of the most common causes of healthcare-associated diseases and is among the top three priority pathogens listed by the World Health Organization (WHO). This Gram-negative pathogen is especially difficult to eradicate because it displays high intrinsic and acquired resistance to many antibiotics. In addition, growing concerns regarding the scarcity of antibiotics against multidrug-resistant (MDR) and extensively drug-resistant (XDR) P. aeruginosa infections necessitate alternative therapies. Bacteriophages, or phages, are viruses that target and infect bacterial cells, and they represent a promising candidate for combatting MDR infections. The aim of this review was to highlight the clinical pharmacology considerations of phage therapy, such as pharmacokinetics, formulation, and dosing, while addressing several challenges associated with phage therapeutics for MDR P. aeruginosa infections. Further studies assessing phage pharmacokinetics and pharmacodynamics will help to guide interested clinicians and phage researchers towards greater success with phage therapy for MDR P. aeruginosa infections.

Isolation and Characterization of Six Vibrio parahaemolyticus Lytic Bacteriophages From Seafood Samples

Vibrio parahaemolyticus is a foodborne pathogen that is frequently isolated from a variety of seafood. To control this pathogenic Vibrio spp., the implementation of bacteriophages in aquaculture and food industries have shown a promising alternative to antibiotics. In this study, six bacteriophages isolated from the seafood samples demonstrated a narrow host range specificity that infecting only the V. parahaemolyticus strains. Morphological analysis revealed that bacteriophages Vp33, Vp22, Vp21, and Vp02 belong to the Podoviridae family, while bacteriophages Vp08 and Vp11 were categorized into the Siphoviridae family. All bacteriophages were composed of DNA genome and showed distinctive restriction fragment length polymorphism. The optimal MOI for bacteriophage propagation was determined to be 0.001 to 1. One-step growth curve revealed that the latent period ranged from 10 to 20 min, and the burst size of bacteriophage was approximately 17 to 51 PFU/cell. The influence of temperature and pH levels on the stability of bacteriophages showed that all bacteriophages were optimally stable over a wide range of temperatures and pH levels. In vitro lytic activity of all bacteriophages demonstrated to have a significant effect against V. parahaemolyticus. Besides, the application of a bacteriophage cocktail instead of a single bacteriophage suspension was observed to have a better efficiency to control the growth of V. parahaemolyticus. Results from this study provided a basic understanding of the physiological and biological properties of the isolated bacteriophages before it can be readily used as a biocontrol agent against the growth of V. parahaemolyticus.

The Role of Antibiotic Resistant A. baumannii in the Pathogenesis of Urinary Tract Infection and the Potential of Its Treatment with the Use of Bacteriophage Therapy

Acinetobacter baumannii are bacteria that belong to the critical priority group due to their carbapenems and third generation cephalosporins resistance, which are last-chance antibiotics. The growing multi-drug resistance and the ability of these bacteria to form biofilms makes it difficult to treat infections caused by this species, which often affects people with immunodeficiency or intensive care unit patients. In addition, most of the infections are associated with catheterization of patients. These bacteria are causative agents, inter alia, of urinary tract infections (UTI) which can cause serious medical and social problems, because of treatment difficulties as well as the possibility of recurrence and thus severely decrease patients' quality of life. Therefore, a promising alternative to standard antibiotic therapy can be bacteriophage therapy, which will generate lower costs and will be safer for the treated patients and has real potential to be much more effective. The aim of the review is to outline the important role of drug-resistant A. baumannii in the pathogenesis of UTI and highlight the potential for fighting these infections with bacteriophage therapy. Further studies on the use of bacteriophages in the treatment of UTIs in animal models may lead to the use of bacteriophage therapy in human urinary tract infections caused by A. baumannii in the future.

Progress and Pitfalls of Bacteriophage Therapy in Critical Care: A Concise Definitive Review

Supplemental Digital Content is available in the text.

Objective:

Bacterial infections caused by antibiotic-resistant pathogens are a major problem for patients requiring critical care. An approach to combat resistance is the use of bacterial viruses known as “phage therapy.” This review provides a brief “clinicians guide” to phage biology and discusses recent applications in the context of common infections encountered in ICUs.

Data Sources:

Research articles were sourced from PubMed using search term combinations of “bacteriophages” or “phage therapy” with either “lung,” “pneumonia,” “bloodstream,” “abdominal,” “urinary tract,” or “burn wound.”

Study Selection:

Preclinical trials using animal models, case studies detailing compassionate use of phage therapy in humans, and randomized controlled trials were included.

Data Extraction:

We systematically extracted: 1) the infection setting, 2) the causative bacterial pathogen and its antibiotic resistance profile, 3) the nature of the phage therapeutic and how it was administered, 4) outcomes of the therapy, and 5) adverse events.

Data Synthesis:

Phage therapy for the treatment of experimental infections in animal models and in cases of compassionate use in humans has been associated with largely positive outcomes. These findings, however, have failed to translate into positive patient outcomes in the limited number of randomized controlled trails that have been performed to date.

Conclusions:

Widespread clinical implementation of phage therapy depends on success in randomized controlled trials. Additional translational and reverse translational studies aimed at overcoming phage resistance, exploiting phage-antibiotic synergies, and optimizing phage administration will likely improve the design and outcome of future trials.

Efficacy of Individual Bacteriophages Does Not Predict Efficacy of Bacteriophage Cocktails for Control of Escherichia coli O157

Effectiveness of bacteriophages AKFV33 (Tequintavirus, T5) and AHP24 (Rogunavirus, T1), wV7 (Tequatrovirus, T4), and AHP24S (Vequintavirus, rV5), as well as 11 cocktails of combinations of the four phages, were evaluated in vitro for biocontrol of six common phage types of Escherichia coli O157 (human and bovine origins) at different multiplicities of infection (MOIs; 0.01–1,000), temperatures (37 or 22°C), and exposure times (10–22 h). Phage efficacy against O157 was highest at MOI 1,000 (P < 0.001) and after 14-18 h of exposure at 22°C (P < 0.001). The activity of individual phages against O157 did not predict the activity of a cocktail of these phages even at the same temperature and MOI. Combinations of phages were neutral (no better or worse than the most effective constituent phages acting alone), displayed facilitation (greater efficacy than the most effective constituent phages acting alone), or antagonistic (lower efficacy than the most effective constituent phages acting alone). Across MOIs, temperatures, exposure time, and O157 strains, a cocktail of T1, T4, and rV5 was most effective (P < 0.05) against O157, although T1 and rV5 were less effective (P < 0.001) than other individual phages. T5 was the most effective individual phages (P < 0.05), but was antagonistic to other phages, particularly rV5 and T4 + rV5. Interactions among phages were influenced by phage genera and phage combination, O157 strains, MOIs, incubation temperatures, and times. Based on this study, future development of phage cocktails should, as a minimum, include confirmation of a lack of antagonism among constituent phages and preferably confirmation of facilitation or synergistic effects.

Identification and complete genome of lytic "Kp34likevirus" phage vB_KpnP_Bp5 and therapeutic potency in the treatment of lethal Klebsiella pneumoniae infections in mice

Klebsiella pneumoniae (K. pneumoniae) infection exist widely in the farming and medical. The treatment of K. pneumoniae infection is primarily based on antibiotics, which not only leads to a large economic burden but also the development of antibiotic resistance. Bacteriophages therapy present a promising alternative. The object of this study was identifying comprehensively a lytic lethal K. pneumoniae phage vB_KpnP_Bp5, and evaluating the phage as an anti-infective agent in an experimental K. pneumoniae infection murine model. The phage Bp5 had the following characteristics: the optimal number of infections was 0.001, the latent period was 5 min, the outbreak period was 40 min, the burst size was 24 plaque-forming unit (PFU)/cell, the phage could withstand 50 °C temperature and the optimal pH value was 4.0-10.0. According to electron microscopy and whole-genome sequence analysis, the phage should be classified as a member of order Caudovirales, family Podoviridae, subfamily Autographiviridae. Meantime, phylogenetic analysis showed high conservation of gene arrangement and gene content. We demonstrated that administration of phage Bp5 significantly reduced colony formation by K. pneumoniae and alleviated damage to lung tissue. In addition, different therapy time point was closely related to body health and the degree of tissue damage. Once treated promptly, it will greatly reduce mortality and alveolar inflammatory exudation and injury.

A Phage Therapy Guide for Clinicians and Basic Scientists: Background and Highlighting Applications for Developing Countries

Approximately 10% of global health research is devoted to 90% of global disease burden (the so-called “10/90 Gap”) and it often neglects those diseases most prevalent in low-income countries. Antibiotic resistant bacterial infections are known to impact on healthcare, food security, and socio-economic fabric in the developing countries. With a global antibiotic resistance crisis currently reaching a critical level, the unmet needs in the developing countries are even more striking. The failure of traditional antimicrobials has led to renewed interest in century-old bacteriophage (phage) therapy in response to the urgent need to develop alternative therapies to treat infections. Phage therapy may have particular value in developing countries where relevant phages can be sourced and processed locally and efficiently, breaking specifically the economic barrier of access to expensive medicine. Hence this makes phage therapy an attractive and feasible option. In this review, we draw our respective clinical experience as well as phage therapy research and clinical trial, and discuss the ways in which phage therapy might reduce the burden of some of the most important bacterial infections in developing countries.

Animal Models of Phage Therapy

Amidst the rising tide of antibiotic resistance, phage therapy holds promise as an alternative to antibiotics. Most well-designed studies on phage therapy exist in animal models. In order to progress to human clinical trials, it is important to understand what these models have accomplished and determine how to improve upon them. Here we provide a review of the animal models of phage therapy in Western literature and outline what can be learned from them in order to bring phage therapy closer to becoming a feasible alternative to antibiotics in clinical practice.

In Vitro and In Vivo Evaluation of Three Newly Isolated Bacteriophage Candidates, phiEF7H, phiEF14H1, phiEF19G, for Treatment of Enterococcus faecalis Endophthalmitis

Post-operative endophthalmitis caused by Enterococcus spp. progresses rapidly and often results in substantial and irreversible vision loss. Therefore, novel alternative treatments that are effective against enterococcal endophthalmitis are required. Bacteriophage therapy has the potential to be an optional therapy for infectious diseases. Therefore, we investigated the therapeutic potential of three newly isolated enterococcal phages, phiEF7H, phiEF14H1, and phiEF19G, in E. faecalis-induced endophthalmitis. These phages could lyse the broad-range E. faecalis, including strains derived from endophthalmitis and vancomycin-resistant E. faecalis in vitro, as determined by the streak test. Morphological and genomic analyses revealed that these phages were classified into the Herelleviridae genus Kochikohdavirus. The whole genomes of these phages contained 143,399, 143,280, and 143,400 bp, respectively. Endophthalmitis was induced in mice by injection of three strains of E. faecalis derived from post-operative endophthalmitis or vancomycin-resistant strains into the vitreous body. The number of viable bacteria and infiltration of neutrophils in the eye were both decreased by intravitreous injection of phiEF7H, phiEF14H1, and phiEF19G 6 h after injection of all E. faecalis strains. Thus, these results suggest that these newly isolated phages may serve as promising candidates for phage therapy against endophthalmitis.

Pulling the Brakes on Fast and Furious Multiple Drug-Resistant (MDR) Bacteria

Life-threatening bacterial infections have been managed by antibiotics for years and have significantly improved the wellbeing and lifetime of humans. However, bacteria have always been one step ahead by inactivating the antimicrobial agent chemically or by producing certain enzymes. The alarming universal occurrence of multidrug-resistant (MDR) bacteria has compelled researchers to find alternative treatments for MDR infections. This is a menace where conventional chemotherapies are no longer promising, but several novel approaches could help. Our current review article discusses the novel approaches that can combat MDR bacteria: starting off with potential nanoparticles (NPs) that efficiently interact with microorganisms causing fatal changes in the morphology and structure of these cells; nanophotothermal therapy using inorganic NPs like AuNPs to destroy pathogenic bacterial cells; bacteriophage therapy against which bacteria develop less resistance; combination drugs that act on dissimilar targets in distinctive pathways; probiotics therapy by the secretion of antibacterial chemicals; blockage of quorum sensing signals stopping bacterial colonization, and vaccination against resistant bacterial strains along with virulence factors. All these techniques show us a promising future in the fight against MDR bacteria, which remains the greatest challenge in public health care.

Mycobacteriophages as Potential Therapeutic Agents against Drug-Resistant Tuberculosis

The current emergence of multi-, extensively-, extremely-, and total-drug resistant strains of Mycobacterium tuberculosis poses a major health, social, and economic threat, and stresses the need to develop new therapeutic strategies. The notion of phage therapy against bacteria has been around for more than a century and, although its implementation was abandoned after the introduction of drugs, it is now making a comeback and gaining renewed interest in Western medicine as an alternative to treat drug-resistant pathogens. Mycobacteriophages are genetically diverse viruses that specifically infect mycobacterial hosts, including members of the M. tuberculosis complex. This review describes general features of mycobacteriophages and their mechanisms of killing M. tuberculosis, as well as their advantages and limitations as therapeutic and prophylactic agents against drug-resistant M. tuberculosis strains. This review also discusses the role of human lung micro-environments in shaping the availability of mycobacteriophage receptors on the M. tuberculosis cell envelope surface, the risk of potential development of bacterial resistance to mycobacteriophages, and the interactions with the mammalian host immune system. Finally, it summarizes the knowledge gaps and defines key questions to be addressed regarding the clinical application of phage therapy for the treatment of drug-resistant tuberculosis.

Bacteriophages Against Pathogenic Bacteria and Possibilities for Future Application in Africa

Bacteriophages (phages) are viruses that infect prokaryotic cells. Phages exist in many shapes and sizes with the majority of them being less than 100 nm in size. Essentially, the majority of phages identified are double-stranded DNA virions with the remaining few being found as RNA or single-stranded DNA viruses. These biological entities are plentiful in different environments, especially in wet sources. Treatment of a bacterial disease using phage application has been documented in the pre-antibiotic era. Different studies have emerging to value the efficacy of phage use in in-vitro and in-vivo based systems against specific bacterial agents of humans, animals or plant diseases. The process represents a natural and nontoxic framework to avert infections due to pathogenic and antimicrobial-resistant bacteria. Most of the published researches on the usefulness of phages against disease-causing bacteria (including antimicrobial-resistant strains) of humans, animals or plants are emerging from the US and European countries with very few studies available from Africa. This review assesses published articles in the area of phage applications against pathogenic or antimicrobial-resistant bacteria from experimental, clinical and field settings. The knowledge and skill of isolating lytic phages against bacteria can be operational for its simpler procedures and economic benefit. Future studies in Africa and other emerging countries may consider in-house phage preparations for effective control and eradication of pathogenic and multidrug resistant bacteria of humans, animals and plants.

Bacteriophage Therapy of Bacterial Infections: The Rediscovered Frontier

Antibiotic-resistant infections present a serious health concern worldwide. It is estimated that there are 2.8 million antibiotic-resistant infections and 35,000 deaths in the United States every year. Such microorganisms include Acinetobacter, Enterobacterioceae, Pseudomonas, Staphylococcus and Mycobacterium. Alternative treatment methods are, thus, necessary to treat such infections. Bacteriophages are viruses of bacteria. In a lytic infection, the newly formed phage particles lyse the bacterium and continue to infect other bacteria. In the early 20th century, d'Herelle, Bruynoghe and Maisin used bacterium-specific phages to treat bacterial infections. Bacteriophages are being identified, purified and developed as pharmaceutically acceptable macromolecular "drugs," undergoing strict quality control. Phages can be applied topically or delivered by inhalation, orally or parenterally. Some of the major drug-resistant infections that are potential targets of pharmaceutically prepared phages are Pseudomonas aeruginosa, Mycobacterium tuberculosis and Acinetobacter baumannii.

Recent Insights into Aeromonas salmonicida and Its Bacteriophages in Aquaculture: A Comprehensive Review

The emergence and spread of antimicrobial resistance in pathogenic bacteria of fish and shellfish have caused serious concerns in the aquaculture industry, owing to the potential health risks to humans and animals. Among these bacteria, Aeromonas salmonicida, which is one of the most important primary pathogens in salmonids, is responsible for significant economic losses in the global aquaculture industry, especially in salmonid farming because of its severe infectivity and acquisition of antimicrobial resistance. Therefore, interest in the use of alternative approaches to prevent and control A. salmonicida infections has increased in recent years, and several applications of bacteriophages (phages) have provided promising results. For several decades, A. salmonicida and phages infecting this fish pathogen have been thoroughly investigated in various research areas including aquaculture. The general overview of phage usage to control bacterial diseases in aquaculture, including the general advantages of this strategy, has been clearly described in previous reviews. Therefore, this review specifically focuses on providing insights into the phages infecting A. salmonicida, from basic research to biotechnological application in aquaculture, as well as recent advances in the study of A. salmonicida.

Antibiotics in Food Chain: The Consequences for Antibiotic Resistance

Antibiotics have been used as essential therapeutics for nearly 100 years and, increasingly, as a preventive agent in the agricultural and animal industry. Continuous use and misuse of antibiotics have provoked the development of antibiotic resistant bacteria that progressively increased mortality from multidrug-resistant bacterial infections, thereby posing a tremendous threat to public health. The goal of our review is to advance the understanding of mechanisms of dissemination and the development of antibiotic resistance genes in the context of nutrition and related clinical, agricultural, veterinary, and environmental settings. We conclude with an overview of alternative strategies, including probiotics, essential oils, vaccines, and antibodies, as primary or adjunct preventive antimicrobial measures or therapies against multidrug-resistant bacterial infections. The solution for antibiotic resistance will require comprehensive and incessant efforts of policymakers in agriculture along with the development of alternative therapeutics by experts in diverse fields of microbiology, biochemistry, clinical research, genetic, and computational engineering.

Plant Viruses and Bacteriophage-Based Reagents for Diagnosis and Therapy

Viral nanotechnology exploits the prefabricated nanostructures of viruses, which are already abundant in nature. With well-defined molecular architectures, viral nanocarriers offer unprecedented opportunities for precise structural and functional manipulation using genetic engineering and/or bio-orthogonal chemistries. In this manner, they can be loaded with diverse molecular payloads for targeted delivery. Mammalian viruses are already established in the clinic for gene therapy and immunotherapy, and inactivated viruses or virus-like particles have long been used as vaccines. More recently, plant viruses and bacteriophages have been developed as nanocarriers for diagnostic imaging, vaccine and drug delivery, and combined diagnosis/therapy (theranostics). The first wave of these novel virus-based tools has completed clinical development and is poised to make an impact on clinical practice.

Phages and their potential to modulate the microbiome and immunity

Bacteriophages (hence termed phages) are viruses that target bacteria and have long been considered as potential future treatments against antibiotic-resistant bacterial infection. However, the molecular nature of phage interactions with bacteria and the human host has remained elusive for decades, limiting their therapeutic application. While many phages and their functional repertoires remain unknown, the advent of next-generation sequencing has increasingly enabled researchers to decode new lytic and lysogenic mechanisms by which they attack and destroy bacteria. Furthermore, the last decade has witnessed a renewed interest in the utilization of phages as therapeutic vectors and as a means of targeting pathogenic or commensal bacteria or inducing immunomodulation. Importantly, the narrow host range, immense antibacterial repertoire, and ease of manipulating phages may potentially allow for their use as targeted modulators of pathogenic, commensal and pathobiont members of the microbiome, thereby impacting mammalian physiology and immunity along mucosal surfaces in health and in microbiome-associated diseases. In this review, we aim to highlight recent advances in phage biology and how a mechanistic understanding of phage-bacteria-host interactions may facilitate the development of novel phage-based therapeutics. We provide an overview of the challenges of the therapeutic use of phages and how these could be addressed for future use of phages as specific modulators of the human microbiome in a variety of infectious and noncommunicable human diseases.

Optimizing bacteriophage engineering through an accelerated evolution platform

The emergence of antibiotic resistance has raised serious concerns within scientific and medical communities, and has underlined the importance of developing new antimicrobial agents to combat such infections. Bacteriophages, naturally occurring bacterial viruses, have long been characterized as promising antibiotic alternatives. Although bacteriophages hold great promise as medical tools, clinical applications have been limited by certain characteristics of phage biology, with structural fragility under the high temperatures and acidic environments of therapeutic applications significantly limiting therapeutic effectiveness. This study presents and evaluates the efficacy of a new accelerated evolution platform, chemically accelerated viral evolution (CAVE), which provides an effective and robust method for the rapid enhancement of desired bacteriophage characteristics. Here, our initial use of this methodology demonstrates its ability to confer significant improvements in phage thermal stability. Analysis of the mutation patterns that arise through CAVE iterations elucidates the manner in which specific genetic modifications bring forth desired changes in functionality, thereby providing a roadmap for bacteriophage engineering.

New Phage cocktail against infantile Sepsis bacteria

A total of 54 positive blood aerobic cultures of suspected blood sepsis in neonates were purified, diagnosed and tested for antibiotic susceptibility. Six bacterial pathogens of Escherichia coli (10 isolates), Klebsiella pneumoniae (10 isolates), Haemophilus influenzae (4 isolates), Pseudomonas aeruginosa (3 isolates), Citrobacter fruendii (1 isolate) and Moraxella catarrhalis (1 isolate) were selected for preparation of phages active against all isolates of each species. Virulent phages towards bacterial isolates were isolated from sewage water by spot lysis method, and a total of 29 phages active towards selected bacterial pathogens were isolated and purified. Phage(s) active against each bacterial species showed activity spectrum within each species of 30-80%, 50-80%, 50%, 50%, 100% and 100% for isolates of Escherichia coli, Klebsiella spp., Haemophilus influenzae, Pseudomonas aeruginosa, Citrobacter fruendii and Moraxella catarrhalis, respectively. A total of 29 phages were formulated in one cocktail in a concentration of 10⁶ PFU/ml in SM buffer for each of a total of 29 phages in SM buffer and showed activity spectrum of 100% against all their bacterial hosts in vitro.

Bacteriophages and Lysins as Possible Alternatives to Treat Antibiotic-Resistant Urinary Tract Infections

Urinary tract infections represent a major public health problem as the rapid emergence of antibiotic-resistant strains among uropathogens is causing the failure of many current treatments. The use of bacteriophages (phages) and their derivatives to combat infectious diseases is an old approach that has been forgotten by the West for a long time, mostly due to the discovery and great success of antibiotics. In the present so-called “post-antibiotic era”, many researchers are turning their attention to the re-discovered phage therapy, as an effective alternative to antibiotics. Phage therapy includes the use of natural or engineered phages, as well as their purified lytic enzymes to destroy pathogenic strains. Many in vitro and in vivo studies have been conducted, and these have proved the great potential for this therapy against uropathogenic bacteria. Nevertheless, to date, the lack of appropriate clinical trials has hindered its widespread clinic application.

Transient carriage and low-level colonization of orally administrated lytic and temperate phages in the gut of mice

Abstract

Many studies have shown the efficacy of phage therapy in reducing gastrointestinal pathogens. However, it is unclear whether phages can successfully colonize the gut when administered in an adequate amount for a long time. About 1 × 108 PFU/mL of purified lytic phage PA13076 or temperate phage BP96115 were fed daily to mice via drinking water over 31 days, to elucidate the distribution of phages in the gastrointestinal tract. At day 16 and 31, six different segments of the gastrointestinal tract with their contents, including stomach, duodenum, jejunum, ileum, cecum, colon, and fresh feces, were aseptically collected. The phage titers were determined using the double-layered plate method with S. Enteritidis ATCC 13076 or S. Pullorum SPu-109 used as host cells. The results indicated that a small portion of administered phages survived exposure to gastric acid and entered the intestinal tract. The prevalence of phages in the gastrointestinal tract was lower than 1% of the primary phage count. Highest phage titers were detected in the cecum with 104 ~ 105 PFU/g, and most of the phages were eliminated from the body via feces with 106 PFU/g. On day 16 and day 31, the same level of phage titers in different segments of the gastrointestinal tract indicated that the colonization of phages had reached saturation at day 16. These results demonstrate transient phage carriage and low-level colonization of orally administrated lytic and temperate gut phages in mice.

Graphical abstract