Special Issue "Bacteriophage Treatment as an Alternative Technology to Inactivate Pathogenic Bacteria: A Generalized Worldwide Growing Acceptance"

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Medical Microbiology".

Deadline for manuscript submissions: closed (31 December 2020).

Special Issue Editor

Prof. Dr. Adelaide Almeida
E-Mail Website
Guest Editor
Departamento de Biologia, CESAM - Centro de Estudos do Ambiente e do Mar, Campus Universitário de Santiago, Universidade de Aveiro, 3810-193 Aveiro, Portugal
Interests: phage therapy; antimicrobial photodynamic therapy; alternative approaches to antibiotics
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Special Issue Information

Dear Colleagues,

The increasing world-wide rate of antibiotic resistance has led to a higher incidence of bacterial infections that require alternative methods for their control not only in human medicine, but also in other areas, such as in veterinary medicine, the agro-food field and wastewater treatment.

Phage therapy has emerged as an effective solution against bacterial resistant strains that can be used as a substitute or adjuvant to antibiotic therapy. Although in the Eastern Europe phage therapy traditions and practices started in 1919 and continue today in the clinical area, in Western Europe and USA, phage therapy continues to lack any market approval, but has been increasingly used as an experimental therapy for the compassionate treatment of patients experiencing antibiotic failure. Nonetheless, soon after the appearance of the first success results of phage therapy in human medicine, the knowledge was quickly translated to other areas such as veterinary medicine, the food industry, and agriculture and aquaculture, where this approach has been well received and some applications have already been approved.

Nevertheless, while the efficacy of phage therapy has proven to be an efficient alternative to conventional antibiotics, there is still need for new developments to translate the approach into routine treatments. Some important applications of phage therapy in the clinical field that require urgent development, besides fighting infections caused by multidrug-resistant bacteria, are the treatment of infections caused by intracellular bacteria, infections caused by bacteria capable of forming biofilms, bacterial chronic infections, and even the treatment of bacterial systemic infections. In non-clinical fields, it is imperative to study the impact of phage use on the environment and also the effect of abiotic factors on phage viability—such as temperature, pH, salinity and UV radiation—particularly if phage treatment will be used outside where these parameters vary greatly throughout the year. The structural and functional stabilization/preservation of phage particles in supports may be an important strategy to overcome the negative effect of these abiotic factors. Another important aspect, for both clinical and non-clinical applications, is the need to prevent potential bacterial regrowth after treatment due to the development of phage-resistant mutants, which can be hampered by the use of phage cocktails (which at the same time can broaden the action spectrum of the phages) and/or by the use of combined approaches, such as the use of antibiotics during phage treatment. Additionally, in general, more ex vivo and in vivo studies are also imperative to translate the technology to the field.

This Special Issue will gather the most recent knowledge from researchers that demonstrates that bacteriophages are promising candidates for controlling bacterial infection, not only in the clinical field, but also in other areas, such as in veterinary medicine, the food industry, and in agriculture and aquaculture.

Prof. Dr. Adelaide Almeida
Guest Editor

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Published Papers (13 papers)

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Research

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Open AccessArticle
Biocontrol of Soft Rot Caused by Pectobacterium odoriferum with Bacteriophage phiPccP-1 in Kimchi Cabbage
Microorganisms 2021, 9(4), 779; https://doi.org/10.3390/microorganisms9040779 - 08 Apr 2021
Viewed by 265
Abstract
Pectobacterium odoriferum has recently emerged as a widely infective and destructive pathogen causing soft-rot disease in various vegetables. Bacteriophage phiPccP-1 isolated from Pyeongchang, South Korea, showed lytic activity against P. odoriferum Pco14 and two other Pectobacterium species. The transmission electron microscopy and genome [...] Read more.
Pectobacterium odoriferum has recently emerged as a widely infective and destructive pathogen causing soft-rot disease in various vegetables. Bacteriophage phiPccP-1 isolated from Pyeongchang, South Korea, showed lytic activity against P. odoriferum Pco14 and two other Pectobacterium species. The transmission electron microscopy and genome phylograms revealed that phiPccP-1 belongs to the Unyawovirus genus, Studiervirinae subfamily of the Autographivirinae family. Genome comparison showed that its 40,487 bp double-stranded DNA genome shares significant similarity with Pectobacterium phage DU_PP_II with the identity reaching 98% of the genome. The phiPccP-1 application significantly inhibited the development of soft-rot disease in the mature leaves of the harvested Kimchi cabbage up to 48 h after Pco14 inoculation compared to the untreated leaves, suggesting that phiPccP-1 can protect Kimchi cabbage from soft-rot disease after harvest. Remarkably, bioassays with phiPccP-1 in Kimchi cabbage seedlings grown in the growth chamber successfully demonstrated its prophylactic and therapeutic potential in the control of bacterial soft-rot disease in Kimchi cabbage. These results indicate that bacteriophage phiPccP-1 can be used as a potential biological agent for controlling soft rot disease in Kimchi cabbage. Full article
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Open AccessArticle
In Vitro Newly Isolated Environmental Phage Activity against Biofilms Preformed by Pseudomonas aeruginosa from Patients with Cystic Fibrosis
Microorganisms 2021, 9(3), 478; https://doi.org/10.3390/microorganisms9030478 - 25 Feb 2021
Viewed by 409
Abstract
As disease worsens in patients with cystic fibrosis (CF), Pseudomonas aeruginosa (PA) colonizes the lungs, causing pulmonary failure and mortality. Progressively, PA forms typical biofilms, and antibiotic treatments determine multidrug-resistant (MDR) PA strains. To advance new therapies against MDR PA, research has reappraised [...] Read more.
As disease worsens in patients with cystic fibrosis (CF), Pseudomonas aeruginosa (PA) colonizes the lungs, causing pulmonary failure and mortality. Progressively, PA forms typical biofilms, and antibiotic treatments determine multidrug-resistant (MDR) PA strains. To advance new therapies against MDR PA, research has reappraised bacteriophages (phages), viruses naturally infecting bacteria. Because few in vitro studies have tested phages on CF PA biofilms, general reliability remains unclear. This study aimed to test in vitro newly isolated environmental phage activity against PA isolates from patients with CF at Bambino Gesù Children’s Hospital (OBG), Rome, Italy. After testing in vitro phage activities, we combined phages with amikacin, meropenem, and tobramycin against CF PA pre-formed biofilms. We also investigated new emerging morphotypes and bacterial regrowth. We obtained 22 newly isolated phages from various environments, including OBG. In about 94% of 32 CF PA isolates tested, these phages showed in vitro PA lysis. Despite poor efficacy against chronic CF PA, five selected-lytic-phages (Φ4_ZP1, Φ9_ZP2, Φ14_OBG, Φ17_OBG, and Φ19_OBG) showed wide host activity. The Φ4_ZP1-meropenem and Φ14_OBG-tobramycin combinations significantly reduced CF PA biofilms (p < 0.001). To advance potential combined phage-antibiotic therapy, we envisage further in vitro test combinations with newly isolated phages, including those from hospital environments, against CF PA biofilms from early and chronic infections. Full article
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Open AccessArticle
Aztreonam Lysine Increases the Activity of Phages E79 and phiKZ against Pseudomonas aeruginosa PA01
Microorganisms 2021, 9(1), 152; https://doi.org/10.3390/microorganisms9010152 - 12 Jan 2021
Cited by 1 | Viewed by 872
Abstract
Pseudomonas aeruginosa is a pernicious bacterial pathogen that is difficult to treat because of high levels of antibiotic resistance. A promising alternative treatment option for such bacteria is the application of bacteriophages; the correct combination of phages plus antibiotics can produce synergistic inhibitory [...] Read more.
Pseudomonas aeruginosa is a pernicious bacterial pathogen that is difficult to treat because of high levels of antibiotic resistance. A promising alternative treatment option for such bacteria is the application of bacteriophages; the correct combination of phages plus antibiotics can produce synergistic inhibitory effects. In this study, we describe morphological changes induced by sub-MIC levels of the antibiotic aztreonam lysine (AzLys) on P. aeruginosa PA01, which may in part explain the observed phage–antibiotic synergy (PAS). One-step growth curves for phage E79 showed increased adsorption rates, decreased infection latency, accelerated time to lysis and a minor reduction in burst size. Phage E79 plus AzLys PAS was also able to significantly reduce P. aeruginosa biofilm growth over 3-fold as compared to phage treatment alone. Sub-inhibitory AzLys-induced filamentation of P. aeruginosa cells resulted in loss of twitching motility and a reduction in swimming motility, likely due to a reduction in the number of polar Type IV pili and flagella, respectively, on the filamented cell surfaces. Phage phiKZ, which uses Type IV pili as a receptor, did not exhibit increased activity with AzLys at lower sub-inhibitory levels, but still produced phage–antibiotic synergistic killing with sub-inhibitory AzLys. A one-step growth curve indicates that phiKZ in the presence of AzLys also exhibits a decreased infection latency and moderately undergoes accelerated time to lysis. In contrast to prior PAS studies demonstrating that phages undergo delayed time to lysis with cell filamentation, these PAS results show that phages undergo accelerated time to lysis, which therefore suggests that PAS is dependent upon multiple factors, including the type of phages and antibiotics used, and the bacterial host being tested. Full article
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Open AccessArticle
The Union Is Strength: The Synergic Action of Long Fatty Acids and a Bacteriophage against Xanthomonas campestris Biofilm
Microorganisms 2021, 9(1), 60; https://doi.org/10.3390/microorganisms9010060 - 28 Dec 2020
Viewed by 603
Abstract
Xanthomonas campestris pv. campestris is known as the causative agent of black rot disease, which attacks mainly crucifers, severely lowering their global productivity. One of the main virulence factors of this pathogen is its capability to penetrate and form biofilm structures in the [...] Read more.
Xanthomonas campestris pv. campestris is known as the causative agent of black rot disease, which attacks mainly crucifers, severely lowering their global productivity. One of the main virulence factors of this pathogen is its capability to penetrate and form biofilm structures in the xylem vessels. The discovery of novel approaches to crop disease management is urgent and a possible treatment could be aimed at the eradication of biofilm, although anti-biofilm approaches in agricultural microbiology are still rare. Considering the multifactorial nature of biofilm, an effective approach against Xanthomonas campestris implies the use of a multi-targeted or combinatorial strategy. In this paper, an anti-biofilm strategy based on the use of fatty acids and the bacteriophage (Xccφ1)-hydroxyapatite complex was optimized against Xanthomonas campestris mature biofilm. The synergic action of these elements was demonstrated and the efficient removal of Xanthomonas campestris mature biofilm was also proven in a flow cell system, making the proposed approach an effective solution to enhance plant survival in Xanthomonas campestris infections. Moreover, the molecular mechanisms responsible for the efficacy of the proposed treatment were explored. Full article
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Open AccessArticle
Refining the Galleria mellonella Model by Using Stress Marker Genes to Assess Clostridioides difficile Infection and Recuperation during Phage Therapy
Microorganisms 2020, 8(9), 1306; https://doi.org/10.3390/microorganisms8091306 - 27 Aug 2020
Cited by 1 | Viewed by 745
Abstract
The Galleria mellonella is an effective model for probing Clostridioides difficile interactions with phages. Despite valuable insights from this model, the larvae are not easily amenable to assessing detailed clinical responses to either bacteria or phages. Here, larval survival, colonisation and toxin levels [...] Read more.
The Galleria mellonella is an effective model for probing Clostridioides difficile interactions with phages. Despite valuable insights from this model, the larvae are not easily amenable to assessing detailed clinical responses to either bacteria or phages. Here, larval survival, colonisation and toxin levels were compared to expression profiles of 17 G. mellonella stress genes to monitor Clostridiodes difficile infection (CDI), and recuperation during phage therapy. The larvae were infected with a ribotype 014/020 isolate and treated with an optimised phage cocktail. Larvae treated prophylactically with phages and the phage-control larval group were protected, showing the highest survival, and low C. difficile colonisation and toxin rates, compared to co-infection, remedial and bacterial-control larval groups. Expression of growth (9) and reproduction (2) genes were enhanced within prophylaxis and phage-control larval groups compared to the co-infection, remedial and bacterial control groups. In contrast, expression of infection (2), humoral (1) and cellular (3) immunity genes declined in the prophylactic and phage-control groups but increased in the co-infection, remedial and bacterial control larvae. The molecular markers augment the survival, colonisation and toxin data and allow detailed monitoring of CDI and recovery. This data support the use of stress marker genes as tools to analyse clinical symptoms in this model. Full article
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Open AccessArticle
Characterization of Bacteriophages against Pseudomonas Syringae pv. Actinidiae with Potential Use as Natural Antimicrobials in Kiwifruit Plants
Microorganisms 2020, 8(7), 974; https://doi.org/10.3390/microorganisms8070974 - 29 Jun 2020
Cited by 3 | Viewed by 1222
Abstract
Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of a bacterial canker in kiwifruit plants and has caused economic losses worldwide. Currently, the primary strategies to control this pathogen include the use of copper-based compounds and even antibiotics. However, the emergence of [...] Read more.
Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of a bacterial canker in kiwifruit plants and has caused economic losses worldwide. Currently, the primary strategies to control this pathogen include the use of copper-based compounds and even antibiotics. However, the emergence of isolates of Psa that are resistant to these agrochemicals has raised the need for new alternatives to control this pathogen. Bacteriophages have been proposed as an alternative to control bacterial infections in agriculture, including Psa. Here, we show the isolation and characterization of 13 phages with the potential to control Psa infections in kiwifruit plants. The phages were characterized according to their host range and restriction fragment length polymorphism (RFLP) pattern. Four phages were selected according to their lytic effect on the bacteria and their tolerance to different environmental conditions of pH (4–7), temperature (4–37 °C), and solar radiation exposure (30 and 60 min). The selected phages (CHF1, CHF7, CHF19, and CHF21) were sequenced, revealing a high identity with the podophage of Psa phiPSA2. In vitro assays with kiwifruit leaf samples demonstrated that the mixture of phages reduced the Psa bacterial load within three hours post-application and was able to reduce the damage index in 50% of cases. Similarly, assays with kiwifruit plants maintained in greenhouse conditions showed that these phages were able to reduce the Psa bacterial load in more than 50% of cases and produced a significant decrease in the damage index of treated plants after 30 days. Finally, none of the selected phages were able to infect the other bacteria present in the natural microbiota of kiwifruit plants. These results show that bacteriophages are an attractive alternative to control Psa infections in kiwifruit plants. Full article
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Open AccessArticle
Isolation and Characterization of Two Bacteriophages and Their Preventive Effects against Pathogenic Vibrio coralliilyticus Causing Mortality of Pacific Oyster (Crassostrea gigas) Larvae
Microorganisms 2020, 8(6), 926; https://doi.org/10.3390/microorganisms8060926 - 19 Jun 2020
Cited by 1 | Viewed by 696
Abstract
Vibrio coralliilyticus is one of the major pathogens causing mass mortality in marine bivalve larvae aquaculture. To prevent and control Vibrio spp. infections in marine bivalve hatcheries, various antibiotics are overused, resulting in environmental pollution and the creation of multi-drug-resistant strains. Therefore, research [...] Read more.
Vibrio coralliilyticus is one of the major pathogens causing mass mortality in marine bivalve larvae aquaculture. To prevent and control Vibrio spp. infections in marine bivalve hatcheries, various antibiotics are overused, resulting in environmental pollution and the creation of multi-drug-resistant strains. Therefore, research on the development of antibiotic substitutes is required. In this study, we isolated two bacteriophages (phages) that specifically infected pathogenic V. coralliilyticus from an oyster hatchery and designated them as pVco-5 and pVco-7. Both phages were classified as Podoviridae and were stable over a wide range of temperatures (4–37 °C) and at pH 7.0–9.0. Thus, both phages were suitable for application under the environmental conditions of an oyster hatchery. The two phages showed confirmed significant bactericidal efficacy against pathogenic V. coralliilyticus in an in vitro test. In the in vivo experiment, the phage pre-treated groups of Pacific oyster larvae showed significantly lower mortality against V. coralliilyticus infection than untreated control larvae. The results of the present study suggest that both phages could be used in the artificial marine bivalve seedling industry; not only to prevent pathogenic V. coralliilyticus infection, but also to reduce antibiotic overuse. Full article
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Open AccessArticle
Combined Application of Bacteriophages and Carvacrol in the Control of Pseudomonas syringae pv. actinidiae Planktonic and Biofilm Forms
Microorganisms 2020, 8(6), 837; https://doi.org/10.3390/microorganisms8060837 - 02 Jun 2020
Cited by 4 | Viewed by 935
Abstract
Pseudomonas syringae pv. actinidiae (Psa) is the causative agent of the bacterial canker of kiwifruit (Actinidia spp.). Phage therapy has been suggested as a viable alternative approach to controlling this disease, but its efficacy is limited by the emergence of phage-resistant mutants. [...] Read more.
Pseudomonas syringae pv. actinidiae (Psa) is the causative agent of the bacterial canker of kiwifruit (Actinidia spp.). Phage therapy has been suggested as a viable alternative approach to controlling this disease, but its efficacy is limited by the emergence of phage-resistant mutants. Carvacrol is an essential oil that may be useful for the control of Psa. Combination therapies can be used to overcome resistance development. Here, the combination of phages (single phage suspensions of phages PN05 and PN09, and a cocktail of both phages) and carvacrol was investigated in controlling Psa planktonic and biofilm forms in vitro. The phage therapy alone (with phages PN05 and PN09), and the carvacrol alone (minimum inhibitory concentration 2.0 mg/mL), inhibited Psa growth, but the combined effect of both therapies was more effective. The phages alone effectively inhibited Psa growth for 24 h, but Psa regrowth was observed after this time. The carvacrol (2.0 mg/mL) alone prevented the biofilm formation for 48 h, but did not destroy the pre-formed biofilms. The combined treatment, phages and carvacrol (2.0 mg/mL), showed a higher efficacy, preventing Psa regrowth for more than 40 h. In conclusion, the combined treatment with phages and carvacrol may be a promising, environment-friendly and cost-effective approach to controlling Psa in the kiwifruit industry. Full article
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Open AccessArticle
Isolation and Characterization of a Novel Phage for Controlling Multidrug-Resistant Klebsiella pneumoniae
Microorganisms 2020, 8(4), 542; https://doi.org/10.3390/microorganisms8040542 - 09 Apr 2020
Cited by 2 | Viewed by 975
Abstract
The emergence of multidrug-resistant bacterial pathogens has severely threatened global health. A phage with the ability to efficiently and specifically lyse bacteria is considered an alternative for controlling multidrug-resistant bacterial pathogens. The discovery of novel agents for controlling the infections caused by K. [...] Read more.
The emergence of multidrug-resistant bacterial pathogens has severely threatened global health. A phage with the ability to efficiently and specifically lyse bacteria is considered an alternative for controlling multidrug-resistant bacterial pathogens. The discovery of novel agents for controlling the infections caused by K. pneumoniae is urgent due to the broad multidrug-resistance of K. pneumoniae. Only a few phage isolates have been reported to infect multidrug-resistant K. pneumoniae. In this study, by using the multidrug-resistant K. pneumoniae strain as an indicator, a novel phage called vB_KleS-HSE3, which maintains high antibacterial activity and high physical stability, was isolated from hospital sewage. This phage infected one of four tested multidrug-resistant K. pneumoniae strains. This phage belongs to the Siphoviridae family and a comparative genomic analysis showed that this phage is part of a novel phage lineage among the Siphoviridae family of phages that infect strains of Klebsiella. Based on its features, the vB_KleS-HSE3 phage has potential for controlling infections caused by multidrug-resistant K. pneumoniae. Full article
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Open AccessArticle
A Frameshift Mutation in wcaJ Associated with Phage Resistance in Klebsiella pneumoniae
Microorganisms 2020, 8(3), 378; https://doi.org/10.3390/microorganisms8030378 - 07 Mar 2020
Cited by 3 | Viewed by 1260
Abstract
Phage therapy is a potential and promising avenue for controlling the emergence and spread of multidrug-resistant (MDR) Klebsiella pneumoniae, however, the rapid development of anti-phage resistance has been identified as an obstacle to the development of phage therapy. Little is known about [...] Read more.
Phage therapy is a potential and promising avenue for controlling the emergence and spread of multidrug-resistant (MDR) Klebsiella pneumoniae, however, the rapid development of anti-phage resistance has been identified as an obstacle to the development of phage therapy. Little is known about the mechanism employed by MDR K. pneumoniae strains and how they protect themselves from lytic phage predation in vitro and in vivo. In this study, comparative genomic analysis shows undecaprenyl-phosphate glucose-1-phosphate transferase (WcaJ), the initial enzyme catalyzing the biosynthesis of colanic acid, is necessary for the adsorption of phage 117 (Podoviridae) to the host strain Kp36 to complete its lytic life cycle. In-frame deletion of wcaJ alone was sufficient to provide phage 117 resistance in the Kp36 wild-type strain. Complementation assays demonstrated the susceptibility of phage 117, and the mucoid phenotype could be restored in the resistant strain Kp36-117R by expressing the wild-type version of wcaJ. Remarkably, we found that bacterial mobile genetic elements (insA and insB) block phage 117 infections by disrupting the coding region of wcaJ, thus preventing phage adsorption to its phage receptor. Further, we revealed that the wcaJ mutation likely occurred spontaneously rather than adapted by phage 117 predation under unfavorable environments. Taken together, our results address a crucial evolutionary question around the mechanisms of phage–host interactions, increasing our current understandings of anti-phage defense mechanisms in this important MDR pathogen. Full article
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Open AccessArticle
Combined Use of the Ab105-2φΔCI Lytic Mutant Phage and Different Antibiotics in Clinical Isolates of Multi-Resistant Acinetobacter baumannii
Microorganisms 2019, 7(11), 556; https://doi.org/10.3390/microorganisms7110556 - 12 Nov 2019
Cited by 6 | Viewed by 1734
Abstract
Phage therapy is an abandoned antimicrobial therapy that has been resumed in recent years. In this study, we mutated a lysogenic phage from Acinetobacter baumannii into a lytic phage (Ab105-2phiΔCI) that displayed antimicrobial activity against A. baumannii clinical strain Ab177_GEIH-2000 (isolated in the [...] Read more.
Phage therapy is an abandoned antimicrobial therapy that has been resumed in recent years. In this study, we mutated a lysogenic phage from Acinetobacter baumannii into a lytic phage (Ab105-2phiΔCI) that displayed antimicrobial activity against A. baumannii clinical strain Ab177_GEIH-2000 (isolated in the GEIH-REIPI Spanish Multicenter A. baumannii Study II 2000/2010, Umbrella Genbank Bioproject PRJNA422585, and for which meropenem and imipenem MICs of respectively, 32 µg/mL, and 16 µg/mL were obtained). We observed an in vitro synergistic antimicrobial effect (reduction of 4 log–7 log CFU/mL) between meropenem and the lytic phage in all combinations analyzed (Ab105-2phiΔCI mutant at 0.1, 1 and 10 MOI and meropenem at 1/4 and 1/8 MIC). Moreover, bacterial growth was reduced by 8 log CFU/mL for the combination of imipenem at 1/4 MIC plus lytic phage (Ab105-2phiΔCI mutant) and by 4 log CFU/mL for the combination of imipenem at 1/8 MIC plus lytic phage (Ab105-2phiΔCI mutant) at both MOI 1 and 10. These results were confirmed in an in vivo model (G. mellonella), and the combination of imipenem and mutant Ab105-2phiΔCI was most effective (p < 0.05). This approach could help to reduce the emergence of phage resistant bacteria and restore sensitivity to antibiotics used to combat multi-resistant strains of Acinetobacter baumannii. Full article
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Open AccessArticle
Efficiency of Phage φ6 for Biocontrol of Pseudomonas syringae pv. syringae: An in Vitro Preliminary Study
Microorganisms 2019, 7(9), 286; https://doi.org/10.3390/microorganisms7090286 - 23 Aug 2019
Cited by 12 | Viewed by 1680
Abstract
Pseudomonas syringae is a plant-associated bacterial species that has been divided into more than 60 pathovars, with the Pseudomonas syringae pv. syringae being the main causative agent of diseases in a wide variety of fruit trees. The most common treatments for biocontrol of [...] Read more.
Pseudomonas syringae is a plant-associated bacterial species that has been divided into more than 60 pathovars, with the Pseudomonas syringae pv. syringae being the main causative agent of diseases in a wide variety of fruit trees. The most common treatments for biocontrol of P. syringae pv. syringae infections has involved copper derivatives and/or antibiotics. However, these treatments should be avoided due to their high toxicity to the environment and promotion of bacterial resistance. Therefore, it is essential to search for new approaches for controlling P. syringae pv. syringae. Phage therapy can be a useful alternative tool to the conventional treatments to control P. syringae pv. syringae infections in plants. In the present study, the efficacy of bacteriophage (or phage) φ6 (a commercially available phage) was evaluated in the control of P. syringae pv. syringae. As the plants are exposed to the natural variability of physical and chemical parameters, the influence of pH, temperature, solar radiation and UV-B irradiation on phage φ6 viability was also evaluated in order to develop an effective phage therapy protocol. The host range analysis revealed that the phage, besides its host (P. syringae pv. syringae), also infects the Pseudomonas syringae pv. actinidiae CRA-FRU 12.54 and P. syringae pv. actinidiae CRA-FRU 14.10 strains, not infecting strains from the other tested species. Both multiplicities of infection (MOIs) tested, 1 and 100, were effective to inactivate the bacterium, but the MOI 1 (maximum reduction of 3.9 log CFU/mL) was more effective than MOI 100 (maximum reduction of 2.6 log CFU/mL). The viability of phage φ6 was mostly affected by exposure to UV-B irradiation (decrease of 7.3 log PFU/mL after 8 h), exposure to solar radiation (maximum reduction of 2.1 PFU/mL after 6 h), and high temperatures (decrease of 8.5 PFU/mL after 6 days at 37 °C, but a decrease of only 2.0 log PFU/mL after 67 days at 15 °C and 25 °C). The host range, high bacterial control and low rates of development of phage-resistant bacterial clones (1.20 × 10−3) suggest that this phage can be used to control P. syringae pv. syringae infections in plants, but also to control infections by P. syringae pv. actinidiae, the causal agent of bacterial canker of kiwifruit. Although the stability of phage φ6 was affected by UV-B and solar radiation, this can be overcome by the application of phage suspensions at the end of the day or at night. Full article
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Review

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Open AccessReview
Exploring Mucin as Adjunct to Phage Therapy
Microorganisms 2021, 9(3), 509; https://doi.org/10.3390/microorganisms9030509 - 28 Feb 2021
Viewed by 500
Abstract
Conventional phage therapy using bacteriophages (phages) for specific targeting of pathogenic bacteria is not always useful as a therapeutic for gastrointestinal (GI) dysfunction. Complex dysbiotic GI disorders such as small intestinal bowel overgrowth (SIBO), ulcerative colitis (UC), or Crohn’s disease (CD) are even [...] Read more.
Conventional phage therapy using bacteriophages (phages) for specific targeting of pathogenic bacteria is not always useful as a therapeutic for gastrointestinal (GI) dysfunction. Complex dysbiotic GI disorders such as small intestinal bowel overgrowth (SIBO), ulcerative colitis (UC), or Crohn’s disease (CD) are even more difficult to treat as these conditions have shifts in multiple populations of bacteria within the microbiome. Such community-level structural changes in the gut microbiota may require an alternative to conventional phage therapy such as fecal virome transfer or a phage cocktail capable of targeting multiple bacterial species. Additionally, manipulation of the GI microenvironment may enhance beneficial bacteria–phage interactions during treatment. Mucin, produced along the entire length of the GI tract to protect the underlying mucosa, is a prominent contributor to the GI microenvironment and may facilitate bacteria–phage interactions in multiple ways, potentially serving as an adjunct during phage therapy. In this review, we will describe what is known about the role of mucin within the GI tract and how its facilitation of bacteria–phage interactions should be considered in any effort directed at optimizing effectiveness of a phage therapy for gastrointestinal dysbiosis. Full article
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