Entrapment of a phage cocktail and cinnamaldehyde on sodium alginate emulsion-based films to fight food contamination by Escherichia coli and Salmonella Enteritidis

Effect of incorporating white pepper (Piper nigrum L.) oleoresin on starch/alginate films

The development of films based on natural components has demonstrated their potential for food preservation. In this research, the effect of the inclusion of white pepper oleoresin (WPO) in a film made from cassava starch and sodium alginate (FWPO) on the antimicrobial, physicochemical, mechanical, optical, and structural properties was evaluated. The films were formulated with different concentrations of WPO (0.0, 0.5, 1.0 and 1.5%). The results obtained indicated that the incorporation of WPO in the film increased the antioxidant activity against the 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH), and an inhibitory effect against Escherichia coli and Staphylococcus aureus bacteria was also observed. Elongation at break (EB), water vapor permeability (WVP), moisture content, solubility, and luminosity (L*) decreased significantly (p < 0.05) with the addition of WPO. On the other hand, the tensile strength (TS), the value of b* (tendency toward yellow) and the opacity increased. Scanning electron microscopy (SEM) images showed a smooth, uniform appearance, and continuous dispersion between cassava starch, alginate and WPO. FTIR spectra showed the interactions between the film components. X-ray diffraction (XRD) patterns showed that the addition of WPO did not affect the structural stability of the films. The results obtained indicate the possible use of WPO in the packaging of food products, contributing to the improvement of food quality and safety.

Application of bacteriophages in biopolymer-based functional food packaging films

Recently, food spoilage caused by pathogens has been increasing. Therefore, applying control strategies is essential. Bacteriophages can potentially reduce this problem due to their host specificity, ability to inhibit bacterial growth, and extend the shelf life of food. When bacteriophages are applied directly to food, their antibacterial activity is lost. In this regard, bacteriophage-loaded biopolymers offer an excellent option to improve food safety by extending their shelf life. Applying bacteriophages in food preservation requires comprehensive and structured information on their isolation, culturing, storage, and encapsulation in biopolymers for active food packaging applications. This review focuses on using bacteriophages in food packaging and preservation. It discusses the methods for phage application on food, their use for polymer formulation and functionalization, and their effect in enhancing food matrix properties to obtain maximum antibacterial activity in food model systems.

Pullulan nanofibrous films incorporated with W/O emulsions via microfluidic solution blow spinning technology

In this work, pullulan (PUL) nanofibrous films incorporated with water-in-oil emulsions (PE) were prepared by microfluidic blowing spinning (MBS). The microstructures of nanofibers were characterized by scanning electron microscopy (SEM), fourier transform infrared (FT-IR), and X-ray diffraction (XRD). With the addition of W/O emulsions, the thermal stability, mechanical, and water barrier properties of PUL nanofibers were improved. Increases in emulsion content significantly affected the antioxidant and antimicrobial properties of nanofibrous films. ABTS and DPPH free radical scavenging rates increased from 10.26 % and 8.57 % to 60.66 % and 57.54 %, respectively. The inhibition zone of PE nanofibers against E. coli and S. aureus increased from 11.00 to 20.00 and from 15.67 to 21.17 mm, respectively. In addition, we investigated the freshness effectiveness of PE nanofibrous films on fresh-cut apples. PE nanofibrous films significantly maintained the firmness, and reduced the weight loss and browning index of the fresh-cut apple, throughout the 4 days of storage. Thus, the PE nanofibrous films exhibited good potential to prolong the shelf life of fresh-cut fruit and promote the development of active food packaging.

An Edible Antibacterial Coating Integrating Lytic Bacteriophage Particles for the Potential Biocontrol of Salmonella enterica in Ripened Cheese

The goal of this research was to create an antibacterial biopolymeric coating integrating lytic bacteriophages against Salmonella enterica for use in ripened cheese. Salmonella enterica is the main pathogen that contaminates food products and the food industry. The food sector still uses costly and non-selective decontamination and disease control methods. Therefore, it is necessary to look for novel pathogen biocontrol technologies. Bacteriophage-based biocontrol seems like a viable option in this situation. The results obtained show promise for food applications since the edible packaging developed (EdiPhage) was successful in maintaining lytic phage viability while preventing the contamination of foodstuff with the aforementioned bacterial pathogen.

Paving the way forward: Escherichia coli bacteriophages in a One Health approach

Escherichia coli is one of the most notorious pathogens for its ability to adapt, colonize, and proliferate in different habitats through a multitude of acquired virulence factors. Its presence affects the food-processing industry and causes food poisoning, being also a major economic burden for the food, agriculture, and health sectors. Bacteriophages are emerging as an appealing strategy to mitigate bacterial pathogens, including specific E. coli pathovars, without exerting a deleterious effect on humans and animals. This review globally analyzes the applied research on E. coli phages for veterinary, food, and human use. It starts by describing the pathogenic E. coli pathotypes and their relevance in human and animal context. The idea that phages can be used as a One Health approach to control and interrupt the transmission routes of pathogenic E. coli is sustained through an exhaustive revision of the recent literature. The emerging phage formulations, genetic engineering and encapsulation technologies are also discussed as a means of improving phage-based control strategies, with a particular focus on E. coli pathogens.

Characterization of Sodium Alginate-Based Films Blended with Olive Leaf and Laurel Leaf Extracts Obtained by Ultrasound-Assisted Technology

Due to environmental concerns, there is an increasing need to reduce the use of synthetic and non-renewable packaging materials to reduce waste and increase sustainability. This study aimed to characterise sodium alginate edible-based films (SA) incorporated with laurel leaf extract (LLE) and olive leaf extract (OLE) obtained by ultrasound-assisted extraction. Determination of total phenolic content, antioxidant, and antimicrobial activity was performed for the extracts and films. Also, thickness, tensile strength, elongation at break, modulus of elasticity, opacity and colour, moisture content, water vapour permeability (WVP), Fourier-transform infrared spectroscopy (FTIR) spectra, and surface morphology by scanning electron microscope (SEM) analyses were performed for the films. LLE yielded better results in terms of phenolic content (195 mg GAE/g), antioxidant (2.1 TE/g extract) and antimicrobial activity (MIC at 1% for Listeria monocytogenes and Staphylococcus aureus, and 1.8% for Enterococcus faecalis). For the films, the simultaneous incorporation of LLE 1% (w/v) and OLE 1% (w/v) resulted in a significant reduction of approximately 2 log CFU/g against S. aureus. The addition of LLE and OLE extracts also proved to improve barrier properties (lower WVP for SA films with LLE 1% + OLE 1%, 3.49 × 10-11 g m-1 s-1 Pa-1) and promoted changes in resistance and flexibility. The results demonstrated that active alginate-based films can be valuable for enhancing food preservation.

Characterization and Genome Study of a Newly Isolated Temperate Phage Belonging to a New Genus Targeting Alicyclobacillus acidoterrestris

The spoilage of juices by Alicyclobacillus spp. remains a serious problem in industry and leads to economic losses. Compounds such as guaiacol and halophenols, which are produced by Alicyclobacillus, create undesirable flavors and odors and, thus, decrease the quality of juices. The inactivation of Alicyclobacillus spp. constitutes a challenge because it is resistant to environmental factors, such as high temperatures, and active acidity. However, the use of bacteriophages seems to be a promising approach. In this study, we aimed to isolate and comprehensively characterize a novel bacteriophage targeting Alicyclobacillus spp. The Alicyclobacillus phage strain KKP 3916 was isolated from orchard soil against the Alicyclobacillus acidoterrestris strain KKP 3133. The bacterial host's range and the effect of phage addition at different rates of multiplicity of infections (MOIs) on the host's growth kinetics were determined using a Bioscreen C Pro growth analyzer. The Alicyclobacillus phage strain KKP 3916, retained its activity in a wide range of temperatures (from 4 °C to 30 °C) and active acidity values (pH from 3 to 11). At 70 °C, the activity of the phage decreased by 99.9%. In turn, at 80 °C, no activity against the bacterial host was observed. Thirty minutes of exposure to UV reduced the activity of the phages by almost 99.99%. Based on transmission-electron microscopy (TEM) and whole-genome sequencing (WGS) analyses, the Alicyclobacillus phage strain KKP 3916 was classified as a tailed bacteriophage. The genomic sequencing revealed that the newly isolated phage had linear double-stranded DNA (dsDNA) with sizes of 120 bp and 131 bp and 40.3% G+C content. Of the 204 predicted proteins, 134 were of unknown function, while the remainder were annotated as structural, replication, and lysis proteins. No genes associated with antibiotic resistance were found in the genome of the newly isolated phage. However, several regions, including four associated with integration into the bacterial host genome and excisionase, were identified, which indicates the temperate (lysogenic) life cycle of the bacteriophage. Due to the risk of its potential involvement in horizontal gene transfer, this phage is not an appropriate candidate for further research on its use in food biocontrol. To the best of our knowledge, this is the first article on the isolation and whole-genome analysis of the Alicyclobacillus-specific phage.

Effect of lipid oxidation on quality attributes and control technologies in dried aquatic animal products: a critical review

Aquatic animals are viewed as a good source of healthy lipids. Although drying is an effective method for the preservation of aquatic animal products (AAPs), the whole process is accompanied by lipid oxidation. This article reviews the main mechanism of lipid oxidation in the drying process. It also summarizes the effects of lipid oxidation on the quality of dried aquatic animal products (DAAPs), including nutrients, color, flavor, and hazard components, especially for those harmful aldehydes and heterocyclic amines. In addition, it concluded that moderate lipid oxidation contributes to improving the quality of products. Still, excessive lipid oxidation produces hazardous substances and induces health risks. Hence, to obtain high-quality DAAPs, some effective control technologies to promote/prevent lipid oxidation are introduced and deeply discussed, including salting, high-pressure processing, irradiation, non-thermal plasma technology, defatting treatments, antioxidants, and edible coating. A systematic review of the effect of lipid oxidation on quality attributes and control technologies in DAAPs is presented, and some perspectives are made for future research.

An Edible Biopolymeric Microcapsular Wrapping Integrating Lytic Bacteriophage Particles for Salmonella enterica: Potential for Integration into Poultry Feed

This research work aimed at developing an edible biopolymeric microcapsular wrapping (EBMW) integrating lytic bacteriophage particles for Salmonella enterica, with potential application in poultry feed for biocontrol of that pathogen. This pathogen is known as one of the main microorganisms responsible for contamination in the food industry and in foodstuff. The current techniques for decontamination and pathogen control in the food industry can be very expensive, not very selective, and even outdated, such as the use of broad-spectrum antibiotics that end up selecting resistant bacteria. Hence, there is a need for new technologies for pathogen biocontrol. In this context, bacteriophage-based biocontrol appears as a potential alternative. As a cocktail, both phages were able to significantly reduce the bacterial load after 12 h of treatment, at either multiplicity of infection (MOI) 1 and 10, by 84.3% and 87.6%, respectively. Entrapment of the phage virions within the EBMW matrix did not exert any deleterious effect upon their lytic activity. The results obtained showed high promise for integration in poultry feed aiming at controlling Salmonella enterica, since the edible biopolymeric microcapsular wrapping integrating lytic bacteriophage particles developed was successful in maintaining lytic phage viability while fully stabilizing the phage particles.

Bacteriophage Delivery Systems for Food Applications: Opportunities and Perspectives

Currently, one-third of all food produced worldwide is wasted or lost, and bacterial contamination is one of the main reasons. Moreover, foodborne diseases are a severe problem, causing more than 420,000 deaths and nearly 600 million illnesses yearly, demanding more attention to food safety. Thus, new solutions need to be explored to tackle these problems. A possible solution for bacterial contamination is using bacteriophages (phages), which are harmless to humans; these natural viruses can be used to prevent or reduce food contamination by foodborne pathogens. In this regard, several studies showed the effectiveness of phages against bacteria. However, when used in their free form, phages can lose infectivity, decreasing the application in foods. To overcome this problem, new delivery systems are being studied to incorporate phages and ensure prolonged activity and controlled release in food systems. This review focuses on the existent and new phage delivery systems applied in the food industry to promote food safety. Initially, an overview of phages, their main advantages, and challenges is presented, followed by the different delivery systems, focused in methodologies, and biomaterials that can be used. In the end, examples of phage applications in foods are disclosed and future perspectives are approached.

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.

Application of Lytic Bacteriophages and Their Enzymes to Reduce Saprophytic Bacteria Isolated from Minimally Processed Plant-Based Food Products-In Vitro Studies

The aim of this study was to isolate phage enzymes and apply them in vitro for eradication of the dominant saprophytic bacteria isolated from minimally processed food. Four bacteriophages-two Enterobacter-specific and two Serratia-specific, which produce lytic enzymes-were used in this research. Two methods of phage enzyme isolation were tested, namely precipitation with acetone and ultracentrifugation. It was found that the number of virions could be increased almost 100 times due to the extension of the cultivation time (72 h). The amplification of phage particles and lytic proteins was dependent on the time of cultivation. Considering the influence of isolated enzymes on the growth kinetics of bacterial hosts, proteins isolated with acetone after 72-hour phage propagation exhibited the highest inhibitory effect. The reduction of bacteria count was dependent on the concentration of enzymes in the lysates. The obtained results indicate that phages and their lytic enzymes could be used in further research aiming at the improvement of microbiological quality and safety of minimally processed food products.

Cinnamaldehyde causes developmental neurotoxicity in zebrafish via the oxidative stress pathway that is rescued by astaxanthin

Toxicology studies provide a reliable dose range for the use of compounds. Zebrafish show unique advantages in toxicology research. Cinnamaldehyde (Cin) is one of the main active compounds isolated from Cinnamon trees and other species of the genus Cinnamomum. In this study, we investigated the developmental neurotoxicity of cinnamaldehyde in zebrafish and preliminarily explored its underlying mechanism. Cinnamaldehyde causes developmental neurotoxicity in zebrafish, as evidenced by the damage to ventricular structures, eye malformations, shortened body length, trunk curvature, decreased neuronal fluorescence, and pericardial oedema. Moreover, it can induce abnormal behaviour and gene expression in zebrafish. After treatment with the oxidative stress inhibitor astaxanthin, the behaviour and abnormal gene expression were reversed. All of these data demonstrated that the developmental neurotoxicity of cinnamaldehyde might be attributed to oxidative stress. In addition, this study also confirmed that zebrafish is a reliable model for toxicity studies.

Sodium alginate as an eco-friendly rheology modifier and salt-tolerant fluid loss additive in water-based drilling fluids

The rheological and filtration performance of drilling fluids greatly depends on the additives used. To address the negative impact on the drilling fluid performance stemming from electrolyte contamination, a sustainable sodium alginate (SA) biopolymer was employed as an additive in water-based drilling fluids to overcome the performance deterioration caused by the polyelectrolyte effect under salt contamination. The results demonstrated that SA performs better than sodium carboxymethyl cellulose (Na-CMC) and polyanionic cellulose (PAC-LV), the widely used drilling fluid additives. Although exposed to highly concentrated salt contamination, the addition of SA can mitigate viscosity variation and maintain a lower filtration volume of a base fluid (BF), whereas an advanced variation in CMC/BF and PAC/BF was observed. The possible rheology and filtration mechanism of SA under highly concentrated salt contamination were investigated through zeta potential, particle size distribution, and scanning electron microscopy (SEM). The results revealed that the anchoring groups on the SA molecular chain enable them to strongly adsorb on the negatively charged bentonite surface via hydrogen and ionic bond interactions, leading to a significant improvement in both rheological and filtration performance. Therefore, SA with excellent salt tolerance and sustainability confers practical applicability that could extend to the preparation of saltwater-based and other inhibitive drilling fluids.

An in vitro fermentation model to study the impact of bacteriophages targeting Shiga toxin-encoding Escherichia coli on the colonic microbiota

Lytic bacteriophages are considered safe for human consumption as biocontrol agents against foodborne pathogens, in particular in ready-to-eat foodstuffs. Phages could, however, evolve to infect different hosts when passing through the gastrointestinal tract (GIT). This underlines the importance of understanding the impact of phages towards colonic microbiota, particularly towards bacterial families usually found in the colon such as the Enterobacteriaceae. Here we propose in vitro batch fermentation as model for initial safety screening of lytic phages targeting Shiga toxin-producing Escherichia coli (STEC). As inoculum we used faecal material of three healthy donors. To assess phage safety, we monitored fermentation parameters, including short chain fatty acid production and gas production/intake by colonic microbiota. We performed shotgun metagenomic analysis to evaluate the outcome of phage interference with colonic microbiota composition and functional potential. During the 24 h incubation, concentrations of phage and its host were also evaluated. We found the phage used in this study, named E. coli phage vB_EcoS_Ace (Ace), to be safe towards human colonic microbiota, independently of the donors’ faecal content used. This suggests that individuality of donor faecal microbiota did not interfere with phage effect on the fermentations. However, the model revealed that the attenuated STEC strain used as phage host perturbed the faecal microbiota as based on metagenomic analysis, with potential differences in metabolic output. We conclude that the in vitro batch fermentation model used in this study is a reliable safety screening for lytic phages intended to be used as biocontrol agents.

Implication of a gene deletion on a Salmonella Enteritidis phage growth parameters

Synthetic biology has been applied countless times for the modification and improvement of bacterial strains and for the synthesis of products that do not exist in nature. Phages are natural predators of bacteria controlling their population levels; however, their genomes carry several genes with unknown functions. In this work, Bacteriophage Recombineering of Electroporated DNA was used to assess the influence of deletion of a single gene with unknown function in the overall replication parameters of Salmonella phage PVP-SE2. Deletion of ORF_01, transcribed immediately after infection, reduced both the latent and rise periods by 5 min in PVP-SE2ΔORF_01 compared to the wild-type phage. A direct consequence of the deletion led to a smaller progeny release per infected cell by the mutant compared to the wild-type phage. Despite the difference in growth characteristics, the mutant phage remained infective towards exponentially growing cells. The mutation engineered endured for at least ten passages, showing that there is no reversion back to the wild-type sequence. This study provides proof of concept that methodologies used for phage engineering should always be complemented by phage growth characterization to assess whether a mutation can trigger undesirable characteristics.

Phages for Africa: The Potential Benefit and Challenges of Phage Therapy for the Livestock Sector in Sub-Saharan Africa

One of the world’s fastest-growing human populations is in Sub-Saharan Africa (SSA), accounting for more than 950 million people, which is approximately 13% of the global population. Livestock farming is vital to SSA as a source of food supply, employment, and income. With this population increase, meeting this demand and the choice for a greater income and dietary options come at a cost and lead to the spread of zoonotic diseases to humans. To control these diseases, farmers have opted to rely heavily on antibiotics more often to prevent disease than for treatment. The constant use of antibiotics causes a selective pressure to build resistant bacteria resulting in the emergence and spread of multi-drug resistant (MDR) organisms in the environment. This necessitates the use of alternatives such as bacteriophages in curbing zoonotic pathogens. This review covers the underlying problems of antibiotic use and resistance associated with livestock farming in SSA, bacteriophages as a suitable alternative, what attributes contribute to making bacteriophages potentially valuable for SSA and recent research on bacteriophages in Africa. Furthermore, other topics discussed include the creation of phage biobanks and the challenges facing this kind of advancement, and the regulatory aspects of phage development in SSA with a focus on Kenya.

Active Carboxymethylcellulose-Based Edible Films: Influence of Free and Encapsulated Curcumin on Films' Properties

Carboxymethylcellulose (CMC)-based films can act as a protective barrier in food surfaces and a carrier of bioactive compounds, such as curcumin. However, incorporating curcumin in hydrophilic matrixes can be a challenge, and new strategies need to be explored. In this work, CMC-based films containing free curcumin and curcumin-loaded nanohydrogels (composed of lactoferrin and glycomacropeptide) were produced and characterized. The incorporation of curcumin-loaded nanohydrogels showed a significant decrease in films’ thickness (from 0.0791 to 0.029 mm). Furthermore, the water vapor permeability of CMC-based films was significantly decreased (62%) by incorporating curcumin-loaded nanohydrogels in the films. The water affinity’s properties (moisture, solubility, and contact angle) of films were also affected by incorporating encapsulated curcumin. The addition of nanohydrogels to CMC-based films reduced the tensile strength values from 16.46 to 9.87 MPa. Chemical interactions were analyzed using Fourier transform infrared spectroscopy. The release profile of curcumin from CMC-based films was evaluated at 25 °C using a hydrophilic food simulant and suggests that the release mechanism of the curcumin happens by Fick’s diffusion and Case II transport. Results showed that protein-based nanohydrogels can be a good strategy for incorporating curcumin in edible films, highlighting their potential for use in food applications.

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.

Development of Biodegradable Films Loaded with Phages with Antilisterial Properties

The inhibitory and bactericidal capacity of Listex P100 bacteriophage has been studied against different concentrations of Listeria monocytogenes in stationary and exponential phases. Three different matrices were employed to developed films incorporating Listex P100: (1) sodium caseinate, (2) sodium alginate mixed with gelatin, and (3) polyvinyl alcohol (PVOH). All the films were successfully developed by casting at room temperature. These active biodegradable films were optical, structural, and thermally characterized, and their antimicrobial capacities against L. monocytogenes were studied. The incorporation of phages did not affect the morphology, colour, opacity, and thermal stability of polymers. The antimicrobial analysis revealed the bacteriophage presented a high antimicrobial capacity against L. monocytogenes in the stationary phase (4.40 and 6.19 log reduction values or bactericide effect depending on the initial inoculum of the pathogen). Developed films showed antimicrobial capacity close to 1 log after 24 h of incubation at 30 °C. The effectiveness of PVOH films was greater under refrigeration conditions, reaching 2 log reduction after eight days of incubation. The use of these films as a coating in a food or as part of a packaging could improve food safety against the growth of pathogenic microorganisms such as Listeria monocytogenes.

A Localized Phage-Based Antimicrobial System: Effect of Alginate on Phage Desorption from β-TCP Ceramic Bone Substitutes

Tricalcium phosphate (TCP) is a prosthetic material commonly used as a bone substitute to repair osteoarticular diseases and injuries. In this type of bone reconstruction surgery, antibiotics remain the common preventive and therapeutic treatment for bacterial infection. Nevertheless, the emergence of multi-resistant strains requires complimentary or alternative treatments. Today, one of the promising alternative approaches is phage therapy. Phages are bacterial viruses that have several advantages over chemotherapy, such as the specificity of bacterial strain, the absence of side effects, and a rapid response. In this work, we studied the impact of alginate hydrogels for overlaying λvir-phage-loaded β-TCP ceramic bone substitutes, delaying the phage desorption. The results show that the use of a 1% alginate-CaCl2 hydrogel overlapping the β-TCP ceramic pellets leads to higher initial phage concentration on the material and extends the released time of phages to two weeks when compared with control pellets. These alginate-coated biomaterials also generate faster bacterial lysis kinetics and could therefore be a good practical prosthetic device for bone and joint surgeries by allowing local treatment of bacterial infections with phage therapy for a longer period of time.