Isolation and characterization of a "phiKMV-like" bacteriophage and its therapeutic effect on mink hemorrhagic pneumonia

Characterization of Pseudomonas aeruginosa bacteriophages and control hemorrhagic pneumonia on a mice model

Pseudomonas aeruginosa is one of the most common pathogens causing hemorrhagic pneumonia in Chinese forest musk deer. Multidrug-resistant P. aeruginosa is frequently isolated from the lungs of affected musk deer in Shaanxi Province, China. With the increasing bacterial drug resistance, commonly used antibiotics have shown limited efficacy against drug-resistant P. aeruginosa. Therefore, phages have garnered attention as a promising alternative to antibiotics among researchers. In this study, phages vB_PaeP_YL1 and vB_PaeP_YL2 (respectively referred to as YL1 and YL2) were isolated from mixed sewage samples from a farm. YL1 and YL2 exhibit an icosahedral head and a non-contractile short tail, belonging to the Podoviridae family. Identification results demonstrate good tolerance to low temperatures and pH levels, with minimal variation in potency within 30 min of UV irradiation. The MOI for both YL1 and YL2 was 0.1, and their one-step growth curve latent periods were 10 min and 20 min, respectively. Moreover, both single phage and phage cocktail effectively inhibited the growth of the host bacteria in vitro, with the phage cocktail showing superior inhibitory effects compared to the single phage. YL1 and YL2 possess double-stranded DNA genomes, with YL1 having a genome size of 72,187 bp and a total G + C content of 55.02%, while YL2 has a genome size of 72,060 bp and a total G + C content of 54.98%. YL1 and YL2 are predicted to have 93 and 92 open reading frames (ORFs), respectively, and no ORFs related to drug resistance or lysogeny were found in both phages. Genome annotation and phylogenetic analysis revealed that YL1 is closely related to vB_PaeP_FBPa1 (ON857943), while YL2 is closely related to vB_PaeP_FBPa1 (ON857943) and Phage26 (NC041907). In a mouse model of hemorrhagic pneumonia, phage cocktail treatment showed better control of the disease and significantly reduced lung bacterial load compared to single phage treatment. Therefore, YL1 and YL2 have the potential for the prevention and treatment of multidrug-resistant P. aeruginosa infections.

Class-Driven Synergy and Antagonism between a Pseudomonas Phage and Antibiotics

The ubiquitous bacterial pathogen Pseudomonas aeruginosa is responsible for severe infections in patients with burns, cystic fibrosis, and neutropenia. Biofilm formation gives physical refuge and a protected microenvironment for sessile cells, rendering cure by antibiotics a challenge. Bacteriophages have evolved to prey on these biofilms over millions of years, using hydrolases and depolymerases to penetrate biofilms and reach cellular targets. Here, we assessed how a newly discovered KMV-like phage (ΦJB10) interacts with antibiotics to treat P. aeruginosa more effectively in both planktonic and biofilm forms. By testing representatives of four classes of antibiotics (cephalosporins, aminoglycosides, fluoroquinolones, and carbapenems), we demonstrated class-dependent interactions between ΦJB10 and antibiotics in both biofilm clearance and P. aeruginosa killing. Despite identifying antagonism between some antibiotic classes and ΦJB10 at early time points, all classes showed neutral to favorable interactions with the phage at later time points. In one notable example where the antibiotic alone had poor activity against both biofilm and high-density planktonic cells, we found that addition of ΦJB10 demonstrated synergy and resulted in effective treatment of both. Further, ΦJB10 seemed to act as an adjuvant to several antibiotics, reducing the concentration of antibiotics required to ablate the biofilm. This report shows that phages such as ΦJB10 may be valuable additions to the armamentarium against difficult-to-treat biofilm-based infections.

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

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

Characterization and complete genome analysis of a bacteriophage vB_EcoM_DE7 infecting donkey-derived Escherichia coli

A lytic bacteriophage vB_EcoM_DE7 (hereafter designated DE7) that could infect donkey-derived Escherichia coli was isolated. The bacteriophage was examined by transmission electron microscopy, and the result showed that DE7 belonged to the family Myoviridae. The microbiological characterization revealed that DE7 was stable over a broad range of pHs (3 ∼10) at 40-50 °C. The latent period was 10 min, and the burst size was 43 PFUs/infected cell. The whole-genome sequencing showed that DE7 was a dsDNA virus and had a genome of 86,130 bp. The genome contained 124 predicted open reading frames (ORFs), 35 of which had known functions, including DNA replication and modification, transcriptional regulation, structural and packaging proteins, and host cell lysis. Twenty tRNA genes were identified, but no genes associated with bacterial pathogenicity, lysogeny and drug resistance were identified. BLASTN analysis revealed that phage DE7 had a high sequence identity (96%) with Salmonella phage vB_SPuM_SP116, but it could not lyse any Salmonella strain tested in this study. DE7 was classified as a Felix O1-like virus based on its general characterization and genomic information. Since phage DE7 exhibited high efficacy in lysing E. coli and lacked genes associated with bacterial virulence, antimicrobial resistance and lysogeny, it could be potentially used to control foal diarrhoea caused by E. coli.

Therapeutic Bacteriophages for Gram-Negative Bacterial Infections in Animals and Humans

Drug-resistant Gram-negative bacterial pathogens are an increasingly serious health threat causing worldwide nosocomial infections with high morbidity and mortality. Of these, the most prevalent and severe are Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Salmonella typhimurium. The extended use of antibiotics has led to the emergence of multidrug resistance in these bacteria. Drug-inactivating enzymes produced by these bacteria, as well as other resistance mechanisms, render drugs ineffective and make treatment of such infections more difficult and complicated. This makes the development of novel antimicrobial agents an urgent necessity. Bacteriophages, which are bacteria-killing viruses first discovered in 1915, have been used as therapeutic antimicrobials in the past, but their use was abandoned due to the widespread availability of antibiotics in the 20th century. The emergence, however, of drug-resistant pathogens has re-affirmed the need for bacteriophages as therapeutic strategies. This review describes the use of bacteriophages as novel agents to combat this rapidly emerging public health crisis by comprehensively enumerating and discussing the innovative use of bacteriophages in both animal models and in patients infected by Gram-negative bacteria.

Characterization and genome analysis of Pseudomonas aeruginosa phage vB_PaeP_Lx18 and the antibacterial activity of its lysozyme

A lytic Pseudomonas aeruginosa phage, vB_PaeP_Lx18 (Lx18), was isolated from the sewage of a dairy farm. Biological characterization revealed that Lx18 was stable from 40 °C to 60 °C and over a wide range of pH values from 4 to 10. It was able to lyse 63.6% (21/33) of the P. aeruginosa strains tested and was able to reduce and disperse biofilms, with a biofilm reduction rate of 76.8%. Whole-genome sequencing showed that Lx18 is a dsDNA virus with a genome of 42,735 bp and G+C content of 62.16%. The genome contains 54 open reading frames (ORFs), 28 of which have known functions, including DNA replication and modification, transcriptional regulation, structural and packaging proteins, and host cell lysis. No virulence or tRNA genes were identified. Phylogenetic analysis showed that phage Lx18 belongs to the genus Phikmvvirus. The lysozyme of Lx18, Lys18, was cloned and expressed. The combined action of Lys18 and ethylenediaminetetraacetic acid (EDTA) had antibacterial activity against Pseudomonas aeruginosa. The study of phage Lx18 and its lysozyme will provide basic information for further research on the treatment of Pseudomonas aeruginosa infections.

Isolation, Characterization, and Genomic Analysis of Three Novel E. coli Bacteriophages That Effectively Infect E. coli O18

Escherichia coli (E. coli) is one of the most common pathogenic bacteria worldwide. Avian pathogenic E. coli (APEC) causes severe systemic disease in poultry (Colibacillosis), and accordingly, has an extreme risk to the poultry industry and public health worldwide. Due to the increased rate of multi-drug resistance among these bacteria, it is necessary to find an alternative therapy to antibiotics to treat such infections. Bacteriophages are considered one of the best solutions. This study aimed to isolate, characterize, and evaluate the potential use of isolated bacteriophages to control E. coli infections in poultry. Three novel phages against E. coli O18 were isolated from sewage water and characterized in vitro. The genome size of the three phages was estimated to be 44,776 bp, and the electron microscopic analysis showed that they belonged to the Siphoviridae family, in the order Caudovirales. Phages showed good tolerance to a broad range of pH and temperature. The complete genomes of three phages were sequenced and deposited into the GenBank database. The closely related published genomes of Escherichia phages were identified using BLASTn alignment and phylogenetic trees. The prediction of the open reading frames (ORFs) identified protein-coding genes that are responsible for functions that have been assigned such as cell lysis proteins, DNA packaging proteins, structural proteins, and DNA replication/transcription/repair proteins.

Characterization and in vitro testing of newly isolated lytic bacteriophages for the biocontrol of Pseudomonas aeruginosa

Aim: Two lytic phages were isolated using P. aeruginosa DSM19880 as host and fully characterized. Materials & methods: Phages were characterized physicochemically, biologically and genomically. Results & conclusion: Host range analysis revealed that the phages also infect some multidrug-resistant (MDR) P. aeruginosa clinical isolates. Increasing MOI from 1 to 1000 significantly increased phage efficiency and retarded bacteria regrowth, but phage ph0034 (reduction of 7.5 log CFU/ml) was more effective than phage ph0031 (reduction of 5.1 log CFU/ml) after 24 h. Both phages belong to Myoviridae family. Genome sequencing of phages ph0031 and ph0034 showed that they do not carry toxin, virulence, antibiotic resistance and integrase genes. The results obtained are highly relevant in the actual context of bacterial resistance to antibiotics.

Isolation of the Novel Phage PHB09 and Its Potential Use against the Plant Pathogen Pseudomonas syringae pv. actinidiae

Bacteriophages are viruses that specifically infect target bacteria. Recently, bacteriophages have been considered potential biological control agents for bacterial pathogens due to their host specificity. Pseudomonas syringae pv. actinidiae (Psa) is a reemerging pathogen that causes bacterial canker of kiwifruit (Actinidia sp.). The economic impact of this pest and the development of resistance to antibiotics and copper sprays in Psa and other pathovars have led to investigation of alternative management strategies. Phage therapy may be a useful alternative to conventional treatments for controlling Psa infections. Although the efficacy of bacteriophage φ6 was evaluated for the control of Psa, the characteristics of other DNA bacteriophages infecting Psa remain unclear. In this study, the PHB09 lytic bacteriophage specific to Psa was isolated from kiwifruit orchard soil. Extensive host range testing using Psa isolated from kiwifruit orchards and other Pseudomonas strains showed PHB09 has a narrow host range. It remained stable over a wide range of temperatures (4-50 °C) and pH values (pH 3-11) and maintained stability for 50 min under ultraviolet irradiation. Complete genome sequence analysis indicated PHB09 might belong to a new myovirus genus in Caudoviricetes. Its genome contains a total of 94,844 bp and 186 predicted genes associated with phage structure, packaging, host lysis, DNA manipulation, transcription, and additional functions. The isolation and identification of PHB09 enrich the research on Pseudomonas phages and provide a promising biocontrol agent against kiwifruit bacterial canker.

HATMSC Secreted Factors in the Hydrogel as a Potential Treatment for Chronic Wounds-In Vitro Study

Mesenchymal stem cells (MSCs) can improve chronic wound healing; however, recent studies suggest that the therapeutic effect of MSCs is mediated mainly through the growth factors and cytokines secreted by these cells, referred to as the MSC secretome. To overcome difficulties related to the translation of cell therapy into clinical use such as efficacy, safety and cost, we propose a hydrogel loaded with a secretome from the recently established human adipose tissue mesenchymal stem cell line (HATMSC2) as a potential treatment for chronic wounds. Biocompatibility and biological activity of hydrogel-released HATMSC2 supernatant were investigated in vitro by assessing the proliferation and metabolic activity of human fibroblast, endothelial cells and keratinocytes. Hydrogel degradation was measured using hydroxyproline assay while protein released from the hydrogel was assessed by interleukin-8 (IL-8) and macrophage chemoattractant protein-1 (MCP-1) ELISAs. Pro-angiogenic activity of the developed treatment was assessed by tube formation assay while the presence of pro-angiogenic miRNAs in the HATMSC2 supernatant was investigated using real-time RT-PCR. The results demonstrated that the therapeutic effect of the HATMSC2-produced factors is maintained following incorporation into collagen hydrogel as confirmed by increased proliferation of skin-origin cells and improved angiogenic properties of endothelial cells. In addition, HATMSC2 supernatant revealed antimicrobial activity, and which therefore, in combination with the hydrogel has a potential to be used as advanced wound-healing dressing.

Efficacy of Phage-Antibiotic Combinations Against Multidrug-Resistant Klebsiella pneumoniae Clinical Isolates

Background: Increasing antibiotic resistance warrants therapeutic alternatives to eradicate resistant bacteria. Combined phage-antibiotic therapy is a promising approach for eliminating bacterial infections and limiting the evolution of therapy-resistant diseases. Objectives: In the present study, we evaluated the effects of combinations of bacteriophages and antibiotics against multidrug-resistant (MDR) Klebsiella pneumoniae. Methods: Two MDR strains (GenBank no. MF953600 & MF953599) of K. pneumoniae were used. Bacteriophages were isolated from hospital sewage samples by employing a double agar overlay assay and identified by transmission electron microscopy. For further characterization of bacteriophages, the killing assay and host range test were performed. To assess therapeutic efficacy, phages (7.5 × 104 PFU/mL) were used in combination with various antibiotics. Results: The phage-cefepime and tetracycline combinations displayed promising therapeutic effects, restricting the growth of K. pneumoniae isolates, as evidenced by recording OD650nm values. Conclusions: The results of the current study showed that phage-antibiotic combination was a potential therapeutic approach to treat the infections caused by MDR K. pneumoniae.

Novel Lytic Phages Protect Cells and Mice against Pseudomonas aeruginosa Infection

With the fast emergence of serious antibiotic resistance and the lagged discovery of novel antibacterial drugs, phage therapy for pathogenic bacterial infections has acquired great attention in the clinics. However, development of therapeutic phages also faces tough challenges, such as laborious screening and time to generate effective phage drugs since each phage may only lyse a narrow scope of bacterial strains. Identifying highly effective phages with broad host ranges is crucial for improving phage therapy. Here, we isolated and characterized several lytic phages from various environments specific for Pseudomonas aeruginosa by testing their growth, invasion, host ranges, and potential for killing targeted bacteria. Importantly, we identified several therapeutic phages (HX1, PPY9, and TH15) with broad host ranges to lyse laboratory strains and clinical isolates of P. aeruginosa with multi-drug resistance (MDR) both in vitro and in mouse models. In addition, we analyzed critical genetic traits related to the high-level broad host coverages by genome sequencing and subsequent computational analysis against known phages. Collectively, our findings establish that these novel phages may have potential for further development as therapeutic options for patients who fail to respond to conventional treatments.IMPORTANCE Novel lytic phages isolated from various environmental settings were systematically characterized for their critical genetic traits, morphology structures, host ranges against laboratory strains and clinical multi-drug resistant (MDR) Pseudomonas aeruginosa, and antibacterial capacity both in vitro and in mouse models. First, we characterized the genetic traits and compared with other existing phages. Furthermore, we utilized acute pneumonia induced by laboratorial strain PAO1, and W19, an MDR clinical isolate and chronic pneumonia by agar beads laden with FDR1, a mucoid phenotype strain isolated from the sputum of a cystic fibrosis (CF) patient. Consequently, we found that these phages not only suppress bacteria in vitro but also significantly reduce the infection symptom and disease progression in vivo, including lowered bug burdens, inflammatory responses and lung injury in mice, suggesting that they may be further developed as therapeutic agents against MDR P. aeruginosa.

Benefits of aerosolized phages for the treatment of pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA): an experimental study in rats

Background

The optimal method for delivering phages in the context of ventilator-associated pneumonia (VAP) is unknown. In the current study, we assessed the utility of aerosolized phages (aerophages) for experimental methicillin-resistant Staphylococcus aureus (MRSA) pneumonia.

Methods

Rats were ventilated for 4 hours before induction of pneumonia. Animals received one of the following: (1) aerophages; (2) intravenous (IV) phages; (3) a combination of IV and aerophages; (4) IV linezolid; or (5) a combination of IV linezolid and aerophages. Phages were administered at 2, 12, 24, 48, and 72 hours, and linezolid was administered at 2, 12, 24, 36, 48, 60, and 72 hours. The primary outcome was survival at 96 hours. Secondary outcomes were bacterial and phage counts in tissues and histopathological scoring of the lungs.

Results

Aerophages and IV phages each rescued 50% of animals from severe MRSA pneumonia (P < .01 compared with placebo controls). The combination of aerophages and IV phages rescued 91% of animals, which was higher than either monotherapy (P < .05). Standard-of-care antibiotic linezolid rescued 38% of animals. However, linezolid and aerophages did not synergize in this setting (55% survival).

Conclusions

Aerosolized phage therapy showed potential for the treatment of MRSA pneumonia in an experimental animal model and warrants further investigation for application in humans.

Genetic Analysis and Characterization of a Bacteriophage ØCJ19 Active against Enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is the major pathogenic E. coli that causes diarrhea and edema in post-weaning piglets. In this study, we describe the morphology and characteristics of ØCJ19, a bacteriophage that infects ETEC, and performed genetic analysis. Phage ØCJ19 belongs to the family Myoviridae. One-step growth curve showed a latent phase of 5 min and burst size of approximately 20 phage particles/infected cell. Phage infectivity was stable for 2 h between 4°C and 55°C, and the phage was stable between pH 3 and 11. Genetic analysis revealed that phage ØCJ19 has a total of 49,567 bases and 79 open reading frames (ORFs). The full genomic sequence of phage ØCJ19 showed the most similarity to an Escherichia phage, vB_EcoS_ESCO41. There were no genes encoding lysogeny, toxins, virulence factors, or antibiotic resistance in this phage, suggesting that this phage can be used safely as a biological agent to control ETEC. Comparative genomic analysis in terms of the tail fiber proteins could provide genetic insight into host recognition and the relationship with other coliphages. These results showed the possibility to improve food safety by applying phage ØCJ19 to foods of animal origin contaminated with ETEC and suggests that it could be the basis for establishing a safety management system in the animal husbandry.

Characterization and Complete Genome Analysis of Pseudomonas aeruginosa Bacteriophage vB_PaeP_LP14 Belonging to Genus Litunavirus

A lytic Pseudomonas aeruginosa phage vB_PaeP_LP14 belonging to the family Podoviridae was isolated from infected mink. The microbiological characterization revealed that LP14 was stable at 40 to 50 °C and stable over a broad range of pH (5 to 12). The latent period was 5 min, and the burst size was 785 pfu/infected cell. The whole-genome sequencing showed that LP14 was a dsDNA virus and has a genome of 73,080 bp. The genome contained 93 predicted open reading frames (ORFs), 17 of which have known functions including DNA replication and modification, transcriptional regulation, structural and packaging proteins, and host cell lysis. No tRNA genes were identified. BLASTn analysis revealed that phage LP14 had a high-sequence identity (96%) with P. aeruginosa phage YH6. Both morphological characterization and genome annotation indicate that phage LP14 is a memberof the family Podoviridae genus Litunavirus. The study of phage LP14 will provide basic information for further research on treatment of P. aeruginosa infections.

Phage display as a tool for vaccine and immunotherapy development

Bacteriophages, or phages, are viruses that specifically infect bacteria and coopt the cellular machinery to create more phage proteins, eventually resulting in the release of new phage particles. Phages are heavily utilized in bioengineering for applications ranging from tissue engineering scaffolds to immune signal delivery. Of specific interest to vaccines and immunotherapies, phages have demonstrated an ability to activate both the innate and adaptive immune systems. The genome of these viral particles can be harnessed for DNA vaccination, or the surface proteins can be exploited for antigen display. More specifically, genes that encode an antigen of interest can be spliced into the phage genome, allowing antigenic proteins or peptides to be displayed by fusion to phage capsid proteins. Phages therefore present antigens to immune cells in a highly ordered and repetitive manner. This review discusses the use of phage with adjuvanting activity as antigen delivery vehicles for vaccination against infectious disease and cancer.

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.

Probiotic and Triticale Silage Fermentation Potential of Pediococcus pentosaceus and Lactobacillus brevis and Their Impacts on Pathogenic Bacteria

The purpose of this study was to identify potent lactic acid bacteria that could have a great impact on triticale silage fermentation at different moisture levels and determine their anti-bacterial activity and high probiotic potential. For this purpose, Pediococcus pentosaceus (TC48) and Lactobacillus brevis (TC50) were isolated from fermented triticale silage. The fermentation ability of these isolates in triticale powder was studied by an ensiling method. TC48 had higher ability to ferment silage powder by increasing the lactic acid content of silage than TC50. Extracellular supernatant (ECS) of TC48 and TC50 exhibited strong antibacterial effects (inhibition zone diameters: 18-28 mm) against tested cattle pathogenic bacteria with minimum inhibitory/ minimum bactericidal concentrations (MIC/MBC) values of 5.0-10 mg/mL and 10-20 mg/mL, respectively. Extracellular supernatant (ECS) of TC48 and TC50 showed antibacterial activities on E. coli, P. aeruoginosa, S. aureus and E. faecalis through destruction of membrane integrity as confirmed by decreased viability, and increased 260 nm absorbing material in culture filtrate of pathogenic bacteria exposed to ECS of both strains. TC48 and TC50 strains exhibited high tolerance to artificial gastric, duodenal and intestinal fluids. TC48 showed good hydrophobicity and auto-aggregations properties. TC48 and TC50 significantly co-aggregated with E. coli, P. aeruoginosa, S. aureus and E. faecalis in a time-dependent manner. In summary, all of the bacteria had a positive impact on at least one functional property of the silage during the fermentation process. However, the addition of P. pentosaceus (TC48) and L. brevis (TC50) yielded the greatest silage quality improvement, having high antibacterial and probiotic properties.

Evaluation of phage therapy in the treatment of Staphylococcus aureus-induced mastitis in mice

Mastitis in dairy cows is generally considered to be the most expensive disease for dairy farmers worldwide. The overuse of antibiotics is a major problem in the treatment of bovine mastitis, and bacteriophage therapy is expected to provide an alternative treatment. The primary aim of this study was to evaluate the efficacy of a phage cocktail against mastitis in a mouse model. First, a Staphylococcus aureus strain was isolated from milk samples taken from mastitis cows from dairy farms in Xinjiang, China, and it was designated as Sau-XJ-21. Next, two phages (designated as vBSM-A1 and vBSP-A2) with strong lytic activity against Sau-XJ-21 were isolated from mixed sewage samples collected from three cattle farms in Xinjiang. Phages vBSM-A1 and vBSP-A2 were identified as members of the Myoviridae and Podoviridae families, respectively. The two phages exhibited a wide range of hosts, especially phage vBSM-A1. To evaluate the effectiveness of the two phages in the treatment against mastitis, female lactating mice were used 10-14 days after giving births. The mice were divided into six groups; one group was kept as healthy control, while the remaining five groups were inoculated with the isolated S. aureus strain to induce mastitis. Four hours after bacterial inoculation, mice in these groups were injected with 25 μL phosphate buffer saline (negative control), ceftiofur sodium (positive control), or phage, either individually or as a cocktail. The mice were sacrificed 20 h later, and the mammary glands were removed and subjected to further analysis, including the quantitation of colony-forming units (CFU), plaque-forming units (PFU), and gross macroscopic as well as histopathology observation. Mice with induced mastitis exhibited significantly improved mastitic pathology and decreased bacterial counts after they had been given phage treatments, with the phage cocktail being more superior than either phage alone. Furthermore, the cocktail treatment also maintained the highest intramammary phage titer without spreading systemically. The effectiveness of the phage cocktail was comparable to that produced by ceftiofur sodium. According to the data obtained for the mouse model of mastitis, phage therapy could be considered as an innovative alternative to antibiotics for the treatment of bovine mastitis.

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.

Phages for Phage Therapy: Isolation, Characterization, and Host Range Breadth

For a bacteriophage to be useful for phage therapy it must be both isolated from the environment and shown to have certain characteristics beyond just killing strains of the target bacterial pathogen. These include desirable characteristics such as a relatively broad host range and a lack of other characteristics such as carrying toxin genes and the ability to form a lysogen. While phages are commonly isolated first and subsequently characterized, it is possible to alter isolation procedures to bias the isolation toward phages with desirable characteristics. Some of these variations are regularly used by some groups while others have only been shown in a few publications. In this review I will describe (1) isolation procedures and variations that are designed to isolate phages with broader host ranges, (2) characterization procedures used to show that a phage may have utility in phage therapy, including some of the limits of such characterization, and (3) results of a survey and discussion with phage researchers in industry and academia on the practice of characterization of phages.

Phage therapy for respiratory infections

A respiratory infection caused by antibiotic-resistant bacteria can be life-threatening. In recent years, there has been tremendous effort put towards therapeutic application of bacteriophages (phages) as an alternative or supplementary treatment option over conventional antibiotics. Phages are natural parasitic viruses of bacteria that can kill the bacterial host, including antibiotic-resistant bacteria. Inhaled phage therapy involves the development of stable phage formulations suitable for inhalation delivery followed by preclinical and clinical studies for assessment of efficacy, pharmacokinetics and safety. We presented an overview of recent advances in phage formulation for inhalation delivery and their efficacy in acute and chronic rodent respiratory infection models. We have reviewed and presented on the prospects of inhaled phage therapy as a complementary treatment option with current antibiotics and as a preventative means. Inhaled phage therapy has the potential to transform the prevention and treatment of bacterial respiratory infections, including those caused by antibiotic-resistant bacteria.

Bovine esophageal and glossal ulceration associated with Pseudomonas aeruginosa and Fusobacterium spp. in a 10-month-old Holstein heifer

An underweight 10-month-old Holstein heifer presented with anorexia and ananastasia and was euthanized. Postmortem examination revealed extensive ulceration in the esophagus, tongue, and omasum. Histopathological examination revealed severe necrotic esophagitis, glossitis, and omasitis. Many Gram-negative bacilli were detected throughout the necrotic area in the digestive tract; these were identified as Pseudomonas aeruginosa on the basis of isolation tests, molecular examinations, and immunohistochemistry. Gram-negative long filamentous organisms in the superficial layers of the necrotic lesions reacted positively with antibodies against Fusobacterium necrophorum subsp. necrophorum. Thus, the necrotic lesions were confirmed to be associated with P. aeruginosa and Fusobacterium spp. This is the first detection of P. aeruginosa in bovine esophageal and glossal ulcers associated with Fusobacterium spp.

Prevalence of fecal viruses and bacteriophage in Canadian farmed mink (Neovison vison)

Recent viral metagenomic studies have demonstrated the diversity of eukaryotic viruses and bacteriophage shed in the feces of domestic species. Although enteric disease is a major concern in the commercial mink farming industry, few etiologic agents have been well characterized. This study aimed to identify viruses shed in the fecal matter of clinically healthy commercial mink from 40 southern Ontario farms. Viral RNA was extracted from 67 pooled fecal samples (30 adult female mink and 37 kit) and amplified for Illumina sequencing on the NextSeq platform, and the resulting contigs were trimmed and assembled using Trimmomatic 0.36.0 and Spades 3.8.0 in iVirus (CyVerse, AZ, USA) and SeqMan NGen 12 (DNAStar, WI, USA). Identification of assembled sequences >100 bp (Geneious 10.1.3) showed an abundance of bacteriophage sequences, mainly from families Siphoviridae (53%), Podoviridae (22%), Myoviridae (20%), Inoviridae (1%), Leviviridae (0.04%), Tectiviridae (0.01%), and Microviridae (0.01%). A diverse range of vertebrate viruses were detected, of which posavirus 3, mink bocavirus, gyroviruses, and avian‐associated viruses were most abundant. Additionally, sequences from nonvertebrate viruses with water and soil‐associated amebal and algal hosts were also highly prevalent. The results of this study show that viruses shed in the fecal matter of healthy commercial mink are highly diverse and could be closely associated with diet, and that more research is necessary to determine how the detected viruses may impact mink health.

Isolation and identification of Salmonella pullorum bacteriophage YSP2 and its use as a therapy for chicken diarrhea

Salmonella pullorum is the major pathogen that is harmful to the poultry industry in developing countries, and the treatment of chicken diarrhea caused by S. pullorum has become increasingly difficult. In this study, a virulent bacteriophage YSP2, which was able to specifically infect Salmonella, was isolated and characterized. Phage YSP2 was classified in the Siphoviridae family and had a short latent period of 10 min. No bacterial virulence- or lysogenesis-related ORF is present in the YSP2 genome, making it eligible for use in phage therapy. Experiments in vivo investigated the potential use of phages as a therapy against diarrhea in chickens caused by S. pullorum in a chicken diarrhea model, demonstrating that a single oral administration of YSP2 (1 × 10¹⁰ PFU/mL, 80 μL/chicken) 2 h after S. pullorum oral administration at a double median lethal dose was sufficient to protect chickens against diarrhea. Gross inspection showed that YSP2 can effectively reduce organ damage and significantly relieve hemorrhage in the intestine and liver tissue. Moreover, YSP2 can maintain a high curative effect when diluted to 10⁸ PFU/mL. In light of its therapeutic effect on chicken diarrhea, YSP2 may serve as an alternative treatment strategy for infections caused by S. pullorum.

Characterization and genomic study of "phiKMV-Like" phage PAXYB1 infecting Pseudomonas aeruginosa

Bacteriophage PAXYB1 was recently isolated from wastewater samples. This phage was chosen based on its lytic properties against clinical isolates of Pseudomonas aeruginosa (P. aeruginosa). In the present study, characterized PAXYB1, clarified its morphological and lytic properties, and analyzed its complete genome sequence. Based on the morphology of PAXYB1, it is a Podoviridae. The linear GC-rich (62.29%) double-stranded DNA genome of PAXYB1 is 43,337 bp including direct terminal repeats (DTRs) of 468 bp. It contains 60 open reading frames (ORFs) that are all encoded within the same strand. We also showed that PAXYB1 is a virulent phage and a new member of the phiKMV-like phages genus. Twenty-eight out of sixty predicted gene products (gps) showed significant homology to proteins of known function, which were confirmed by analyzing the structural proteome. Altogether, our work identified a novel lytic bacteriophage that lyses P. aeruginosa PAO1 and efficiently infects and kills several clinical isolates of P. aeruginosa. This phage has potential for development as a biological disinfectant to control P. aeruginosa infections.

Effects of storage conditions on the stability of spray dried, inhalable bacteriophage powders

This study aimed to develop inhalable powders containing phages active against antibiotic-resistant Pseudomonas aeruginosa for pulmonary delivery. A Pseudomonas phage, PEV2, was spray dried into powder matrices comprising of trehalose (0-80%), mannitol (0-80%) and l-leucine (20%). The resulting powders were stored at various relative humidity (RH) conditions (0, 22 and 60% RH) at 4°C. The phage stability and in vitro aerosol performance of the phage powders were examined at the time of production and after 1, 3 and 12 months storage. After spray drying, a total of 1.3 log titer reduction in phage was observed in the formulations containing 40%, 60% and 80% trehalose, whereas 2.4 and 5.1 log reductions were noted in the formulations containing 20% and no trehalose, respectively. No further reduction in titer occurred for powders stored at 0 and 22% RH even after 12 months, except the formulation containing no trehalose. The 60% RH storage condition had a destructive effect such that no viable phages were detected after 3 and 12 months. When aerosolised, the total lung doses for formulations containing 40%, 60% and 80% trehalose were similar (in the order of 10⁵ pfu). The results demonstrated that spray drying is a suitable method to produce stable phage powders for pulmonary delivery. A powder matrix containing ≥40% trehalose provided good phage preservation and aerosol performances after storage at 0 and 22% RH at 4°C for 12 months.

Genome Analysis of a Novel Broad Host Range Proteobacteria Phage Isolated from a Bioreactor Treating Industrial Wastewater

Bacteriophages are viruses that infect bacteria, and consequently they have a major impact on the development of a microbial population. In this study, the genome of a novel broad host range bacteriophage, Aquamicrobium phage P14, isolated from a wastewater treatment plant, was analyzed. The Aquamicrobium phage P14 was found to infect members of different Proteobacteria classes (Alphaproteobacteria and Betaproteobacteria). This phage contains a 40,551 bp long genome and 60% of its genes had blastx hits. Furthermore, the bacteriophage was found to share more than 50% of its genes with several podoviruses and has the same gene order as other polyvalent bacteriophages. The results obtained in this study led to the conclusion that indeed general features of the genome of the Aquamicrobium phage P14 are shared with other broad host range bacteriophages, however further analysis of the genome is needed in order to identify the specific mechanisms which enable the bacteriophage to infect both Alphaproteobacteria and Betaproteobacteria.

Potential of a lytic bacteriophage to disrupt Acinetobacter baumannii biofilms in vitro

AIM

The ability of Acinetobacter baumannii to form biofilms and develop antibiotic resistance makes it difficult to control infections caused by this bacterium. In this study, we explored the potential of a lytic bacteriophage to disrupt A. baumannii biofilms.

MATERIALS & METHODS

The potential of the lytic bacteriophage to disrupt A. baumannii biofilms was assessed by performing electron microscopy, live/dead bacterial staining, crystal violet staining and by determining adenosine triphosphate release.

RESULTS

The bacteriophage inhibited the formation of and disrupted preformed A. baumannii biofilms. Results of disinfection assay showed that the lytic bacteriophage lysed A. baumannii cells suspended in blood or grown on metal surfaces.

CONCLUSION

These results suggest the potential of the lytic bacteriophage to disrupt A. baumannii biofilms.

Use of phages to control Vibrio splendidus infection in the juvenile sea cucumber Apostichopus japonicus

In the present study, we isolated 3 bacteriophages with the ability to control Vibrio splendidus, a bacterium known to cause disease in the juvenile sea cucumber. These bacteriophages were designated as vB_VspS_VS-ABTNL-1 (PVS-1), vB_VspS_VS-ABTNL-2 (PVS-2) and vB_VspS_VS-ABTNL-3 (PVS-3). The ability of the 3 phages to inhibit the growth of V. splendidus VS-ABTNL was tested in vitro using each of the 3 phages individually or in the form of a cocktail of all 3 phages in the proportion of 1:1:1. All treated cultures produced a significant (P < 0.05) inhibition of growth of V. splendidus VS-ABTNL compared with untreated V. splendidus VS-ABTNL with the cocktail being superior to any of the 3 phages used individually. The lytic capability of the 3 phages was subsequently determined with a Spot Assay Technique performed with 4 isolates of V. splendidus, 3 other Vibrio species and 2 environmental isolates. Both PVS-1 and PVS-2 were lytic to all 4 isolates of V. splendidus while PVS-3 only inhibited the growth of 3 of them. V. splendidus VS-ABTNL was more susceptible to phage PVS-2 than the other 2 phages. In an in vivo performance trial, 360 sea cucumbers (23 ± 2 g) were randomly assigned to 1 of 6 treatments. Each treatment was housed in 3 PVC tanks (38 cm × 54 cm × 80 cm) with 20 sea cucumbers per tank. Six diets were prepared including an unsupplemented control diet, antibiotic treatment diet, 3 diets containing 1 of the 3 phages individually and a diet containing a cocktail of all 3 phages. After 60 days of feeding, all sea cucumber were challenged with V. splendidus VS-ABTNL by immersion in sea water containing a bacterial concentration of 6 × 10(6) CFU/mL for 2 days. The survival rate of sea cucumbers during the next 10 days was 18% for the unsupplemented diet, 82% for the antibiotic treatment, 82% for the phage cocktail, 65% for phage PVS-1, 58% for phage PVS-2 and 50% for phage PVS-3. There were no significant differences in weight gain, ingestion rate or feed conversion among sea cucumber fed the 4 phage treatments compared with those fed the unsupplemented diet (P > 0.05). The levels of nitric oxide synthase and acid phosphatase of sea cucumbers fed phage-containing diets were significantly (P < 0.05) increased compared with those fed the control diet. However, no significant differences (P > 0.05) were detected among the 4 phage-fed treatments. An additional study was conducted in which 60 healthy sea cucumbers (23 ± 2 g) were randomly assigned to a control, an untreated group and a test group to investigate the effects of injecting phages by coelomic injection on the survival rate and enzyme activities in the coelomic fluid of the sea cucumbers. The control was injected with 1 ml of sterilized seawater while the untreated group and the test group were injected with the same volume of V. splendidus-ABTNL culture (3 × 10(5) CFU/mL). Then, the test group was injected with 1 ml of the 3 phage cocktail (MOI = 10). After 48 h, the activities of lysozyme, acid phosphatase and superoxide dismutase were elevated in the untreated group while the levels of these enzymes in the test group were similar to the blank control. After 10-day observation, the survival rate of the sea cucumber was 100% for the blank control, 80% for the test group and 20% for the negative control. The overall results of this experiment indicate that phage therapy increased the survival of sea cucumber infected with V. splendidus VS-ABTNL. The above results demonstrate that using phages, especially a combination of different phages, may be a feasible way to control Vibrio infection in the sea cucumber industry.

Therapeutic effect of Pseudomonas aeruginosa phage YH30 on mink hemorrhagic pneumonia

Hemorrhagic pneumonia caused by Pseudomonas aeruginosa remains one of the most costly infectious diseases among farmed mink and commonly leads to large economic losses during mink production. The objective of this study was to investigate the potential of using phages as a therapy against hemorrhagic pneumonia in mink. A broad-host-range phage from the Podoviridae family, YH30, was isolated using the mink-originating P. aeruginosa (serotype G) D7 strain as a host. The genome of YH30 was 72,192bp (54.92% G+C), contained 86 open reading frames and lacked regions encoding known virulence factors, integration-related proteins or antibiotic resistance determinants. These characteristics make YH30 eligible for use in phage therapy. The results of a curative treatment experiment demonstrated that a single intranasal administration of YH30 was sufficient to cure hemorrhagic pneumonia in mink. The mean colony count of P. aeruginosa in the blood and lung of YH30-protected mink was less than 10(3) CFU/mL (g) within 24h of bacterial challenge and ultimately became undetectable, whereas that in unprotected mink reached more than 10(8) CFU/mL (g). Additionally, YH30 dramatically improved the pathological manifestations of lung injury in mink with hemorrhagic pneumonia. Our work demonstrates the potential of phages to treat P. aeruginosa-caused hemorrhagic pneumonia in mink.

Intranasal treatment with bacteriophage rescues mice from Acinetobacter baumannii-mediated pneumonia

AIM

With the emergence of drug-resistant bacteria, finding alternative agents to treat antibiotic-resistant bacterial infections is imperative.

MATERIALS & METHODS

A mouse pneumonia model was developed by combining cyclophosphamide pretreatment and Acinetobacter baumannii challenge, and a lytic bacteriophage was evaluated for its therapeutic efficacy in this model by examining the survival rate, bacterial load in the lung and lung pathology.

RESULTS

Intranasal instillation with bacteriophage rescued 100% of mice following lethal challenge with A. baumannii. Phage treatment reduced bacterial load in the lung. Microcomputed tomography indicated a reduction in lung inflammation in mice given phage.

CONCLUSION

This research demonstrates that intranasal application of bacteriophage is viable, and could provide complete protection from pneumonia caused by A. baumannii.

Development of expanded host range phage active on biofilms of multi-drug resistant Pseudomonas aeruginosa

Phage therapy is a promising treatment of multi-drug resistant (MDR) bacterial infections but is limited by the narrow host range of phage. To overcome this limitation, we developed a host range expansion (HRE) protocol that expands the host range of Pseudomonas aeruginosa-specific phage by cycles of co-incubation of phage with multiple P. aeruginosa strains. Application of the HRE protocol to a mixture of 4 phages, using 16 P. aeruginosa strains for development, resulted in undefined phage mixtures with greatly expanded host range. Individual phage clones derived from the undefined mixture had expanded host ranges but no individual clone could lyse all of the strains covered by the undefined mixture from which it was isolated. Reconstituting host range-characterized clones into cocktails produced defined cocktails with predictable and broad host ranges. The undefined mixture from the 30th cycle of the mixed-phage HRE (4ϕC30) showed a dose-dependent ability to prevent biofilm formation by, and to reduce a pre-existing biofilm of, 3 P. aeruginosa clinical isolates that produced high amounts of biofilm. A defined cocktail reconstituted from 3 host range-characterized clones had activity on high biofilm-formers susceptible to the phage. Phage therapy was superior to antibiotic therapy (levofloxacin) in a strain of P. aeruginosa that was resistant to levofloxacin. The HRE protocol establishes a rapid approach to create libraries of phage clones and phage cocktails with broad host range, defined composition and anti-biofilm activity.

Therapeutic effect of the YH6 phage in a murine hemorrhagic pneumonia model

The treatment, in farmed mink, of hemorrhagic pneumonia caused by multidrug-resistant Pseudomonas aeruginosa strains has become increasingly difficult. This study investigated the potential use of phages as a therapy against hemorrhagic pneumonia caused by P. aeruginosa in a murine hemorrhagic pneumonia model. An N4-like phage designated YH6 was isolated using P. aeruginosa strain D9. YH6 is a virulent phage with efficient and broad host lytic activity against P. aeruginosa. No bacterial virulence- or lysogenesis-related ORF is present in the YH6 genome, making it eligible for use in phage therapy. In our murine experiments, a single intranasal administration of YH6 (2 × 10(7) PFU) 2 h after D9 intranasal injections at double minimum lethal dose was sufficient to protect mice against hemorrhagic pneumonia. The bacterial load in the lungs of YH6-protected mice was less than 10(3) CFU/g within 24 h after challenge and ultimately became undetectable, whereas the amount of bacteria in the lung tissue derived from unprotected mice was more than 10(8) CFU/g within 24 h after challenge. In view of its protective efficacy in this murine hemorrhagic pneumonia model, YH6 may serve as an alternative treatment strategy for infections caused by multidrug-resistant P. aeruginosa.

Phage therapy of pulmonary infections

It is generally agreed that a bacteriophage-associated phenomenon was first unambiguously observed one-hundred years ago with the findings of Twort in 1915. This was independently followed by complementary observations by d'Hérelle in 1917. D'Hérelle's appreciation of the bacteriophage phenomenon appears to have directly led to the development of phages as antibacterial agents within a variety of contexts, including medical and agricultural. Phage use to combat nuisance bacteria appears to be especially useful where targets are sufficiently problematic, suitably bactericidal phages exist, and alternative approaches are lacking in effectiveness, availability, safety, or cost effectiveness, etc. Phage development as antibacterial agents has been strongest particularly when antibiotics have been less available or useful, e.g., such as in the treatment of chronic infections by antibiotic-resistant bacteria. One relatively under-explored or at least not highly reported use of phages as therapeutic agents has been to combat bacterial infections of the lungs and associated tissues. These infections are diverse in terms of their etiologies, manifestations, and also in terms of potential strategies of phage delivery. Here I review the literature considering the phage therapy of pulmonary and pulmonary-related infections, with emphasis on reports of clinical treatment along with experimental treatment of pulmonary infections using animal models.