Enhancing the Stability of Bacteriophages Using Physical, Chemical, and Nano-Based Approaches: A Review

Multipronged impact of environmental temperature on Staphylococcus aureus infection by phage Kayvirus rodi: Implications for biofilm control

Environmental cues sometimes have a direct impact on phage particle stability, as well as bacterial physiology and metabolism, having a profound effect on phage infection outcome. Here, we explore the impact of temperature on the interplay between phage Kayvirus rodi (phiIPLA-RODI) and its host, Staphylococcus aureus. Our results show that phiIPLA-RODI is a more effective predator at room (25 °C) compared to body temperature (37 °C) against planktonic cultures of several strains with varying degrees of phage susceptibility. This result differs from most known examples of temperature-dependent phage infection, in which optimum infection is correlated with the host growth rate. Further characterization of this phenomenon was carried out with strains IPLA15 and IPLA16, whose respective MICs were 7 log units and a 1-log unit higher at 37 °C than at 25 °C. Our results demonstrated that the phage also had a greater impact at room temperature during biofilm development and for the treatment of preformed biofilms. There was no difference in phage adsorption between the two temperatures for strain IPLA16. Conversely, adsorption of phiIPLA-RODI to IPLA15 was reduced at 37 °C compared to 25 °C. Moreover, confocal microscopy analysis indicated that the biofilm matrix of both strains has a greater content of PIA/PNAG at 37 °C than at 25 °C. Regarding infection parameters, we observed longer duration of the lytic cycle at 25 °C for both strains, and infection of IPLA15 by phiIPLA-RODI resulted in a smaller burst size at 37 °C than at 25 °C. Finally, we also found that the rate of phage resistant mutant selection was higher at 37 °C for both strains. Altogether, this information highlights the impact that bacterial responses to environmental factors have on phage-host interactions. Moreover, phage phiIPLA-RODI appears to be a highly effective candidate for biofilm disinfection at room temperature, while its efficacy in biofilm-related infections will require combination with other antimicrobials.

Potential of a phage cocktail in the treatment of multidrug-resistant Klebsiella pneumoniae pulmonary infection in mice

The emergence of multidrug-resistant Klebsiella pneumoniae, including carbapenem-resistant K. pneumoniae (CRKP), as one of the most common and notable superbugs, has long been a major threat to public health. As natural predators of bacteria, bacteriophages (or phages) can induce the lysis of bacterial cells. Herein, we report the isolation and characterization of two phages and their efficacy in the control of CRKP. Using the sequence type 11 (ST11) CRKP strain THR60 and its related strain THR60r as the host bacteria, phages GZ7 and GZ9 were isolated from hospital sewage, respectively. GZ7 is a myovirus with a head of 64 nm in diameter and a tail of 97 nm in length, and GZ9 is a siphovirus with a head of 67 nm in diameter and a tail of 175 nm in length. The host spectrum of a phage cocktail consisting of phages GZ7 and GZ9 was 82.4% (42/51 strains). An in vitro antibacterial activity assay demonstrated that the phage cocktail consisting of GZ7 and GZ9 effectively inhibited bacterial growth and suppressed the production of phage-resistant bacteria. In vivo experiment revealed that phage-treated mice exhibited lower K. pneumoniae burdens in the lungs compared to untreated control mice. Additionally, phage-treated mice experienced less body weight loss and had reduced levels of inflammatory cytokines in their lungs. Lung lesion conditions were significantly improved by phage therapy. Notably, the therapeutic effects of the GZ7 + GZ9 cocktail and GZ7 alone on mouse pulmonary infections were nearly equivalent. Therefore, phages GZ7 and GZ9 showed potential as alternatives to antibiotics for treating pneumonia caused by multidrug-resistant K. pneumoniae.

Pseudomonas Phage Lydia and the Evolution of the Mesyanzhinovviridae Family

Phage Lydia, a newly isolated siphovirus infecting Pseudomonas aeruginosa, was characterized with respect to its basic kinetic properties and subjected to comparative bioinformatic analysis with related phages. The phage exhibited a restricted host range, with lytic activity observed against 7 of 30 tested isolates. The genome of phage Lydia consists of a 61,986 bp dsDNA molecule and contains 89 predicted genes. Bioinformatic analysis suggests the presence of a DNA modification system, but no apparent genes associated with lysogeny or antibiotic resistance were identified. Taxonomic classification places Lydia within the Mesyanzhinovviridae family, Rabinowitzvirinae subfamily, and Yuavirus genus, with the closest relation to Pseudomonas virus M6. Comprehensive bioinformatic studies, including structural modelling and analysis of phage proteins, as well as comparative taxonomic, phylogenomic, and pangenomic analyses of the Mesyanzhinovviridae family, revealed relationships between proteins of Mesyanzhinovviridae phages, proteins from other phage groups, encapsulins, and a gene transfer agent (GTA) particle from Rhodobacter capsulatus. These analyses uncovered patterns of evolutionary history within the family, characterized by genetic exchange events alongside the maintenance of a common genomic architecture, leading to the emergence of new groups within the family.

Synergistic antimicrobial efficacy of phage cocktails and essential oils against Escherichia coli

This study was designed to evaluate the combined antimicrobial activity of selected phage cocktail (MS2+T7 phages) and essential oils (cinnamon, clove, oregano, and thymol) against Escherichia coli ATCC 15597. To select most effective phages, the lytic abilities of individual phages (MS2, phiX174, and T7) and their phage combinations were assessed using the phage spot test and plaque assay at various multiplicity of infections (MOIs) ranging from 0.01 to 100. The inhibitory effectiveness of selected phage combinations (MS2+T7), treated with and without essential oils (cinnamon, clove, oregano, and thymol; 1/2 × MIC each), against E. coli hosts was evaluated at various MOIs of 0, 0.1, and 1. The antimicrobial effect of phage cocktail (MS2+T7) combined with cinnamon (1/2 × MIC) and thymol (1/2 × MIC) were evaluated using time-kill curve assay for 48 h at 37°C. The 48-h treated cells, including the control, cinnamon, thymol, phage cocktail, and cinnamon-phage cocktail, and thymol-phage cocktail, were further tested for relative fitness, and phage mutant frequency assays. The highest lytic activity of MS2 and T7 phages was observed against E. coli (>6 log reduction) at an MOI of 0.1. The phage combination (MS2+T7) was considerably reduced the number of E. coli by 7 logs (p < 0.05). The lytic activity of MS2+T7 was significantly enhanced in the presence of cinnamon, clove, oregano, and thymol (1/2 × MIC each) after 24-h incubation at 37°C. The combinations of cinnamon-phage cocktail and thymol-phage cocktail effectively reduced the numbers of E. coli by more than 5 log CFU/mL compared to the control after 48 h of incubation at 37°C. The lowest relative fitness (<0.5) and mutant frequency (<10 %) were observed for E. coli treated with the combinations. These findings suggest that combining phage cocktails with essential oils can serve as synergistic antimicrobial agents. Consequently, this study provides valuable insights for developing effective phage therapy strategies and ensuring the sustained effectiveness of phage treatments.

The Role of Active Packaging in the Defense Against Foodborne Pathogens with Particular Attention to Bacteriophages

The increasing demand for food safety and the need to combat emerging foodborne pathogens have driven the development of innovative packaging solutions. Active packaging, particularly those incorporating antimicrobial agents, has emerged as a promising approach to enhance food preservation and safety. Among these agents, bacteriophages (phages) have gained significant attention due to their specificity, efficacy, and natural origin. This manuscript explores the role of active packaging in protecting against foodborne pathogens, with a particular focus on bacteriophages. The review overviews recent advances in antimicrobials in food packaging, followed by a detailed discussion of bacteriophages, including their classification, mode of action, multidisciplinary applications, and their use as antimicrobial agents in active food packaging. The manuscript also highlights commercially available bacteriophage-based products and addresses the challenges and limitations associated with their integration into packaging materials. Despite their potential, issues such as stability, regulatory hurdles, and consumer acceptance remain critical considerations. In conclusion, bacteriophages represent a promising tool in active packaging for enhancing food safety, but further research and innovation are needed to overcome existing barriers and fully realize their potential in the food industry.

The activity of indigo carmine against bacteriophages: an edible antiphage agent

Bacteriophage infections in bacterial cultures pose a significant challenge to industrial bioprocesses, necessitating the development of innovative antiphage solutions. This study explores the antiphage potential of indigo carmine (IC), a common FDA-approved food additive. IC demonstrated selective inactivation of DNA phages (P001, T4, T1, T7, λ) with the EC50 values ranging from 0.105 to 0.006 mg/mL while showing no activity against the RNA phage MS2. Fluorescence correlation spectroscopy (FCS) revealed that IC selectively binds to dsDNA, demonstrated by a significant reduction in the diffusion coefficient, whereas no binding was observed with ssDNA or RNA. Mechanistically, IC permeates the phage capsid, leading to genome ejection and capsid deformation, as confirmed by TEM imaging. Under optimal conditions (50 °C, 220 rpm), IC achieved up to a 7-log reduction in phage titer, with kinetic theory supporting the enhanced collision frequency induced by agitation. Additionally, IC protected E. coli cultures from phage-induced lysis without affecting bacterial growth or protein production, as demonstrated by GFP expression assays. IC's effectiveness and environmental safety, combined with its FDA approval and cost-effectiveness, make it a promising antiphage agent for industrial applications. KEY POINTS: • Indigo carmine effectively inactivates a broad spectrum of bacteriophages, offering protection to bacteria in industrial cultures. • A novel application of indigo carmine as a food-grade, environmentally safe, and FDA-approved antiphage agent protecting bacterial cultures. • Antiphage activity arises from indigo carmine's interaction with DNA within the phage capsid without harming bacterial cells or compromising protein production in bacterial cultures.

Isolation, characterization and liposome-loaded encapsulation of a novel virulent Salmonella phage vB-SeS-01

Introduction

Salmonella is a common foodborne pathogenic bacterium, displaying facultative intracellular parasitic behavior, which can help the escape against antibiotics treatment. Bacteriophages have the potential to control both intracellular and facultative intracellular bacteria and can be developed as antibiotic alternatives.

Methods

This study isolated and characterized vB-SeS-01, a novel Guernseyvirinae phage preying on Salmonella enterica, whose genome is closely related to those of phages SHWT1 and vB-SenS-EnJE1. Furthermore, nine phage-carrying liposome formulations were developed by film hydration method and via liposome extruder.

Results and Discussion

Phage vB-SeS-01 displays strong lysis ability against 9 out of 24 tested S. enterica strains (including the pathogenic "Sendai" and "Enteritidis" serovars), high replicability with a burst size of 111 ± 15 PFU/ cell and a titre up to 2.1 × 1011 PFU/mL, and broad pH (4.0 ~ 13.0) and temperature (4 ~ 80°C) stabilities. Among the nine vB-SeS-01 liposome-carrying formulations, the one encapsulated with PC:Chol:T80:SA = 9:1:2:0.5 without sonication displayed the optimal features. This formulation carried up to 1011 PFU/mL, with an encapsulation rate of 80%, an average size of 172.8 nm, and a polydispersity index (PDI) of 0.087. It remained stable at 4°C and 23°C for at least 21 days and at 37°C for 7 days. Both vB-SeS-01 and vB-SeS-01-loaded liposomes displayed intracellular antimicrobial effects and could reduce the transcription level of some tested intracellular inflammatory factors caused by the infected S. enterica sv. Sendai 16,226 and Enteritidis 50041CMCC.

Chitosan nano-formulation enhances stability and bactericidal activity of the lytic phage HK6

BACKGROUND

Successful treatment of pathogenic bacteria like Enterobacter Cloacae with bacteriophage (phage) counteract some hindrance such as phage stability and immunological clearance. Our research is focused on the encapsulation of phage HK6 within chitosan nanoparticles.

RESULT

Encapsulation significantly improves stability, efficacy, and delivery of phages. Chitosan nanoparticles (CS-NPs) achieve a phage entrapment efficiency of 97%. Fourier-transform infrared spectroscopy (FT-IR) reveals shifts towards higher wavenumbers and a new peak, indicating amide bond formation and successful phage encapsulation. The average particle sizes for CS-NP and phage HK6 encapsulated CS-NPs were 180 ± 10 nm and 297 ± 18 nm, respectively. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses reveal that phage HK6 encapsulated CS-NPs are larger on average than CS-NPs, highlighting successful phage encapsulation. Encapsulated bacteriophages maintain its effectiveness at higher pH levels of 11 and 12. Both encapsulated and free bacteriophages are thermostable between 25 and 60 °C; while at higher temperatures (up to 80 °C), the encapsulated phage is thermally stable. Over four days, 70.57% of phages were released from encapsulated CS-NPs. Encapsulation of bacteriophage HK6 in CS-NPs enhances antibacterial activity within the first 2 h, compared to phage or nanoparticles alone.

CONCLUSION

This suggests that the phage HK6 encapsulated CS-NPs exhibit potentiality as biocontrol agents against resistant microorganisms offering an alternative to phage alone.

Genome sequencing of Escherichia coli phage UFJF_EcSW4 reveals a novel lytic Kayfunavirus species

The Escherichia coli phage UFJF_EcSW4 was isolated from polluted stream water and showed clear lysis plaques on the host, measuring 0.67 ± 0.43 mm, with a titer of 9.57 ± 0.23 log PFU/ml. It demonstrated a very narrow host range, infecting only its host. Additionally, it has a short latent period of 9 min, a burst size of 49 PFU/infected cell, and stability over a wide range of pH, temperature, and free residual chlorine. The phage has a double-stranded DNA genome spanning 40,299 bp, with a GC content of 49.87% and short-direct terminal repeats (DTR) sequences of 286 bp. The UFJF_EcSW4 genome contains 55 genes, organized into functional modules with a unidirectional arrangement, regulated by 22 promoters (three from the phage and 19 from the host) and three Rho-independent terminators. Comparative analysis revealed that the UFJF_EcSW4 genome shares an average genomic similarity of 77.82% with the genome sequences of phages from the Kayfunavirus genus but does not surpass the 95% threshold necessary for species classification. Therefore, the UFJF_EcSW4 is a novel Kayfunavirus UFJF_EcSW4 species belonging to the Studiervirinae subfamily.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04172-7.

Real-time monitoring by interferometric light microscopy of phage suspensions for personalised phage therapy

Phage therapy uses viruses (phages) against antibiotic resistance. Tailoring treatments to specific patient strains requires stocks of various highly concentrated purified phages. It, therefore, faces challenges: titration duration and specificity to a phage/bacteria couple; purification affecting stability; and highly concentrated suspensions tending to aggregate. To address these challenges, interferometric light microscopy (ILM), characterising particles (size, concentration, and visual homogeneity) within minutes, was applied herein to anti-Staphylococcus aureus myovirus phage suspensions. Particle concentration was linearly correlated with phage infectious titre (R2 > 0.97, slope: 3 particles/plaque forming units (PFU)) at various degrees of purification, allowing to approximate the infectious titre for suspensions ≥ 3 × 108 PFU/mL, thereby encompassing most therapeutic doses. Purification narrowed and homogenised particle distribution while maintaining therapeutic concentrations. When compared to dynamic light scattering, electrophoretic mobility, and UV/Visible-spectroscopy, ILM best detected aggregates according to our homemade scoring. Although ILM has certain limitations, such as the inability to detect podoviruses (hydrodynamic diameter < 80 nm), or to measure particles in low-concentrated suspensions (< 108 particles/mL), the present proof-of-concept positions this technique as a valuable quality control tool, as a complement to titration rather than a replacement for this technique, for phage suspensions, paving the way for further investigations.

Synergistic efficacy of phage Henu10 with antibiotics against Shigella dysenteriae with insight into phage resistance and fitness trade-offs

Introduction

The irrational use of antibiotics has facilitated the emergence of multidrug- resistant Shigella spp., undermining the effectiveness of the currently available antibiotics. Consequently, there is an urgent need to explore new approaches, with phage therapy emerging as a promising alternative.

Methods

In this study, we isolated a phage targeting Shigella dysenteriae from sewage samples using DLA methold, designated Henu10. The morphology, biological characteristics, genomic composition, and phylogenetic relationships of Henu10 were thoroughly characterized. To investigate the trade-off relationship between phage resistance and bacterial fitness, phage Henu10-resistant strains R6 and R11 were identified using continuous passage and bidirectional validation methods.

Results

Phage-resistant strains R6 and R11 exhibited impaired adsorption, increased sensitivity to temperature and pH stress, heightened susceptibility to certain antibiotics (such as ciprofloxacin and kanamycin), reduced biofilm-forming capacity, and diminished colonization ability in vivo compared to the wild-type strain.

Discussion

These results indicate that phage Henu10 may effectively control the pathogenic bacteria associated with S. dysenteriae, representing a promising new therapeutic option for treating S. dysenteriae infections.

Bacteriophage entrapment strategies for the treatment of chronic wound infections: a comprehensive review

The growing threat of antimicrobial resistance has made the quest for antibiotic alternatives or synergists one of the most pressing priorities of the 21st century. The emergence of multidrug-resistance in most of the common wound pathogens has amplified the risk of antibiotic-resistant wound infections. Bacteriophages, with their self-replicating ability and targeted specificity, can act as suitable antibiotic alternatives. Nevertheless, targeted delivery of phages to infection sites remains a crucial issue, specifically in the case of topical infections. Hence, different phage delivery systems have been studied in recent years. However, there have been no recent reviews of phage delivery systems focusing exclusively on phage application on wounds. This review provides a compendium of all the major delivery systems that have been used to deliver phages to wound infection sites. Special focus has also been awarded to phage-embedded hydrogels with a discussion on the different aspects to be considered during their preparation.

Formulation of Dual-Functional Nonionic Cetomacrogol Creams Incorporated with Bacteriophage and Human Platelet Lysate for Effective Targeting of MDR P. aeruginosa and Enhanced Wound Healing

Successful development of phage-based therapeutics and their utility predominantly depend on the mode and route of phage administration. Topical and site-directed phage application evokes minimal immune clearance and allows more phage-host adsorption, thereby ensuring higher phage efficacy. However, a notable drawback of conventional topical phage applications is the absence of sustained release. Occlusive emollients guarantee the controlled release of active pharmaceutical ingredients (APIs), thereby facilitating administration, preventing moisture loss, and acting as a skin barrier. In this study, we developed phage and human platelet lysate (h-PL) incorporated cetomacrogol-based creams for combined phage therapy and wound healing. The base material for phage immobilization was formulated by emulsifying paraffin and sterile water with cetomacrogol (emulsifying agent). Specifically, we incorporated a Pseudomonas aeruginosa-infecting lytic phage vB_PaeM_M12PA in the formulation and characterized its genome in this study. Cetomacrogol, a nonionic PEG (polyethylene glycol) based ether, rendered phage stability and allowed initial burst release followed by continuous controlled release of phages from the embedding matrix in the initial 6-8 h. Rheological studies showed that the material has elastic properties with storage moduli (G') values ranging from 109.51 ± 2.10 to 126.02 ± 3.13 kPa, indicating frequency-independent deformation. Platelet lysates in the cream acted as wound healing agents, and in vitro evaluation of cell migration and wound healing capacity of h-PL showed a significant enhancement by the sixth hour compared to untreated groups. The phage-incorporated cream showed sustained phage release in solid media and a significant reduction in bacterial growth in liquid cultures. In vivo wound healing studies in 6-week-old Wistar rats with full-thickness excision wounds and subsequent histopathological studies showed that the formulation enhanced wound healing and tissue restoration efficiency. In conclusion, the study unveils a promising approach for integrated phage therapy and wound healing strategies.

Advancements in Bacteriophages for the Fire Blight Pathogen Erwinia amylovora

Erwinia amylovora, the causative agent of fire blight, causes significant economic losses for farmers worldwide by inflicting severe damage to the production and quality of plants in the Rosaceae family. Historically, fire blight control has primarily relied on the application of copper compounds and antibiotics, such as streptomycin. However, the emergence of antibiotic-resistant strains and growing environmental concerns have highlighted the need for alternative control methods. Recently, there has been a growing interest in adopting bacteriophages (phages) as a biological control strategy. Phages have demonstrated efficacy against the bacterial plant pathogen E. amylovora, including strains that have developed antibiotic resistance. The advantages of phage therapy includes its minimal impact on microbial community equilibrium, the lack of a detrimental impact on plants and beneficial microorganisms, and its capacity to eradicate drug-resistant bacteria. This review addresses recent advances in the isolation and characterization of E. amylovora phages, including their morphology, host range, lysis exertion, genomic characterization, and lysis mechanisms. Furthermore, this review evaluates the environmental tolerance of E. amylovora phages. Despite their potential, E. amylovora phages face certain challenges in practical applications, including stability issues and the risk of lysogenic conversion. This comprehensive review examines the latest developments in the application of phages for controlling fire blight and highlights the potential of E. amylovora phages in plant protection strategies.

A review of the fighting Acinetobacter baumannii on three fronts: antibiotics, phages, and nanoparticles

In the current era of antibiotic resistance, researchers are exploring alternative ways to treat bacterial infections that are resistant to multiple drugs. Acinetobacter baumannii (A. baumannii) is a bacterium that is commonly encountered in clinical settings and is known to be resistant to several drugs. Due to the increase in drug-resistant infections caused by this bacteria, there is an urgent need to investigate alternative treatment options such as phage therapy and combination therapy. Despite the success of phages in some cases, there are some limitations in their clinical application that can be overcome by combining phages with other substrates such as nanoparticles to improve their function. The integration of nanotechnology with phage therapy against A. baumannii promises to overcome antibiotic resistance. By exploiting the targeted delivery and controlled release capabilities of nanoparticles, we can enhance the therapeutic potential of phages while minimizing their limitations. Continued research in this field will undoubtedly pave the way for more effective and precise treatments against A. baumannii infections and provide hope in the fight against antibiotic-resistant bacteria.

Evaluation of Different Formulations on the Viability of Phages for Use in Agriculture

Bacteriophages have been proposed as biological controllers to protect plants against different bacterial pathogens. In this scenario, one of the main challenges is the low viability of phages in plants and under adverse environmental conditions. This work explores the use of 12 compounds and 14 different formulations to increase the viability of a phage mixture that demonstrated biocontrol capacity against Pseudomonas syringae pv. actinidiae (Psa) in kiwi plants. The results showed that the viability of the phage mixture decreases at 44 °C, at a pH lower than 4, and under UV radiation. However, using excipients such as skim milk, casein, and glutamic acid can prevent the viability loss of the phages under these conditions. Likewise, it was demonstrated that the use of these compounds prolongs the presence of phages in kiwi plants from 48 h to at least 96 h. In addition, it was observed that phages remained stable for seven weeks when stored in powder with skim milk, casein, or sucrose after lyophilization and at 4 °C. Finally, the phages with glutamic acid, sucrose, or skim milk maintained their antimicrobial activity against Psa on kiwi leaves and persisted within kiwi plants when added through roots. This study contributes to overcoming the challenges associated with the use of phages as biological controllers in agriculture.

Nanomechanical resilience and thermal stability of RSJ2 phage

As the world moves toward a green economy and sustainable agriculture, bacterial viruses or bacteriophages (phages) become attractive biocontrol agents for controlling crop diseases. Effective utilization of phages in farms requires integrated knowledge of crops, pathogens, phages, and surroundings. Phages must encounter environmental fluctuations, including temperature, and must remain infectious for successful bacteria lysis. This work studied a soilborne RSJ2 phage discovered in Thailand, which can eliminate Ralstonia solanacearum, causing bacterial wilt disease in chili. We investigated how phage infectivity and nanomechanics responded to thermal changes. The plaque-based assay showed that the infectivity of the RSJ2 phage was stable within 24-40 °C, an average temperature fluctuation in tropical regions. The structural examination also showed that the phage remained intact. The nanomechanical property of the phage was inspected by the atomic force microscopy-based nanoindentation. The result revealed that the phage stiffness within 24-40 °C was statistically similar (0.05-0.06 N/m). Upon heating at 40 °C for 1, 5, and 10 h and resting at 25 °C, the stiffness of the phage particles increased to 0.09-0.11 N/m (54-83% increase). The stiffness results suggest structural adaptation of the protein subunits as a response to thermal alteration. The study exhibits that the phage structure is highly dynamic and can nanomechanically respond to varying temperatures. The phage stiffness may reveal insight into phage adaptation to environmental factors. Equipped with the knowledge of phage infectivity, structure, and nanomechanics, we can design practical guidelines for effective phage usage in farming and propelling green and safe agriculture.

Evaluating the Stability of Lytic and Lysogenic Bacteriophages in Various Protectants

Phage therapy has regained value as a potential alternative and a complementary anti-infective approach to antibiotics in the fight against bacterial pathogens. Due to their host specificity, non-pathogenic nature for humans, and low production cost, phages offer an effective opportunity for utilization in healthcare, agriculture, and food preservation. Well-defined storage conditions are essential for commercialization and dissemination of phage usage. For this purpose, in our study, after the isolation and characterization of two different phages, one lytic and the other lysogenic; storage and shelf-life studies of phages were evaluated in a presence of various protectants (glycerol, sodium azide, DMSO with chloroform) and without any protectant during 8-month period at four different temperatures. The short-time stability of the lytic P. syringae phage and lysogenic MRSA phage, which were determined by STEM analysis to belong to the Straboviridae and Siphoviridae families, respectively were also examined for the different temperatures and the pH levels ranging from 1.0 to 14.0. This study revealed the storage-model of phages that exhibit distinct lifecycles, for the first time and provided a theoretical basis for development and application of phages, has yielded valuable findings contributing to understanding of phage biology.

Phage formulations and delivery strategies: Unleashing the potential against antibiotic-resistant bacteria

Bacterial control promoted by bacteriophages (phages) is an attractive tool in the face of the antibiotic crisis triggered by the exacerbated use of these drugs. Despite the growing interest in using these viruses, some gaps still need answers, such as the protection and delivery of phages. Some limitation points involve the degradation of phage proteins by enzymes or inactivation in low-pH environments. In this review, a literature search using keywords related to the field of virus delivery formulations was done to understand the current scenario of using delivery techniques and phage formulations. A total of 2096 raw results were obtained, which resulted in 140 publications after refinement. These studies were analyzed for main application techniques and areas, keywords, and countries. Of the total, 57% of the publications occurred in the last five years, and the encapsulation technique was the most used among the articles analyzed. As excipient agents, lactose, trehalose, mannitol, PEG, and Leucine stand out. The development of phage formulations, protection approaches, their delivery routes, and the knowledge about the best application strategy enables the use of these organisms in several sectors. It can act as a powerful tool against antibiotic-resistant bacteria.

Alginate- and Chitosan-Modified Gelatin Hydrogel Microbeads for Delivery of E. coli Phages

Bacterial infections are among the most significant health problems/concerns worldwide. A very critical concern is the rapidly increasing number of antibiotic-resistant bacteria, which requires much more effective countermeasures. As nature's antibacterial entities, bacteriophages shortly ("phages") are very important alternatives to antibiotics, having many superior features compared with antibiotics. The development of phage-carrying controlled-release formulations is still challenging due to the need to protect their activities in preparation, storage, and use, as well as the need to create more user-friendly forms by considering their application area/site/conditions. Here, we prepared gelatin hydrogel microbeads by a two-step process. Sodium alginate was included for modification within the initial recipes, and these composite microbeads were further coated with chitosan. Their swelling ratio, average diameters, and Zeta potentials were determined, and degradations in HCl were demonstrated. The target bacteria Escherichia coli (E.coli) and its specific phage (T4) were obtained from bacterial culture collections and propagated. Phages were loaded within the microbeads with a simple method. The phage release characteristics were investigated comparatively and were demonstrated here. High release rates were observed from the gelatin microbeads. It was possible to reduce the phage release rate using sodium alginate in the recipe and chitosan coating. Using these gelatin-based microbeads as phage carrier matrices-especially in lyophilized forms-significantly improved the phage stability even at room temperature. It was concluded that phage release from gelatin hydrogel microbeads could be further controlled by alginate and chitosan modifications and that user-friendly lyophilized phage formulations with a much longer shelf life could be produced.

Xanthomonas Phage PBR31: Classifying the Unclassifiable

The ability of bacteriophages to destroy bacteria has made them the subject of extensive research. Interest in bacteriophages has recently increased due to the spread of drug-resistant bacteria, although genomic research has not kept pace with the growth of genomic data. Genomic analysis and, especially, the taxonomic description of bacteriophages are often difficult due to the peculiarities of the evolution of bacteriophages, which often includes the horizontal transfer of genes and genomic modules. The latter is particularly pronounced for temperate bacteriophages, which are capable of integration into the bacterial chromosome. Xanthomonas phage PBR31 is a temperate bacteriophage, which has been neither described nor classified previously, that infects the plant pathogen Xanthomonas campestris pv. campestris. Genomic analysis, including phylogenetic studies, indicated the separation of phage PBR31 from known classified bacteriophages, as well as its distant relationship with other temperate bacteriophages, including the Lederbervirus group. Bioinformatic analysis of proteins revealed distinctive features of PBR31, including the presence of a protein similar to the small subunit of D-family DNA polymerase and advanced lysis machinery. Taxonomic analysis showed the possibility of assigning phage PBR31 to a new taxon, although the complete taxonomic description of Xanthomonas phage PBR31 and other related bacteriophages is complicated by the complex evolutionary history of the formation of its genome. The general biological features of the PBR31 phage were analysed for the first time. Due to its presumably temperate lifestyle, there is doubt as to whether the PBR31 phage is appropriate for phage control purposes. Bioinformatics analysis, however, revealed the presence of cell wall-degrading enzymes that can be utilised for the treatment of bacterial infections.

Bacteriophage therapy for drug-resistant Staphylococcus aureus infections

Drug-resistant Staphylococcus aureus stands as a prominent pathogen in nosocomial and community-acquired infections, capable of inciting various infections at different sites in patients. This includes Staphylococcus aureus bacteremia (SaB), which exhibits a severe infection frequently associated with significant mortality rate of approximately 25%. In the absence of better alternative therapies, antibiotics is still the main approach for treating infections. However, excessive use of antibiotics has, in turn, led to an increase in antimicrobial resistance. Hence, it is imperative that new strategies are developed to control drug-resistant S. aureus infections. Bacteriophages are viruses with the ability to infect bacteria. Bacteriophages, were used to treat bacterial infections before the advent of antibiotics, but were subsequently replaced by antibiotics due to limited theoretical understanding and inefficient preparation processes at the time. Recently, phages have attracted the attention of many researchers again because of the serious problem of antibiotic resistance. This article provides a comprehensive overview of phage biology, animal models, diverse clinical case treatments, and clinical trials in the context of drug-resistant S. aureus phage therapy. It also assesses the strengths and limitations of phage therapy and outlines the future prospects and research directions. This review is expected to offer valuable insights for researchers engaged in phage-based treatments for drug-resistant S. aureus infections.

Bacteriophage entrapped chitosan microgel for the treatment of biofilm-mediated polybacterial infection in burn wounds

Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria are most commonly present in burn wound infections. Multidrug resistance (MDR) and biofilm formation make it difficult to treat these infections. Bacteriophages (BPs) are proven as an effective therapy against MDR as well as biofilm-associated wound infections. In the present work, a naturally inspired bacteriophage cocktail loaded chitosan microparticles-laden topical gel has been developed for the effective treatment of these infections. Bacteriophages against MDR S. aureus (BPSAФ1) and P. aeruginosa (BPPAФ1) were isolated and loaded separately and in combination into the chitosan microparticles (BPSAФ1-CHMPs, BPPAФ1-CHMPs, and MBP-CHMPs), which were later incorporated into the SEPINEO™ P 600 gel (BPSAФ1-CHMPs-gel, BPPAФ1-CHMPs-gel, and MBP-CHMPs-gel). BPs were characterized for their morphology, lytic activity, burst size, and hemocompatibility, and BPs belongs to Caudoviricetes class. Furthermore, BPSAФ1-CHMPs, BPPAФ1-CHMPs, and MBP-CHMPs had an average particle size of 1.19 ± 0.11, 1.42 ± 0.21, and 2.84 ± 0.28 μm, respectively, and expressed promising in vitro antibiofilm eradication potency. The ultrasound and photoacoustic imaging in infected burn wounds demonstrated improved wound healing reduced inflammation and increased oxygen saturation following treatment with BPs formulations. The obtained results suggested that the incorporation of the BPs in the MP-gel protected the BPs, sustained the BPs release, and improved the antibacterial activity.

Phenotypic Characterization and Comparative Genomic Analyses of Mycobacteriophage WIVsmall as A New Member Assigned to F1 Subcluster

In this study, we conducted the morphological observation, biological and genomic characterization, evolutionary analysis, comparative genomics description, and proteome identification of a recently isolated mycobacteriophage, WIVsmall. Morphologically, WIVsmall is classified as a member of the Siphoviridae family, characterized by a flexible tail, measuring approximately 212 nm in length. The double-stranded phage genome DNA of WIVsmall spans 53,359 base pairs, and exhibits a G + C content of 61.01%. The genome of WIVsmall comprises 103 protein-coding genes, while no tRNA genes were detected. The genome annotation unveiled the presence of functional gene clusters responsible for mycobacteriophage assembly and maturation, replication, cell lysis, and functional protein synthesis. Based on the analysis of the phylogenetic tree, the genome of WIVsmall was classified as belonging to subgroup F1. A comparative genomics analysis indicated that the WIVsmall genome exhibited the highest similarity to the phage SG4, with a percentage of 64%. The single-step growth curve analysis of WIVsmall revealed a latent period of 120 min, and an outbreak period of 200 min.

Recent advancements in nanotechnology-based bacteriophage delivery strategies against bacterial ocular infections

Antibiotic resistance is growing as a critical challenge in a variety of disease conditions including ocular infections leading to disastrous effects on the human eyes. Staphylococcus aureus (S. aureus) mediated ocular infections are very common affecting different parts of the eye viz. vitreous chamber, conjunctiva, cornea, anterior and posterior chambers, tear duct, and eyelids. Blepharitis, dacryocystitis, conjunctivitis, keratitis, endophthalmitis, and orbital cellulitis are some of the commonly known ocular infections caused by S. aureus. Some of these infections are so fatal that they could cause bilateral blindness like panophthalmitis and orbital cellulitis, which is caused by methicillin-resistant S. aureus (MRSA) and vancomycin-resistance S. aureus (VRSA). The treatment of S. aureus infections with known antibiotics is becoming gradually difficult because of the development of resistance against multiple antibiotics. Apart from the different combinations and formulation strategies, bacteriophage therapy is growing as an effective alternative to treat such infections. Although the superiority of bacteriophage therapy is well established, yet physical factors (high temperatures, acidic pH, UV-rays, and ionic strength) and pharmaceutical barriers (poor stability, low in-vivo retention, controlled and targeted delivery, immune system neutralization, etc.) have the greatest influence on the viability of phage virions (also phage proteins). A variety of Nanotechnology based formulations such as polymeric nanoparticles, liposomes, dendrimers, nanoemulsions, and nanofibres have been recently reported to overcome the above-mentioned obstacles. In this review, we have compiled all these recent reports and discussed bacteriophage-based nanoformulations techniques for the successful treatment of ocular infections caused by multidrug-resistant S. aureus and other bacteria.