T4 phages against Escherichia coli diarrhea: Potential and problems

Antimicrobial resistance: use of phage therapy in the management of resistant infections

The emergence and increase in antimicrobial resistance (AMR) is now widely recognized as a major public health challenge. Traditional antimicrobial drugs are becoming increasingly ineffective, while the development of new antibiotics is waning. As a result, alternative treatments for infections are garnering increased interest. Among these alternatives, bacteriophages, also known as phages, are gaining renewed attention and are reported to offer a promising solution to alleviate the burden of bacterial infections. This review discusses the current successes of phage therapy (PT) against multidrug-resistant organisms (MDROs), such as Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Enterobacter spp. The review also compares the efficacy of PT with that of chemical antibiotics, reporting on its benefits and limitations, while highlighting its impact on the human gut microbiome and immune system. Despite its potential, phage therapy is reported to face challenges such as the narrow antibacterial range, the complexity of developing phage cocktails, and the need for precise dosing and duration protocols. Nevertheless, continued research, improved regulatory frameworks, and increased public awareness are essential to realize its full potential and integration into standard medical practice, paving the way for innovative treatments that can effectively manage infections in an era of rising antimicrobial resistance.

Paving the way forward: Escherichia coli bacteriophages in a One Health approach

Escherichia coli is one of the most notorious pathogens for its ability to adapt, colonize, and proliferate in different habitats through a multitude of acquired virulence factors. Its presence affects the food-processing industry and causes food poisoning, being also a major economic burden for the food, agriculture, and health sectors. Bacteriophages are emerging as an appealing strategy to mitigate bacterial pathogens, including specific E. coli pathovars, without exerting a deleterious effect on humans and animals. This review globally analyzes the applied research on E. coli phages for veterinary, food, and human use. It starts by describing the pathogenic E. coli pathotypes and their relevance in human and animal context. The idea that phages can be used as a One Health approach to control and interrupt the transmission routes of pathogenic E. coli is sustained through an exhaustive revision of the recent literature. The emerging phage formulations, genetic engineering and encapsulation technologies are also discussed as a means of improving phage-based control strategies, with a particular focus on E. coli pathogens.

Phages for treatment of Escherichia coli infections

Diseases due to infections by pathogenic Escherichia coli strains are on the rise and with the growing antimicrobial resistance among bacterial pathogens, including this group. Thus, alternative therapeutic options are actively investigated. Among these alternatives is phage therapy. In the case of E. coli, the combination of the well understood biology of this species and its bacteriophages represents a good guiding example for the establishment of phage therapy principles against this and other pathogenic bacteria. In this chapter, the procedures toward the development of phage therapy against pathogenic E. coli with the use of T-even group of phages are discussed. These steps involve the isolation, purification, characterisation and large-scale production of these phages, with formulation of phage cocktails for in vitro and in vivo studies. The main emphasis is made on phage therapy of enteropathogenic E. coli O157:H, which is one of the prominent human pathogens but persists as a commensal bacterium in many food animals. The implementation of phage therapy against E. coli O157:H within the One Health framework in carrier animals and for treatment of meat, vegetables, fruits and other agricultural produce thus would allow controlling and interrupting the transmission routes of this pathogen to the human food chain and preventing human disease. Examples of successful control and elimination of E. coli O157:H are given, while the problems encountered in phage treatment of this pathogen are also discussed.

Microfluidics: Insights into Intestinal Microorganisms

Microfluidics is a system involving the treatment or manipulation of microscale (10^-9 to 10^-18 L) fluids using microchannels (10 to 100 μm) contained on a microfluidic chip. Among the different methodologies used to study intestinal microorganisms, new methods based on microfluidic technology have been receiving increasing attention in recent years. The intestinal tracts of animals are populated by a vast array of microorganisms that have been established to play diverse functional roles beneficial to host physiology. This review is the first comprehensive coverage of the application of microfluidics technology in intestinal microbial research. In this review, we present a brief history of microfluidics technology and describe its applications in gut microbiome research, with a specific emphasis on the microfluidic technology-based intestine-on-a-chip, and also discuss the advantages and application prospects of microfluidic drug delivery systems in intestinal microbial research.

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.

Two Novel Yersinia pestis Bacteriophages with a Broad Host Range: Potential as Biocontrol Agents in Plague Natural Foci

Bacteriophages (phages) have been successfully used as disinfectors to kill bacteria in food and the environment and have been used medically for curing human diseases. The objective of this research was to elucidate the morphological and genomic characteristics of two novel Yersinia pestis phages, vB_YpeM_ MHS112 (MHS112) and vB_YpeM_GMS130 (GMS130), belonging to the genus Gaprivervirus, subfamily Tevenvirinae, family Myoviridae. Genome sequencing showed that the sizes of MHS112 and GMS130 were 170507 and 168552 bp, respectively. A total of 303 and 292 open reading frames with 2 tRNA and 3 tRNA were predicted in MHS112 and GMS130, respectively. The phylogenetic relationships were analysed among the two novel Y. pestis phages, phages in the genus Gaprivervirus, and several T4-like phages infecting the Yersinia genus. The bacteriophage MHS112 and GMS130 exhibited a wider lytic host spectrum and exhibited comparative temperature and pH stability. Such features signify that these phages do not need to rely on Y. pestis as their host bacteria in the ecological environment, while they could be based on more massive Enterobacteriales species to propagate and form ecological barriers against Y. pestis pathogens colonised in plague foci. Such characteristics indicated that the two phages have potential as biocontrol agents for eliminating the endemics of animal plague in natural plague foci.

Impact of a phage cocktail targeting Escherichia coli and Enterococcus faecalis as members of a gut bacterial consortium in vitro and in vivo

Escherichia coli and Enterococcus faecalis have been implicated as important players in human gut health that have been associated with the onset of inflammatory bowel disease (IBD). Bacteriophage (phage) therapy has been used for decades to target pathogens as an alternative to antibiotics, but the ability of phage to shape complex bacterial consortia in the lower gastrointestinal tract is not clearly understood. We administered a cocktail of six phages (either viable or heat-inactivated) targeting pro-inflammatory Escherichia coli LF82 and Enterococcus faecalis OG1RF as members of a defined community in both a continuous fermenter and a murine colitis model. The two target strains were members of a six species simplified human microbiome consortium (SIHUMI-6). In a 72-h continuous fermentation, the phage cocktail caused a 1.1 and 1.5 log (log10 genome copies/mL) reduction in E. faecalis and E. coli numbers, respectively. This interaction was accompanied by changes in the numbers of other SIHUMI-6 members, with an increase of Lactiplantibacillus plantarum (1.7 log) and Faecalibacterium prausnitzii (1.8 log). However, in germ-free mice colonized by the same bacterial consortium, the same phage cocktail administered twice a week over nine weeks did not cause a significant reduction of the target strains. Mice treated with active or inactive phage had similar levels of pro-inflammatory cytokines (IFN-y/IL12p40) in unstimulated colorectal colonic strip cultures. However, histology scores of the murine lower GIT (cecum and distal colon) were lower in the viable phage-treated mice, suggesting that the phage cocktail did influence the functionality of the SIHUMI-6 consortium. For this study, we conclude that the observed potential of phages to reduce host populations in in vitro models did not translate to a similar outcome in an in vivo setting, with this effect likely brought about by the reduction of phage numbers during transit of the mouse GIT.

Considerations for the Use of Phage Therapy in Clinical Practice

Increasing antimicrobial resistance and medical device-related infections have led to a renewed interest in phage therapy as an alternative or adjunct to conventional antimicrobials. Expanded access and compassionate use cases have risen exponentially but have varied widely in approach, methodology, and clinical situations in which phage therapy might be considered. Large gaps in knowledge contribute to heterogeneity in approach and lack of consensus in many important clinical areas. The Antibacterial Resistance Leadership Group (ARLG) has convened a panel of experts in phage therapy, clinical microbiology, infectious diseases, and pharmacology, who worked with regulatory experts and a funding agency to identify questions based on a clinical framework and divided them into three themes: potential clinical situations in which phage therapy might be considered, laboratory testing, and pharmacokinetic considerations. Suggestions are provided as answers to a series of questions intended to inform clinicians considering experimental phage therapy for patients in their clinical practices.

Impact of Phage Therapy on Multidrug-Resistant Escherichia coli Intestinal Carriage in a Murine Model

INTRODUCTION

The growing resistance of bacteria to antibiotics is a major global public health concern. An important reservoir of this resistance is the gut microbiota. However, limited data are available on the ability of phage therapy to reduce the digestive carriage of multidrug-resistant bacteria.

MATERIALS AND METHODS

Four novel lytic phages were isolated in vitro for efficacy against an extended-spectrum beta-lactamase-producing (ESBL) Escherichia coli strain also resistant to carbapenems through a carbapenemase OXA-48. The first step was to develop models of ESBL E. coli digestive carriage in mice. The second step was to test the efficacy of an oral and rectal phage therapy (a cocktail of four phages or microencapsulated phage) to reduce this carriage.

RESULTS

The two most intense models of digestive carriage were obtained by administering amoxicillin (0.5 g·L^-1) continuously in the drinking water (Model 1) or pantoprazole (0.1 g·L^-1) continuously in the drinking water, combined with amoxicillin (0.5 g·L^-1), for the first 8 days (Model 2). Oral administration of the phage cocktail to Model 1 resulted in a transient reduction in the concentration of ESBL E. coli in the faeces 9 days after the bacterial challenge (median = 5.33 × 10⁸ versus 2.76 × 10⁹ CFU·g^-1, p = 0.02). In contrast, in Model 2, oral or oral + rectal administration of this cocktail did not alter the bacterial titre compared to the control (area under the curve, AUC, 3.49 × 10⁹; 3.41 × 10⁹ and 3.82 × 10⁹ for the control, oral and oral + rectal groups, respectively; p-value > 0.8 for each two-by-two group comparison), as well as the administration of an oral microencapsulated phage in Model 1 (AUC = 8.93 × 10⁹ versus 9.04 × 10⁹, p = 0.81).

CONCLUSIONS

Oral treatment with amoxicillin promoted digestive carriage in mice, which was also the case for the addition of pantoprazole. However, our study confirms the difficulty of achieving efficacy with phage therapy to reduce multidrug-resistant bacterial digestive carriage in vivo.

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.

Tailed Lytic Bacteriophages of Soft Rot Pectobacteriaceae

The study of the ecological and evolutionary traits of Soft Rot Pectobacteriaceae (SRP) comprising genera Pectobacterium and Dickeya often involves bacterial viruses (bacteriophages). Bacteriophages are considered to be a prospective tool for the ecologically safe and highly specific protection of plants and harvests from bacterial diseases. Information concerning bacteriophages has been growing rapidly in recent years, and this has included new genomics-based principles of taxonomic distribution. In this review, we summarise the data on phages infecting Pectobacterium and Dickeya that are available in publications and genomic databases. The analysis highlights not only major genomic properties that assign phages to taxonomic families and genera, but also the features that make them potentially suitable for phage control applications. Specifically, there is a discussion of the molecular mechanisms of receptor recognition by the phages and problems concerning the evolution of phage-resistant mutants.

Encapsulation of bacteriophage cocktail into chitosan for the treatment of bacterial diarrhea

The therapeutic effectiveness of a chitosan encapsulated bacteriophage cocktail as a smart biocontrol agent was evaluated in this study to be used as a preventative and treatment option for gastrointestinal infections. To evaluate the effect of the bacteriophage formulation on the treatment of gastrointestinal infection, rats were infected with Salmonella enterica, Shigella flexneri, and Escherichia coli. The rats were weighed and their stools cultured. The results showed that the group which had the chitosan encapsulated bacteriophage cocktail did not lose weight after 3 days and had significantly lower group weight changes. Weight loss was significant in the rats that had cefixime administered instead. Positive cultured stools were reduced after 4 days compared to 2 days in the treated group with the chitosan encapsulated bacteriophage cocktail. The chitosan encapsulated bacteriophage cocktail can therefore be effective in the treatment of gastrointestinal infections.

Phage Biocontrol of Campylobacter: A One Health Approach

Human infections by Campylobacter species are among the most reported bacterial gastrointestinal diseases in the European Union and worldwide with severe outcomes in rare cases. Considering the transmission routes and farm animal reservoirs of these zoonotic pathogens, a comprehensive One Health approach will be necessary to reduce human infection rates. Bacteriophages are viruses that specifically infect certain bacterial genera, species, strains or isolates. Multiple studies have demonstrated the general capacity of phage treatments to reduce Campylobacter loads in the chicken intestine. However, phage treatments are not yet approved for extensive use in the agro-food industry in Europe. Technical inconvenience is mainly related to the efficacy of phages, depending on the optimal choice of phages and their combination, as well as application route, concentration and timing. Additionally, regulatory uncertainties have been a major concern for investment in commercial phage-based products. This review addresses the question as to how phages can be put into practice and can help to solve the issue of human campylobacteriosis in a sustainable One Health approach. By compiling the reported findings from the literature in a standardized manner, we enabled inter-experimental comparisons to increase our understanding of phage infection in Campylobacter spp. and practical on-farm studies. Further, we address some of the hurdles that still must be overcome before this new methodology can be adapted on an industrial scale. We envisage that phage treatment can become an integrated and standardized part of a multi-hurdle anti-bacterial strategy in food production. The last part of this chapter deals with some of the issues raised by legal authorities, bringing together current knowledge on Campylobacter-specific phages and the biosafety requirements for approval of phage treatment in the food industry.

Phage-specific antibodies

Antibodies specific to phage virions have been observed many times, both in animals and in humans. Phages induce the T-dependent type of immune response, which is fundamental for immunological memory and long retention of abilities to recognize and respond to foreign epitopes. Experimental models have shown that phage-specific antibodies can be devastating for a phage in vivo. Observations from phage treatment in humans demonstrate however that antibodies do not necessarily hinder phage therapy. Controlling effective doses may help in controlling the immune response to phage and to create 'therapeutic windows' for the phage. Phage therapy design may also benefit from understanding phage antigenicity and predicting possible cross-reactions between antibodies specific to different phages.

Isolation and Characterization of Pectobacterium Phage vB_PatM_CB7: New Insights into the Genus Certrevirus

To date, Certrevirus is one of two genera of bacteriophage (phage), with phages infecting Pectobacterium atrosepticum, an economically important phytopathogen that causes potato blackleg and soft rot disease. This study provides a detailed description of Pectobacterium phage CB7 (vB_PatM_CB7), which specifically infects P. atrosepticum. Host range, morphology, latent period, burst size and stability at different conditions of temperature and pH were examined. Analysis of its genome (142.8 kbp) shows that the phage forms a new species of Certrevirus, sharing sequence similarity with other members, highlighting conservation within the genus. Conserved elements include a putative early promoter like that of the Escherichia coli sigma70 promoter, which was found to be shared with other genus members. A number of dissimilarities were observed, relating to DNA methylation and nucleotide metabolism. Some members do not have homologues of a cytosine methylase and anaerobic nucleotide reductase subunits NrdD and NrdG, respectively. Furthermore, the genome of CB7 contains one of the largest numbers of homing endonucleases described in a single phage genome in the literature to date, with a total of 23 belonging to the HNH and LAGLIDADG families. Analysis by RT-PCR of the HNH homing endonuclease residing within introns of genes for the large terminase, DNA polymerase, ribonucleotide reductase subunits NrdA and NrdB show that they are splicing competent. Electrospray ionization-tandem mass spectrometry (ESI-MS/MS) was also performed on the virion of CB7, allowing the identification of 26 structural proteins-20 of which were found to be shared with the type phages of the genera of Vequintavirus and Seunavirus. The results of this study provide greater insights into the phages of the Certrevirus genus as well as the subfamily Vequintavirinae.

Isolation and characterization of a novel Escherichia coli O157:H7-specific phage as a biocontrol agent

PURPOSE

Escherichia coli O157:H7 is one of the major foodborne pathogens of global public concern. Bacteriophages (phages) have emerged as a promising alternative to antibiotics for controlling pathogenic bacteria. Here, a lytic E. coli O157:H7-specific phage (KFS-EC) was isolated, identified, and characterized to evaluate its potential as a biocontrol agent for E. coli O157:H7.

METHODS

KFS-EC was isolated from slaughterhouse in Korea. Morphological analysis, genomic analysis and several physiological tests were performed to identify and characterize the KFS-EC.

RESULTS

A specificity test indicated KFS-EC was strictly specific to E. coli O157:H7 strains among 60 bacterial strains tested. Morphological and phylogenetic analyses confirmed that KFS-EC belongs to the Rb49virus genus, Tevenvirinae subfamily, and the Myoviridae family of phages. KFS-EC genome consists of 164,725 bp and a total of 270 coding sequence features, of which 114 open reading frames (ORFs) were identified as phage functional genes. KFS-EC does not contain genes encoding lysogenic property and pathogenicity, which ensure its safe application. KFS-EC was relatively stable (~1 log decrease) under stressed conditions such as temperatures (20 °C-50 °C), pHs (3-11), organic solvents (ethanol and chloroform), and biocides (0.1% citric acid, 1% citric acid, and 0.1% peracetic acid). KFS-EC was able to inhibit E. coli O157:H7 efficiently at a multiplicity of infection (MOI) of 0.01 for 8 h with greater inhibitory effect and durability and was stable at 4 °C and 22 °C over a 12-week storage period.

CONCLUSIONS

Our results suggest that KFS-EC could be used as a biocontrol agent to E. coli O157:H7.

Impact of Bacteriophage-Supplemented Drinking Water on the E. coli Population in the Chicken Gut

Among intestinal coliform microbes in the broiler gut, there are potentially pathogenic Escherichia (E.) coli that can cause avian colibacillosis. The treatment with antibiotics favors the selection of multidrug-resistant bacteria and an alternative to this treatment is urgently required. A chicken model of intestinal colonization with an apathogenic model strain of E. coli was used to test if oral phage application can prevent or reduce the gut colonization of extraintestinal pathogenic E. coli variants in two individual experiments. The E. coli strain E28 was used as a model strain, which could be differentiated from other E. coli strains colonizing the broiler gut, and was susceptible to all cocktail phages applied. In the first trial, a mixture of six phages was continuously applied via drinking water. No reduction of the model E. coli strain E28 occurred, but phage replication could be demonstrated. In the second trial, the applied mixture was limited to the four phages, which showed highest efficacy in vitro. E. coli colonization was reduced in this trial, but again, no reduction of the E. coli strain E28 was observed. The results of the trials presented here can improve the understanding of the effect of phages on single strains in the multi-strain microbiota of the chicken gut.

Pharmacologically Aware Phage Therapy: Pharmacodynamic and Pharmacokinetic Obstacles to Phage Antibacterial Action in Animal and Human Bodies

The use of viruses infecting bacteria (bacteriophages or phages) to treat bacterial infections has been ongoing clinically for approximately 100 years. Despite that long history, the growing international crisis of resistance to standard antibiotics, abundant anecdotal evidence of efficacy, and one successful modern clinical trial of efficacy, this phage therapy is not yet a mainstream approach in medicine. One explanation for why phage therapy has not been subject to more widespread implementation is that phage therapy research, both preclinical and clinical, can be insufficiently pharmacologically aware. Consequently, here we consider the pharmacological obstacles to phage therapy effectiveness, with phages in phage therapy explicitly being considered to serve as drug equivalents. The study of pharmacology has traditionally been differentiated into pharmacokinetic and pharmacodynamic aspects. We therefore separately consider the difficulties that phages as virions can have in traveling through body compartments toward reaching their target bacteria (pharmacokinetics) and the difficulties that phages can have in exerting antibacterial activity once they have reached those bacteria (pharmacodynamics). The latter difficulties, at least in part, are functions of phage host range and bacterial resistance to phages. Given the apparently low toxicity of phages and the minimal side effects of phage therapy as practiced, phage therapy should be successful so long as phages can reach the targeted bacteria in sufficiently high numbers, adsorb, and then kill those bacteria. Greater awareness of what obstacles to this success generally or specifically can exist, as documented in this review, should aid in the further development of phage therapy toward wider use.

Microencapsulation of Enteric Bacteriophages in a pH-Responsive Solid Oral Dosage Formulation Using a Scalable Membrane Emulsification Process

A scalable low-shear membrane emulsification process was used to produce microencapsulated Escherichia coli-phages in a solid oral dosage form. Uniform pH-responsive composite microparticles (mean size ~100 µm) composed of Eudragit® S100 and alginate were produced. The internal microstructure of the gelled microcapsules was studied using ion-milling and imaging, which showed that the microparticles had a solid internal core. The microencapsulation process significantly protected phages upon prolonged exposure to a simulated gastric acidic environment. Encapsulated phages that had been pre-exposed to simulated gastric acid were added to actively growing bacterial cells using in vitro cell cultures and were found to be effective in killing E. coli. Encapsulated phages were also shown to be effective in killing actively growing E. coli in the presence of human epithelial cells. Confocal microscopy images showed that the morphology of encapsulated phage-treated epithelial cells was considerably better than controls without phage treatment. The encapsulated phages were stable during refrigerated storage over a four-week period. The process of membrane emulsification is highly scalable and is a promising route to produce industrial quantities of pH-responsive oral solid dosage forms suitable for delivering high titres of viable phages to the gastrointestinal tract.

Dynamic Modulation of the Gut Microbiota and Metabolome by Bacteriophages in a Mouse Model

The human gut microbiome is comprised of densely colonizing microorganisms including bacteriophages, which are in dynamic interaction with each other and the mammalian host. To address how bacteriophages impact bacterial communities in the gut, we investigated the dynamic effects of phages on a model microbiome. Gnotobiotic mice were colonized with defined human gut commensal bacteria and subjected to predation by cognate lytic phages. We found that phage predation not only directly impacts susceptible bacteria but also leads to cascading effects on other bacterial species via interbacterial interactions. Metabolomic profiling revealed that shifts in the microbiome caused by phage predation have a direct consequence on the gut metabolome. Our work provides insight into the ecological importance of phages as modulators of bacterial colonization, and it additionally suggests the potential impact of gut phages on the mammalian host with implications for their therapeutic use to precisely modulate the microbiome.

Still Something to Discover: Novel Insights intoEscherichia coli Phage Diversity and Taxonomy

The aim of this study was to gain further insight into the diversity of Escherichia coli phagesfollowed by enhanced work on taxonomic issues in that field. Therefore, we present the genomiccharacterization and taxonomic classification of 50 bacteriophages against E. coli isolated fromvarious sources, such as manure or sewage. All phages were examined for their host range on a setof different E. coli strains, originating, e.g., from human diagnostic laboratories or poultry farms.Transmission electron microscopy revealed a diversity of morphotypes (70% Myo-, 22% Sipho-, and8% Podoviruses), and genome sequencing resulted in genomes sizes from ~44 to ~370 kb.Annotation and comparison with databases showed similarities in particular to T4- and T5-likephages, but also to less-known groups. Though various phages against E. coli are already describedin literature and databases, we still isolated phages that showed no or only few similarities to otherphages, namely phages Goslar, PTXU04, and KWBSE43-6. Genome-based phylogeny andclassification of the newly isolated phages using VICTOR resulted in the proposal of new generaand led to an enhanced taxonomic classification of E. coli phages.

Phage therapy: What factors shape phage pharmacokinetics and bioavailability? Systematic and critical review

Bacteriophages are not forgotten viruses anymore: scientists and practitioners seek to understand phage pharmacokinetics in animals and humans, investigating bacteriophages as therapeutics, nanocarriers or microbiome components. This review provides a comprehensive overview of factors that determine phage circulation, penetration, and clearance, and that in consequence determine phage applicability for medicine. It makes use of experimental data collected by the phage community so far (PubMed 1924‐2016, including non‐English reports), combining elements of critical and systematic review.

This study covers phage ability to enter a system by various routes of administration, how (and if) the phage may access various tissues and organs, and finally what mechanisms determine the courses of phage clearance. The systematic review method was applied to analyze (i) phage survival in the gut (gut transit) and (ii) phage ability to enter the mammalian system by many administration routes. Aspects that have not yet been covered by a sufficient number of reports for mathematical analysis, as well as mechanisms underlying trends, are discussed in the form of a critical review.

In spite of the extraordinary diversity of bacteriophages and possible phage applications, the analysis revealed that phage morphology, phage specificity, phage dose, presence of sensitive bacteria or the characteristics of treated individuals (age, taxonomy) may affect phage bioavailability in animals and humans. However, once phages successfully enter the body, they reach most organs, including the central nervous system. Bacteriophages are cleared mainly by the immune system: innate immunity removes phages even when no specific response to bacteriophages has yet developed.

A scaled-down model for the translation of bacteriophage culture to manufacturing scale

Therapeutic bacteriophages are emerging as a potential alternative to antibiotics and synergistic treatment of antimicrobial-resistant infections. This is reflected by their use in an increasing number of recent clinical trials. Many more therapeutic bacteriophage is being investigated in preclinical research and due to the bespoke nature of these products with respect to their limited infection spectrum, translation to the clinic requires combined understanding of the biology underpinning the bioprocess and how this can be optimized and streamlined for efficient methods of scalable manufacture. Bacteriophage research is currently limited to laboratory scale studies ranging from 1-20 ml, emerging therapies include bacteriophage cocktails to increase the spectrum of infectivity and require multiple large-scale bioreactors (up to 50 L) containing different bacteriophage-bacterial host reactions. Scaling bioprocesses from the milliliter scale to multi-liter large-scale bioreactors is challenging in itself, but performing this for individual phage-host bioprocesses to facilitate reliable and robust manufacture of phage cocktails increases the complexity. This study used a full factorial design of experiments approach to explore key process input variables (temperature, time of infection, multiplicity of infection, agitation) for their influence on key process outputs (bacteriophage yield, infection kinetics) for two bacteriophage-bacterial host bioprocesses (T4 - Escherichia coli; Phage K - Staphylococcus aureus). The research aimed to determine common input variables that positively influence output yield and found that the temperature at the point of infection had the greatest influence on bacteriophage yield for both bioprocesses. The study also aimed to develop a scaled down shake-flask model to enable rapid optimization of bacteriophage batch bioprocessing and translate the bioprocess into a scale-up model with a 3 L working volume in stirred tank bioreactors. The optimization performed in the shake flask model achieved a 550-fold increase in bacteriophage yield and these improvements successfully translated to the large-scale cultures.

Interactions between Bacteriophage, Bacteria, and the Mammalian Immune System

The human body is host to large numbers of bacteriophages (phages)⁻a diverse group of bacterial viruses that infect bacteria. Phage were previously regarded as bystanders that only impacted immunity indirectly via effects on the mammalian microbiome. However, it has become clear that phages also impact immunity directly, in ways that are typically anti-inflammatory. Phages can modulate innate immunity via phagocytosis and cytokine responses, but also impact adaptive immunity via effects on antibody production and effector polarization. Phages may thereby have profound effects on the outcome of bacterial infections by modulating the immune response. In this review we highlight the diverse ways in which phages interact with human cells. We present a computational model for predicting these complex and dynamic interactions. These models predict that the phageome may play important roles in shaping mammalian-bacterial interactions.

Propionibacterium (Cutibacterium) acnes Bacteriophage Therapy in Acne: Current Evidence and Future Perspectives

Acne vulgaris is the most common dermatological disorder worldwide. It is a multifactorial disease that involves increased sebum production, hyperkeratinization of the pilosebaceous unit, Propionibacterium acnes (Cutibacterium acnes) colonization, and inflammation. The human skin microbiome hosts a wide variety of microorganisms, including bacteria, viruses, and fungi. A delicate balance of these microorganisms is essential for the barrier function of the skin. Propionibacterium acnes represents nearly 90% of the human skin microbiome of healthy adults. Acne is a chronic recurrent disease that requires long-lasting treatment, which has led to the emergence of antibiotic resistance. New alternatives to traditional therapy are emerging, including antimicrobial peptides, natural engineered antibodies, and bacteriophages. Bacteriophages have been shown to play a role in human skin health and disease. There is evidence supporting phage therapy in many types of skin infections. P. acnes bacteriophages have been isolated and characterized. However, only a few in vitro studies have tested the ability of bacteriophages to kill P. acnes. Furthermore, there is no evidence on bacteriophage therapy in the treatment of acne in humans. In this review, we summarize the most recent evidence regarding P. acnes bacteriophages and the potential role of these bacteriophages in the treatment of acne. Further research on this field will provide the evidence to use phage therapy to decrease rates of antibiotic resistance and restore antibiotic susceptibility of P. acnes.

Nanoencapsulation of Bacteriophages in Liposomes Prepared Using Microfluidic Hydrodynamic Flow Focusing

Increasing antibiotic resistance in pathogenic microorganisms has led to renewed interest in bacteriophage therapy in both humans and animals. A “Trojan Horse” approach utilizing liposome encapsulated phages may facilitate access to phagocytic cells infected with intracellular pathogens residing therein, e.g., to treat infections caused by Mycobacterium tuberculosis, Listeria, Salmonella, and Staphylococcus sp. Additionally, liposome encapsulated phages may adhere to and diffuse within mucosa harboring resistant bacteria which are challenges in treating respiratory and gastrointestinal infections. Orally delivered phages tend to have short residence times in the gastrointestinal tract due to clinical symptoms such as diarrhea; this may be addressed through mucoadhesion of liposomes. In the present study we have evaluated the use of a microfluidic based technique for the encapsulation of bacteriophages in liposomes having mean sizes between 100 and 300 nm. Encapsulation of two model phages was undertaken, an Escherichia coli T3 podovirus (size ~65 nm) and a myovirus Staphylococcus aureus phage K (capsid head ~80 nm and phage tail length ~200 nm). The yield of encapsulated T3 phages was 10⁹ PFU/ml and for phage K was much lower at 10⁵ PFU/ml. The encapsulation yield for E. coli T3 phages was affected by aggregation of T3 phages. S. aureus phage K was found to interact with the liposome lipid bilayer resulting in large numbers of phages bound to the outside of the formed liposomes instead of being trapped inside them. We were able to inactivate the liposome bound S. aureus K phages whilst retaining the activity of the encapsulated phages in order to estimate the yield of microfluidic encapsulation of large tailed phages. Previous published studies on phage encapsulation in liposomes may have overestimated the yield of encapsulated tailed phages. This overestimation may affect the efficacy of phage dose delivered at the site of infection. Externally bound phages would be inactivated in the stomach acid resulting in low doses of phages delivered at the site of infection further downstream in the gastrointestinal tract.

Design of a Broad-Range Bacteriophage Cocktail That Reduces Pseudomonas aeruginosa Biofilms and Treats Acute Infections in Two Animal Models

The alarming diffusion of multidrug-resistant (MDR) bacterial strains requires investigations on nonantibiotic therapies. Among such therapies, the use of bacteriophages (phages) as antimicrobial agents, namely, phage therapy, is a promising treatment strategy supported by the findings of recent successful compassionate treatments in Europe and the United States. In this work, we combined host range and genomic information to design a 6-phage cocktail killing several clinical strains of Pseudomonas aeruginosa, including those collected from Italian cystic fibrosis (CF) patients, and analyzed the cocktail performance. We demonstrated that the cocktail composed of four novel phages (PYO2, DEV, E215 and E217) and two previously characterized phages (PAK_P1 and PAK_P4) was able to lyse P. aeruginosa both in planktonic liquid cultures and in biofilms. In addition, we showed that the phage cocktail could cure acute respiratory infection in mice and treat bacteremia in wax moth (Galleria mellonella) larvae. Furthermore, administration of the cocktail to larvae prior to bacterial infection provided prophylaxis. In this regard, the efficiency of the phage cocktail was found to be unaffected by the MDR or mucoid phenotype of the pseudomonal strain. The cocktail was found to be superior to the individual phages in destroying biofilms and providing a faster treatment in mice. We also found the Galleria larva model to be cost-effective for testing the susceptibility of clinical strains to phages, suggesting that it could be implemented in the frame of developing personalized phage therapies.

Characterization of a newly isolated phage infecting pathogenic Escherichia coli and analysis of its mosaic structural genes

The outbreak of multidrug-resistant pathogenic bacteria made the discovery of novel control strategies necessary. Phages have regained attention for their specific lytic activity against pathogenic bacterium. A newly isolated phage infecting the clinical Escherichia coli isolates, including several multidrug-resistant strains, was isolated, and this phage showed high control effects against the tested pathogenic E. coli strains. Host range analysis revealed that although the phage exhibited broad lytic spectrum against the tested E. coli strains, it could not lyse strains from the other species. Comparative genomic analysis showed that phages had undergone at least three genome recombination events during the evolutionary process at the position of the three phage tail genes, which was reported to be associated with the host range determination of the phage. The recombinant tail proteins contained functional domains that were highly similar with genes of the Salmonella phage and genes of Pseudomonas and Neisseria. The findings of this study not only provide resources for developing phage therapy against E. coli, but also showed the highly variable genome structure of the phage.

Bacteriophage cocktail for biocontrol of Escherichia coli O157:H7: Stability and potential allergenicity study

Escherichia coli O157:H7 has become a global public health and a food safety problem. Despite the implementation of control strategies that guarantee the safety in various products, outbreaks persist and new alternatives are necessary to reduce this pathogen along the food chain. Recently, our group isolated and characterised lytic bacteriophages against E. coli O157:H7 with potential to be used as biocontrol agents in food. To this end, phages need certain requirements to allow their manufacture and application. The aim of this study was to determine the physical stability and allergenic potential of free and microencapsulated (ME) bacteriophage cocktails against E. coli O157:H7. In vitro and in vivo studies were performed to determine phage survival under different pH, gastrointestinal conditions, temperature and UV light intensities. Results showed that the stability of ME phages was significantly (P<0.05) higher than free phages after ultraviolet irradiation, pH conditions between 3 to 7, and exposure to temperatures between at -80°C and 70°C. Both formulations were highly sensitive to very low pH in simulated gastric fluid, but stable in bile salts. In vivo studies in mice confirmed these phages passed through the gastrointestinal tract and were excreted in faeces. In silico, full-length alignment analysis showed that all phage proteins were negative for allergenic potential, but different predicting criteria classified seven phage proteins with a very low probability to be an allergen. In conclusion, these data demonstrated that microencapsulation provided a greater stability to phage formulation under stress conditions and assure a more suitable commercial formulation for the biological control of E. coli O157:H7.

Formulation, stabilisation and encapsulation of bacteriophage for phage therapy

Against a backdrop of global antibiotic resistance and increasing awareness of the importance of the human microbiota, there has been resurgent interest in the potential use of bacteriophages for therapeutic purposes, known as phage therapy. A number of phage therapy phase I and II clinical trials have concluded, and shown phages don't present significant adverse safety concerns. These clinical trials used simple phage suspensions without any formulation and phage stability was of secondary concern. Phages have a limited stability in solution, and undergo a significant drop in phage titre during processing and storage which is unacceptable if phages are to become regulated pharmaceuticals, where stable dosage and well defined pharmacokinetics and pharmacodynamics are de rigueur. Animal studies have shown that the efficacy of phage therapy outcomes depend on the phage concentration (i.e. the dose) delivered at the site of infection, and their ability to target and kill bacteria, arresting bacterial growth and clearing the infection. In addition, in vitro and animal studies have shown the importance of using phage cocktails rather than single phage preparations to achieve better therapy outcomes. The in vivo reduction of phage concentration due to interactions with host antibodies or other clearance mechanisms may necessitate repeated dosing of phages, or sustained release approaches. Modelling of phage-bacterium population dynamics reinforces these points. Surprisingly little attention has been devoted to the effect of formulation on phage therapy outcomes, given the need for phage cocktails, where each phage within a cocktail may require significantly different formulation to retain a high enough infective dose. This review firstly looks at the clinical needs and challenges (informed through a review of key animal studies evaluating phage therapy) associated with treatment of acute and chronic infections and the drivers for phage encapsulation. An important driver for formulation and encapsulation is shelf life and storage of phage to ensure reproducible dosages. Other drivers include formulation of phage for encapsulation in micro- and nanoparticles for effective delivery, encapsulation in stimuli responsive systems for triggered controlled or sustained release at the targeted site of infection. Encapsulation of phage (e.g. in liposomes) may also be used to increase the circulation time of phage for treating systemic infections, for prophylactic treatment or to treat intracellular infections. We then proceed to document approaches used in the published literature on the formulation and stabilisation of phage for storage and encapsulation of bacteriophage in micro- and nanostructured materials using freeze drying (lyophilization), spray drying, in emulsions e.g. ointments, polymeric microparticles, nanoparticles and liposomes. As phage therapy moves forward towards Phase III clinical trials, the review concludes by looking at promising new approaches for micro- and nanoencapsulation of phages and how these may address gaps in the field.

Prospects of Phage Application in the Treatment of Acne Caused by Propionibacterium acnes

Propionibacterium acnes is associated with purulent skin infections, and it poses a global problem for both patients and doctors. Acne vulgaris (acne) remains a problem due to its chronic character and difficulty of treatment, as well as its large impact on patients' quality of life. Due to the chronic course of the disease, treatment is long lasting, and often ineffective. Currently there are data regarding isolation of P. acnes phages, and there have been numerous studies on phage killing of P. acnes, but no data are available on phage application specifically in acne treatment. In this review, we have summarized the current knowledge on the phages active against P. acnes described so far and their potential application in the treatment of acne associated with P. acnes. The treatment of acne with phages may be important in order to reduce the overuse of antibiotics, which are currently the main acne treatment. However, more detailed studies are first needed to understand phage functioning in the skin microbiome and the possibility to use phages to combat P. acnes.

Bacteriophage Procurement for Therapeutic Purposes

Bacteriophages (phages), discovered 100 years ago, are able to infect and destroy only bacterial cells. In the current crisis of antibiotic efficacy, phage therapy is considered as a supplementary or even alternative therapeutic approach. Evolution of multidrug-resistant and pandrug-resistant bacterial strains poses a real threat, so it is extremely important to have the possibility to isolate new phages for therapeutic purposes. Our phage laboratory and therapy center has extensive experience with phage isolation, characterization, and therapeutic application. In this article we present current progress in bacteriophages isolation and use for therapeutic purposes, our experience in this field and its practical implications for phage therapy. We attempt to summarize the state of the art: properties of phages, the methods for their isolation, criteria of phage selection for therapeutic purposes and limitations of their use. Perspectives for the use of genetically engineered phages to specifically target bacterial virulence-associated genes are also briefly presented.

Prohead RNA: a noncoding viral RNA of novel structure and function

Prohead RNA (pRNA) is an essential component of the powerful Φ29-like bacteriophage DNA packaging motor. However, the specific role of this unique RNA in the Φ29 packaging motor remains unknown. This review examines pRNA as a noncoding RNA of novel structure and function. In order to highlight the reasons for exploring the structure and function of pRNA, we (1) provide an overview of Φ29-like bacteriophage and the Φ29 DNA packaging motor, including putative motor mechanisms and structures of its component parts; (2) discuss pRNA structure and possible roles for pRNA in the Φ29 packaging motor; (3) summarize pRNA self-assembly; and (4) describe the prospective therapeutic applications of pRNA. Many questions remain to be answered in order to connect what is currently known about pRNA structure to its novel function in the Φ29 packaging motor. The knowledge gained from studying the structure, function, and sequence variation in pRNA will help develop tools to better navigate the conformational landscapes of RNA. WIREs RNA 2016, 7:428-437. doi: 10.1002/wrna.1330 For further resources related to this article, please visit the WIREs website.

Three New Escherichia coli Phages from the Human Gut Show Promising Potential for Phage Therapy

With the emergence of multi-drug resistant bacteria the use of bacteriophages (phages) is gaining renewed interest as promising anti-microbial agents. The aim of this study was to isolate and characterize phages from human fecal samples. Three new coliphages, ɸAPCEc01, ɸAPCEc02 and ɸAPCEc03, were isolated. Their phenotypic and genomic characteristics, and lytic activity against biofilm, and in combination with ciprofloxacin, were investigated. All three phages reduced the growth of E. coli strain DPC6051 at multiplicity of infection (MOI) between 10-3 and 105. A cocktail of all three phages completely inhibited the growth of E. coli. The phage cocktail also reduced biofilm formation and prevented the emergence of phage-resistant mutants which occurred with single phage. When combined with ciprofloxacin, phage alone or in cocktail inhibited the growth of E. coli and prevented the emergence of resistant mutants. These three new phages are promising biocontrol agents for E. coli infections.

From bench to bed and back again: phage therapy of childhood Escherichia coli diarrhea

Over the last 20 years, the Nestlé Research Center in Switzerland and the International Center for Diarrhoeal Diseases Research in Bangladesh have explored the efficacy of alternative biological agents for the treatment of diarrheal diseases. This paper reviews the work of this collaborative effort, particularly on Escherichia coli phage therapy (PT), and discusses the development of the project, starting with the isolation of T4-like coliphages from the stool of diarrhea patients, their pilot plant amplification and purification, and the constitution and testing of a cocktail of T4-like phages in mice. A series of phase I clinical trials has demonstrated the safety of PT. Oral phage given without protection survived gastric passage and was recovered in the feces. Oral T4 phage cocktail was then tested in parallel to a commercial phage product in a phase II randomized, placebo-controlled single-center trial in Bangladeshi children hospitalized with acute E. coli diarrhea. It was found that oral phage did not perform better than the current standard of care by oral rehydration/zinc treatment. Furthermore, fecal E. coli pathogen titers were low and mixed infections were found to be frequent. Microbiota analysis showed a correlation between diarrhea and increased levels of Streptococcus, which raises fundamental questions on the causative agent of diarrhea that may explain PT clinical failure.

Bacteriophage Therapy: Advances in Formulation Strategies and Human Clinical Trials

Recently, a number of phage therapy phase I and II safety trials have been concluded, showing no notable safety concerns associated with the use of phage. Though hurdles for efficient treatment remain, these trials hold promise for future phase III clinical trials. Interestingly, most phage formulations used in these clinical trials are straightforward phage suspensions, and not much research has focused on the processing of phage cocktails in specific pharmaceutical dosage forms. Additional research on formulation strategies and the stability of phage-based drugs will be of key importance, especially with phage therapy advancing toward phase III clinical trials.

Safety of using Escherichia coli bacteriophages as a sanitizing agent based on inflammatory responses in rats

Use of bacteriophages as sanitizing agents has received much attention. However, safety in humans is debatable. To determine inflammatory immune responses against bacteriophages, rats were treated with a 8 log plaque-forming cocktail of 5 bacteriophages for pathogenic Escherichia coli per day for 4 weeks. Food consumption, feeding efficiency, and body weight of rats treated with the cocktail were not different from controls. Phages were not detected in the sera of phage-fed rats with no changes in organ weights. Notable changes were not observed upon histopathological examination of the liver, kidney, and spleen. Pro-inflammatory cytokine mRNA expression, except COX-2 (2.4x increase), remained unaffected after treatment with the phage cocktail. No remarkable changes were observed for levels of 12 pro-inflammatory cytokines in sera. Inflammatory responses in rats orally treated with a phage cocktail were not observed. Bacteriophages for E. coli are indicated as immunologically safe in rats.

Oral Phage Therapy of Acute Bacterial Diarrhea With Two Coliphage Preparations: A Randomized Trial in Children From Bangladesh

Background

Antibiotic resistance is rising in important bacterial pathogens. Phage therapy (PT), the use of bacterial viruses infecting the pathogen in a species-specific way, is a potential alternative.

Method

T4-like coliphages or a commercial Russian coliphage product or placebo was orally given over 4 days to Bangladeshi children hospitalized with acute bacterial diarrhea. Safety of oral phage was assessed clinically and by functional tests; coliphage and Escherichia coli titers and enteropathogens were determined in stool and quantitative diarrhea parameters (stool output, stool frequency) were measured. Stool microbiota was studied by 16S rRNA gene sequencing; the genomes of four fecal Streptococcus isolates were sequenced.

Findings

No adverse events attributable to oral phage application were observed (primary safety outcome). Fecal coliphage was increased in treated over control children, but the titers did not show substantial intestinal phage replication (secondary microbiology outcome). 60% of the children suffered from a microbiologically proven E. coli diarrhea; the most frequent diagnosis was ETEC infections. Bacterial co-pathogens were also detected. Half of the patients contained phage-susceptible E. coli colonies in the stool. E. coli represented less than 5% of fecal bacteria. Stool ETEC titers showed only a short-lived peak and were otherwise close to the replication threshold determined for T4 phage in vitro. An interim analysis after the enrollment of 120 patients showed no amelioration in quantitative diarrhea parameter by PT over standard care (tertiary clinical outcome). Stool microbiota was characterized by an overgrowth with Streptococcus belonging to the Streptococcus gallolyticus and Streptococcus salivarius species groups, their abundance correlated with quantitative diarrhea outcome, but genome sequencing did not identify virulence genes.

Interpretation

Oral coliphages showed a safe gut transit in children, but failed to achieve intestinal amplification and to improve diarrhea outcome, possibly due to insufficient phage coverage and too low E. coli pathogen titers requiring higher oral phage doses. More knowledge is needed on in vivo phage–bacterium interaction and the role of E. coli in childhood diarrhea for successful PT.

Funding

The study was supported by a grant from Nestlé Nutrition and Nestlé Health Science. The trial was registered with Identifier NCT00937274 at ClinicalTrials.gov.

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Coliphages given orally to children with bacterial diarrhea appeared in the stool, but did not improve clinical outcome.

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In microbiologically diagnosed E. coli diarrhea, pathogen titers were close to the replication threshold of coliphages.

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Acute bacterial diarrhea displayed a marked dysbiosis with fecal streptococci that stabilized with recovery from diarrhea.

Antibiotic resistance of bacterial infections reached alarming levels. Phage therapy is a potential alternative antimicrobial. We demonstrated that two different oral phage preparations did not improve acute bacterial diarrhea in children from Bangladesh. We observed fecal excretion of the oral phage, but no major phage amplification in the gut. E. coli pathogen levels were low and the fecal microbiota showed a transient overgrowth with streptococci. Future phage trials should first verify the titer and association of the targeted pathogen with the disease.

Isolation and characterization of a T4-like phage with a relatively wide host range within Escherichia coli

Avian pathogenic Escherichia coli (APEC) causes colibacillosis in poultry, resulting in severe economic losses worldwide. Coliphages represent alternative antibacterial substitutes based on high lytic efficiency and few side-effects. However, the complete genome sequences information of APEC phages are limited, and knowledge of undesired genes and the narrow host range restrict their applications. In this study, we isolated a virulent phage QL01, with a relatively broad lytic spectrum (41 of 78 APEC strains). Transmission electron micrography showed it belonged to the family Myoviridae with an elongated head and a contractile tail. Whole genome sequencing revealed a linear double-stranded DNA (170,527 kb; GC content, 39.6%) with 275 possible ORFs. Comparative genome analysis revealed high homology between QL01 and other T4-like phages. However, it also showed some unique features, for example, ORF142 and ORF143, which encode IP9 and IP8, respectively, and may counteract host resistance only exist in a few T4-like phages such as IME08 and vB_EcoM_VR5. Furthermore, phage therapy in artificially infected ducks showed a 26.67% decrease in mortality compared with the untreated group. Our study indicates the potential antibacterial function of phage QL01 against APEC infections and highlights unique molecular features underlying the relatively broad host range.

Bacteriophage therapy against Enterobacteriaceae

The Enterobacteriaceae are a class of gram-negative facultative anaerobic rods, which can cause a variety of diseases, such as bacteremia, septic arthritis, endocarditis, osteomyelitis, lower respiratory tract infections, skin and soft-tissue infections, urinary tract infections, intra-abdominal infections and ophthalmic infections, in humans, poultry, animals and fish. Disease caused by Enterobacteriaceae cause the deaths of millions of people every year, resulting in enormous economic loss. Drug treatment is a useful and efficient way to control Enterobacteriaceae infections. However, with the abuse of antibiotics, drug resistance has been found in growing number of Enterobacteriaceae infections and, as such, there is an urgent need to find new methods of control. Bacteriophage therapy is an efficient alternative to antibiotics as it employs a different antibacterial mechanism. This paper summarizes the history of bacteriophage therapy, its bacterial lytic mechanisms, and the studies that have focused on Enterobacteriaceae and bacteriophage therapy.