Isolation of a T7-Like Lytic Pasteurella Bacteriophage vB_PmuP_PHB01 and Its Potential Use in Therapy against Pasteurella multocida Infections

Protocol for establishing CRISPR-Cas12a for efficient genome editing of Pseudomonas aeruginosa phages

We developed an efficient type V CRISPR-Cas12a system tailored specifically for Pseudomonas aeruginosa phages, showcasing its remarkable cleavage activity and the ability to precisely introduce genetic modifications, including point mutations, deletions, and insertions, into phage genomes. Here, we present a protocol for establishing CRISPR-Cas12a for genome editing of Pseudomonas aeruginosa phages. We describe steps for the construction of pCRISPR-12a plasmid and guide RNA and the utilization of the type V CRISPR-Cas12a system for precise genetic editing of phages. For complete details on the use and execution of this protocol, please refer to Chen et al.1.

Advancing Phage Therapy: A Comprehensive Review of the Safety, Efficacy, and Future Prospects for the Targeted Treatment of Bacterial Infections

BACKGROUND

Phage therapy, a treatment utilizing bacteriophages to combat bacterial infections, is gaining attention as a promising alternative to antibiotics, particularly for managing antibiotic-resistant bacteria. This study aims to provide a comprehensive review of phage therapy by examining its safety, efficacy, influencing factors, future prospects, and regulatory considerations. The study also seeks to identify strategies for optimizing its application and to propose a systematic framework for its clinical implementation.

METHODS

A comprehensive analysis of preclinical studies, clinical trials, and regulatory frameworks was undertaken to evaluate the therapeutic potential of phage therapy. This included an in-depth assessment of key factors influencing clinical outcomes, such as infection site, phage-host specificity, bacterial burden, and immune response. Additionally, innovative strategies-such as combination therapies, bioengineered phages, and phage cocktails-were explored to enhance efficacy. Critical considerations related to dosing, including inoculum size, multiplicity of infection, therapeutic windows, and personalized medicine approaches, were also examined to optimize treatment outcomes.

RESULTS

Phage therapy has demonstrated a favorable safety profile in both preclinical and clinical settings, with minimal adverse effects. Its ability to specifically target harmful bacteria while preserving beneficial microbiota underpins its efficacy in treating a range of infections. However, variable outcomes in some studies highlight the importance of addressing critical factors that influence therapeutic success. Innovative approaches, including combination therapies, bioengineered phages, expanded access to diverse phage banks, phage cocktails, and personalized medicine, hold significant promise for improving efficacy. Optimizing dosing strategies remains a key area for enhancement, with critical considerations including inoculum size, multiplicity of infection, phage kinetics, resistance potential, therapeutic windows, dosing frequency, and patient-specific factors. To support the clinical application of phage therapy, a streamlined four-step guideline has been developed, providing a systematic framework for effective treatment planning and implementation.

CONCLUSION

Phage therapy offers a highly adaptable, targeted, and cost-effective approach to addressing antibiotic-resistant infections. While several critical factors must be thoroughly evaluated to optimize treatment efficacy, there remains significant potential for improvement through innovative strategies and refined methodologies. Although phage therapy has yet to achieve widespread approval in the U.S. and Europe, its accessibility through Expanded Access programs and FDA authorizations for food pathogen control underscores its promise. Established practices in countries such as Poland and Georgia further demonstrate its clinical feasibility. To enable broader adoption, regulatory harmonization and advancements in production, delivery, and quality control will be essential. Notably, the affordability and scalability of phage therapy position it as an especially valuable solution for developing regions grappling with escalating rates of antibiotic resistance.

Characterization and Potential Application of Phage vB_PmuM_CFP3 for Phage Therapy Against Avian Pasteurella multocida

The rise of antibiotic-resistant bacterial infections necessitates alternative therapeutic strategies, such as phage therapy. This study investigates the potential of phage vB_PmuM_CFP3 (CFP3) as a therapeutic agent against avian cholera caused by Pasteurella multocida (P. multocida). Phage CFP3 was isolated from the feces and wastewater of a laying hen farm and underwent comprehensive biological characterization, including host range, lytic activity, and environmental stability. Transmission electron microscopy revealed CFP3's typical myovirus morphology, with a head diameter of approximately 60 nm and a tail length of about 120 nm. CFP3 demonstrated high stability across a pH range of 4-10 and temperatures of 30-40 °C, making it suitable for oral administration in poultry. The phage exhibited a latent period of about 90 min and an optimal multiplicity of infection (MOI) of 1. Despite its narrow host range, with a lysis rate of 28.2% against avian-derived type A P. multocida, CFP3's specificity minimizes impact on non-target bacteria. Whole-genome sequencing revealed a 32,696 bp linear double-stranded DNA genome with 46 predicted open reading frames (ORFs) and no tRNA or antibiotic resistance genes, enhancing its safety profile. Phylogenetic analysis indicated a close evolutionary relationship with Haemophilus phages HP1, HP2, and Pasteurella phage F108. While CFP3 shows promise as a precision therapeutic tool, further in vivo studies are required to evaluate its efficacy and safety. Future research should focus on expanding the phage library, optimizing phage mixtures, and exploring synergistic effects with other antimicrobial strategies. This study provides foundational data supporting the development of CFP3 as a viable alternative to antibiotics for controlling avian cholera.

Development of the CRISPR-Cas12a system for editing of Pseudomonas aeruginosa phages

Pseudomonas aeruginosa is a common opportunistic pathogen. The potential efficacy of phage therapy has attracted the attention of researchers, but efficient gene-editing tools are lacking, limiting the study of their biological properties. Here, we designed a type V CRISPR-Cas12a system for the gene editing of P. aeruginosa phages. We first evaluated the active cutting function of the CRISPR-Cas12a system in vitro and discovered that it had a higher gene-cutting efficiency than the type II CRISPR-Cas9 system in three different P. aeruginosa phages. We also demonstrated the system's ability to precisely edit genes in Escherichia coli phages, Salmonella phages, and P. aeruginosa phages. Using the aforementioned strategies, non-essential P. aeruginosa phage genes can be efficiently deleted, resulting in a reduction of up to 5,215 bp (7.05%). Our study has provided a rapid, efficient, and time-saving tool that accelerates progress in phage engineering.

The applications of animal models in phage therapy: An update

The rapid increase in antibiotic resistance presents a dire situation necessitating the need for alternative therapeutic agents. Among the current alternative therapies, phage therapy (PT) is promising. This review extensively summarizes preclinical PT approaches in various in-vivo models. PT has been evaluated in several recent clinical trials. However, there are still several unanswered concerns due to a lack of appropriate regulation and pharmacokinetic data regarding the application of phages in human therapeutic procedures. In this review, we also presented the current state of PT and considered how animal models can be used to adapt these therapies for humans. The development of realistic solutions to circumvent these constraints is critical for advancing this technology.

Bacteriophage Therapy as an Application for Bacterial Infection in China

Antibiotic resistance has emerged as a significant issue to be resolved around the world. Bacteriophage (phage), in contrast to antibiotics, can only kill the target bacteria with no adverse effect on the normal bacterial flora. In this review, we described the biological characteristics of phage, and summarized the phage application in China, including in mammals, ovipara, aquatilia, and human clinical treatment. The data showed that phage had a good therapeutic effect on drug-resistant bacteria in veterinary fields, as well as in the clinical treatment of humans. However, we need to take more consideration of the narrow lysis spectrum, the immune response, the issues of storage, and the pharmacokinetics of phages. Due to the particularity of bacteriophage as a bacterial virus, there is no unified standard or regulation for the use of bacteriophage in the world at present, which hinders the application of bacteriophage as a substitute for antibiotic biological products. We aimed to highlight the rapidly advancing field of phage therapy as well as the challenges that China faces in reducing its reliance on antibiotics.

Phage-Derived Depolymerase: Its Possible Role for Secondary Bacterial Infections in COVID-19 Patients

As of 29 July 2022, there had been a cumulative 572,239,451 confirmed cases of COVID-19 worldwide, including 6,390,401 fatalities. COVID-19 patients with severe symptoms are usually treated with a combination of virus- and drug-induced immuno-suppression medicines. Critical clinical complications of the respiratory system due to secondary bacterial infections (SBIs) could be the reason for the high mortality rate in COVID-19 patients. Unfortunately, antimicrobial resistance is increasing daily, and only a few options are available in our antimicrobial armory. Hence, alternative therapeutic options such as enzymes derived from bacteriophages can be considered for treating SBIs in COVID-19 patients. In particular, phage-derived depolymerases have high antivirulent potency that can efficiently degrade bacterial capsular polysaccharides, lipopolysaccharides, and exopolysaccharides. They have emerged as a promising class of new antibiotics and their therapeutic role for bacterial infections is already confirmed in animal models. This review provides an overview of the rising incidence of SBIs among COVID-19 patients. We present a practicable novel workflow for phage-derived depolymerases that can easily be adapted for treating SBIs in COVID-19 patients.

Disarm The Bacteria: What Temperate Phages Can Do

In the field of phage applications and clinical treatment, virulent phages have been in the spotlight whereas temperate phages received, relatively speaking, less attention. The fact that temperate phages often carry virulent or drug-resistant genes is a constant concern and drawback in temperate phage applications. However, temperate phages also play a role in bacterial regulation. This review elucidates the biological properties of temperate phages based on their life cycle and introduces the latest work on temperate phage applications, such as on host virulence reduction, biofilm degradation, genetic engineering and phage display. The versatile use of temperate phages coupled with their inherent properties, such as economy, ready accessibility, wide variety and host specificity, make temperate phages a solid candidate in tackling bacterial infections.

Characterization of a lytic Escherichia coli phage CE1 and its potential use in therapy against avian pathogenic Escherichia coli infections

The high incidence of Avian pathogenic Escherichia coli (APEC) in poultry has resulted in significant economic losses. It has become necessary to find alternatives to antibiotics due to the alarming rise in antibiotic resistance. Phage therapy has shown promising results in numerous studies. In the current study, a lytic phage vB_EcoM_CE1 (short for CE1) against Escherichia coli (E. coli) was isolated from broiler feces, showing a relatively wide host range and lysing 56.9% (33/58) of high pathogenic strains of APEC. According to morphological observations and phylogenetic analysis, phage CE1 belongs to the Tequatrovirus genus, Straboviridae family, containing an icosahedral capsid (80 ~ 100 nm in diameter) and a retractable tail (120 nm in length). This phage was stable below 60°C for 1 h over the pH range of 4 to 10. Whole-genome sequencing revealed that phage CE1 contained a linear double-stranded DNA genome spanning 167,955 bp with a GC content of 35.4%. A total of 271 ORFs and 8 tRNAs were identified. There was no evidence of virulence genes, drug-resistance genes, or lysogeny genes in the genome. The in vitro test showed high bactericidal activity of phage CE1 against E. coli at a wide range of MOIs, and good air and water disinfectant properties. Phage CE1 showed perfect protection against broilers challenged with APEC strain in vivo. This study provides some basic information for further research into treating colibacillosis, or killing E. coli in breeding environments.

In Vitro Activity, Stability and Molecular Characterization of Eight Potent Bacteriophages Infecting Carbapenem-Resistant Klebsiella pneumoniae

BACKGROUND

Members of the genus Klebsiella are among the leading microbial pathogens associated with nosocomial infection. The increased incidence of antimicrobial resistance in these species has propelled the need for alternate/combination therapeutic regimens to aid clinical treatment, including bacteriophage therapy. Bacteriophages are considered very safe and effective in treating bacterial infections. In this study, we characterize eight lytic bacteriophages that were previously isolated by our team against carbapenem-resistant Klebsiella pneumoniae.

METHODS

The one-step-growth curves, stability and lytic ability of eight bacteriophages were characterized. Restriction fragment length polymorphism (RFLP), random amplification of polymorphic DNA (RAPD) typing analysis and protein profiling were used to characterize the microbes at the molecular level. Phylogenetic trees of four important proteins were constructed for the two selected bacteriophages.

RESULTS AND CONCLUSIONS

All eight bacteriophages showed high efficiency for reducing bacterial concentration with high stability under different physical and chemical conditions. We found four major protein bands out of at least ten 15-190 KDa bands that were clearly separated by SDS-PAGE, which were assumed to be the major head and tail proteins. The genomes were found to be dsDNA, with sizes of approximately 36-87 Kb. All bacteriophages reduced the optical density of the planktonic K. pneumoniae abruptly, indicating great potential to reduce K. pneumoniae infection. In this study, we have found that tail fiber protein can further distinguished closely related bacteriophages. The characterised bacteriophages showed promising potential as candidates against carbapenem-resistant Klebsiella pneumoniae via bacteriophage therapy.

Selection of phage display peptides against Pasteurella multocida using suspension method of biopanning

multocida contain various surface-associated antigens that could be used as a target for both therapeutics as well as diagnostics. The current study was planned to select ligands using Ph.D.-12 phage display library. This library was amplified and subjected to the alternate selection/subtraction methodology of biopanning using the suspension method in which alternate rounds of positive selection against P. multocida and negative selection against Haemophilus influenzae and Actinobacillus lignieresii were performed. After completing biopanning, out of 48 selected phages, 16 clonal phages were selected for indirect phage ELISA to check their binding efficiency with P. multocida. Out of these 16, five clonal phages bound their target with high intensity giving higher OD values at 450 nm and their binding efficiency was compared with closely related Actinobacillus lignieresii and Hemophilus influenzae using 107 pfu/ml at 450 nm wavelength which was found to be less against these bacteria.

Efficacy of phage therapy in preclinical models of bacterial infection: a systematic review and meta-analysis

BACKGROUND

Antimicrobial resistance of bacterial pathogens is an increasing clinical problem and alternative approaches to antibiotic chemotherapy are needed. One of these approaches is the use of lytic bacterial viruses known as phage therapy. We aimed to assess the efficacy of phage therapy in preclinical animal models of bacterial infection.

METHODS

In this systematic review and meta-analysis, MEDLINE/Ovid, Embase/Ovid, CINAHL/EbscoHOST, Web of Science/Wiley, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Google Scholar were searched from inception to Sept 30, 2021. Studies assessing phage efficacy in animal models were included. Only studies that assessed the efficacy of phage therapy in treating established bacterial infections in terms of survival and bacterial abundance or density were included. Studies reporting only in-vitro or ex-vivo results and those with incomplete information were excluded. Risk-of-bias assessment was performed using the Systematic Review Centre for Laboratory Animal Experimentation tool. The main endpoints were animal survival and tissue bacterial burden, which were reported using pooled odds ratios (ORs) and mean differences with random-effects models. The I² measure and its 95% CI were also calculated. This study is registered with PROSPERO, CRD42022311309.

FINDINGS

Of the 5084 references screened, 124 studies fulfilled the selection criteria. Risk of bias was high for 70 (56%) of the 124 included studies; therefore, only studies classified as having a low-to-moderate risk of bias were considered for quantitative data synthesis (n=32). Phage therapy was associated with significantly improved survival at 24 h in systemic infection models (OR 0·08 [95% CI 0·03 to 0·20]; I²=55% [95% CI 8 to 77]), skin infection (OR 0·08 [0·04 to 0·19]; I² = 0% [0 to 79]), and pneumonia models (OR 0·13 [0·06 to 0·31]; I²=0% [0 to 68]) when compared with placebo. Animals with skin infections (mean difference -2·66 [95% CI -3·17 to -2·16]; I² = 95% [90 to 96]) and those with pneumonia (mean difference -3·35 [-6·00 to -0·69]; I² = 99% [98 to 99]) treated with phage therapy had significantly lower tissue bacterial loads at 5 ± 2 days of follow-up compared with placebo.

INTERPRETATION

Phage therapy significantly improved animal survival and reduced organ bacterial loads compared with placebo in preclinical animal models. However, high heterogeneity was observed in some comparisons. More evidence is needed to identify the factors influencing phage therapy performance to improve future clinical application.

FUNDING

Swiss National Foundation and Swiss Heart Foundation.

Biocontrol of methicillin-resistant Staphylococcus aureus using a virulent bacteriophage derived from a temperate one

Methicillin-resistant Staphylococcus aureus (MRSA) poses a serious threat to global public health due to its resistance to specific antibiotics. Bacteriophages particularly the lytic ones are promoted as a potential powerful-tool to combat infections caused by drug resistant bacteria; while several disadvantages limited the application of the temperate ones. In this study, we isolated 14 phages against MRSA strains, and found three ones showed the capacity of killing most of the target MRSA strains. However, whole genome sequencing and generation of lysogens indicated that these three bacteriophage candidates were temperate ones. Therefore, we mutated one (4PHSA25) of them to a virulent bacteriophage (4PHCISA25). Phenotypical characterization assays revealed that 4PHCISA25 had similar lytic spectrum, temperature, pH, and UV sensitivities to 4PHSA25. However, 4PHCISA25 displayed increased lytic activities and decreased bacteriophage insensitive mutant frequency. Biofilm removing assays showed that 4PHCISA25 exhibited a better capacity than 4PHSA25 on eliminating biofilms formed by MRSA strains. Mouse experiments demonstrated that injection of 4PHCISA25 was safe to the mice and treatment with it (10⁹ PFU per mouse) inhibited the development of abscess induced by MRSA within 24 h and promoted the recovery from the clinical signs. Taken together, this study highlights the use of phages combating MRSA.

Complete genome sequencing of a Tequintavirus bacteriophage with a broad host range against Salmonella Abortus equi isolates from donkeys

Salmonella enterica subspecies enterica serovar abortus equi (S. Abortus equi) is the most common cause of abortion in mares. It has recently been found to cause abortion in donkeys more frequently in China. A novel virulent bacteriophage vB_SabS_Sds2 (hereafter designated as Sds2) was isolated from the feces of donkeys using a S. Abortus equi strain as a host. Phage Sds2 had an isometric polyhedral head and an uncontracted long tail, belonging to the Tequintavirus, Markadamsvirinae, Demerecviridae, Caudovirales. The genome of phage Sds2 was 114,770 bp, with a GC content of 40.26%. The genome contained 160 open reading frames (ORFs), and no ORFs were associated with pathogenicity, drug resistance, or lysogenization by sequence analysis. Both genome annotation and phylogenetic analysis indicated that phage Sds2 was highly similar to T5-like bacteriophages. Phage Sds2 could lyse 100% (30/30) of S. Abortus equi strains, 25.3% (24/95) of other serotypes of Salmonella strains, and 27.6% (8/29) of Escherichia coli strains using the double-layer agar plate method. The in vitro test showed that phage Sds2 had high bactericidal activity against S. Abortus equi at a wide range of MOIs. The in vivo test indicated that phage Sds2 had an inhibitory effect on abortion in mice challenged with S. Abortus equi. In general, phage Sds2 is a novel lytic phage with a wide host range and has the potential to prevent abortion caused by S. Abortus equi.

Identification of a broad-spectrum lytic Myoviridae bacteriophage using multidrug resistant Salmonella isolates from pig slaughterhouses as the indicator and its application in combating Salmonella infections

Background

Salmonella is a leading foodborne and zoonotic pathogen, and is widely distributed in different nodes of the pork supply chain. In recent years, the increasing prevalence of antimicrobial resistant Salmonella poses a threat to global public health. The purpose of this study is to the prevalence of antimicrobial resistant Salmonella in pig slaughterhouses in Hubei Province in China, and explore the effect of using lytic bacteriophages fighting against antimicrobial resistant Salmonella.

Results

We collected a total of 1289 samples including anal swabs of pigs (862/1289), environmental swabs (204/1289), carcass surface swabs (36/1289) and environmental agar plates (187/1289) from eleven slaughterhouses in seven cities in Hubei Province and recovered 106 Salmonella isolates. Antimicrobial susceptibility testing revealed that these isolates showed a high rate of antimicrobial resistance; over 99.06% (105/106) of them were multidrug resistant. To combat these drug resistant Salmonella, we isolated 37 lytic phages using 106 isolates as indicator bacteria. One of them, designated ph 2–2, which belonged to the Myoviridae family, displayed good capacity to kill Salmonella under different adverse conditions (exposure to different temperatures, pHs, UV, and/or 75% ethanol) and had a wide lytic spectrum. Evaluation in mouse models showed that ph 2–2 was safe and saved 80% (administrated by gavage) and 100% (administrated through intraperitoneal injection) mice from infections caused by Salmonella Typhimurium.

Conclusions

The data presented herein demonstrated that Salmonella contamination remains a problem in some pig slaughter houses in China and Salmonella isolates recovered in slaughter houses displayed a high rate of antimicrobial resistance. In addition, broad-spectrum lytic bacteriophages may represent a good candidate for the development of anti-antimicrobial resistant Salmonella agents.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03372-8.

Isolation of Three Coliphages and the Evaluation of Their Phage Cocktail for Biocontrol of Shiga Toxin-Producing Escherichia coli O157 in Milk

Shiga toxin-producing Escherichia coli (STEC) O157 is a well-known foodborne pathogen and a leading cause of many intestinal diseases. In this study, we explore the use of a phage cocktail to help control STEC O157 in broth and milk. We isolated three virulent phages from sanitary sewages using a STEC O157 as the indicator bacterium. Phenotypical characterizations revealed that these three phages belong to the Myoviridae family and were stable at different temperatures and pH. They displayed a short latent period between 10 and 20 min, and a burst size (32-65 per infected cell). No virulence factors and drug resistance genes were found in their genomes. Bacterial lysis assays showed that a phage cocktail comprising these three phages was more effective (at least 4.32 log reduction) against STEC O157 at 25 °C with multiplicity of infection (MOI) = 1000 in broth medium. At 4 °C, a 3.8 log reduction in the number of viable STEC O157 after 168-h treatment with phage cocktail at MOI = 1000 was observed in milk, compared to phage-free bacterial control group. Characterizations of phages suggest they could be developed into novel therapeutic agents to control STEC O157 in milk production.

A temperate Siphoviridae bacteriophage isolate from Siberian tiger enhances the virulence of methicillin-resistant Staphylococcus aureus through distinct mechanisms

The emergence and worldwide spread of Methicillin-resistant Staphylococcus aureus (MRSA) pose a threat to human health. While bacteriophages are recognized as an effective alternative to treat infections caused by drug resistant pathogens, some bacteriophages in particular the temperate bacteriophage may also influence the virulence of the host bacteria in distinct ways. In this study, we isolated a bacteriophage vB_Saus_PHB21 from an epidermal sample of Siberian tiger (Panthera tigris altaica) using an MRSA strain SA14 as the indicator. Our following laboratory tests and whole genome sequencing analyses revealed that vB_Saus_PHB21 was a temperate bacteriophage belonging to the Siphoviridae family, and this bacteriophage did not contain any virulence genes. However, the integration of PHB21 genome into the host MRSA increased the bacterial capacities of cell adhesion, anti-phagocytosis, and biofilm formation. Challenge of the lysogenic strain (SA14⁺) caused severe mortalities in both Galleria mellonella and mouse models. Mice challenged with SA14⁺ showed more serious organ lesions and produced higher inflammatory cytokines (IL-8, IFN-γ and TNF-α) compared to those challenged with SA14. In mechanism, we found the integration of PHB21 genome caused the upregulated expression of many genes encoding products involved in bacterial biofilm formation, adherence to host cells, anti-phagocytosis, and virulence. This study may provide novel knowledge of “bacteria-phage-interactions” in MRSA.

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.

Therapeutic Efficacy of Phage PIZ SAE-01E2 against Abortion Caused by Salmonella enterica Serovar Abortusequi in Mice

Salmonella enterica subsp. enterica serovar Abortusequi is a frequently reported pathogen causing abortion in mares. In this study, the preventive and therapeutic effects of phage P_IZ SAE-01E2 against S Abortusequi in a mouse model of abortion were investigated. Phage P_IZ SAE-01E2 was stable at different temperatures (4 to 70°C) and pH values (pH 4 to 10) and could lyse the majority of the Salmonella serogroup O:4 and O:9 strains tested (25/28). There was no lysogeny-related, toxin, or antibiotic resistance-related gene in the genome of P_IZ SAE-01E2. All of these characteristics indicate that P_IZ SAE-01E2 has the potential for use in phage therapy. In in vivo experiments, 2 × 10³ CFU/mouse of S Abortusequi ATCC 9842 was sufficient to lead to murine abortion (gestational day 14.5) within 48 h. A single intraperitoneal inoculation of P_IZ SAE-01E2 (10⁸ PFU/mouse, multiplicity of infection = 10⁵) 1 h before or after S Abortusequi challenge provided effective protection to all pregnant mice (10/10). After 24 h of treatment with phage P_IZ SAE-01E2, the bacterial loads in both the placenta and the uterus of the infected mice were significantly decreased (<10² CFU/g) compared to those in the placenta and the uterus of the mice in the control group (>10⁶ CFU/g). In addition, the levels of inflammatory cytokines in the placenta and blood of the mice in the phage administration groups were significantly reduced (P < 0.05) compared to those in the placenta and blood of the mice in the control group. Altogether, these findings indicate that P_IZ SAE-01E2 shows the potential to block abortions induced by S Abortusequi in vivo IMPORTANCE S Abortusequi is an important pathogen that can induce abortions in mares. Although S Abortusequi has been well controlled in Europe and the United States due to strict breeding and health policies, it is still widespread in African and Asian countries and has proven difficult to control. In China, abortions caused by S Abortusequi have also been reported in donkeys. So far, there is no commercial vaccine. Thus, exploiting alternative efficient and safe strategies to control S Abortusequi infection is essential. In this study, a new lytic phage, P_IZ SAE-01E2, infecting S Abortusequi was isolated, and the characteristics of P_IZ SAE-01E2 indicated that it has the potential for use in phage therapy. A single intraperitoneal inoculation of P_IZ SAE-01E2 before or after S Abortusequi challenge provided effective protection to all pregnant mice. Thus, P_IZ SAE-01E2 showed the potential to block abortions induced by S Abortusequi in vivo.

Diversity and Function of Phage Encoded Depolymerases

Bacteriophages of the Podoviridae family often exhibit so-called depolymerases as structural components of the virion. These enzymes appear as tail spike proteins (TSPs). After specific binding to capsular polysaccharides (CPS), exopolysaccharides (EPS) or lipopolysaccharide (LPS) of the host bacteria, polysaccharide-repeating units are specifically cleaved. Finally, the phage reaches the last barrier, the cell wall, injects its DNA, and infects the cell. Recently, similar enzymes from bacteriophages of the Ackermannviridae, Myoviridae, and Siphoviridae families were also described. In this mini-review the diversity and function of phage encoded CPS-, EPS-, and LPS-degrading depolymerases is summarized. The function of the enzymes is described in terms of substrate specificity and applications in biotechnology.

Complete genome sequence of the novel phage vB_EcoS_PHB17, which infects Shiga-toxin-producing Escherichia coli

The complete genome of the novel phage vB_EcoS_PHB17, which infects Shiga-toxin-producing Escherichia coli, was sequenced, revealing a linear double-stranded DNA genome of 48,939 bp with 46% GC content and protruding 150-bp 5' cohesive termini. The genome contained 85 open reading frames, 28 of which were annotated with known functions. No tRNA-encoding genes were detected. Phylogenetic analysis suggested that phage PHB17 is a novel phage of family Siphoviridae.

Genetic Engineering of Bacteriophages Against Infectious Diseases

Bacteriophages (phages) are the most abundant and widely distributed organisms on Earth, constituting a virtually unlimited resource to explore the development of biomedical therapies. The therapeutic use of phages to treat bacterial infections (“phage therapy”) was conceived by Felix d’Herelle nearly a century ago. However, its power has been realized only recently, largely due to the emergence of multi-antibiotic resistant bacterial pathogens. Progress in technologies, such as high-throughput sequencing, genome editing, and synthetic biology, further opened doors to explore this vast treasure trove. Here, we review some of the emerging themes on the use of phages against infectious diseases. In addition to phage therapy, phages have also been developed as vaccine platforms to deliver antigens as part of virus-like nanoparticles that can stimulate immune responses and prevent pathogen infections. Phage engineering promises to generate phage variants with unique properties for prophylactic and therapeutic applications. These approaches have created momentum to accelerate basic as well as translational phage research and potential development of therapeutics in the near future.