Application of bacteriophages in post-harvest control of human pathogenic and food spoiling bacteria

The Novel Concept of Synergically Combining: High Hydrostatic Pressure and Lytic Bacteriophages to Eliminate Vegetative and Spore-Forming Bacteria in Food Products

The article focuses on the ongoing challenge of eliminating vegetative and spore-forming bacteria from food products that exhibit resistance to the traditional preservation methods. In response to this need, the authors highlight an innovative approach based on the synergistic utilization of high-hydrostatic-pressure (HHP) and lytic bacteriophages. The article reviews the current research on the use of HHP and lytic bacteriophages to combat bacteria in food products. The scope includes a comprehensive review of the existing literature on bacterial cell damage following HHP application, aiming to elucidate the synergistic effects of these technologies. Through this in-depth analysis, the article aims to contribute to a deeper understanding of how these innovative techniques can improve food safety and quality. There is no available research on the use of HHP and bacteriophages in the elimination of spore-forming bacteria; however, an important role of the synergistic effect of HHP and lytic bacteriophages with the appropriate adjustment of the parameters has been demonstrated in the more effective elimination of non-spore-forming bacteria from food products. This suggests that, when using this approach in the case of spore-forming bacteria, there is a high chance of the effective inactivation of this biological threat.

Quorum sensing autoinducers AHLs protect Shewanella baltica against phage infection

Quorum sensing (QS) plays an important role in phage-host interactions. Shewanella baltica can't produce the N-acyl-homoserine lactones (AHLs) signal molecules but can eavesdrop on exogenous AHLs through its LuxR receptor. However, no clear evidence exists regarding the involvement of AHLs-mediated QS systems in S. baltica in regulating phage infection. Here, we report that AHLs modulated the phage resistance of S. baltica OS155. Specifically, we characterized a S. baltica phage vB_Sb_QDWS and preliminarily identified that lipopolysaccharide (LPS) is an important receptor for phage vB_Sb_QDWS. AHLs could protect S. baltica against phage infection by decreasing LPS-mediated phage adsorption. The expression of genes galU and tkt, which are essential for LPS synthesis, down-regulated significantly in response to AHLs autoinducers. Our finding confirms the important roles of QS in virus-host interactions and would be helpful to develop novel phage strategies for food spoilage control.

Recent trends in the use of bacteriophages as replacement of antimicrobials against food-animal pathogens

A major public health impact is associated with foodborne illnesses around the globe. Additionally, bacteria are becoming more resistant to antibiotics, which pose a global threat. Currently, many scientific efforts have been made to develop and implement new technologies to combat bacteria considering the increasing emergence of multidrug-resistant bacteria. In recent years, there has been considerable interest in using phages as biocontrol agents for foodborne pathogens in animals used for food production and in food products themselves. Foodborne outbreaks persist, globally, in many foods, some of which lack adequate methods to control any pathogenic contamination (like fresh produce). This interest may be attributed both to consumers' desire for more natural food and to the fact that foodborne outbreaks continue to occur in many foods. Poultry is the most common animal to be treated with phage therapy to control foodborne pathogens. A large number of foodborne illnesses worldwide are caused by Salmonella spp. and Campylobacter, which are found in poultry and egg products. Conventional bacteriophage-based therapy can prevent and control humans and animals from various infectious diseases. In this context, describing bacteriophage therapy based on bacterial cells may offer a breakthrough for treating bacterial infections. Large-scale production of pheasants may be economically challenging to meet the needs of the poultry market. It is also possible to produce bacteriophage therapy on a large scale at a reduced cost. Recently, they have provided an ideal platform for designing and producing immune-inducing phages. Emerging foodborne pathogens will likely be targeted by new phage products in the future. In this review article, we will mainly focus on the Bacteriophages (phages) that have been proposed as an alternative strategy to antibiotics for food animal pathogens and their use for public health and food safety.

Bacteriophages as Biocontrol Agents in Livestock Food Production

Bacteriophages have been regarded as biocontrol agents that can be used in the food industry. They can be used in various applications, such as pathogen detection and bio-preservation. Their potential to improve the quality of food and prevent foodborne illness is widespread. These bacterial viruses can also be utilized in the preservation of various other food products. The specificity and high sensitivity of bacteriophages when they lyse bacterial targets have been regarded as important factors that contribute to their great potential utility in the food industry. This review will provide an overview of their current and potential applications.

Isolation and characterization of Escherichia coli O157: H7 novel bacteriophage for controlling this food-borne pathogen

Escherichia coli O157: H7 is known as a high-risk food-born pathogen, and its removal is vital for maintaining food safety. The increasing trend of food-borne diseases caused by this bacterium and other pathogens indicates the low efficiency of the methods to remove pathogens from foodstuffs. One of the new and effective methods is to use of a bio-control agent called bacteriophage, which has shown good function in eliminating and reducing pathogens. In this study, a novel bacteriophage was isolated and identified from the slaughterhouse wastewater to control E. coli O157: H7. This bacteriophage belonged to the Myoviridae family. Two bacterial genera including E. coli and Salmonella, were allocated to determine the bacteriophage host range; the result showed that the anti- Salmonella effect of phage was low. The phage was stable at high temperature (80°C) and caused an acceptable reduction in the E. coli O157: H7 (4.18 log CFU / mL for 10 hours). The isolated bacteriophage was corroborated to be completely safe based on the whole genome sequencing and lack of any virulence factor from the host bacteria. Considering the characteristics of this phage and its function in vitro, this bacteriophage may be used as an effective bio-control agent in foods with the possible E. coli O157: H7 -induced contamination.

Biosynthesis of a Novel Antibacterial Dipeptide, Using Proteases From South American Native Fruits, Useful as a Food Preservative

Antiacanthain and granulosain are the partially purified proteolytic extracts from the South American native fruits of Bromelia antiacantha (Bertol. ) and Solanum granuloso leprosum, respectively. The aim of this work was to compare the ability of both soluble and immobilized antiacanthain and granulosain f or the synthesis of Z-Tyr-Val-OH, a novel antibacterial dipeptide, in different reaction systems formed by almost anhydrous organic solvents (X_w: 1 × 10⁻⁵) and several percentages of immiscible organic solvents in 100 mM Tris(hydroxymethyl)aminomethane hydrochloride buffer pH 8.0. Soluble antiacanthain in half of the 24 different organic biphasic media showed higher catalytic potential than in 100 mM Tris(hydroxymethyl)aminomethane hydrolchloride buffer pH 8.0. Soluble granulosain showed lower catalytic potential in all liquid-liquid biphasic media than in the same buffer. However, 50% (v/v) ethyl ethanoate in 100 mM Tris(hydroxymethyl)aminomethane hydrolchloride buffer pH 8.0 allowed to express the highest catalytic potential of both soluble enzymes. In 50% v/v ethyl ethanoate, soluble antiacanthain and granulosain catalyzed the synthesis of Z-Tyr-Val-OH with 72 ± 0.15 and 60 ± 0.10% maximal peptide yields, respectively. Multi-point immobilization in glyoxyl-silica did not lead to better peptide yields than soluble enzymes, in that liquid-liquid biphasic medium under the same reaction conditions. Soluble and glyoxyl-silica immobilized antiacanthain in almost anhydrous ethyl ethanoate (X_w: 1 × 10⁻⁵) were able to retain 17.3 and 45% of the initial proteolytic activity of antiacanthain in 100 mM Tris hydrolchloride buffer pH 8.0, respectively, at 40°C under agitation (200 rpm). Soluble and glyoxyl-silica immobilized granulosain were inactivated under the same reaction conditions. Glyoxyl-silica immobilized antiacanthain showed to be a robust biocatalyst in almost anhydrous ethyl ethanoate (X_w: 1 × 10⁻⁵), eliciting the best peptide yield (75 ± 0.13%). The synthesis reaction of Z-Tyr-Val-OH could not proceed when soluble antiacanthain was used under the same conditions. Both peptidases only catalyzed the synthesis reaction under kinetic control, using activated acyl donor substrates. Finally, this work reports a novel broad-spectrum antibacterial peptide that significantly decreased (p ≤ 0.05) the specific growth rates of Gram positive and Gram negative microorganisms at very low concentrations (≥15 and 35 μg/ml, respectively); contributing with a new safe food preservative of applying for different food systems.

How Broad Is Enough: The Host Range of Bacteriophages and Its Impact on the Agri-Food Sector

Novel bacteriophages (phages) possessing a broad host range are consistently and routinely reported, yet there is presently no consensus on the definition of "broad host range." As phages are increasingly being used in the development of methods for the detection and biocontrol of human pathogens, it is important to address the limitations associated with the host range. For instance, unanticipated host range breadth may result in the detection of nonpathogenic targets, thereby increasing the false-positive rate. Moreover, a broad host range is generally favored in biocontrol applications despite the risk of undesirable ancillary effects against nontarget species. Here, we discuss the research progress, applications, and implications of broad host range phages with a focus on tailed broad host range phages infecting human pathogens of concern in the Agri-Food sector.

In Vitro Evaluation of Anti-biofilm Agents Against Salmonella enterica

Salmonella enterica is able to establish robust adherent communities called biofilms that allow for long-term colonization of both biotic and abiotic surfaces. These biofilm communities pose a significant challenge to successful eradication of the bacteria from contaminated surfaces and the infected host, as entry into the biofilm phenotype confers the bacterial population with tolerance to a variety of environmental and therapeutic insults to which it would otherwise be susceptible. The identification of antimicrobial strategies that specifically target the Salmonella biofilm state is therefore of great importance in order to both prevent and treat biofilm-mediated disease. Here, we provide detailed methods for the in vitro cultivation of Salmonella biofilms that can easily be scaled up for use in high-throughput screening of candidate anti-biofilm agents. These assays may also be utilized to further characterize the inhibitory and/or disruptive capabilities of lead anti-biofilm agents, as well as to identify combination treatments that demonstrate enhanced anti-biofilm effects. Furthermore, the assays may be slightly modified (e.g., optimal growth conditions) to evaluate other bacterial genera.

Microbiome approaches provide the key to biologically control postharvest pathogens and storability of fruits and vegetables

Microbes play an important role in plants and interact closely with their host starting from sprouting seeds, continuing during growth and after harvest. The discovery of their importance for plant and postharvest health initiated a biotechnological development of various antagonistic bacteria and fungi for disease control. Nevertheless, their application often showed inconsistent effects. Recently, high-throughput sequencing-based techniques including advanced microscopy reveal fruits and vegetables as holobionts. At harvest, all fruits and vegetables harbor a highly abundant and specific microbiota including beneficial, pathogenic and spoilage microorganisms. Especially, a high microbial diversity and resilient microbial networks were shown to be linked to fruit and vegetable health, while diseased products showed severe dysbiosis. Field and postharvest handling of fruits and vegetables was shown to affect the indigenous microbiome and therefore has a substantial impact on the storability of fruits and vegetables. Microbiome tracking can be implemented as a new tool to evaluate and assess all postharvest processes and contribute to fruit and vegetable health. Here, we summarize current research advancements in the emerging field of postharvest microbiomes and elaborate its importance. The generated knowledge provides profound insights into postharvest microbiome dynamics and sets a new basis for targeted, microbiome-driven and sustainable control strategies.

Comprehensive Evaluation of the Safety and Efficacy of BAFASAL® Bacteriophage Preparation for the Reduction of Salmonella in the Food Chain

Bacteriophages are bacterial predators, which are garnering much interest nowadays vis-à-vis the global phenomenon of antimicrobial resistance. Bacteriophage preparations seem to be an alternative to antibiotics, which can be used at all levels of the food production chain. Their safety and efficacy, however, are of public concern. In this study, a detailed evaluation of BAFASAL^® preparation was performed. BAFASAL^® is a bacteriophage cocktail that reduces Salmonella in poultry farming. In vivo acute and sub-chronic toxicity studies on rats and tolerance study on targeted animals (chicken broiler) conducted according to GLP and OECD guidelines did not reveal any signs of toxicity, which could be associated with BAFASAL^® administration. In addition, no evidences of genotoxicity were observed. The tolerance study with 100-times concentrated dose also did not show any statistically significant differences in the assessed parameters. The in vitro crop assay, mimicking normal feed storage and feed application conditions showed that BAFASAL^® reduced the number of Salmonella bacteria in experimentally contaminated feed. Moreover, reductions were observed for all examined forms (liquid, powder, spray). Furthermore, the in vivo efficacy study showed that treatment with BAFASAL^® significantly decreased Salmonella content in caeca of birds infected with Salmonella Enteritidis. Detailed examination of BAFASAL^® in terms of safety and efficacy, adds to the body of evidence that bacteriophages are harmless to animals and effective in the struggle against bacteria.

Metatranscriptomics reveals the gene functions and metabolic properties of the major microbial community during Chinese Sichuan Paocai fermentation

Chinese Sichuan Paocai (CSP) is one of the world's best-known fermented vegetables with a large presence in the Chinese market. The dynamic microbial community is the main contributor to Paocai fermentation. However, little is known about the ecological distribution and functional importance of these community members. In this study, metatranscriptomics was used to comprehensively explore the active microbial community members and key transcripts with significant functions in the Paocai fermentation process. Enterobacter, Leuconostoc, and Lactobacillus dominated the three-fermentation stages (Pre-, Mid- and Lat-), respectively. Carbon metabolism was the most abundant pathway. GH (glycoside hydrolase) and GT (lycosyl transferase) were the two most highly expressed carbohydrate-active enzymes. The most highly differentially expressed genes were grouped in the biosynthesis of amino acids, followed by glycolysis. Meta-pathways in the Sichuan Paocai fermentation ecosystem were reconstructed, Lactobacillaceae and Enterobacteriaceae were the two most important metabolic contributors. In addition, the nrfA and nirB were two genes referred to distinct nitrite reductase enzymes and 9 specialized genes, such as eclo, ron and ent were expressed to produce autoinducer 2 (AI-2) kinase in response to population density. The present study revealed functional enzymes and meta-pathways of the active microbial communities, which provide a deeper understanding of their contribution to CSP products.

Isolation of Polygalacturonase-Producing Bacterial Strain from Tomatoes (Lycopersicon esculentum Mill.)

Background

Polygalacturonase (EC 3.2.1.15) enzyme aids in microbial spoilage of fruits and vegetables. It is very important to find economical ways to producing the enzyme so as to achieve maximum yield in industries due to its use at different areas of production process.

Methods

Isolation of polygalacturonase-producing bacterial strain from tomatoes (Lycopersicon esculentum Mill.) was studied. Polygalacturonase-producing bacterial strains were isolated and screened from tomatoes stored at normal laboratory temperature (25 ± 2°C). They were identified based on their morphological, biochemical, and molecular characteristics. The enzyme produced was partially purified by the ammonium sulphate precipitation method. Molecular weights and optimum conditions for best enzyme activity were obtained by SDS PAGE technique.

Results

Five bacterial isolates resulted after screening. Bacterial strain code B5 showed highest polygalacturonase activity. Optimum conditions for polygalacturonase PEC B5 were maintained at pH 4.5; temperature 35°C; substrate concentration 0.3 mg/ml, and best activity at less than 5 min of heating. The enzyme PEC B5 was found to weigh 65 kDa and 50 kDa for crude and partially purified aliquots, respectively. The result of 16S rRNA gene sequencing revealed bacterial strain code B5 as Enterobacter tabaci NR146667 having 79% similarity with the NCBI GenBank.

Conclusion

Microorganisms should be developed for large-scale production of enzymes in developing countries.

Complete genome sequence of PFP1, a novel T7-like Pseudomonas fluorescens bacteriophage

The complete genomic sequence of Pseudomonas fluorescens bacteriophage PFP1, isolated from sewage samples collected in Liaoning Province, China, were sequenced in this study and found to be 40,914 bp long. The PFP1 genome is composed of linear double-stranded DNA with 55.81% G+C content and 45 putative protein-coding genes, and no rRNA and tRNA genes. Comparative genomics and phylogenetic analysis revealed that the Pseudomonas fluorescens phage PFP1 is a new member of the genus T7virus. This information can be used to develop novel phage-based control strategies against Pseudomonas fluorescens.

Novel Biocontrol Methods for Listeria monocytogenes Biofilms in Food Production Facilities

High mortality and hospitalization rates have seen Listeria monocytogenes as a foodborne pathogen of public health importance for many years and of particular concern for high-risk population groups. Food manufactures face an ongoing challenge in preventing the entry of L. monocytogenes into food production environments (FPEs) due to its ubiquitous nature. In addition to this, the capacity of L. monocytogenes strains to colonize FPEs can lead to repeated identification of L. monocytogenes in FPE surveillance. The contamination of food products requiring product recall presents large economic burden to industry and is further exacerbated by damage to the brand. Poor equipment design, facility layout, and worn or damaged equipment can result in Listeria hotspots and biofilms where traditional cleaning and disinfecting procedures may be inadequate. Novel biocontrol methods may offer FPEs effective means to help improve control of L. monocytogenes and decrease cross contamination of food. Bacteriophages have been used as a medical treatment for many years for their ability to infect and lyse specific bacteria. Endolysins, the hydrolytic enzymes of bacteriophages responsible for breaking the cell wall of Gram-positive bacteria, are being explored as a biocontrol method for food preservation and in nanotechnology and medical applications. Antibacterial proteins known as bacteriocins have been used as alternatives to antibiotics for biopreservation and food product shelf life extension. Essential oils are natural antimicrobials formed by plants and have been used as food additives and preservatives for many years and more recently as a method to prevent food spoilage by microorganisms. Competitive exclusion occurs naturally among bacteria in the environment. However, intentionally selecting and applying bacteria to effect competitive exclusion of food borne pathogens has potential as a biocontrol application. This review discusses these novel biocontrol methods and their use in food safety and prevention of spoilage, and examines their potential to control L. monocytogenes within biofilms in food production facilities.

Bacteriophage Clinical Use as Antibacterial "Drugs": Utility and Precedent

For phage therapy-the treatment of bacterial infections using bacterial viruses-a key issue is the conflict between apparent ease of clinical application, on the one hand, and on the other hand, numerous difficulties that can be associated with undertaking preclinical development. These conflicts between achieving efficacy in the real world versus rigorously understanding that efficacy should not be surprising because equivalent conflicts have been observed in applied biology for millennia: exploiting the inherent, holistic tendencies of useful systems, e.g., of dairy cows, inevitably is easier than modeling those systems or maintaining effectiveness while reducing such systems to isolated parts. Trial and error alone, in other words, can be a powerful means toward technological development. Undertaking trial and error-based programs, especially in the clinic, nonetheless is highly dependent on those technologies possessing both inherent safety and intrinsic tendencies toward effectiveness, but in this modern era we tend to forget that ideally there would exist antibacterials which could be thus developed, that is, with tendencies toward both safety and effectiveness, and which are even relatively inexpensive. Consequently, we tend to demand rigor as well as expense of development even to the point of potentially squandering such utility, were it to exist. In this review I lay out evidence that in phage therapy such potential, in fact, does exist. Advancement of phage therapy unquestionably requires effective regulation as well as rigorous demonstration of efficacy, but after nearly 100 years of clinical practice, perhaps not as much emphasis on strictly laboratory-based proof of principle.

Bacteriophage application for biocontrolling Shigella flexneri in contaminated foods

Shigellosis (bacillary dysentery) is an acute enteric infection caused by members of Shigella genus. It causes annual deaths of approximately five million children in developing countries. Among Shigella spp., S. flexneri causes more serious forms of dysentery than other Shigella species. Due to the appearance of multidrug-resistant strains of Shigella spp., it is necessary to find alternative antimicrobial agents. The aims of this study were the isolation of a novel species-specific phage against S. flexneri and to evaluate its potential and efficacy for biocontrolling of S. flexneri in foods. Shigella flexneri PTCC 1234 was used as the host strain for bacteriophage isolation from waste water. A lytic phage of the Siphoviridae family was isolated and designated as vB_SflS-ISF001. The phage activity remained at high levels after 1 h of incubation at - 20 to 50 °C and was fairly stable for 1 h at pH values ranging from 7 to 9. The latent period and burst size were approximately 20 min and 53 ± 4 phages per host cell, respectively. Raw and cooked chicken breast were inoculated with a predetermined amount of S. flexneri and subjected to biocontrol test. The results showed that using vB_SflS-ISF001 phage led to more than two logs reduction in the count of viable S. flexneri. It was demonstrated that using vB_SflS-ISF001 phage is of high potential for developing an alternative strategy against S. flexneri contamination in foodstuffs.

Evaluation of the efficacy of nisin-loaded chitosan nanoparticles against foodborne pathogens in orange juice

The current study aimed to fabricate nisin-loaded chitosan (N-CS) nanoparticles through ionic interactions between positive amino groups of chitosan and negatively charged tripolyphosphate ions in the presence of nisin and to evaluate their efficacy against foodborne pathogens in orange juice. The synthesized nanoparticles were sphere-shaped and homogenous with an average size of 64.34 ± 2.1 and 147.93 ± 2.9 for chitosan and N-CS nanoparticles, respectively. The encapsulation efficiency of nisin into nanoparticles was 67.32 ± 0.63%. Both chitosan and N-CS nanoparticles showed greater stability, as indicated by a higher zeta potential value of + 49.3 and + 33.4 mV, respectively. The in vitro antibacterial activities of chitosan and N-CS nanoparticles were investigated against the Gram-positive bacteria Staphylococcus aureus and Listeria monocytogenes and the Gram-negative bacteria Escherichia coli O157:H7 and Salmonella Typhimurium. N-CS nanoparticles showed higher activity compared with chitosan nanoparticles. The highest reduction of microorganisms was recorded for S. aureus of 3.82 log CFU/ml and L. monocytogenes of 3.61 log CFU/ml. The antimicrobial activity of N-CS nanoparticles in orange juice for 48 h revealed higher activity compared with the control against all the tested strains. The highest microbial reduction was recorded for N-CS nanoparticles against S. aureus with a 3.84 log CFU/ml reduction. L. monocytogenes and E. coli 0157:H7 were reduced by 3.54 and 3.44 log CFU/ml, respectively. The results showed high potential for the N-CS nanoparticles to be used as potent antibacterial agents in food and other related areas.

Molecular analysis of the low-temperature Escherichia coli phage vB_EcoS_NBD2

A novel low-temperature Escherichia coli phage vB_EcoS_NBD2 was isolated in Lithuania from agricultural soil. With an optimum temperature for plating around 20 °C, vB_EcoS_NBD2 efficiently produced plaques on Escherichia coli NovaBlue (DE3) at a temperature range of 10-30 °C, yet failed to plate at temperatures above 35 °C. Phage vB_EcoS_NBD2 virions have a siphoviral morphology with an isometric head (65 nm in diameter), and a non-contractile flexible tail (170 nm). The 51,802-bp genome of vB_EcoS_NBD2 has a G + C content of 49.8%, and contains 87 probable protein-encoding genes as well as 1 gene for tRNA^Ser. Comparative sequence analysis revealed that 22 vB_EcoS_NBD2 ORFs encode unique proteins that have no reliable identity to database entries. Based on homology to biologically defined proteins and/or proteomics analysis, 36 vB_EcoS_NBD2 ORFs were given a putative functional annotation, including 20 genes coding for morphogenesis-related proteins and 13 associated with DNA metabolism. Phylogenetic analysis revealed that vB_EcoS_NBD2 belongs to the subfamily Tunavirinae, but cannot be assigned to any genus currently recognized by ICTV.

Short communication: Characterization of Salmonella phages from dairy calves on farms with history of diarrhea

Salmonella enterica can cause disease and mortality in calves. This pathogen is also a zoonosis that can be transmitted by animal contact or by food. The prevalence of Salmonella in dairy farms has been reported to range from 0 to 64%, and, due to the diversity of Salmonella serovars that can be circulating, Salmonella is an important concern for dairy production. Bacteriophages that infect Salmonella have been documented to be abundant and widely distributed in the dairy environment. The current study investigated the diversity of Salmonella serovars and Salmonella phages in 8 dairy farms with a history of diarrhea in southern Chile. A total of 160 samples from sick calves, healthy calves, and the environment were analyzed for Salmonella and phage. Isolated phages were characterized and classified by their host range using a panel of 26 Salmonella isolates representing 23 serovars. Host ranges were classified according to lysis profiles (LP) and their spatial distribution was mapped. Salmonella-infecting phages were identified, but none of the 160 samples were positive for Salmonella. A total of 45 phage isolates were obtained from sick calves (11), healthy calves (16), or the environment (18). According to their host range, 19 LP were identified, with LP1 being the most common on all 8 farms; LP1 represents phages that only lyse serogroup D Salmonella. The identification of Salmonella phages but not Salmonella in the same samples could suggest that these phages are controlling Salmonella in these farms.