Application of a novel phage vB_SalS-LPSTLL for the biological control of Salmonella in foods

Exploration of the feasibility of clinical application of phage treatment for multidrug-resistant Serratia marcescens-induced pulmonary infection

Serratia marcescens (S. marcescens) commonly induces refractory infection due to its multidrug-resistant nature. To date, there have been no reports on the application of phage treatment for S. marcescens infection. This study was conducted to explore the feasibility of phage application in treating refractory S. marcescens infection by collaborating with a 59-year-old male patient with a pulmonary infection of multidrug-resistant S. marcescens. Our experiments included three domains: i) selection of the appropriate phage, ii) verification of the efficacy and safety of the selected phage, iii) confirmation of phage-bacteria interactions. Our results showed that phage Spe5P4 is appropriate for S. marcescens infection. Treatment with phage Spe5P4 showed good efficacy, manifested as amelioration of symptoms, hydrothorax examinations, and chest computed tomography findings. Phage treatment did not worsen hepatic and renal function, immunity-related indices, or indices of routine blood examination. It did not induce or deteriorate drug resistance of the involved antibiotics. Importantly, no adverse events were reported during the treatment or follow-up periods. Thus, phage treatment showed satisfactory safety. Finally, we found that phage treatment did not increase the bacterial load, cytotoxicity, virulence, or phage resistance of S. marcescens, indicating satisfactory phage-bacteria interactions between Spe5P4 and S. marcescens, which are useful for the future application of phage Spe5P4 against S. marcescens. This work provides evidence and a working basis for further application of phage Spe5P4 in treating refractory S. marcescens infections. We also provided a methodological basis for investigating clinical application of phage treatment against multidrug-resistant bacterial infections in the future.

Isolation, characterization and genomic analysis of the novel Listeria bacteriophage LMLPA3 as a potential antimicrobial in foods

Listeria monocytogenes (LM) is an opportunistic foodborne pathogen responsible for listeriosis in both humans and animals. The disease manifests in a variety of ways, including febrile gastroenteritis, septicemia, meningitis, and in some cases, preterm birth and spontaneous abortion. It is therefore crucial to develop effective strategies to control this bacterium. In this study, we isolated and characterized a novel Listeria phage, named LMLPA3. Morphological and genomic analyses revealed that phage LMLPA3 belongs to the class Caudovirales, family Herelleviridae, Myovirus-like. Phage LMLPA3 demonstrated remarkable stability across a range of pH values (4-10), temperatures (4-50 °C), and high NaCl concentrations (12% w/v). A total of 68 strains, comprising nine serotypes of L. monocytogenes and five other Listeria species, were found to be susceptible to lysis by phage LMLPA3. It is noteworthy that treatment with phage LMLPA3 resulted in a significant disruption of the biofilms formed by seven different serotype strains of L. monocytogenes, in comparison to the control. Furthermore, phage LMLPA3 effectively reduced the number of L. monocytogenes cells by 4 log10 CFU/mL and 2.9 log10 CFU/sample, respectively, in milk and on the surface of raw beef at an MOI of 10000. In light of these findings, it can be concluded that phage LMLPA3 has the potential to serve as an effective antimicrobial in the elimination of L. monocytogenes contamination in foodstuffs.

Characterization of phage vB_EcoP_HC25 and its therapeutic effect on chicken colibacillosis

Bacteriophage therapy has proved to be an attractive candidate for decreasing drug-resistant bacteria. In this study, a novel E. coli phage vB_EcoP_HC25 was isolated from sewage. Phage vB_EcoP_HC25 has an elongated head and a short tail, exhibiting the typical features of the rare C3 morphotype. The burst size was approximately 105 PFU/cell. Phage vB_EcoP_HC25 exhibited good pH range (pH 5-11) and temperature tolerance (<60 °C). The genomic analysis revealed that phage vB_EcoP_HC25 does not carry any virulence factor genes or antibiotic resistance genes. Moreover, it was found that vB_EcoP_HC25 is a promising candidate phage for biocontrol against antibiotic-resistant E. coli in milk and chicken meat. In addition, the results of the mental state, behavior, serum inflammatory factors, and intestinal morphology analyses indicated that phage vB_EcoP_HC25 was effective to control colibacillosis in chicks infected with E. coli.

Prevalence of hypervirulent Klebsiella pneumoniae and application of the novel Klebsiella phage vB_KpnP_D39 for biocontrol of serotypes K1, K2, and K57 in prepared food-related samples

In recent years, the contamination of Klebsiella pneumoniae has raised significant concerns about the potential risks to human health. The presence of K. pneumoniae in prepared food-related samples and efficient control is of importance for ensuring food safety. In this study, 300 samples were collected from markets in Hefei, China, and 45 K. pneumoniae isolates were isolated from aquatic products (n = 30), vegetables (n = 9), and ready-to-eat foods (n = 6), respectively. Among these isolates, the capsular serotypes K1, K2, and K57 accounted for the highest percentage, totaling 33.33 % (15/45), and the predominant sequence types were ST23, ST412, and ST11. Additionally, twenty-six isolates (26.9 %) were identified as hypervirulent K. pneumoniae (hvKp), and all were multidrug-resistant (MDR). Notably, the strains carrying iucA generate higher levels of siderophores compared to those that were negative for iucA (P < 0.01). Furthermore, a novel lytic phage vB_KpnP_D39 (D39), which specifically targets multiple hypervirulent capsular serotypes (K1, K2, and K57), was isolated from sewage samples collected from an effluent treatment plant in Hefei, China. D39 maintained highly lytic activity over a pH range of 3.0 to 11.0 and from 20 to 60 °C. Using transmission electron microscopy, a typical podovirus morphotype of D39 was observed. Genomic analysis indicated that D39 belongs to a novel species within genus Przondovirus, and genes associated with virulence and antibiotic resistance were not identified. In practical applications, D39 has been confirmed to significantly destroy biofilm formation and effectively prevent contamination by K. pneumoniae in food production. These findings provide information about the contamination of prepared food-related samples by MDR-hvKp, and a potential biocontrol agent for prevention and control.

Effectiveness of newly isolated bacteriophages targeting multidrug-resistant Extraintestinal Pathogenic Escherichia coli strain (TZ1_3) in food preservation and mice health modulation

Bacteriophages are promising alternatives for combating multidrug-resistant bacterial infections. Two lytic bacteriophages, named P1 and P3, targeting pathogenic Escherichia coli (ExPEC; strain TZ1_3) were isolated and evaluated for their potential ability to control pathogenic numbers either in ExPEC-contaminated food or ExPEC-infected mice. Results showed that phages significantly reduced ExPEC numbers within 6 and 12 h in contaminated water, milk, beef, and chicken when applied at 106 plaque-forming units (PFU). Notably, phage therapy administered via intraperitoneal injection (1012 PFU) effectively reduced ExPEC numbers in the heart, liver, spleen and kidney, restored α-diversity of gut microbes, and increased levels of acetic (13.98 %-37.58 %) and valeric acid (10.27 %-31.51 %) in ExPEC-infected mice. Additionally, phage injections caused no detrimental effects on body weight (which increased by 6.49 %-8.11 %), and on gut microbes in healthy mice. Overall, this study highlights the potential of phages in controlling foodborne microorganisms.

Bacteriophage application in inhibiting corrosion- producing bacteria

Sulfate-reducing bacteria (SRB) are a major cause of microbially-induced corrosion (MIC) and souring (MIS), leading to significant challenges in industries like oil recovery and wastewater treatment. Due to SRB's resistance to antimicrobial agents, bacteriophage (phage) therapy offers a promising alternative for SRB control. In this study, a novel lytic phage, SRB7757, targeting Desulfovibrio vulgaris, was isolated from sewage. SRB7757 inhibited sulfide production by 92.3% within 24 h and significantly reduced corrosion on metal specimens after 28 days, highlighting its potential in controlling MIC and MIS. Genome analysis revealed SRB7757 has a genome size of 142,573 bp, 217 ORFs, and 6 tRNAs, and belongs to the Chaseviridae family. SRB7757 exhibits a latent period of 4 h, a burst size of ~ 100 PFU/cell, and is stable between 4 °C and 60 °C across a pH range of 2.0-12.0. Two predicted lytic enzymes of SRB7757 demonstrated higher inactivation and biofilm removal rates.

Characterization and release of casein‑sodium alginate embedding phage edible film and the application in controlling of Salmonella contamination in food

Salmonella remains a major foodborne pathogen responsible for food poisoning and poses a serious threat to public health. This study has developed an edible antimicrobial film using bacteriophage (phage) SaTp-04, specifically designed to capture and eliminate Salmonella in food. Optimal film conditions were achieved using casein (CA) and sodium alginate (SA) as the matrix, glycerol as the plasticizer, and phage protector. The mechanical properties and phage encapsulation rate were used as response variables. The presence of phage SaTp-04 did not significantly alter the thickness, tensile strength, elongation at break, water vapor permeability, moisture content, or water solubility of the film. Furthermore, the Fourier Transform Infrared spectroscopy, X-ray diffraction, and microscopic morphology of the phage film were similar to those of the phage-free film. The phage titer in the film remained stable for up to five weeks at 4 °C. Phage release from the film in water followed a first-order kinetics model (y = 85.312 × (1-e-0.106x), R2 = 0.9687). The release amount and rate were lower at 4 °C on LB plate surfaces than at 25 °C. The phage film inhibited Salmonella growth on fresh chicken breast and carrots at 4 and 10 °C. The surface of chicken breast packaged with the phage film showed a reduction of approximately 6 log CFU/cm2 in Salmonella compared to the control, while the carrot surface demonstrated a reduction in Salmonella to below the detection limit (10 CFU/cm2) at 37 °C. These results confirm the feasibility of using phage SaTp-04 CA-SA edible films for food safety, providing a viable strategy for developing targeted capture packaging for foodborne pathogenic bacteria.

Can Bacteriophages Be Effectively Utilized for Disinfection in Animal-Derived Food Products? A Systematic Review

Food safety is a paramount public health concern, particularly with the rise of antimicrobial-resistant bacteria. This systematic review explores the efficacy of bacteriophages as a novel and environmentally sustainable approach to controlling multi-resistant and non-resistant bacterial pathogens in animal-derived food products. Following PRISMA guidelines, data from multiple studies were synthesized to evaluate bacteriophage applications across diverse food matrices, including beef, poultry, seafood, and dairy. The findings highlight significant variability in bacteriophage efficacy, influenced by factors such as food matrix properties, bacterial strains, and application methods. Phage cocktails and their combination with thermal treatments consistently demonstrated superior bacterial reduction compared to single-phage applications, which yielded variable results. Interestingly, the absence of a clear dose-response relationship underscores the need for a more detailed understanding of phage-host interactions and environmental influences. This review addresses a critical gap in the literature by advocating for matrix-specific, targeted phage applications over generalized approaches. Additionally, it underscores the transformative potential of bacteriophages as sustainable alternatives to chemical disinfectants in modern food safety practices. These insights provide a framework for future research aimed at optimizing bacteriophage efficacy and scaling their application in real-world food production systems.

Isolation and characterization of multi-drug-resistant Salmonella phages: Genomic insights and antibacterial efficacy evaluation

Salmonella, a significant foodborne pathogen, is widely associated with foodborne diseases and poses a substantial threat to public health. This study successfully screened and identified three highly effective bacteriophages (GP1-6, GP3-1, GP3-8) capable of lysing multi-drug-resistant Salmonella. These phages were classified as tailed, circular phages belonging to the Jerseyvirus family. Efficiency of plating (EOP) tests demonstrated significant lytic activity of these phages against a wide range of Salmonella strains. They exhibited exceptional stability across a broad range of environmental conditions, including temperature, pH, UV exposure, chloroform treatment, and metal ion concentrations. Notably, these phages possess advantages such as a short latency period and high burst size, with GP3-1 achieving 889 PFU/cell-significantly higher than that reported for other Salmonella phages. In addition to effectively inhibiting Salmonella biofilm formation, these phages were also able to disrupt existing biofilms. We also evaluated the therapeutic effects of the phages and their mixtures on chicken, goose, and tilapia. The results showed that phages significantly inhibited Salmonella growth, especially at 25 °C, where the maximum reduction was 2.28 log CFU/cm2. Notably, while single phages caused a rebound in Salmonella counts after 24 h, the phage cocktail (GP1-6, GP3-1, GP3-8) did not, demonstrating stronger and more sustained inhibitory effects. This study highlights the potential of phage cocktails as an effective strategy for controlling Salmonella contamination in meat products, offering a promising alternative to traditional antimicrobial treatments and contributing to improved food safety and public health.

A Review on Recent Trends in Bacteriophages for Post-Harvest Food Decontamination

Infectious diseases resulting from unsafe food consumption are a global concern. Despite recent advances and control measures in the food industry aimed at fulfilling the growing consumer demand for high-quality and safe food products, infection outbreaks continue to occur. This review stands out by providing an overview of post-harvest food decontamination methods against some of the most important bacterial foodborne pathogens, with particular focus on the advantages and challenges of using phages, including their most recent post-harvest applications directly to food and integration into active food packaging systems, highlighting their potential in providing safer and healthier food products. The already approved commercial phage products and the numerous available studies demonstrate their antibacterial efficacy against some of the most problematic foodborne pathogens in different food products, reinforcing their possible use in the future as a current practice in the food industry for food decontamination. Moreover, the incorporation of phages into packaging materials holds particular promise, providing protection against harsh conditions and enabling their controlled and continuous release into the food matrix. The effectiveness of phage-added packaging materials in reducing the growth of pathogens in food systems has been well-demonstrated. However, there are still some challenges associated with the development of phage-based packaging systems that need to be addressed with future research.

Isolation and characterization of Salmonella Typhimurium monophasic variant phage and its application in foods

Salmonella Typhimurium monophasic variant (STm) is an emerging Salmonella serotype that causes food poisoning through the contamination of various foods, including animal products, vegetables, and fruits. In particular, the increasing prevalence of multidrug-resistant STm highlights the urgent need to develop effective strategies to control this pathogen. In this work, a novel and broad-spectrum Salmonella phage named vB_Sal_TmvP009 was isolated and characterized. Morphological and genomic analyses revealed that phage vB_Sal_TmvP009 belonged to the genus Jerseyvirus. Phage vB_Sal_TmvP009 was tolerant to a wide range of temperatures (-20°C∼60°C) and pH values (3∼12). The optimal multiplicity of phage infection was 0.0001, and it had a shorter latent period (8 min), longer lysis period (70 min), and a burst size of 292 PFU/cell. A total of 13 Salmonella serotypes could be lysed by phage vB_Sal_TmvP009. Furthermore, phage vB_Sal_TmvP009 inhibited the growth of multidrug-resistant Salmonella in lettuce or milk with the highest suppression of 3.4 and 3.7 log CFU/mL within 24 h, respectively. The genome of phage vB_Sal_TmvP009 contains lysin and spanin protein, but no tRNA, virulence factors, or drug resistance-related genes. These findings suggest that phage vB_Sal_TmvP009 is a promising antibacterial agent for controlling Salmonella in the food industry.

Evaluation of the potential of phage phSE-5 to fight Salmonella Typhimurium in milk, liquid whole egg, and eggshell

AIMS

This study aimed to evaluate the potential of phage phSE-5 to inactivate Salmonella enterica serovar Typhimurium in milk (at 4, 10, and 25°C), liquid whole egg, and eggshell (at 25°C for both matrices).

METHODS AND RESULTS

Since the success of phage treatment in food depends on maintaining phage viability towards different food conditions, firstly the stability of phage phSE-5 at different temperatures and pHs was assessed. The effect of phage phSE-5 against S. Typhimurium was then assessed in vitro (liquid culture medium-TSB) and finally in the selected food matrices. Phage phSE-5 was stable for long storage periods (56 days) at pH 7-8 and 4-25°C. At 25°C, the efficacy of phage phSE-5 was matrix-dependent with differences in the sample, relatively to the bacterial control, of 2.7, 4.6, 1.8, and 1.3 log colony-forming units (CFU) ml-1 in TSB, milk, liquid whole egg, and eggshell, respectively. Also, phage phSE-5 led to reductions relatively to the initial bacterial concentration only in TSB and milk with 1.9 and 2.1 log CFU ml-1 reduction, respectively. Additionally, this phage was more efficient at 25°C in the tested matrices than at 10°C (no reduction and 1.7 log CFU ml-1 reduction in TSB and milk, respectively; maximum difference of 1.7 and 3.3 log CFU ml-1 in TSB and milk, respectively) and 4°C (no bacterial reduction/difference was observed in both TSB and milk). However, the decrease in temperature from 25 to 10°C slowed down bacterial regrowth after phage treatment.

CONCLUSIONS

Our results show that phages are promising and environmentally friendly candidates for use as biocontrol agents against S. Typhimurium in milk, liquid whole egg, and eggshell, allowing a reduction in energy costs if carried out at 10°C.

Application of a novel lytic phage to control enterotoxigenic Escherichia coli in dairy food matrices

A novel Escherichia coli phage designated as EC BD was isolated from cattle dung samples. Transmission electron microscopy demonstrated that the morphology of phage EC BD belongs to the family Myoviridae. The efficiency of plating (EOP) and scanning electron microscopy revealed the strong lytic activity of phage EC BD with a large burst size and a short latent period. Whole genome data analysis suggested that phage EC BD was inclined towards being completely lytic and revealed the absence of toxins, virulence and antibiotic resistance genes. Phylogenomic analysis of phage EC BD receptor binding proteins (RBPs) showed 74-100 % similarity with sixteen Enterobacter phages, representing their broad host range. The phage genome contains 262 ORFs, of which 107 displayed a unique pattern and additionally, the presence of a tRNA gene directed their fast replication and high stability. Comparative genome analysis suggested phage EC BD as a novel member of the genus Duplodnaviria and family Myoviridae. The efficiency of phage EC BD was determined in dairy food matrices (milk, cheese and paneer) artificially contaminated with enterotoxigenic E. coli strains ETEC H10407, ETEC K 12S and ETEC PB 176 with a significant reduction of 4.8, 6.0 and 5.3 log CFU/mL in milk and a substantial 4.9, 5.8 and 4.6 log CFU/mL reduction in cheese samples after 6 days at low storage temperature (4 °C); furthermore, within the similar conditions, paneer samples showed 4, 5.1 and 3.5 log CFU/mL reduction. EC BD phage treatment represents the complete eradication of three ETEC strains in liquid and semisolid dairy food matrices. This study suggested that phage EC BD might have potential as a biocontrol approach against ETEC foodborne infections.

Exploration of Phage-Agrochemical Interaction Based on a Novel Potent Phage LPRS20-Targeting Ralstonia solanacearum

Phage therapy has the potential to alleviate plant bacterial wilt. However, the knowledge gap concerning the phage-agrochemical interaction impedes the broader application of phages in agriculture. This study characterized a phage isolate and investigated its interactions with agrochemicals. A novel species within the Ampunavirus genus was proposed, serving phage LPRS20 as a type phage with a broad lytic range and significant antibacterial activity against Ralstonia solanacearum strains infecting tobacco, chili, or tomato. Sensory evaluation of the morphology of tobacco leaves suggested that phage application resulted in negligible harm to plants. Investigations into phage-agrochemical interactions revealed synergisms when LPRS20 was delivered 4 h before thiodiazole-copper as well as LPRS20 in combination with low-concentration berberine. Overall, our findings reveal that phage LPRS20 represents a novel, effective, and eco-friendly biocontrol agent against tobacco bacterial wilt in vivo and in vitro and contributes to the potential integration of phages and agrochemicals for controlling soil-borne pathogens.

Phenotypic Characterization and Genome Analysis of New Broad-Spectrum Virulent Salmophage, Salmonella Phage KKP_3822, for Biocontrol of Multidrug-Resistant Salmonella enterica Strains

Salmonella is one of the main foodborne pathogens. Irrational antibiotic management has led to an increase in the incidence of multidrug-resistant strains. Bacteriophages may be an alternative method of food biopreservation and contribute to reducing the number of food poisonings requiring pharmacotherapy. This study aimed to isolate a bacteriophage (phage) targeting indigenous multidrug-resistant (MDR) Salmonella strains, followed by their biological, morphological, and genomic characterization. In this study we isolated Salmonella phage KKP_3822, targeting MDR Salmonella Manchester strain KKP 1213. Salmonella phage KKP_3822 retained high activity in the temperature range from -20 °C to 40 °C and active acidity from pH 3 to 11. Temperatures of 70 °C and 80 °C and extreme pH values (2 and 12) significantly reduced the phage titer. Its activity decreased proportionally to the time of UV exposure. Genome analysis (linear dsDNA with a length of 114,843 bp) revealed the presence of 27 tRNA genes. Proteins encoded by the vB_Sen-IAFB3822 phage were divided into functional modules related to (i) phage structure/assembly, (ii) DNA replication/modification/regulation, (iii) phage lysis, and (iv) DNA packaging into the capsid. No genes associated with antibiotic resistance or integration into the host genome, markers of temperate bacteriophages, were annotated in the Salmonella phage KKP_3822 genome. Based on morphological features and whole-genome sequence analysis, the newly isolated Salmonella phage KKP_3822 shows the greatest similarity to representatives of tailed phages from the Caudoviricetes class, Demerecviridae family, and Epseptimavirus genus. Genome analysis confirmed the virulent nature of the Salmonella phage KKP_3822, making it a potential candidate for food biocontrol.

Salmonella Phage vB_SpuM_X5: A Novel Approach to Reducing Salmonella Biofilms with Implications for Food Safety

Salmonella, a prevalent foodborne pathogen, poses a significant social and economic strain on both food safety and public health. The application of phages in the control of foodborne pathogens represents an emerging research area. In this study, Salmonella pullorum phage vB_SpuM_X5 (phage X5) was isolated from chicken farm sewage samples. The results revealed that phage X5 is a novel Myoviridae phage. Phage X5 has adequate temperature tolerance (28 °C-60 °C), pH stability (4-12), and a broad host range of Salmonella bacteria (87.50% of tested strains). The addition of phage X5 (MOI of 100 and 1000) to milk inoculated with Salmonella reduced the number of Salmonella by 0.72 to 0.93 log10 CFU/mL and 0.66 to 1.06 log10 CFU/mL at 4 °C and 25 °C, respectively. The addition of phage X5 (MOI of 100 and 1000) to chicken breast inoculated with Salmonella reduced bacterial numbers by 1.13 to 2.42 log10 CFU/mL and 0.81 to 1.25 log10 CFU/mL at 4 °C and 25 °C, respectively. Phage X5 has bactericidal activity against Salmonella and can be used as a potential biological bacteriostatic agent to remove mature biofilms of Salmonella or for the prevention and control of Salmonella.

Potential of bacteriophage phT4A as a biocontrol agent against Escherichia coli in food matrices

Escherichia coli is one of the most prevalent foodborne pathogens, frequently found in meat and dairy products. Current decontamination methods are often associated with changes in organoleptic characteristics, nutrient loss, and potentially harmful side effects. Furthermore, despite the array of available methods, foodborne outbreaks still frequently occur. For this reason, bacteriophages (or simply phages) emerged as a natural alternative for the biocontrol of bacterial contamination in food without altering their organoleptic properties. In this study, the potential of phage phT4A was assessed in the biocontrol of E. coli in liquid (milk) and solid (ham) food matrices. Firstly, as foods have different pH and temperature values, the influence of these parameters on phage phT4A viability was also assessed to develop an effective protocol. Phage phT4A proved to be stable for long storage periods at pH 7-8 (56 days) and temperatures of 4-37 °C (21 days). Before application of phages to inactivate pathogenic bacteria in food, previous assays were carried out in Tryptic Soy Broth (TSB) to study the dynamics of phage-bacteria interaction. Then, the antibacterial potential of phage phT4A was evaluated in the two food matrices at different temperatures (4, 10 and 25 °C). This phage was more efficient at 25 °C in all tested matrices (maximum inactivation of 6.6, 3.9 and 1.8 log CFU/mL in TSB, milk and ham, respectively) than at 10 °C (maximum decrease of 4.7, 2.1 and 1.0 log CFU/mL in TSB, milk and ham, respectively) and 4 °C (maximum reduction of 2.6 and 0.7 log CFU/mL in TSB and milk, respectively). However, the decrease of temperature from 25 °C to 10 and 4 °C prevented bacterial regrowth. The results suggest that during phage treatment, a balance between an incubation temperature that provide effective results in terms of bacterial inactivation by the phages and at the same time prevents or delays bacterial regrowth, is needed. The application of phage phT4A at a temperature of 10 °C can be an effective strategy in terms of bacterial inactivation, delaying bacterial regrowth and also reducing energy costs.

Isolation, characterization, and application of a novel Pseudomonas fluorescens phage vB_PF_Y1-MI in contaminated milk

The food industry has incurred substantial losses from contamination by Pseudomonas fluorescens, emphasizing the critical importance of implementing effective control strategies. Phages are potential sterilizers due to their specific killing abilities and the difficulty bacteria face in developing resistance. However, a significant barrier to their development is the lack of diversity among phage types. In this study, we characterized a novel lytic P. fluorescens phage, named vB_PF_Y1-MI. Phage vB_PF_Y1-MI displayed a latent period of nearly 10 min and a high burst size of 1493 PFU/cell. This phage showed good activity over a wide range of temperature (up to 70 °C) and pH (3-12). The genome of phage vB_PF_Y1-MI spans 93,233 bp with a GC content of 45%. It encompasses 174 open-reading frames and 19 tRNA genes, while no lysogeny or virulence-associated genes were detected. Phylogenetic analysis positions it as a novel unassigned evolutionary lineage within the Caudoviricetes class among related dsDNA phages. Our study provides foundational insights into vB_PF_Y1-MI and emphasizes its potential as an effective biological control agent against P. fluorescens. This research offers crucial theoretical groundwork and technical support for subsequent efforts in preventing and controlling P. fluorescens contamination.

Isolation and Characterization of Two Novel Lytic Bacteriophages against Salmonella typhimurium and Their Biocontrol Potential in Food Products

Foodborne pathogens, such as Salmonella, are major factors that pose significant threats to global food safety and public health. Salmonella typhimurium is a prominent serotype contributing to non-typhoidal salmonellosis, which is a prevalent foodborne illness affecting humans and animals. Bacteriophages are considered one of the most environmentally friendly biocontrol agents, particularly in the food industry, owing to their high specificity and high safety. However, the emergency of phage-resistant mutants limits the biocontrol effect of phage treatment, leading to the requirement for a high diversity of lytic phages. Therefore, the study isolated and characterized two novel lytic Salmonella bacteriophages (SPYS_1 and SPYS_2) targeting S. typhimurium ATCC14028 and evaluated their effectiveness in reducing the contamination rates for milk and chicken tenders. Morphological and genomic analyses indicated that Salmonella phages SPYS_1 and SPYS_2 are novel species classified under the genus Skatevirus and the genus Berlinvirus, respectively. Both phages exhibited high stability across a broad range of thermal and pH conditions. The one-step growth curve result suggested that both phages had a short adsorption time and a large burst size in a single lytic cycle. The phage SPYS_1 demonstrated a noteworthy inhibition effect on the growth of S. typhimurium ATCC14028 in milk, resulting in a ~2-log reduction within the 2 to 4 h range. Overall, both phages have shown significant potential for application in food safety in the future.

Isolation and Characterization of Novel Escherichia coli O157:H7 Phage SPEC13 as a Therapeutic Agent for E. coli Infections In Vitro and In Vivo

Escherichia coli O157:H7 is a recognized food-borne pathogen causing severe food poisoning at low doses. Bacteriophages (phages) are FDA-approved for use in food and are suggested as natural preservatives against specific pathogens. A novel phage must be identified and studied to develop a new natural preservative or antimicrobial agent against E. coli O157:H7. The phage SPEC13 displayed broad host range and was classified within the Ackermannviridae family based on its observed characteristics by a TEM and genome analysis. In 10 min, this phage achieves a remarkable 93% adsorption rate with the host. Its latency period then lasts about 20 min, after which it bursts, releasing an average of 139 ± 3 PFU/cell. It exhibited robustness within a pH range of 4 to 12, indicating resilience under diverse environmental circumstances. Furthermore, SPEC13 demonstrated stability at an ambient temperature up to 60 °C. A whole genome and phylogenetics analysis revealed that SPEC13 is a novel identified phage, lacking a lysogenic life cycle, antibiotic resistance genes, or genes associated with virulence, thereby presenting a promising biological agent for therapeutic application. Animal studies showed that SPEC13 effectively controlled the growth of harmful bacteria, resulting in a significant improvement in colon health, marked by reduced swelling (edema) and tissue damage (mucosal injury). The introduction of SPEC13 resulted in a substantial decrease in quantities of E. coli O157:H7, reducing the bacterial load to approximately 5 log CFU/g of feces. In conclusion, SPEC13 emerges as a promising inclusion in the array of phage therapy, offering a targeted and efficient approach for addressing bacterial infections.

Isolation, characterization, and application of bacteriophage on Vibrio parahaemolyticus biofilm to control seafood contamination

OBJECTIVE

This study intended to isolate a Vibrio-particular phage from the natural environment, analyse its characteristics and genome sequence, and investigate its reduction effect on V. parahaemolyticus biofilm as a biocontrol agent in squid and mackerel.

METHODS

Among 21 phages, phage CAU_VPP01, isolated from beach mud, was chosen for further experiments based on host range and EOP tests. When examining the reduction effect of phage CAU_VPP01 against Vibrio parahaemolyticus biofilms on surfaces (stainless steel [SS] and polyethylene terephthalate [PET]) and food surfaces (squid and mackerel).

RESULTS

The phage showed the most excellent reduction effect at a multiplicity-of-infection (MOI) 10. Three-dimensional images acquired with confocal laser scanning microscopy (CLSM) analysis were quantified using COMSTAT, which showed that biomass, average thickness, and roughness coefficient decreased when treated with the phage. Colour and texture analysis confirmed that the quality of squid and mackerel was maintained after the phage treatment. Finally, a comparison of gene expression levels determined by qRT-PCR analysis showed that the phage treatment induced a decrease in the gene expression of flaA, vp0962, andluxS, as examples.

CONCLUSION

This study indicated that Vibrio-specific phage CAU_VPP01 effectively controlled V. parahaemolyticus biofilms under various conditions and confirmed that the isolated phage could possibly be used as an effective biocontrol weapon in the seafood manufacturing industry.

Evaluating the efficacy of a phage cocktail against Pseudomonas fluorescens group strains in raw milk: microbiological, physical, and chemical analyses

The objective of this study was to investigate the effectiveness of a phage cocktail against Pseudomonas fluorescens group and its effect on the microbial, physical and chemical properties of raw milk during different storage conditions. A phage cocktail consisting of Pseudomonas fluorescens, Pseudomonas tolaasii, and Pseudomonas libanensis phages was prepared. As a result, reductions in fluorescent Pseudomonas counts of up to 3.44 log units for the storage at 4 °C and 2.38 log units for the storage at 25 °C were achieved. Following the phage application, it is found that there was no significant difference in the total mesophilic aerobic bacteria and Enterobacteriaceae counts. However, it was observed that the number of lactic acid bacteria was higher in phage-treated groups. The results also showed that pH values in the phage added groups were lower than the others and the highest titratable acidity was obtained only in the bacteria-inoculated group. As a future perspective, this study suggests that, while keeping the number of target microorganisms under control in the milk with the use of phages during storage, the microbiota and accordingly the quality parameters of the milk can be affected. This work contributes to the development of effective strategies for maintaining the quality and extending the shelf life of milk and dairy products.

Characterization of a novel high-efficiency cracking Burkholderia gladiolus phage vB_BglM_WTB and its application in black fungus

Burkholderia gladiolus (B. gladiolus) is foodborne pathogenic bacteria producing bongkrekic acid (BA), which causes food poisoning and has a mortality rate of up to 40 % or more. However, no drugs have been reported in the literature for the prevention and treatment of this infection. In this study, a phage was identified to control B. gladiolus. The novel phage vB_BglM_WTB (WTB), which lyse B. gladiolus with high efficiency, was isolated from sewage of Huaihe Road Throttle Well Sewage Treatment Plant in Hefei. Transmission electron microscopy showed that WTB had an icosahedral head (69 ± 2 nm) and a long retractable tail (108 ± 2 nm). Its optimal temperature and pH ranges to control B. gladiolus were 25 °C -65 °C and 3-11 respectively. The phage WTB was identified as a linear double-stranded DNA phage of 68, 541 bp with 60.04 % G + C content, with a long latent period of 60 min. Phylogenetic analysis and comparative genetic analysis indicated that phage WTB has low identity (<50 %) with other phages, with the highest similarity to Burkholderia phage Maja (25.7 %), which showed that it does not belong to any previous genera recognized by the International Committee on Taxonomy of Viruses (ICTV) and was a candidate for a new genus within the Caudoviricetes. We have submitted a new proposal to ICTV to create a new genus, Bglawtbvirus. No transfer RNA (tRNA), virulence associated and antibiotic resistance genes were detected in phage WTB. Experimental results indicated that WTB at 4 °C and 25 °C had excellent inhibition activity against B. gladiolus in the black fungus, with an inhibition efficiency of over 99 %. The amount of B. gladiolus in the black fungus was reduced to a minimum of 89 CFU/mL when treated by WTB at 25 °C for 2 h. The inhibition rate remained at 99.97 % even after 12 h. The findings showed that the phage WTB could be applied as a food-cleaning agent for enhancing food safety and contributed to our understanding of phage biology and diversity.

Isolation and characterization of Bacillus cereus bacteriophage DZ1 and its application in foods

Bacillus cereus is a pathogenic bacterium that causes food contamination, resulting in food poisoning such as diarrhea and emesis. Therefore, it is crucial to develop effective strategies to control this bacterium. In this study, we isolated and characterized a novel B. cereus phage, named DZ1. Morphological and genomic analyses revealed that phage DZ1 is a new species belonging to the Andromedavirus genus. Phage DZ1 was tolerant to a wide range of pH values (5-9), temperatures (4-55 ℃), and high concentrations of NaCl solution (1000 mM). B. cereus with 21 different sequence types (STs) can be lysed by phage DZ1. Importantly, phage DZ1 inhibited B. cereus growth in spiked rice substrates or milk up to 36 and 72 h, respectively, with suppression of 3 log. Therefore, phage DZ1 is a useful biocontrol agent for the control of B. cereus in the food industry.

Systematic review and meta-analysis: the efficiency of bacteriophages previously patented against pathogenic bacteria on food

Food-borne diseases are a global public health issue with 1 in 10 people falling ill after eating contaminated food every year. In response, the food industry has implemented several new pathogen control strategies, such as biotechnological tools using the direct application of bacteriophages for biological control. We have undertaken a systematic review and meta-analysis that evaluated the efficiency of patented phages as a biological control for food-borne pathogens and determined the physical-chemical characteristics of the antimicrobial effect. Included and excluded criteria was developed. Included criteria: Phage patent files with an application in biological control on food and scientific articles and book chapters that used phages patented for food biological control. Excluded criteria: Patent documents, scientific articles, and book chapters that included phage therapy in humans, animals, and biological control on plants but did not have an application on food were not considered in our study. The systematic analysis identified 77 documents, 46 scientific articles, and 31 documents of patents and 23 articles was included in the meta-analysis. Listeria monocytogenes and Salmonella sp. comprised most of the targets identified in the screening, so that we focused on these strains to do the meta-analysis. There are a total of 383 and 192 experiments for Listeria and Salmonella phages for quantitative data analysis.Indexing databases for the bibliographic search (Scopus, Web of Science (WoS) and PubMed (Medline) were addressed by an automated script written in Python 3 Python Core Team (2015) and deposited on GitHub ( https://github.com/glenjasper ).A random-effects meta-analysis revealed (i) significant antimicrobial effect of Listeria phages in apple, apple juice, pear, and pear juice, (ii) significant antimicrobial effect of Salmonella phages in eggs, apple, and ready-to-eat chicken, (iii) no heterogeneity was identified in either meta-analysis, (iv) publication bias was detected for Listeria phages but not for Salmonella phages. (v) ListShield and Felix01 phages showed the best result for Listeria and Salmonella biological control, respectively, (vi) concentration of phage and bacteria, time and food had significant effect in the biological control of Listeria, (vii) temperature and time had a significant effect on the antimicrobial activity of Salmonella phages. The systematic review and meta-analyses to determine the efficiency of bacteriophages previously patented against pathogenic bacteria on dairy products, meat, fruits and vegetables. Besides, the discovering of key factors for efficacy, so that future applications of phage biotechnology in foods can be optimally deployed.

Biocontrol of Salmonella Typhimurium in milk, lettuce, raw pork meat and ready-to-eat steamed-chicken breast by using a novel bacteriophage with broad host range

Salmonella spp., one of the most frequently reported bacteria, causes foodborne illness and economic losses. Due to the threat of increasing antibiotic resistant foodborne pathogens, application of bacteriophages as novel antibacterial agents in food matrices has become an emerging strategy. In this study, a novel Salmonella phage PS3-1 with high lytic activity against Salmonella Typhimurium was identified from previously isolated phages. PS3-1 belonged to the class Caudoviricetes with a broad host range, and had relatively short latent period (15 min), large burst size (92 PFU/cell), high pH stability (pH 3.0-11.0) and thermal tolerance (4-60 °C). Genome sequencing analysis showed that PS3-1 genome consisted of 107,110 bp DNA, without antibiotic resistance and virulence related genes. The results of growth curve and time-kill assay showed that PS3-1 not only inhibited the growth of S. Typhimurium, but also effectively decreased the viable cell counts (0.30-4.72 log) after 24-h incubation at 7, 25 and 37 °C (P < 0.05). Moreover, >1.28 log of established biofilm cells were effectively removed after 24-h treatment with PS3-1. Besides, PS3-1 significantly reduced the viability of S. Typhimurium in milk, lettuce, raw pork meat and ready-to-eat steamed-chicken breast at different temperatures (P < 0.05). These results demonstrated that PS3-1 may be an excellent antibacterial agent for controlling S. Typhimurium in food industry.

Isolation, characterization, and application of a novel, lytic phage vB_SalA_KFSST3 with depolymerase for the control of Salmonella and its biofilm on cantaloupe under cold temperature

This study investigated the efficacy of a novel Salmonella phage with depolymerase activity to control S. Typhimurium (ST) and its biofilm on cantaloupes, for the first time, under simulated cold temperature. vB_SalA_KFSST3 forming a halo zone was isolated and purified from a slaughterhouse with a final concentration of 12.1 ± 0.1 log PFU/mL. Based on the morphological and bioinformatics analyses, vB_SalA_KFSST3 was identified as a novel phage belonging to the family Ackermannviridae. Before employing the phage on cantaloupe, its genetic characteristics, specificity, stability, and bactericidal effect were investigated. Genetic analyses confirmed its safety and identified endolysin and two depolymerase domains possessing antibiofilm potential. In addition, the phage exhibited a broad specificity with great efficiencies toward five Salmonella strains at 4 °C, 22 °C, and 37 °C, as well as stable lytic activity over a wide range of pHs (3 to 11) and temperatures (-20 °C to 60 °C). The optimal multiplicity of infection (MOI) and exposure time of phage were determined to be 100 and 2 h, respectively, based on the highest bacterial reduction of ∼2.7 log CFU/mL. Following the formation of ST biofilm on cantaloupe at 4 °C and 22 °C, the cantaloupe was treated with phage at an MOI of 100 for 2 h. The antibiofilm efficacy of phage was evaluated via the plate count method, confocal laser scanning microscopy, and scanning electron microscopy (SEM). The initial biofilm population at 22 °C was significantly greater and more condensed than that at 4 °C. After phage treatment, biofilm population and the percentage of viable ST in biofilm were reduced by ∼4.6 log CFU/cm2 and ∼90% within 2 h, respectively, which were significantly greater than those at 22 °C (∼2.0 log CFU/cm2 and ∼45%) (P < 0.05). SEM images also confirmed more drastic destruction of the cohesive biofilm architecture at 4 °C than at 22 °C. As a result of its cold temperature-robust lytic activity and the contribution of endolysin and two depolymerases, vB_SalA_KFSST3 demonstrated excellent antibiofilm efficacy at cold temperature, highlighting its potential as a promising practical biocontrol agent for the control of ST and its biofilm.

Advanced strategies to overcome the challenges of bacteriophage-based antimicrobial treatments in food and agricultural systems

Bacteriophages (phages), highly prevalent in aquatic and terrestrial environments, have emerged as novel antimicrobial agents in food and agricultural systems. Owing to their efficient and unique infection mechanism, phages offer an alternative to antibiotic therapy as they specifically target their host bacteria without causing antibiotic resistance. However, the real-world applications of phages as antimicrobials are still limited due to their low survivability under harsh conditions and reduced antimicrobial efficacy. There is an unmet need to understand the challenges of using phages in food and agricultural systems and potential strategies to enhance their stability and delivery. This review overviews the challenges of using phages, including acidic conditions, improper temperatures, UV-light irradiation, desiccation, and inefficient delivery. It also summarizes novel strategies such as encapsulation, embedding, and immobilization, which enable improved viability and enhanced delivery. The protein capsid and nucleic acid components of phages are delicate and sensitive to physicochemical stresses. Incorporating phages into biocompatible materials can provide a physical barrier for improving phage stability and enhancing phage delivery, resulting in a high antimicrobial efficacy. In conclusion, the development of phage delivery systems can significantly overcome the challenges associated with phage treatments and reduce the risk of foodborne diseases in the industry.

Biological Characterization of Pseudomonas fluorescens Phage Pf17397_F_PD1 and Its Application in Food Preservation

In order to explore the application prospects of phages for controlling bacterial contamination, a lytic phage Pf17397_F_PD1 (Later abbreviated as PD1) was isolated from fish guts using Pseudomonas fluorescens ATCC 17397 as the host bacterium. The phage displayed short latency (18 min), long lysis period (212 min), and high lysis volume (1.47 × 102 PFU/each cell). It displayed wide temperature (30-70°C) and pH (4-11) tolerance. Genomic comparison revealed a maximum sequence identity of 48.65% between phage PD1 and other identified phages, indicating that PD1 was a new phage. The phage PD1 significantly inhibited the growth of P. fluorescens in milk and grass carp at 4°C and 25°C. Compared to the negative control, bacterial levels in milk stored at 25°C for 48 h were reduced by 2.71 log CFU/mL and 2.84 log CFU/mL at the multiplicity of infection (MOI) of 100 and 1,000, respectively. In contrast, when grass carp were stored at 25°C for 24 h, the bacterial load was reduced by 1.28 log CFU/g and 2.64 log CFU/g compared to the control (MOI of 100 and 1,000). When the phage was applied for preservation of grass carp blocks, total volatile salt nitrogen (TVB-N) values of phage-treated samples increased by 6.8 mg/100 g and 7.5 mg/100 g at MOI of 100 and 1,000, respectively, after 7 days of storage, which was significantly lower than that of the control group (15.83 mg/100 g). This study showed that phage PD1 was a good natural biological antimicrobial agent against P. fluorescens ATCC 17397.

Characterization and application of a lytic jumbo phage ZPAH34 against multidrug-resistant Aeromonas hydrophila

Aeromonas hydrophila is an emerging foodborne pathogen causing human gastroenteritis. Aeromonas species isolated from food such as seafood presented multidrug-resistance (MDR), raising serious concerns regarding food safety and public health. The use of phages to infect bacteria is a defense against drug-resistant pathogens. In this study, phage ZPAH34 isolated from the lake sample exerted lytic activity against MDR A. hydrophila strain ZYAH75 and inhibited the biofilm on different food-contacting surfaces. ZPAH34 has a large dsDNA genome of 234 kb which belongs to a novel jumbo phage. However, its particle size is the smallest of known jumbo phages so far. Based on phylogenetic analysis, ZPAH34 was used to establish a new genus Chaoshanvirus. Biological characterization revealed that ZPAH34 exhibited wide environmental tolerance, and a high rapid adsorb and reproductive capacity. Food biocontrol experiments demonstrated that ZPAH34 reduces the viable count of A. hydrophila on fish fillets (2.31 log) and lettuce (3.28 log) with potential bactericidal effects. This study isolated and characterized jumbo phage ZPAH34 not only enriched the understanding of phage biological entity diversity and evolution because of its minimal virion size with large genome but also was the first usage of jumbo phage in food safety to eliminate A. hydrophila.

Virulent Phage vB_EfaS_WH1 Removes Enterococcus faecalis Biofilm and Inhibits Its Growth on the Surface of Chicken Meat

Enterococcus faecalis is a potential animal and human pathogen. Improper use of antibiotics encourages resistance. Bacteriophages and their derivatives are promising for treating drug-resistant bacterial infections. In this study, phylogenetic and electron microscopy analyses of phage vB_EfaS_WH1 (WH1) isolated from chicken feces revealed it to be a novel phage in the family Siphoviridae. WH1 showed good pH stability (4-11), temperature tolerance (4-60 °C), and broad E. faecalis host range (60% of isolates). Genome sequencing revealed a 56,357 bp double-stranded DNA genome with a G+C content of 39.21%. WH1 effectively destroyed E. faecalis EF01 biofilms, even at low concentrations. When WH1 was applied at 1 × 10⁵ to 1 × 10⁹ PFU/g to chicken breast samples stored at 4 °C, surface growing E. faecalis were appreciably eradicated after 24 h. The phage WH1 showed good antibacterial activity, which could be used as a potential biocontrol agent to reduce the formation of E. faecalis biofilm, and could also be used as an alternative for the control of E. faecalis in chicken products.

Immobilization of Natural Antimicrobial Compounds on Food-Grade Supports as a New Strategy to Preserve Fruit-Derived Foods

The use of natural antimicrobials in the food industry is being proposed as an eco-friendly postharvest technology to preserve fruit-derived foods. In this context, this systematic review aims to describe and discuss the application of naturally occurring antimicrobial compounds in the processing of fruit-derived foods by the PRISMA methodology. In a first step, the use of free natural antimicrobials was investigated as an approach to identify the main families of bioactive compounds employed as food preservatives and the current limitations of this dosage form. Then, the use of immobilized antimicrobials, in an innovative dosage form, was studied by distinguishing two main applications: addition to the food matrix as preservatives or use during processing as technological aids. Having identified the different examples of the immobilization of natural antimicrobial compounds on food-grade supports, the mechanisms of immobilization were studied in detail to provide synthesis and characterization guidelines for future developments. Finally, the contribution of this new technology to decarbonization and energy efficiency of the fruit-derived processing sector and circular economy is discussed in this review.

A systematic review and modeling of the effect of bacteriophages on Salmonella spp. Reduction in chicken meat

Prevention and control of foodborne pathogens are of vital public health importance, and poultry meat is recognized as a major source of Salmonella infection in humans. Therefore, it is necessary to reduce the presence of salmonella in poultry meat. This article provided a systematic review and modeling to assess the effect of various factors on bacteriophages' function on Salmonella spp. Reduction in poultry meat. Twenty-two studies were included based on the inclusion and exclusion criteria mentioned in the methodology. The results showed that each unit increase in bacterial dose, phage dose, and temperature increases the Salmonella reduction by about 7%, 20%, and 1%, respectively. In addition, wild-type phages were more efficient than commercial-type phages, and this result was statistically significant (β = 1.124; p-value <0.001). This multivariate analysis is a helpful tool to predict the role of various factors in the role of phage in reducing Salmonella in poultry meat.

Application of the lytic bacteriophage Rostam to control Salmonella enteritidis in eggs

Foodborne Salmonella enteritidis infections place human health at risk, driven by regular outbreaks and individual cases by different contaminated food materials. This study was conducted to characterize and employ a single bacteriophage as a potential biocontrol agent. Phage Rostam was isolated, characterized and then applied as biocontrol agent against S. enteritidis in liquid whole eggs and eggshell. Rostam is a novel myovirus belonging to the Rosemountvirus genus and active against Escherichia coli and Salmonella spp. Rostam is stable in a pH range from 4 to 10, a salt concentration of 1-9 %, whereas UV radiation gradually reduces phage stability, and its 53 kb genome sequence indicates this phage does not contain known toxins or lysogeny-associated genes. Its latent period is short with a burst size of 151 PFU/cell, under standard growth conditions. Killing curves indicate that at higher multiplicities of infection (MOI), the reduction in S. enteritidis count is more pronounced. Phage Rostam (MOI 10,000) reduces S. enteritidis growth to below the detection limit at 4 °C in both liquid whole eggs and on the eggshell within 24 h. Due to its high lytic activity and stability in relevant conditions, Rostam has the potential to be an efficient biopreservative for egg and egg products.

Combine thermal processing with polyvalent phage LPEK22 to prevent the Escherichia coli and Salmonella enterica contamination in food

Thermal processing is the most frequently used method to destruct bacteria in food processing. However, insufficient thermal processing may lead to the outbreak of foodborne illness. This study combined thermal processing with thermostable phage to prevent food contamination. The thermostable phages were screened which can retain activity at 70 °C for 1 h. Among them, the polyvalent phage LPEK22 was obtained to lyse Escherichia coli and Salmonella enterica, especially several multi-drug resistant bacteria. In milk (liquid food matrix), LPEK22 significantly reduced the E. coli by 5.00 ± 0.18 log₁₀ CFU/mL and S. enterica by 4.20 ± 0.23 log₁₀ CFU/mL after thermal processing at 63 °C for 30 min. For beef sausage (solid food matrix), LPEK22 significantly reduced the E. coli by 2.34 ± 0.17 log₁₀ CFU/cm² and S. enterica by 1.54 ± 0.13 log₁₀ CFU/cm² after thermal processing at 66 °C for 90 s. Genome analysis revealed that LPEK22 was a novel phage with a unique tail spike protein belonging to the family of Ackermannviridae. LPEK22 did not contain lysogenic, drug-resistant, and virulent genes that may compromise the safety of food application. These results determined that LPEK22, a novel polyvalent Ackermannviridae phage, could combine with thermal processing to prevent drug-resistant E. coli and S. enterica both in vitro and in foods.

Characterization of Phage vB_SalM_SPJ41 and the Reduction of Risk of Antibiotic-Resistant Salmonella enterica Contamination in Two Ready-to-Eat Foods

Salmonella enterica is a major cause of foodborne illness, and the emergence of antibiotic-resistant bacteria has led to huge pressures on public health. Phage is a promising strategy for controlling foodborne pathogens. In this study, a novel Salmonella phage vB_SalM_SPJ41 was isolated from poultry farms in Shanghai, China. Phage vB_SalM_SPJ41 was able to lyse multiple serotypes of antibiotic-resistant S. enterica, including S. Enteritidis, S. Typhimurium, S. Shubra, S. Derby, and S. Nchanga. It had a short incubation period and was still active at a temperature <80 °C and in the pH range of 3~11. The phage can effectively inhibit the growth of S. enterica in liquid culture and has a significant inhibitory and destructive effect on the biofilm produced by antibiotic-resistant S. enterica. Moreover, the phage was able to reduce S. Enteritidis and MDR S. Derby in lettuce to below the detection limit at 4 °C. Furthermore, the phage could reduce S. Enteritidis and S. Derby in salmon below the limit of detection at 4 °C, and by 3.9 log₁₀ CFU/g and· 2.1 log₁₀ CFU/g at 15 °C, respectively. In addition, the genomic analysis revealed that the phages did not carry any virulence factor genes or antibiotic resistance genes. Therefore, it was found that vB_SalM_SPJ41 is a promising candidate phage for biocontrol against antibiotic-resistant Salmonella in ready-to-eat foods.

CAM-21, a novel lytic phage with high specificity towards Escherichia coli O157:H7 in food products

Escherichia coli O157:H7 is a foodborne pathogen that has become a serious global concern for food safety. Despite the application of different traditional biocontrol methods in the food industry, food borne disease outbreaks linked to this organism remain. Due to their high specificity, lytic bacteriophages are promising antimicrobial agents that could be utilized to control pathogens in foods. In this study, a novel Escherichia phage, CAM-21, was isolated from a dairy farm environment. CAM-21 showed targeted host specificity towards various serotypes of Shiga toxin-producing E. coli, including O157:H7, O26, O103, and O145. Morphological analyses revealed that CAM-21 has a polyhedron capsid and a contractile tail with a diameter of about 92.83 nm, and length of about 129.75 nm, respectively. CAM-21 showed a strong inhibitory effect on the growth of E. coli O157:H7, even at a multiplicity of infection (MOI) of as low as 0.001. Phage adsorption and one-step growth analysis indicated that the target pathogen was rapidly lysed by CAM-21 that exhibited a short latent time (20 min). Electron microscopic and genomic DNA analyses suggested that CAM-21 is a lytic phage, classified as a new species in the Tequatrovirus genus of the Myoviridae Family. Based on whole genome sequencing, CAM-21 has a double-stranded DNA with 166,962 bp, 265 open reading frames and 11 tRNA. The genome of CAM-21 did not encode toxins, virulence factors, antibiotic resistance, lysogeny or allergens. Phylogenetic and genomic comparative analyses suggested that CAM-21 is a T4-like phage species. The growth of E. coli O157:H7 was effectively controlled in milk, ground beef and baby spinach at MOIs of 1000 and 10,000. CAM-21 significantly (P ≤ 0.05) reduced the bacterial counts of the treated foods, ranging from 1.4-2.0 log CFU/mL in milk to 1.3-1.4 log CFU/g in ground beef and baby spinach. These findings suggest that the lytic phage, CAM-21, is a potential candidate for controlling E. coli O157:H7 contamination in foods.

Properties of a Novel Salmonella Phage L66 and Its Application Based on Electrochemical Sensor-Combined AuNPs to Detect Salmonella

Salmonella is widespread in nature and poses a significant threat to human health and safety. Phage is considered as a new tool for the control of food-borne pathogens. In this study, Salmonella phage L66 (phage L66) was isolated from sewage by using Salmonella Typhimurium ATCC 14028 as the host bacterium, and its basic properties were obtained by biological and bioinformatics analysis. Phage L66 had a broad host spectrum, with an optimal infection complex of 0.1 and an optimal adsorption rate of 90.06%. It also exhibited thermal stability between 30 °C~60 °C and pH stability pH from 3 to 12, and the average lysis amount was 46 PFU/cell. The genome sequence analysis showed that the genome length of phage L66 was 157,675 bp and the average GC content was 46.13%. It was predicted to contain 209 genes, 97 of which were annotated with known functions based on the evolutionary analysis, and phage L66 was attributed to the Kuttervirus genus. Subsequently, an electrochemical sensor using phage L66 as a recognition factor was developed and the working electrode GDE-AuNPs-MPA-Phage L66 was prepared by layer-by-layer assembly for the detection of Salmonella. The slope of the impedance was 0.9985 within the scope from 20 to 2 × 10⁷ CFU/mL of bacterial concentration. The minimum detection limit of the method was 13 CFU/mL, and the average spiked recovery rate was 102.3% with a relative standard deviation of 5.16%. The specificity and stability of this sensor were excellent, and it can be applied for the rapid detection of Salmonella in various foods. It provides a phage-based electrochemical biosensor for the detection of pathogenic bacteria.

From Farm to Fork: Streptococcus suis as a Model for the Development of Novel Phage-Based Biocontrol Agents

Bacterial infections of livestock threaten the sustainability of agriculture and public health through production losses and contamination of food products. While prophylactic and therapeutic application of antibiotics has been successful in managing such infections, the evolution and spread of antibiotic-resistant strains along the food chain and in the environment necessitates the development of alternative or adjunct preventive and/or therapeutic strategies. Additionally, the growing consumer preference for "greener" antibiotic-free food products has reinforced the need for novel and safer approaches to controlling bacterial infections. The use of bacteriophages (phages), which can target and kill bacteria, are increasingly considered as a suitable measure to reduce bacterial infections and contamination in the food industry. This review primarily elaborates on the recent veterinary applications of phages and discusses their merits and limitations. Furthermore, using Streptococcus suis as a model, we describe the prevalence of prophages and the anti-viral defence arsenal in the genome of the pathogen as a means to define the genetic building blocks that are available for the (synthetic) development of phage-based treatments. The data and approach described herein may provide a framework for the development of therapeutics against an array of bacterial pathogens.

An Engineered λ Phage Enables Enhanced and Strain-Specific Killing of Enterohemorrhagic Escherichia coli

Bacteriophages (phages) are ideal alternatives to traditional antimicrobial agents in a world where antimicrobial resistance (AMR) is emerging and spreading at an unprecedented speed. In addition, due to their narrow host ranges, phages are also ideal tools to modulate the gut microbiota in which alterations of specific bacterial strains underlie human diseases, while dysbiosis caused by broad-spectrum antibiotics can be harmful. Here, we engineered a lambda phage (Eλ) to target enterohemorrhagic Escherichia coli (EHEC) that causes a severe, sometimes lethal intestinal infection in humans. We enhanced the killing ability of the Eλ phage by incorporating a CRISPR-Cas3 system into the wild-type λ (wtλ) and the specificity by introducing multiple EHEC-targeting CRISPR spacers while knocking out the lytic gene cro. In vitro experiments showed that the Eλ suppressed the growth of EHEC up to 18 h compared with only 6 h with the wtλ; at the multiplicity of infection (MOI) of 10, the Eλ killed the EHEC cells with ~100% efficiency and did not affect the growth of other laboratory- and human-gut isolated E. coli strains. In addition, the EHEC cells did not develop resistance to the Eλ. Mouse experiments further confirmed the enhanced and strain-specific killing of the Eλ to EHEC, while the overall mouse gut microbiota was not disturbed. Our methods can be used to target other genes that are responsible for antibiotic resistance genes and/or human toxins, engineer other phages, and support in vivo application of the engineered phages. IMPORTANCE Pathogenic strains of Escherichia coli are responsible for 0.8 million deaths per year and together ranked the first among all pathogenic species. Here, we obtained, for the first time, an engineered phage, Eλ, that could specifically and efficiently eliminate EHEC, one of the most common and often lethal pathogens that can spread from person to person. We verified the superior performance of the Eλ over the wild-type phage with in vitro and in vivo experiments and showed that the Eλ could suppress EHEC growth to nondetectable levels, fully rescue the EHEC-infected mice, and rescore disturbed mouse gut microbiota. Our results also indicated that the EHEC did not develop resistance to the Eλ, which has been the biggest challenge in phage therapy. We believe our methods can be used to target other pathogenic strains of E. coli and support in vivo application of the engineered phages.

Application of a novel lytic phage vB_EcoM_SQ17 for the biocontrol of Enterohemorrhagic Escherichia coli O157:H7 and Enterotoxigenic E. coli in food matrices

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 and Enterotoxigenic E. coli (ETEC) are important foodborne pathogens, causing serious food poisoning outbreaks worldwide. Bacteriophages, as novel antibacterial agents, have been increasingly exploited to control foodborne pathogens. In this study, a novel broad-host range lytic phage vB_EcoM_SQ17 (SQ17), was isolated, characterized, and evaluated for its potential to control bacterial counts in vitro and in three different food matrices (milk, raw beef, and fresh lettuce). Phage SQ17 was capable of infecting EHEC O157:H7, ETEC, and other E. coli strains. Morphology, one-step growth, and stability assay showed that phage SQ17 belongs to the Caudovirales order, Myoviridae family, and Mosigvirus genus. It has a short latent period of 10 min, a burst size of 71 PFU/infected cell, high stability between pH 4 to 12 as well as thermostability between 30°C and 60°C for 60 min. Genome sequencing analysis revealed that the genome of SQ17 does not contain any genes associated with antibiotic resistance, toxins, lysogeny, or virulence factors, indicating the potential safe application of phage SQ17 in the food industry. In Luria-Bertani (LB) medium, phage SQ17 significantly decreased the viable counts of EHEC O157:H7 by more than 2.40 log CFU/ml (p < 0.05) after 6 h of incubation at 37°C. Phage SQ17 showed great potential to be applied for biocontrol of EHEC O157:H7 in milk and raw beef. In fresh lettuce, treatment with SQ17 also resulted in significant reduction of viable cell counts of EHEC O157:H7 and ETEC at both 4°C and 25°C. Our results demonstrate that SQ17 is a good candidate for application as an EHEC O157:H7 and ETEC biocontrol agent in the processing stages of food production and food preservation.

Characterization and Preliminary Application of Phage Isolated From Listeria monocytogenes

Listeria monocytogenes (LM) is one of the four major foodborne bacteria that cause bacteremia and meningitis. To explore the control of listeriosis with natural phages, we used the double-layer agar plate method to isolate LM from slaughterhouse sewage and designated LP8. The result of electron microscopy indicated that the phage belonged to the family of Myoviridae. Whole-genome sequencing indicated that the genome size of LP8 is 87,038 bp and contains 120 genes. Mice were infected with LM and treated with penicillin G sodium, LP8, and the combination of these two. From the levels of lymphocyte subsets (CD4+, CD8+), the expression of cytokines (TNF-α, IL1β, IL-10, and IFN-γ), observation of pathological changes in organs (heart, liver, spleen, kidney, and brain), and the bacterial load of the spleen, we concluded the therapeutic effect of LP8 against listeriosis and demonstrate the feasibility of a combined therapy to reduce the use of antibiotics. This provides a new avenue for the treatment of listeriosis.

A Cocktail of Three Virulent Phages Controls Multidrug-Resistant Salmonella Enteritidis Infection in Poultry

Salmonella enterica is not only the most common pathogen of poultry and poultry-derived products but is also a significant foodborne pathogen. In recent years, many S. enterica isolates have exhibited multi-drug resistance, which places huge pressure on global economy and health. Since phages are an attractive alternative to biocontrol pathogens, we isolated a total of 15 Salmonella phages from sewage effluent, sediment, and chicken manure. The GRNsp1, GRNsp3, GRNsp6, GRNsp21, GRNsp27, GRNsp30, GRNsp50, and GRNsp51 phages exhibited a wide host range against S. enterica serovars Enteritidis and Typhimurium in vitro. In particular, GRNsp51 exerted highly efficient lytic effects against a large proportion of S. Enteritidis and S. Typhimurium strains isolated from different regions of China. Meanwhile, GRNsp8 expanded the host range of GRNsp6 and GRNsp51. Based on their host ranges and lytic capacities, GRNsp6, GRNssp8, and GRNsp51 were selected for further investigation. Morphology, one-step growth curves, and stability assays revealed that GRNsp6, GRNsp8, and GRNsp51 all belong to the Caudovirales order and display relatively short latency periods with broad pH and thermal stability. Genomic analysis indicated that the genomes of these three phages contained no genes related to virulence, antibiotic resistance, or lysogeny. In addition, we tested the effectiveness of a cocktail composed of these three phages against S. Enteritidis in a chicken model. Treatment with the oral phage cocktail 24 h before or alongside Salmonella challenge significantly reduced colonization of the intestinal tract and decreased the mRNA expression of IL-6, IFN-γ, and IL-1β in the duodenum. Together, these findings indicate that a cocktail of the GRNsp6, GRNsp8, and GRNsp51 phages could serve as an effective antimicrobial therapeutic agent against multidrug-resistant Salmonella in animal production to mitigate infections by multiple zoonotic Salmonella species.

Salmonella phage akira, infecting selected Salmonella enterica Enteritidis and Typhimurium strains, represents a new lineage of bacteriophages

Some serovars of Salmonella can cause life-threatening diarrhoeal diseases and bacteriemia. The emergence of multidrug-resistant strains has led to a need for alternative treatments such as phage therapy, which requires available, well-described, diverse, and suitable phages. Phage akira was found to lyse 19 out of 32 Salmonella enterica serovars and farm isolates tested, although plaque formation was observed with only two S. Enteritidis and one S. Typhimurium strain. Phage akira encodes anti-defence genes against type 1 R-M systems, is distinct (<65% nucleotide sequence identity) from related phages and has siphovirus morphology. We propose that akira represents a new genus in the class Caudoviricetes.

Bacteriophage therapy in aquaculture: current status and future challenges

The escalation of antibiotic resistance has revitalized bacteriophage (phage) therapy. Recently, phage therapy has been gradually applied in medicine, agriculture, food, and environmental fields due to its distinctive features of high efficiency, specificity, and environmental friendliness compared to antibiotics. Likewise, phage therapy also holds great promise in controlling pathogenic bacteria in aquaculture. The application of phage therapy instead of antibiotics to eliminate pathogenic bacteria such as Vibrio, Pseudomonas, Aeromonas, and Flavobacterium and to reduce fish mortality in aquaculture has been frequently reported. In this context, the present review summarizes and analyzes the current status of phage therapy in aquaculture, focusing on the key parameters of phage application, such as phage isolation, selection, dosage, and administration modes, and introducing the strategies and methods to boost efficacy and restrain the emergence of resistance. In addition, we discussed the human safety, environmental friendliness, and techno-economic practicability of phage therapy in aquaculture. Finally, this review outlines the current challenges of phage therapy application in aquaculture from the perspectives of phage resistance, phage-mediated resistance gene transfer, and effects on the host immune system.

Characterization of a T4-like Bacteriophage vB_EcoM-Sa45lw as a Potential Biocontrol Agent for Shiga Toxin-Producing Escherichia coli O45 Contaminated on Mung Bean Seeds

Application of lytic bacteriophages is a promising and alternative intervention technology to relieve antibiotic resistance pressure and control bacterial pathogens in the food industry. Despite the increase of produce-associated outbreaks caused by non-O157 Shiga toxin-producing E. coli (STEC) serogroups, the information of phage application on sprouts to mitigate these pathogens is lacking. Therefore, the objective of this study was to characterize a T4-like Escherichia phage vB_EcoM-Sa45lw (or Sa45lw) for the biocontrol potential of STEC O45 on mung bean seeds. Phage Sa45lw belongs to the Tequatrovirus genus under the Myoviridae family and displays a close evolutionary relationship with a STEC O157-infecting phage AR1. Sa45lw contains a long-tail fiber gene (gp37), sharing high genetic similarity with the counterpart of Escherichia phage KIT03, and a unique tail lysozyme (gp5) to distinguish its host range (STEC O157, O45, ATCC 13706, and Salmonella Montevideo and Thompson) from phage KIT03 (O157 and Salmonella enterica). No stx, antibiotic resistance, and lysogenic genes were found in the Sa45lw genome. The phage has a latent period of 27 min with an estimated burst size of 80 PFU/CFU and is stable at a wide range of pH (pH 3 to pH 10.5) and temperatures (-80°C to 50°C). Phage Sa45lw is particularly effective in reducing E. coli O45:H16 both in vitro (MOI = 10) by 5 log and upon application (MOI = 1,000) on the contaminated mung bean seeds for 15 min by 2 log at 25°C. These findings highlight the potential of phage application against non-O157 STEC on sprout seeds. IMPORTANCE Seeds contaminated with foodborne pathogens, such as Shiga toxin-producing E. coli, are the primary sources of contamination in produce and have contributed to numerous foodborne outbreaks. Antibiotic resistance has been a long-lasting issue that poses a threat to human health and the food industry. Therefore, developing novel antimicrobial interventions, such as bacteriophage application, is pivotal to combat these pathogens. This study characterized a lytic bacteriophage Sa45lw as an alternative antimicrobial agent to control pathogenic E. coli on the contaminated mung bean seeds. The phage exhibited antimicrobial effects against both pathogenic E. coli and Salmonella without containing virulent or lysogenic genes that could compromise the safety of phage application. In addition, after 15 min of phage treatment, Sa45lw mitigated E. coli O45:H16 on the contaminated mung bean seeds by a 2-log reduction at room temperature, demonstrating the biocontrol potential of non-O157 Shiga toxin-producing E. coli on sprout seeds.

Characterization and Genome Study of Novel Lytic Bacteriophages against Prevailing Saprophytic Bacterial Microflora of Minimally Processed Plant-Based Food Products

The food industry is still searching for novel solutions to effectively ensure the microbiological safety of food, especially fresh and minimally processed food products. Nowadays, the use of bacteriophages as potential biological control agents in microbiological food safety and preservation is a promising strategy. The aim of the study was the isolation and comprehensive characterization of novel bacteriophages with lytic activity against saprophytic bacterial microflora of minimally processed plant-based food products, such as mixed leaf salads. From 43 phages isolated from municipal sewage, four phages, namely Enterobacter phage KKP 3263, Citrobacter phage KKP 3664, Enterobacter phage KKP 3262, and Serratia phage KKP 3264 have lytic activity against Enterobacter ludwigii KKP 3083, Citrobacter freundii KKP 3655, Enterobacter cloacae KKP 3082, and Serratia fonticola KKP 3084 bacterial strains, respectively. Transmission electron microscopy (TEM) and whole-genome sequencing (WGS) identified Enterobacter phage KKP 3263 as an Autographiviridae, and Citrobacter phage KKP 3664, Enterobacter phage KKP 3262, and Serratia phage KKP 3264 as members of the Myoviridae family. Genome sequencing revealed that these phages have linear double-stranded DNA (dsDNA) with sizes of 39,418 bp (KKP 3263), 61,608 bp (KKP 3664), 84,075 bp (KKP 3262), and 148,182 bp (KKP 3264). No antibiotic resistance genes, virulence factors, integrase, recombinase, or repressors, which are the main markers of lysogenic viruses, were annotated in phage genomes. Serratia phage KKP 3264 showed the greatest growth inhibition of Serratia fonticola KKP 3084 strain. The use of MOI 1.0 caused an almost 5-fold decrease in the value of the specific growth rate coefficient. The phages retained their lytic activity in a wide range of temperatures (from -20 °C to 50 °C) and active acidity values (pH from 4 to 11). All phages retained at least 70% of lytic activity at 60 °C. At 80 °C, no lytic activity against tested bacterial strains was observed. Serratia phage KKP 3264 was the most resistant to chemical factors, by maintaining high lytic activity across a broader range of pH from 3 to 11. The results indicated that these phages could be a potential biological control agent against saprophytic bacterial microflora of minimally processed plant-based food products.

Characterization of a New and Efficient Polyvalent Phage Infecting E. coli O157:H7, Salmonella spp., and Shigella sonnei

Ongoing outbreaks of foodborne diseases remain a significant public health concern. Lytic phages provide promising attributes as biocontrol agents. This study characterized KFS-EC3, a polyvalent and lytic phage, which was isolated from slaughterhouse sewage and purified by cesium chloride density centrifugation. Host range and efficiency of plating analyses revealed that KFS-EC3 is polyvalent and can efficiently infect E. coli O157:H7, Salmonella spp., and Shigella sonnei. KFS-EC3 had a latent time of 20 min and burst size of ~71 phages/infected cell. KFS-EC3 was stable and infectious following storage at a pH range of 3 to 11 and a temperature range of -70 °C to 60 °C. KFS-EC3 could inhibit E. coli O157:H7 growth by 2 logs up to 52 h even at the lowest MOI of 0.001. Genomic analysis of KFS-EC3 revealed that it consisted of 167,440 bp and 273 ORFs identified as functional genes, without any genes associated with antibiotic resistance, virulence, allergenicity, and lysogenicity. This phage was finally classified into the Tequatrovirus genus of the Myoviridae family. In conclusion, KFS-EC3 could simultaneously infect E. coli O157:H7, S. sonnei, and Salmonella spp. with the lowest MOI values over long periods, suggesting its suitability for simultaneous pathogen control in foods.