Development of a broad-spectrum Salmonella phage cocktail containing Viunalike and Jerseylike viruses isolated from Thailand

Bacteriophage-based control of Salmonella on table eggs and breeding eggs in poultry

Salmonella is a major foodborne pathogen, that poses a serious threat to poultry farm production. Phage-based biocontrol offered a promising alternative strategy to eradicate the persistent and challenging infections caused by Salmonella in this setting. This study isolated and purified the lytic Salmonella phage vB_SenM_BP13076 (simple as BP13076) using its host strain Salmonella Enteritidis ATCC 13076. Its genome was extensively analyzed, and its potential biocontrol application towards eggs was investigated. Morphological analyses revealed that phage BP13076 is characterized by an icosahedral head and a contractile tail, placing it among Caudoviricetes. The phage demonstrated a broad host range, lysing 66 out of 68 tested Salmonella strains, including eight globally prevalent serovars. Moreover, it also exhibited a short latent period of approximately 5 min and a burst size of about 105 PFU/cell. It also demonstrates good thermal stability and a wide pH range tolerance. The genome of phage BP13076 consists of 160, 318 bp of dsDNA with a G + C content of 37.13% with nucleotide homology placing it among phages of the genus Gelderlandvirus. Notably, the genomic analysis revealed no known genes associated with virulence, antibiotic resistance, or lysogeny, making it a safe candidate for biocontrol applications. In vitro, bacteriostatic tests indicated higher MOI (multiplicity of infection), resulting in a more significant reduction in Salmonella counts. When applied to table and breeding eggs, phage BP13076 at MOIs of 100 and 1000 resulted in a significant decrease in Salmonella levels compared to the positive control groups. These findings highlight the efficacy of phage BP13076 as a promising biocontrol agent for managing Salmonella contamination and transmission for table and breeding eggs, offering a foundation for its potential application in the prevention and control of Salmonella in the poultry industry.

The change of long tail fibers expanded the host range of a T5-like Salmonella phage and its application in milk

We engineered novel T5-like bacteriophage (phage) with extended host ranges by editing the long-tail fibers (PB3 and PB4) to combat Salmonella Enteritidis. By replacing the long-tail fibers PB3 and PB4 regions of phage PH204 with those from phage SP76, we created phages RPA1 - 3 and RPB1 - 3, which exhibited expanded host ranges, lysing 54 strains compared to the original 30 strains. These phages retained the biological characteristics of PH204, including temperature, pH stability and adsorption rate. In milk, RPA1 - 3 and RPB1 - 3 inhibited Salmonella ZWSA605 growth, reducing bacterial counts to 1.51 log10 CFU/mL and 2.18 log10 CFU/mL after 8 h, respectively. Although the bacteriolytic activity of recombinant phages is lower than that of the parent phage, our findings suggest that these phages hold promise as candidates for future phage biocontrol applications in food.

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, characterization, and genome sequencing analysis of a novel phage HBW-1 of Salmonella

Salmonella presents a significant threat to the health of animals and humans, especially with the rise of strains resistant to multiple drugs. This highlights the necessity for creating sustainable and efficient practical approaches to managing salmonellosis. The most recent and safest approach to combat antimicrobial resistance-associated infections is lytic bacteriophages. This study recovered a Salmonella-specific phage HBW-1 from sewage and faecal samples from commercial chicken farms in Henan, China. Transmission electron microscopy showed that the phage possesses a polyhedral head and a tailed structure characteristic of bacteriophages. The phage HBW-1 exhibited favorable stability when subjected to elevated temperatures between 30 °C and 60 °C and pH levels between 3 and 12 for 1 h. The phage genome consists of double-stranded, circular DNA with a size of 43,095 bp and a GC content of 49.54 %. Notably, phage HBW-1 contains 62 genes encoding proteins and does not contain virulence or resistance genes commonly found in bacteria. Phage spectrum analysis indicates that the phage HBW-1 is strictly a lytic, exhibiting antibacterial activity against Salmonella Pullorum (100 %, n = 11), Salmonella Typhimurium (92.86 %, n = 42) and Salmonella Enteritidis (58.97 %, n = 39). Therefore, this study suggests that phage HBW-1 holds promise as a potential alternative for prevention and control of Pullorum Disease.

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.

Molecular characterization and safety properties of multi drug-resistant Escherichia coli O157:H7 bacteriophages

The increase in multi drug resistance (MDR) amongst food-borne pathogens such as Escherichia coli O157:H7, coupled with the upsurge of food-borne infections caused by these pathogens is a major public health concern. Lytic phages have been employed as an alternative to antibiotics for use against food-borne pathogens. However, for effective application, phages should be selectively toxic. Therefore, the objective of this study was to characterise lytic E. coli O157:H7 phages isolated from wastewater as possible biocontrol agents and access their genomes for the absence of genes that denotes virulence, resistance, toxins, and lysogeny using whole genome sequencing. E. coli O157:H7 bacteriophages showed clear plaques ranging in size from 1.0 mm to 2.0 mm. Spot test and Efficiency of plating (EOP) analysis demonstrated that isolated phages could infect various environmental E. coli strains. Four phages; vB_EcoM_EP32a, vB_EcoP_EP32b, vB_EcoM_EP57, and vB_EcoM_EP69 demonstrated broad lytic spectra against E. coli O157:H7 strains. Transmission Electron Microscopy (TEM) showed that all phages have tails and were classified as Caudoviricetes. Growth parameters showed an average latent period of 15 ± 3.8 min, with a maximum burst size of 392 PFU/cell. The phages were stable at three distinct temperatures (4 °C, 28 °C, and 37 °C) and at pH values of 3.5, 5.0, 7.0, 9.0, and 11.0. Based on their morphological distinctiveness, three phages were included in the Whole Genome Sequencing (WGS) analysis. WGS results revealed that E. coli O157:H7 phages (vB_EcoM_EP32a, vB_EcoP_EP32b, and vB_EcoM_EP57) were composed of linear double-stranded DNA (dsDNA) with genome sizes 163,906, 156,698, and 130,723 bp and GC contents of 37.61, 37, and 39% respectively. Phages vB_EcoM_EP32a and vB_EcoP_EP32b genomes were classified under the class Caudoviricetes, Straboviridae family, and the new genus "Phapecoctavirus", while vB_EcoM_EP57 was classified under the class Caudoviricetes, Autographiviridae family. Genome analysis revealed no lysogenic (integrase), virulence, or antimicrobial resistance sequences in all three Escherichia phage genomes. The overall results provided evidence that lytic E. coli O157:H7 bacteriophages in this study, are relatively stable, can infect diverse E. coli strains, and does not contain genes responsible for virulence, resistance, toxins, and lysogeny. Thus, they can be considered as biocontrol candidates against MDR pathogenic E. coli O157:H7 strains in the food industry.

Lytic Spectra of Tailed Bacteriophages: A Systematic Review and Meta-Analysis

As natural predators of bacteria, tailed bacteriophages can be used in biocontrol applications, including antimicrobial therapy. Also, phage lysis is a detrimental factor in technological processes based on bacterial growth and metabolism. The spectrum of bacteria bacteriophages interact with is known as the host range. Phage science produced a vast amount of host range data. However, there has been no attempt to analyse these data from the viewpoint of modern phage and bacterial taxonomy. Here, we performed a meta-analysis of spotting and plaquing host range data obtained on strains of production host species. The main metric of our study was the host range value calculated as a ratio of lysed strains to the number of tested bacterial strains. We found no boundary between narrow and broad host ranges in tailed phages taken as a whole. Family-level groups of strictly lytic bacteriophages had significantly different median plaquing host range values in the range from 0.18 (Drexlerviridae) to 0.70 (Herelleviridae). In Escherichia coli phages, broad host ranges were associated with decreased efficiency of plating. Bacteriophage morphology, genome size, and the number of tRNA-coding genes in phage genomes did not correlate with host range values. From the perspective of bacterial species, median plaquing host ranges varied from 0.04 in bacteriophages infecting Acinetobacter baumannii to 0.73 in Staphylococcus aureus phages. Taken together, our results imply that taxonomy of bacteriophages and their bacterial hosts can be predictive of intraspecies host ranges.

Bacteriophages: a potential game changer in food processing industry

In the food industry, despite the widespread use of interventions such as preservatives and thermal and non-thermal processing technologies to improve food safety, incidences of foodborne disease continue to happen worldwide, prompting the search for alternative strategies. Bacteriophages, commonly known as phages, have emerged as a promising alternative for controlling pathogenic bacteria in food. This review emphasizes the potential applications of phages in biological sciences, food processing, and preservation, with a particular focus on their role as biocontrol agents for improving food quality and preservation. By shedding light on recent developments and future possibilities, this review highlights the significance of phages in the food industry. Additionally, it addresses crucial aspects such as regulatory status and safety concerns surrounding the use of bacteriophages. The inclusion of up-to-date literature further underscores the relevance of phage-based strategies in reducing foodborne pathogenic bacteria's presence in both food and the production environment. As we look ahead, new phage products are likely to be targeted against emerging foodborne pathogens. This will further advance the efficacy of approaches that are based on phages in maintaining the safety and security of food.

Characterization of Salmonella phages isolated from poultry coops and its effect with nisin on food bio-control

Salmonella is a bacterium associated with food contaminated by various animals, primarily poultry. Interest and research on bacteriophages are increasing because they can be used as an alternative against increasing antibiotic resistance. In our study, eight Salmonella-specific lytic bacteriophages were isolated from chicken feces. Two of the isolated phages (AUFM_Sc1 and AUFM_Sc3) were chosen for their characterization due to their broader host range. Based on morphological and genomic analysis, AUFM_Sc1 was identified to be close to similar Enterobacteria spp. CC31 (Myoviridae) and AUFM_Sc3 was identified to be close to Salmonella phage vB_Sen_I1 (Demerecviridae (formerly Siphoviridae)). Although these phages have shown promise for use in phage therapy applications for chickens, further studies are needed on their suitability. When a cocktail of these phages (AUFM_Sc1 + AUFM_Sc3) and nisin combination was applied on chicken breast meat, it was determined that it was effective against Salmonella contamination and while a good inhibitory effect was observed on the food, especially during the first 48 h, the effect decreased later, but the bacterial concentration was still low compared to the control group. Therefore, it is considered that the combination of AUFM_Sc1 + AUFM_Sc3 + nisin can be used as a food preservative against Salmonella.

Genomic and Proteomic Analysis of Six Vi01-like Phages Reveals Wide Host Range and Multiple Tail Spike Proteins

Enterobacteriaceae is a large family of Gram-negative bacteria composed of many pathogens, including Salmonella and Shigella. Here, we characterize six bacteriophages that infect Enterobacteriaceae, which were isolated from wastewater plants in the Wasatch front (Utah, United States). These phages are highly similar to the Kuttervirus vB_SenM_Vi01 (Vi01), which was isolated using wastewater from Kiel, Germany. The phages vary little in genome size and are between 157 kb and 164 kb, which is consistent with the sizes of other phages in the Vi01-like phage family. These six phages were characterized through genomic and proteomic comparison, mass spectrometry, and both laboratory and clinical host range studies. While their proteomes are largely unstudied, mass spectrometry analysis confirmed the production of five hypothetical proteins, several of which unveiled a potential operon that suggests a ferritin-mediated entry system on the Vi01-like phage family tail. However, no dependence on this pathway was observed for the single host tested herein. While unable to infect every genus of Enterobacteriaceae tested, these phages are extraordinarily broad ranged, with several demonstrating the ability to infect Salmonella enterica and Citrobacter freundii strains with generally high efficiency, as well as several clinical Salmonella enterica isolates, most likely due to their multiple tail fibers.

Pathogen genomics and phage-based solutions for accurately identifying and controlling Salmonella pathogens

Salmonella is a food-borne pathogen often linked to poultry sources, causing gastrointestinal infections in humans, with the numbers of multidrug resistant (MDR) isolates increasing globally. To gain insight into the genomic diversity of common serovars and their potential contribution to disease, we characterized antimicrobial resistance genes, and virulence factors encoded in 88 UK and 55 Thai isolates from poultry; the presence of virulence genes was detected through an extensive virulence determinants database compiled in this study. Long-read sequencing of three MDR isolates, each from a different serovar, was used to explore the links between virulence and resistance. To augment current control methods, we determined the sensitivity of isolates to 22 previously characterized Salmonella bacteriophages. Of the 17 serovars included, Salmonella Typhimurium and its monophasic variants were the most common, followed by S. Enteritidis, S. Mbandaka, and S. Virchow. Phylogenetic analysis of Typhumurium and monophasic variants showed poultry isolates were generally distinct from pigs. Resistance to sulfamethoxazole and ciprofloxacin was highest in isolates from the UK and Thailand, respectively, with 14-15% of all isolates being MDR. We noted that >90% of MDR isolates were likely to carry virulence genes as diverse as the srjF, lpfD, fhuA, and stc operons. Long-read sequencing revealed the presence of global epidemic MDR clones in our dataset, indicating they are possibly widespread in poultry. The clones included MDR ST198 S. Kentucky, harboring a Salmonella Genomic Island-1 (SGI)-K, European ST34 S. 1,4,[5],12:i:-, harboring SGI-4 and mercury-resistance genes, and a S. 1,4,12:i:- isolate from the Spanish clone harboring an MDR-plasmid. Testing of all isolates against a panel of bacteriophages showed variable sensitivity to phages, with STW-77 found to be the most effective. STW-77 lysed 37.76% of the isolates, including serovars important for human clinical infections: S. Enteritidis (80.95%), S. Typhimurium (66.67%), S. 1,4,[5],12:i:- (83.3%), and S. 1,4,12: i:- (71.43%). Therefore, our study revealed that combining genomics and phage sensitivity assays is promising for accurately identifying and providing biocontrols for Salmonella to prevent its dissemination in poultry flocks and through the food chain to cause infections in humans.

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.

Activity of a Bacteriophage Cocktail to Control Salmonella Growth Ex Vivo in Avian, Porcine, and Human Epithelial Cell Cultures

We examined the activity of phages to control the growth of chicken and swine Salmonella strains in avian (CHIC-8E11), porcine (IPEC-1), and human (HT-29) cell cultures. We optimized a six-phage cocktail by selecting the five most effective myoviruses and a siphovirus that have optimal lysis on prevalent serovars. We observed ∼20% of 7 log10 PFU/well phage and 3-6 log10 CFU bacterial adhesions, and 3-5 log10 CFU bacterial invasion per 2 cm2 of the cultured cells at 2 h post-treatment. The invasive bacteria when plated had a variable reduced susceptibility to the phages. After phage application at an MOI of 10, the prophylaxis regimen had better efficacy at controlling bacterial growth with an up to 6 log10 CFU/well reduction as compared with the 1-2 log10 CFU/well bacterial reduction observed in the remedial and coinfection regimens. Our data support the development of these phages to control salmonellosis in chickens, pigs, and humans.

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.

Evaluation of phage-antibiotic combinations in the treatment of extended-spectrum β-lactamase-producing Salmonella enteritidis strain PT1

Foodborne infections caused by Salmonella spp. are among the most common foodborne diseases in the world. We isolated a lytic phage against extended-spectrum beta-lactam producing S. Enteritidis strain PT1 derived from chicken carcass. Results from electronmicrography indicated that phiPT1 belonged to the family, Siphoviridae, in the order, Caudovirales. Phage phiPT1 was stable at temperatures from 4 °C to 60 °C and inactivated at 90 °C. phiPT1 retained a high titer from pH 4 to pH 10 for at least 1 h. Nevertheless, it displayed a significant decrease (p < 0.05) in titer at pH 11 and 12, with phage titers of 5.5 and 2.4 log₁₀ PFU/mL, respectively. The latent time and burst size of phiPT1 were estimated to be 30 min and 252 PFU/infected cell, respectively. The virulence of phage phiPT1 was evaluated against S. Enteritidis strain PT1 at different MOIs. phiPT1 reduced Salmonella proliferation relative to the negative control (MOI 0) at all MOIs (P < 0.05). However, there is no significant difference among the MOIs (P > 0.05). The phage-antibiotic combination analysis (PAS) indicated that synergism was not detected at higher phiPT1 titer (10¹² PFU/mL) with all tested antibiotics at all subinhibitory concentrations. However, synergistic activities were recorded at 0.25 × MIC of four tested antibiotics: cefixime, gentamicin, ciprofloxacin, and aztreonam in combination with phage at 10⁴, 10⁶ and 10⁸ PFU/mL (ΣFIC ≤0.5). Synergism was detected for all antibiotics (0.1 × MIC) except meropenem and colistin in combination with phiPT1 at 10⁴, 10⁶ and 10⁸ PFU/mL (ΣFIC ≤0.5). Synergism also displayed at the lowest concentrations of all antibiotics (0.01 MIC) in combination with phiPT1 at all titers except 10¹² PFU/mL. Such characteristic features make phiPT1 to be a potential candidate for therapeutic uses.

Tailoring the Host Range of Ackermannviridae Bacteriophages through Chimeric Tailspike Proteins

Host range is a major determinant in the industrial utility of a bacteriophage. A model host range permits broad recognition across serovars of a target bacterium while avoiding cross-reactivity with commensal microbiota. Searching for a naturally occurring bacteriophage with ideal host ranges is challenging, time-consuming, and restrictive. To address this, SPTD1.NL, a previously published luciferase reporter bacteriophage for Salmonella, was used to investigate manipulation of host range through receptor-binding protein engineering. Similar to related members of the Ackermannviridae bacteriophage family, SPTD1.NL possessed a receptor-binding protein gene cluster encoding four tailspike proteins, TSP1-4. Investigation of the native gene cluster through chimeric proteins identified TSP3 as the tailspike protein responsible for Salmonella detection. Further analysis of chimeric phages revealed that TSP2 contributed off-target Citrobacter recognition, whereas TSP1 and TSP4 were not essential for activity against any known host. To improve the host range of SPTD1.NL, TSP1 and TSP2 were sequentially replaced with chimeric receptor-binding proteins targeting Salmonella. This engineered construct, called RBP-SPTD1-3, was a superior diagnostic reporter, sensitively detecting additional Salmonella serovars while also demonstrating improved specificity. For industrial applications, bacteriophages of the Ackermannviridae family are thus uniquely versatile and may be engineered with multiple chimeric receptor-binding proteins to achieve a custom-tailored host range.

Therapeutic effects of oral administration of lytic Salmonella phages in a mouse model of non-typhoidal salmonellosis

Acute non-typhoidal salmonellosis (NTS) caused by a Gram-negative bacterium Salmonella enterica serovar Typhimurium (S. Tm) is one of the most common bacterial foodborne diseases worldwide. Bacteriophages (phages) can specifically target and lyse their host bacteria, including the multidrug-resistant strains, without collateral damage to other bacteria in the community. However, the therapeutic use of Salmonella phages in vivo is still poorly investigated. Salmonella phages ST-W77 and SE-W109 have previously been shown by our group to be useful for biocontrol properties. Here, we tested whether phages ST-W77 and SE-W109 can reduce Salmonella invasion into cultured human cells and confer a therapeutic benefit for acute NTS in a mammalian host. Human colonocytes, T84 cells, were treated with phages ST-W77, SE-W109, and its combination for 5 min before S. Tm infection. Gentamicin protection assays demonstrated that ST-W77 and SE-W109 significantly reduced S. Tm invasion and inflammatory response in human colonocytes. Next, streptomycin-pretreated mice were orally infected with S. Tm (108 CFU/mouse) and treated with a single or a combination of ST-W77 and SE-W109 (1010 PFU/mouse for 4 days) by oral feeding. Our data showed that phage-treated mice had lower S. Tm numbers and tissue inflammation compared to the untreated mice. Our study also revealed that ST-W77 and SE-W109 persist in the mouse gut lumen, but not in systemic sites. Together, these data suggested that Salmonella phages ST-W77 and SE-W109 could be further developed as an alternative approach for treating an acute NTS in mammalian hosts.

Application and challenge of bacteriophage in the food protection

In recent years, foodborne diseases caused by pathogens have been increasing. Therefore, it is essential to control the growth and transmission of pathogens. Bacteriophages (phages) have the potential to play an important role in the biological prevention, control, and treatment of these foodborne diseases due to their favorable advantages. Phages not only effectively inhibit pathogenic bacteria and prolong the shelf life of food, but also possess the advantages of specificity and an absence of chemical residues. Currently, there are many cases of phage applications in agriculture, animal disease prevention and control, food safety, and the treatment of drug-resistant disease. In this review, we summarize the recent research progress on phages against foodborne pathogenic bacteria, including Escherichia coli, Salmonella, Campylobacter, Listeria monocytogenes, Shigella, Vibrio parahaemolyticus, and Staphylococcus aureus. We also discuss the main issues and their corresponding solutions in the application of phages in the food industry. In recent years, although researchers have discovered more phages with potential applications in the food industry, most researchers use these phages based on their host spectrum, and the application environment is mostly in the laboratory. Therefore, the practical application of these phages in different aspects of the food industry may be unsatisfactory and even have some negative effects. Thus, we suggest that before using these phages, it is necessary to identify their specific receptors. Using their specific receptors as the selection basis for their application and combining phages with other phages or phages with traditional antibacterial agents may further improve their safety and application efficiency. Collectively, this review provides a theoretical reference for the basic research and application of phages in the food industry.

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.

Isolation and identification of new source of bacteriocin-producing Lactobacillus plantarum C010 and growth kinetics of its batch fermentation

The control of food-borne pathogens and spoilage organisms in meat and related products is urgently needed. Bacteriocins produced by lactic acid bacteria (LAB) are promising natural food preservatives. In this study, six bacteriocin-producing bacteria were screened from soil and fresh cow dung. Pseudomonas koreensis PS1, a specific spoilage organism from spoiled chilled pork, was used as the indicator bacteria. From the analyses, the strain C010 was selected due to its high yield, broad spectrum, and subculture stability. Through morphological, biochemical, and 16S rDNA gene sequence analysis, this strain was identified as Lactobacillus plantarum. Crude bacteriocin extracted from the cell-free supernatant (CFS) of L. plantarum C010 was stable under high temperature, ultraviolet radiation, and protease attack (pepsin, trypsin, and proteinase K). The kinetics of bacterial growth and bacteriocin production by L. plantarum C010 were analyzed during batch fermentation. Bacteriocin was produced throughout the logarithmic growth phase, and the Leudeking-Piret model characterized the synthesis of bacteriocins. The present study indicates that this novel bacteriocin produced by bacteria is a promising option for reducing spoilage microorganisms and can be widely used as a bio-preservative in meat and other foods.

Using Phages to Reduce Salmonella Prevalence in Chicken Meat: A Systematic Review

Salmonellosis is an infection that significantly impacts chicken and humans who consume it; it is a burden on public health and a contributor to commercial losses in the chicken industry worldwide. To tackle chicken meat-related bacterial infections, significant quantities of antibiotics alongside several infection prevention measures are used worldwide. However, chemical additives, such as organic acids, and chlorine-based interventions all have different limitations. These include feed refusal due to a change of taste, and incompatibility between organic acids and other inoculated preservative agents such as antimicrobial agents. Phages are host-specific viruses that interact with bacteria in a specific manner. Therefore, they possess unique biological and therapeutic features that can be used to reduce bacterial contamination, leading to improved food safety and quality. This systematic review examines the current evidence regarding the effectiveness of various phages on Salmonella colonization in chicken meat. This review summarizes findings from 17 studies that were conducted in vitro with similar experimental conditions (temperature and incubation parameters) to test the efficacy of isolated and commercially available phages on chicken raw meat samples. The current evidence suggests that most of the in vitro studies that used phages as a biocontrol to eradicate Salmonella contamination in chicken meat were successful. This indicates that phages constitute a promising solution worldwide for tackling foodborne bacteria, including Salmonella.

Characterization and genomic analysis of a Demerecviridae phage SP76 with lytic multiple-serotypes of Salmonella

With the increase in antimicrobial resistance of Salmonella, phages have been paid more attention to as an alternative to antibiotics. In this study, a phage designated as SP76 was isolated from sewage. It can lyse several serotypes of Salmonella, including S. typhimurium (21/33), S. enteritidis (7/7), S. dublin (4/4), S. pullorum (2/2) and S. choleraesuis (1/2). SP76 showed a latent time of about 10 min, and maintained good lytic activity at a pH range of 3-10 and temperatures between 4 and 37 °C. Moreover, its optimal multiplicity of infection (MOI) was 0.0001. Based on the results of genomic sequence and analysis, SP76 was found to have a genome of 111,639 bp that encoded 166 predicted ORFs and belong to the Demerecviridae family, order Caudovirales. No virulence or lysogen formation gene clusters were identified in the SP76 genome. A pan-genome analysis based on 100 phages within the subfamily Markadamsvirinae indicated that SP76 had 23 core genes and 1199 accessory genes. We grouped the subfamily Markadamsvirinae and found that the main difference was in group III. In vitro bacteriostasis, experiments showed that the phage SP76 reduced planktonic bacteria by 1.52 log10 CFU/mL, and biofilms (24 h old) by 0.372 log10 CFU/mL, respectively. Thus, we isolated a safe and efficient phage that might be a good antibacterial agent.

Phage Revolution Against Multidrug-Resistant Clinical Pathogens in Southeast Asia

Southeast Asia (SEA) can be considered a hotspot of antimicrobial resistance (AMR) worldwide. As recent surveillance efforts in the region reported the emergence of multidrug-resistant (MDR) pathogens, the pursuit of therapeutic alternatives against AMR becomes a matter of utmost importance. Phage therapy, or the use of bacterial viruses called bacteriophages to kill bacterial pathogens, is among the standout therapeutic prospects. This narrative review highlights the current understanding of phages and strategies for a phage revolution in SEA. We define phage revolution as the radical use of phage therapy in infectious disease treatment against MDR infections, considering the scientific and regulatory standpoints of the region. We present a three-phase strategy to encourage a phage revolution in the SEA clinical setting, which involves: (1) enhancing phage discovery and characterization efforts, (2) creating and implementing laboratory protocols and clinical guidelines for the evaluation of phage activity, and (3) adapting regulatory standards for therapeutic phage formulations. We hope that this review will open avenues for scientific and policy-based discussions on phage therapy in SEA and eventually lead the way to its fullest potential in countering the threat of MDR pathogens in the region and worldwide.

The lytic siphophage vB_StyS-LmqsSP1 reduces Salmonella Typhimurium isolates on chicken skin

Phage-based biocontrol of bacteria is considered as a natural approach to combat food-borne pathogens. Salmonella spp. are notifiable and highly prevalent pathogens that cause foodborne diseases globally. In this study, six bacteriophages were isolated and further characterized that infect food-derived Salmonella isolates from different meat sources. The siphovirus VB_StyS-LmqsSP1, which was isolated from a cow´s nasal swab, was further subjected to in-depth characterization. Phage-host interaction investigations in liquid medium showed that vB_StyS-LmqsSP1 can suppress the growth of Salmonella spp. isolates at 37°C for ten hours and reduce the bacterial titer at 4°C significantly. A reduction of 1.4 to 3 log units was observed in investigations with two food-derived Salmonella isolates and one reference strain under cooling conditions using MOIs of 10⁴ and 10⁵. Phage application on chicken skin resulted in a reduction of about 2 log units in the tested Salmonella isolates from the first three hours throughout a one-week experiment at cooling temperature and an MOI of 10⁵. The one-step growth curve analysis using vB_StyS-LmqsSP1 demonstrated a 60-min latent period and a burst size of 50-61 PFU/infected cell for all tested hosts. Furthermore, the genome of the phage was determined to be free from genes causing undesired effects. Based on the phenotypic and genotypic properties, LmqsSP1 was assigned as a promising candidate for biocontrol of Salmonella Typhimurium in food. Importance: Salmonella enterica is one of the major global causes of foodborne enteritis in humans. The use of chemical sanitizers for reducing bacterial pathogens in the food chain can result in the spread of bacterial resistance. Targeted and clean label intervention strategies can reduce Salmonella contamination in food. The significance of our research demonstrates the suitability of a bacteriophage (vB_StyS-LmqsSP1) for biocontrol of Salmonella enterica serovar Typhimurium on poultry due to its lytic efficacy under conditions prevailing in food production environments.

Isolation and Characterization of a Novel Salmonella Phage vB_SalP_TR2

Salmonella is a widely distributed foodborne pathogen. The use of Salmonella phages as biocontrol agents has recently gained significant interest. Because the Salmonella genus has high diversity, efforts are necessary to identify lytic Salmonella phages focusing on different serovars. Here, five Salmonella phages were isolated from soil samples, and vB_SalP_TR2 was selected as a novel phage with high lytic potential against the host Salmonella serovar Albany, as well as other tested serovars, including Corvallis, Newport, Kottbus, and Istanbul. Morphological analyses demonstrated that phage vB_SalP_TR2 belongs to the Podoviridae family, with an icosahedral head (62 ± 0.5 nm in diameter and 60 ± 1 nm in length) and a short tail (35 ± 1 nm in length). The latent period and burst size of phage vB_SalP_TR2 was 15 min and 211 PFU/cell, respectively. It contained a linear dsDNA of 71,453 bp, and G + C content was 40.64%. Among 96 putative open reading frames detected, only 35 gene products were found in database searches, with no virulence or antibiotic resistance genes being identified. As a biological control agent, phage vB_SalP_TR2 exhibited a high temperature and pH tolerance. In vitro, it lysed most S. Albany after 24 h at 37°C with multiplicities of infection of 0.0001, 0.001, 0.01, 0.1, 1, 10, and 100. In food matrices (milk and chicken meat), treatment with phage vB_SalP_TR2 also reduced the number of S. Albany compared with that in controls. These findings highlighted phage vB_SalP_TR2 as a potential antibacterial agent for the control of Salmonella in food samples.

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

Salmonella is one of the most common foodborne pathogens around the world. Phages are envisioned as a new strategy to control foodborne pathogenic bacteria and food safety. A Salmonella specific lytic phage vB_SalS-LPSTLL (LPSTLL) was selected for food applications on the basis of lytic range, lytic efficiency, functional stability and characteristics. Phage LPSTLL was able to lyse 11 Salmonella serotypes, which represents the broadest range reported Salmonella phages, and was able to suppress the growth of Salmonella enterica in liquid culture over nine hours. LPSTLL exhibited rapid reproductive activity with a short latent period and a large burst size in one-step growth experiment. LPSTLL remained active over a pH range of 3.0 to 12.0, and at incubation temperatures up to 60 °C for 60 min, indicating wide applicability for food processing and storage. Significant reductions of viable Salmonella were observed in diverse foods (milk, apple juice, chicken and lettuce) with reductions up to 2.8 log CFU/mL recorded for milk. Sensory evaluation indicated that treatment with phage LPSTLL did not alter the visual or tactile quality of food matrices. Genome analysis of LPSTLL indicated the absence of any virulence or antimicrobial resistance genes. Genomic comparisons suggest phage LPSTLL constitutes a novel member of a new genus, the LPSTLLvirus with the potential for Salmonella biocontrol in the food industry.

Recent Advances in the Detection of Antibiotic and Multi-Drug Resistant Salmonella: An Update

Antibiotic and multi-drug resistant (MDR) Salmonella poses a significant threat to public health due to its ability to colonize animals (cold and warm-blooded) and contaminate freshwater supplies. Monitoring antibiotic resistant Salmonella is traditionally costly, involving the application of phenotypic and genotypic tests over several days. However, with the introduction of cheaper semi-automated devices in the last decade, strain detection and identification times have significantly fallen. This, in turn, has led to efficiently regulated food production systems and further reductions in food safety hazards. This review highlights current and emerging technologies used in the detection of antibiotic resistant and MDR Salmonella.

Isolation and Characterization of Two Lytic Bacteriophages Infecting a Multi-Drug Resistant Salmonella Typhimurium and Their Efficacy to Combat Salmonellosis in Ready-to-Use Foods

Foodborne salmonellosis is a global threat to public health. In the current study, we describe the isolation and characterization of two broad-spectrum, lytic Salmonella phages: SPHG1 and SPHG3 infecting a multidrug-resistant Salmonella Typhimurium EG.SmT3. Electron microscopy and whole genome analysis identified SPHG1 as a Myovirus, while SPHG3 as a new member of the genus "Kuttervirus" within the family Ackermannviridae. SPHG1 and SPHG3 had a lysis time of 60 min. with burst sizes of 104 and 138 PFU/cell, respectively. The two phages were robust at variable temperatures and pH ranges that match the corresponding values of most of the food storage and processing conditions. A phage cocktail containing the two phages was stable in the tested food articles for up to 48 h. The application of the phage cocktail at MOIs of 1000 or 100 resulted in a significant reduction in the viable count of S. Typhimurium by 4.2 log10/sample in milk, water, and on chicken breast. Additionally, the phage cocktail showed a prospective ability to eradicate and reduce the biofilm that formed by S. Typhimurium EG.SmT3. A phage cocktail of SPHG1 and SPHG3 is considered as a promising candidate as a biocontrol agent against foodborne salmonellosis due to its broad host ranges, highly lytic activities, and the absence of any virulence or lysogeny-related genes in their genomes.

An Optimized Bacteriophage Cocktail Can Effectively Control Salmonella in vitro and in Galleria mellonella

Salmonella spp. is a leading cause of gastrointestinal enteritis in humans where it is largely contracted via contaminated poultry and pork. Phages can be used to control Salmonella infection in the animals, which could break the cycle of infection before the products are accessible for consumption. Here, the potential of 21 myoviruses and a siphovirus to eliminate Salmonella in vitro and in vivo was examined with the aim of developing a biocontrol strategy to curtail the infection in poultry and swine. Together, the phages targeted the twenty-three poultry and ten swine prevalent Salmonella serotype isolates tested. Although individual phages significantly reduced bacterial growth of representative isolates within 6 h post-infection, bacterial regrowth occurred 1 h later, indicating proliferation of resistant strains. To curtail bacteriophage resistance, a novel three-phage cocktail was developed in vitro, and further investigated in an optimized Galleria mellonella larva Salmonella infection model colonized with representative swine, chicken and laboratory strains. For all the strains examined, G. mellonella larvae given phages 2 h prior to bacterial exposure (prophylactic regimen) survived and Salmonella was undetectable 24 h post-phage treatment and throughout the experimental time (72 h). Administering phages with bacteria (co-infection), or 2 h post-bacterial exposure (remedial regimen) also improved survival (73-100% and 15-88%, respectively), but was less effective than prophylaxis application. These pre-livestock data support the future application of this cocktail for further development to effectively treat Salmonella infection in poultry and pigs. Future work will focus on cocktail formulation to ensure stability and incorporation into feeds and used to treat the infection in target animals.