Aerosol Spray Treatment with Bacteriophages and Competitive Exclusion Reduces Salmonella Enteritidis Infection in Chickens

Combined application of bacteriophages with a competitive exclusion culture and carvacrol with organic acids can reduce Campylobacter in primary broiler production

For reducing Campylobacter (C.) in the food production chain and thus the risk to the consumer, the combined application of different measures as a multiple-hurdle approach is currently under discussion. This is the first study to investigate possible synergistic activities in vivo, aiming at reducing intestinal C. jejuni counts by administering (i) bacteriophages (phages) in combination with a competitive exclusion (CE) product and (ii) carvacrol combined with organic acids. The combined application of the two selected phages (Fletchervirus phage NCTC 12673 and Firehammervirus phage vB_CcM-LmqsCPL1/1) and the CE product significantly reduced C. jejuni loads by 1.0 log10 in cecal and colonic contents as well as in cloacal swabs at the end of the trial (33 and 34 days post hatch). The proportion of bacterial isolates showing reduced phage susceptibility ranged from 10.9% (isolates from cecal content) to 47.8% (isolates from cloacal swabs 32 days post hatch) for the Fletchervirus phage, while all tested isolates remained susceptible to the Firehammervirus phage. The use of carvacrol combined with an organic acid blend (sorbic acid, benzoic acid, propionic acid, and acetic acid) significantly reduced Campylobacter counts by 1.0 log10 in cloacal swabs on day 30 only.

Role of bacteriophages in shaping gut microbial community

Phages are the most diversified and dominant members of the gut virobiota. They play a crucial role in shaping the structure and function of the gut microbial community and consequently the health of humans and animals. Phages are found mainly in the mucus, from where they can translocate to the intestinal organs and act as a modulator of gut microbiota. Understanding the vital role of phages in regulating the composition of intestinal microbiota and influencing human and animal health is an emerging area of research. The relevance of phages in the gut ecosystem is supported by substantial evidence, but the importance of phages in shaping the gut microbiota remains unclear. Although information regarding general phage ecology and development has accumulated, detailed knowledge on phage-gut microbe and phage-human interactions is lacking, and the information on the effects of phage therapy in humans remains ambiguous. In this review, we systematically assess the existing data on the structure and ecology of phages in the human and animal gut environments, their development, possible interaction, and subsequent impact on the gut ecosystem dynamics. We discuss the potential mechanisms of prophage activation and the subsequent modulation of gut bacteria. We also review the link between phages and the immune system to collect evidence on the effect of phages on shaping the gut microbial composition. Our review will improve understanding on the influence of phages in regulating the gut microbiota and the immune system and facilitate the development of phage-based therapies for maintaining a healthy and balanced gut microbiota.

Phage-Based Biosanitation Strategies for Minimizing Persistent Salmonella and Campylobacter Bacteria in Poultry

Control strategies to minimize pathogenic bacteria in food animal production are one of the key components in ensuring safer food for consumers. The most significant challenges confronting the food industry, particularly in the major poultry and swine sectors, are antibiotic resistance and resistance to cleaning and disinfection in zoonotic bacteria. In this context, bacteriophages have emerged as a promising tool for zoonotic bacteria control in the food industry, from animals and farm facilities to the final product. Phages are viruses that infect bacteria, with several advantages as a biocontrol agent such as high specificity, self-replication, self-limitation, continuous adaptation, low inherent toxicity and easy isolation. Their development as a biocontrol agent is of particular interest, as it would allow the application of a promising and even necessary "green" technology to combat pathogenic bacteria in the environment. However, bacteriophage applications have limitations, including selecting appropriate phages, legal restrictions, purification, dosage determination and bacterial resistance. Overcoming these limitations is crucial to enhance phage therapy's effectiveness against zoonotic bacteria in poultry. Thus, this review aims to provide a comprehensive view of the phage-biosanitation strategies for minimizing persistent Salmonella and Campylobacter bacteria in poultry.

Modulation of Caecal Microbiota and Metabolome Profile in Salmonella-Infected Broilers by Phage Therapy

Bacteriophage therapy is considered one of the most promising tools to control zoonotic bacteria, such as Salmonella, in broiler production. Phages exhibit high specificity for their targeted bacterial hosts, causing minimal disruption to the niche microbiota. However, data on the gut environment's response to phage therapy in poultry are limited. This study investigated the influence of Salmonella phage on host physiology through caecal microbiota and metabolome modulation using high-throughput 16S rRNA gene sequencing and an untargeted metabolomics approach. We employed 24 caecum content samples and 24 blood serum samples from 4-, 5- and 6-week-old broilers from a previous study where Salmonella phages were administered via feed in Salmonella-infected broilers, which were individually weighed weekly. Phage therapy did not affect the alpha or beta diversity of the microbiota. Specifically, we observed changes in the relative abundance of 14 out of the 110 genera using the PLS-DA and Bayes approaches. On the other hand, we noted changes in the caecal metabolites (63 up-accumulated and 37 down-accumulated out of the 1113 caecal metabolites). Nevertheless, the minimal changes in blood serum suggest a non-significant physiological response. The application of Salmonella phages under production conditions modulates the caecal microbiome and metabolome profiles in broilers without impacting the host physiology in terms of growth performance.

An Experimental Field Trial Investigating the Use of Bacteriophage and Manure Slurry Applications in Beef Cattle Feedlot Pens for Salmonella Mitigation

Post-harvest Salmonella mitigation techniques are insufficient at addressing Salmonella harbored in cattle lymph nodes, necessitating the exploration of pre-harvest alternatives that reduce Salmonella prior to dissemination to the lymph nodes. A 2 × 2, unbalanced experiment was conducted to determine the effectiveness of pre-harvest treatments applied to the pen surface for Salmonella mitigation in cattle. Treatments included manure slurry intended to mimic pen run-off water (n = 4 pens), a bacteriophage cocktail (n = 4), a combination of both treatments (n = 5), and a control group (n = 5) that received no treatment. Environment samples from 18 feedlot pens and fecal grabs, hide swabs, and subiliac lymph nodes from 178 cattle were collected and selectively enriched for Salmonella, and Salmonella isolates were sequenced. The combination treatment was most effective at reducing Salmonella, and the prevalence was significantly lower compared with the control group for rump swabs on Days 14 and 21. The treatment impact on Salmonella in the lymph nodes could not be determined due to low prevalence. The reduction on cattle hides suggests that bacteriophage or water treatments applied to the feedlot pen surface may reduce Salmonella populations in cattle during the pre-harvest period, resulting in reduced contamination during slaughter and processing.

Use of Phages to Treat Antimicrobial-Resistant Salmonella Infections in Poultry

Simple Summary

Salmonellosis, an infection in humans and animals caused by Salmonella spp., poses a major concern to public health and food safety worldwide. Antibiotics are mostly prescribed to treat salmonellosis. Unfortunately, indiscriminate use of antibiotics leads to the emergence and transmission of multidrug-resistant Salmonella spp. As antibiotics are becoming increasingly ineffective, infections caused by MDR strains will be difficult to manage. The search for an alternative to antibiotics has led scientists to give renewed attention on phage therapy. Though commercial use of phages for controlling Salmonella in poultry is still in its early stage, the use of lytic phages is considered an environmentally friendly, cost-effective, and sustainable antimicrobial approach. Moreover, it provides advantages over antibiotics in terms of specificity, cost of development, resistance, and genetic amenability. Studies on laboratory and field scale use show promise on the effectiveness of phages against MDR Salmonella spp. However, inadequate data on safety of phage use, phage stability, and lack of regulatory framework remain major obstacles in the commercial application of phages. Our article provides a comprehensive overview on global prevalence and antimicrobial resistance of Salmonella in poultry, the efforts to control Salmonella using phage therapy, and challenges as well as future prospects of phage therapy.

Abstract

Salmonellosis is one of the most common bacterial infections that impacts both human health and poultry production. Although antibiotics are usually recommended for treating Salmonella infections, their misuse results in the evolution and spread of multidrug-resistant (MDR) bacteria. To minimize the health and economic burdens associated with antimicrobial resistance, a novel antibacterial strategy that can obliterate pathogens without any adverse effects on humans and animals is urgently required. Therefore, therapeutic supplementation of phages has gained renewed attention because of their unique ability to lyse specific hosts, cost-effective production, environmentally-friendly properties, and other potential advantages over antibiotics. In addition, the safety and efficacy of phage therapy for controlling poultry-associated Salmonella have already been proven through experimental studies. Phages can be applied at every stage of poultry production, processing, and distribution through different modes of application. Despite having a few limitations, the optimized and regulated use of phage cocktails may prove to be an effective option to combat infections caused by MDR pathogens in the post-antibiotic era. This article mainly focuses on the occurrence of salmonellosis in poultry and its reduction with the aid of bacteriophages. We particularly discuss the prevalence of Salmonella infections in poultry and poultry products; review the trends in antibiotic resistance; and summarize the application, challenges, and prospects of phage therapy in the poultry industry.

Bacteriophage Cocktail Can Effectively Control Salmonella Biofilm in Poultry Housing

Salmonella enterica serovar Enteritidis (S. Enteritidis) is the major contaminant of poultry products, and its ability to form biofilms on produced food and poultry farm processing surfaces contributes to Salmonella transmission to humans. Bacteriophages have come under increasing interest for anti-Salmonella biofilm control. In this study, we used the three previously sequenced and described phages UPWr_S1, UPWr_S3, and UPWr_S4 and a phage cocktail, UPWr_S134, containing these three phages to degrade biofilms formed by two S. Enteritidis strains, 327 lux and ATCC 13076, in vitro. It was found that treatment with bacteriophages significantly reduced biofilm on a 96-well microplate (32–69%) and a stainless steel surface (52–98%) formed by S. Enteritidis 327 lux. The reduction of biofilm formed by S. Enteritidis ATCC 13076 in the 96-well microplate and on a stainless steel surface for bacteriophage treatment was in the range of 73–87% and 60–97%, respectively. Under laboratory conditions, an experimental model utilizing poultry drinkers artificially contaminated with S. Enteritidis 327 lux and treated with UPWr_S134 phage cocktail was applied. In in vitro trials, the phage cocktail significantly decreased the number of Salmonella on the surface of poultry drinkers. Moreover, the phage cocktail completely eradicated Salmonella from the abundant bacterial load on poultry drinkers in an experimentally infected chickens. Therefore, the UPWr_S134 phage cocktail is a promising candidate for Salmonella biocontrol at the farm level.

Limitations of Phage Therapy and Corresponding Optimization Strategies: A Review

Bacterial infectious diseases cause serious harm to human health. At present, antibiotics are the main drugs used in the treatment of bacterial infectious diseases, but the abuse of antibiotics has led to the rapid increase in drug-resistant bacteria and to the inability to effectively control infections. Bacteriophages are a kind of virus that infects bacteria and archaea, adopting bacteria as their hosts. The use of bacteriophages as antimicrobial agents in the treatment of bacterial diseases is an alternative to antibiotics. At present, phage therapy (PT) has been used in various fields and has provided a new technology for addressing diseases caused by bacterial infections in humans, animals, and plants. PT uses bacteriophages to infect pathogenic bacteria so to stop bacterial infections and treat and prevent related diseases. However, PT has several limitations, due to a narrow host range, the lysogenic phenomenon, the lack of relevant policies, and the lack of pharmacokinetic data. The development of reasonable strategies to overcome these limitations is essential for the further development of this technology. This review article described the current applications and limitations of PT and summarizes the existing solutions for these limitations. This information will be useful for clinicians, people working in agriculture and industry, and basic researchers.

Salmonella phage CKT1 significantly relieves the body weight loss of chicks by normalizing the abnormal intestinal microbiome caused by hypervirulent Salmonella Pullorum

Pullorum disease caused by Salmonella Pullorum remains an important disease for the poultry industry due to high morbidity and mortality in many countries. Phage therapy is becoming an alternative strategy to control multidrug-resistant Salmonella infections in young chicks. However, how bacteriophages affect the growth performance of chicks infected with S. Pullorum remains poorly understood. Herein, we assessed the therapeutic efficacy of Salmonella phage CKT1 against hypervirulent arthritis-causing S. Pullorum. The results showed that single phage treatment after hypervirulent S. Pullorum infection significantly improved body weight loss of chicks. Compared with enlarged liver and spleen in only Salmonella challenged group, phage administration substantially reduced the liver/body and spleen/body weight ratios, bacterial loads in organs and the degree of hepatic sinusoidal dilatation and congestion. Moreover, phage CKT1 can enter the organs of chicks and stay for at least 3 d in liver and spleen, and promote higher serum levels of IL-6 production within 6 d postinfection, indicating phage-induced bacterial lysis may be involved in inflammatory immune response to S. Pullorum infection. Analysis of the microbiome of gastrointestinal tract of chicks demonstrated that Salmonella challenge significantly reduced the relative abundances of Lachnoclostridium and Blautia, resulting in remarkably increased Escherichia-Shigella and Klebsiella becoming the predominant bacterial taxa. In contrast, the use of phage CKT1 significantly reduced Escherichia-Shigella and Klebsiella populations in intestine, permitting the proliferation of beneficial microbiota in Firmicutes including Lachnoclostridium, Ruminococcus, Lactobacillus, and Pseudoflavonifractor. In addition, phage alone treatments did not affect the normal gut microbiota structure of chicks, and phage therapy on Salmonella infected chicks increased bacteria species richness in the cecum. These results suggest that Salmonella phage CKT1 could improve growth performance of chicks challenged with S. Pullorum by normalizing the abnormal intestinal microbiome.

Non-Antibiotics Strategies to Control Salmonella Infection in Poultry

Salmonella spp. is a facultative intracellular pathogen causing localized or systemic infections, involving economic and public health significance, and remains the leading pathogen of food safety concern worldwide, with poultry being the primary transmission vector. Antibiotics have been the main strategy for Salmonella control for many years, which has allowed producers to improve the growth and health of food-producing animals. However, the utilization of antibiotics has been reconsidered since bacterial pathogens have established and shared a variety of antibiotic resistance mechanisms that can quickly increase within microbial communities. The use of alternatives to antibiotics has been recommended and successfully applied in many countries, leading to the core aim of this review, focused on (1) describing the importance of Salmonella infection in poultry and the effects associated with the use of antibiotics for disease control; (2) discussing the use of feeding-based (prebiotics, probiotics, bacterial subproducts, phytobiotics) and non-feeding-based (bacteriophages, in ovo injection, vaccines) strategies in poultry production for Salmonella control; and (3) exploring the use of complementary strategies, highlighting those based on -omics tools, to assess the effects of using the available antibiotic-free alternatives and their role in lowering dependency on the existing antimicrobial substances to manage bacterial infections in poultry effectively.

Isolation, Characterization, and Efficacy of Three Lytic Phages Infecting Multidrug-Resistant Salmonella Serovars from Poultry Farms in Egypt

Multidrug-resistant (MDR) Salmonella serovars are considered a significant threat to veterinary and public health. Developing new antimicrobial compounds that can treat the infection caused by these notorious pathogens is a big challenge. Bacteriophages can be adsorbed on and inhibit the growth of bacteria, providing optimal and promising alternatives to chemical antimicrobial compounds against foodborne pathogens due to their abundance in nature and high host specificity. The objective of the current study was to isolate and characterize new phages from poultry farms and sewage and to evaluate their efficacy against S. Enteritidis isolates. The study reports three lytic phages designated as ϕSET1, ϕSET2, and ϕSET3 isolated from poultry carcasses and sewage samples in Qalubiya governorate Egypt. The effectiveness of phages was evaluated against multidrug-resistant S. Enteritidis strains. Electron microscopy showed that these phages belong to the Siphoviridae family. Phages were tested against 13 bacterial strains to determine their host range. They could infect four S. Enteritidis and one S. Typhimurium; however, they did not infect other tested bacterial species, indicating their narrow infectivity. The bacteriophage's single-step growth curves revealed a latent period of 20 min for ϕSET1 and 30 min for ϕSET2 and ϕSET3. The isolated Salmonella phages prevented the growth of S. Enteritidis for up to 18 hrs. The findings revealed that Salmonella phages could be used as alternative natural antibacterial compounds to combat infection with MDR S. Enteritidis in the poultry industry and represent a step forward to using large panels of phages for eliminating Salmonella from the food chain.

Efficacy of phage therapy in poultry: a systematic review and meta-analysis

The increasing prevalence of antimicrobial resistant bacteria has sparked a renewed interest in alternative bacterial control methods, including bacteriophage administration. In order to determine the overall efficacy of bacteriophage administration for the reduction of bacterial concentrations in poultry, a systematic literature review and a meta-analysis were conducted. The systematic review included studies in which 1) live chickens were challenged with a known quantity of bacteria; and 2) challenged chickens were administered a known quantity of bacteriophages; and 3) concentrations of the challenge bacteria were measured in tissue/fluid samples from both challenged and unchallenged chickens after phage administration; and 4) either standard deviation or standard error was reported. Results of a meta-analysis of the 12 studies included in this review (total inputs: n = 41; total observations: n = 711) indicated that concentrations of challenge bacteria were significantly lower (P < 0.001) in challenged, phage-treated chickens than in challenged, untreated chickens (effect size = -0.82 log₁₀ cfu/g). Phage treatment effects were significantly greater (P < 0.01) in chickens administered phages via feed than in chickens administered phages via drinking water or aerosol spray. No significant differences were observed between subgroups when data were disaggregated by various other experimental characteristics, though some significant differences were observed across subgroups after further disaggregation by sampling time and animal age. As a whole, findings from the systematic review and meta-analysis indicate that phage administration can significantly lower concentrations of targeted bacteria in chickens and that, in some instances, the effect may be greater in the short-term vs. the long-term and in older vs. younger chickens.

Salmonella enterica Serovar Enteritidis Control in Poultry Litter Mediated by Lytic Bacteriophage Isolated from Swine Manure

We report the use of bacteriophages for control of Salmonella Enteritidis in poultry production. Phage was isolated by the double-agar plate assay from agricultural waste samples, and one isolate, named SM1, was selected and propagated for application in poultry litter. Two experimental protocols were tested: single treatment and repeated treatment (re-application of phage SM1 after 6 h and 12 h). Each treatment cycle involved 25 g of poultry litter placed in plastic boxes and contaminated with 10⁵ Colony Forming Units mL⁻¹ (CFU mL⁻¹) of S. Enteritidis, in independent duplicates. The contaminated litter was treated with 10⁶ Plaque Forming Units mL⁻¹ (PFU mL⁻¹) of SM1 phage by dripping. Repeated application of phage SM1 reduced Salmonella counts by over 99.9%; the phage persisted in poultry litter for over 35 days. This study illustrates the application of SM1 treatment as a promising technology for bacterial control in production matrices that could allow safe and sustainable use of agricultural waste products as biofertilizers.

Overcoming bacterial resistance to antibiotics: the urgent need – a review

The discovery of antibiotics is considered one of the most crucial breakthroughs in medicine and veterinary science in the 20th century. From the very beginning, this type of drug was used as a ‘miraculous cure’ for every type of infection. In addition to their therapeutic uses, antibiotics were also used for disease prevention and growth promotion in livestock. Though this application was banned in the European Union in 2006, antibiotics are still used in this way in countries all over the world. The unlimited and unregulated use of antibiotics has increased the speed of antibiotic resistance’s spread in different types of organisms. This phenomenon requires searching for new strategies to deal with hard-to-treat infections. The antimicrobial activity of some plant derivatives and animal products has been known since ancient times. At the beginning of this century, even more substances, such as antimicrobial peptides, were considered very promising candidates for becoming new alternatives to commonly used antimicrobials. However, many preclinical and clinical trials ended without positive results. A variety of strategies to fight microbes exist, but we are a long way from approving them as therapies. This review begins with the discovery of antibiotics, covers the modes of action of select antimicrobials, and ends with a literature review of the newest potential alternative approaches to overcoming the drug resistance phenomenon.

Anti-Salmonella Potential of New Lactobacillus Strains with the Application in the Poultry Industry

Probiotics are considered an alternative to antibiotics in the prevention and treatment of Salmonella diseases in poultry. However, to use probiotics as proposed above, it is necessary to evaluate their properties in detail and to select the most effective bacterial strains in the application targeted. In this study, probiotic properties of new Lactobacillus sp. strains were investigated and their antimicrobial activity against 125 environmental strains of Salmonella sp. was determined using the agar slab method. Furthermore, their survival in the presence of bile salts and at low pH, antibiotics susceptibility, aggregation and coaggregation ability, adherence to polystyrene and Caco-2 cells, and cytotoxicity were investigated. Each strain tested showed antagonistic activity against at least 96% of the environmental Salmonella sp. strains and thus representing a highly epidemiologically differentiated collection of poultry isolates. In addition, the probiotic properties of new Lactobacillus strains are promising. Therefore, all strains examined showed a high potential for use in poultry against salmonellosis.

Probiotics are considered an alternative to antibiotics in the prevention and treatment of Salmonella diseases in poultry. However, to use probiotics as proposed above, it is necessary to evaluate their properties in detail and to select the most effective bacterial strains in the application targeted. In this study, probiotic properties of new Lactobacillus sp. strains were investigated and their antimicrobial activity against 125 environmental strains of Salmonella sp. was determined using the agar slab method. Furthermore, their survival in the presence of bile salts and at low pH, antibiotics susceptibility, aggregation and coaggregation ability, adherence to polystyrene and Caco-2 cells, and cytotoxicity were investigated. Each strain tested showed antagonistic activity against at least 96% of the environmental Salmonella sp. strains and thus representing a highly epidemiologically differentiated collection of poultry isolates. In addition, the probiotic properties of new Lactobacillus strains are promising. Therefore, all strains examined showed a high potential for use in poultry against salmonellosis.

Pharmacologically Aware Phage Therapy: Pharmacodynamic and Pharmacokinetic Obstacles to Phage Antibacterial Action in Animal and Human Bodies

The use of viruses infecting bacteria (bacteriophages or phages) to treat bacterial infections has been ongoing clinically for approximately 100 years. Despite that long history, the growing international crisis of resistance to standard antibiotics, abundant anecdotal evidence of efficacy, and one successful modern clinical trial of efficacy, this phage therapy is not yet a mainstream approach in medicine. One explanation for why phage therapy has not been subject to more widespread implementation is that phage therapy research, both preclinical and clinical, can be insufficiently pharmacologically aware. Consequently, here we consider the pharmacological obstacles to phage therapy effectiveness, with phages in phage therapy explicitly being considered to serve as drug equivalents. The study of pharmacology has traditionally been differentiated into pharmacokinetic and pharmacodynamic aspects. We therefore separately consider the difficulties that phages as virions can have in traveling through body compartments toward reaching their target bacteria (pharmacokinetics) and the difficulties that phages can have in exerting antibacterial activity once they have reached those bacteria (pharmacodynamics). The latter difficulties, at least in part, are functions of phage host range and bacterial resistance to phages. Given the apparently low toxicity of phages and the minimal side effects of phage therapy as practiced, phage therapy should be successful so long as phages can reach the targeted bacteria in sufficiently high numbers, adsorb, and then kill those bacteria. Greater awareness of what obstacles to this success generally or specifically can exist, as documented in this review, should aid in the further development of phage therapy toward wider use.

Phage therapy: What factors shape phage pharmacokinetics and bioavailability? Systematic and critical review

Bacteriophages are not forgotten viruses anymore: scientists and practitioners seek to understand phage pharmacokinetics in animals and humans, investigating bacteriophages as therapeutics, nanocarriers or microbiome components. This review provides a comprehensive overview of factors that determine phage circulation, penetration, and clearance, and that in consequence determine phage applicability for medicine. It makes use of experimental data collected by the phage community so far (PubMed 1924‐2016, including non‐English reports), combining elements of critical and systematic review.

This study covers phage ability to enter a system by various routes of administration, how (and if) the phage may access various tissues and organs, and finally what mechanisms determine the courses of phage clearance. The systematic review method was applied to analyze (i) phage survival in the gut (gut transit) and (ii) phage ability to enter the mammalian system by many administration routes. Aspects that have not yet been covered by a sufficient number of reports for mathematical analysis, as well as mechanisms underlying trends, are discussed in the form of a critical review.

In spite of the extraordinary diversity of bacteriophages and possible phage applications, the analysis revealed that phage morphology, phage specificity, phage dose, presence of sensitive bacteria or the characteristics of treated individuals (age, taxonomy) may affect phage bioavailability in animals and humans. However, once phages successfully enter the body, they reach most organs, including the central nervous system. Bacteriophages are cleared mainly by the immune system: innate immunity removes phages even when no specific response to bacteriophages has yet developed.

Autophage as a control measure for Salmonella in laying hens

Notwithstanding the National Salmonella Control Programs, the latest data published by the European Food Safety Authority show an increase in Salmonella Enteritidis prevalence in laying hen flocks. For this reason, the implementation of innovative techniques such as phage therapy is needed to control Salmonella at farm level. Most common bacteriophage applications are a cocktail of 2 or more bacteriophages, as it has been described that cocktails could remove different Salmonella serotypes, thus providing cross efficacy. Nevertheless, resistance to the bacteriophage cocktail has been reported, resulting in a decrease in their effectiveness. Along these lines, some authors have reported the possibility of using autophage when commercial bacteriophage cocktails are not active against field strains. To our best knowledge, no autophage (bacteriophage isolated from the same environment where the pathogen is isolated) has been found to control Salmonella in laying hens. In this context, the aim of this study was to assess the application of autophage in reducing Salmonella Enteritidis in environmental and fecal samples in a layer farm. To this end, the bacteriophage was isolated from the same farm where the bacteria was present and was applied onto the facility installations and the animals, at 2 different times. After bacteriophage challenges, swab cloths from facility surfaces and feces samples were collected at 3 times according to the time spent after the bacteriophage challenge. The results obtained in our study showed that all the surface samples collected from the farm facilities after phage therapy were negative for Salmonella. Concerning faces samples, statistical differences were found in Salmonella counts, with the strongest decrease (1.78log10) occurring after the second challenge. Otherwise, depending of the moment of sampling, the results obtained were 2.34log10, 1.39log10, 0.56log10, and 0.97log10 cfu/g for T0, T1, T2, and T3 respectively. The study highlights the use of autophage therapy not only for Salmonella Enteritidis control in animals, but as a sanitizer in cleaning and disinfection.

Phages for biocontrol in foods: What opportunities for Salmonella sp. control along the dairy food chain?

Controlling the presence of pathogenic bacteria, such as Salmonella sp., in dairy products production is a burning issue since contamination with Salmonella can occur at any stage of the production chain. The use of Salmonella-phages applied as control agents has gained considerable interest. Nonetheless, Salmonella-phage applications specifically intended for ensuring the safety of dairy products are scarce. This review identifies recent advances in the use of Salmonella-phages that are or could be applied along the dairy food chain, in a farm-to-fork approach. Salmonella-phages can be promising tools to reduce the shedding of Salmonella in cattle, and to reduce and control Salmonella occurrence in postharvest food (such as food additives), and in food processing facilities (such as biosanitizing agents). These control measures, combined with existing methods and other biocontrol agents, constitute new opportunities to reduce Salmonella occurrence along the dairy food production, and consequently to alleviate the risk of Salmonella contamination in dairy products.

Framing the Future with Bacteriophages in Agriculture

The ability of agriculture to continually provide food to a growing world population is of crucial importance. Bacterial diseases of plants and animals have continually reduced production since the advent of crop cultivation and animal husbandry practices. Antibiotics have been used extensively to mitigate these losses. The rise of antimicrobial resistant (AMR) bacteria, however, together with consumers’ calls for antibiotic-free products, presents problems that threaten sustainable agriculture. Bacteriophages (phages) are proposed as bacterial population control alternatives to antibiotics. Their unique properties make them highly promising but challenging antimicrobials. The use of phages in agriculture also presents a number of unique challenges. This mini-review summarizes recent development and perspectives of phages used as antimicrobial agents in plant and animal agriculture at the farm level. The main pathogens and their adjoining phage therapies are discussed.

Isolation and characterization of polyvalent bacteriophages infecting multi drug resistant Salmonella serovars isolated from broilers in Egypt

In this study, we isolated and characterized three phages named as Salmacey1, Salmacey2 and Salmacey3, infecting multi drug resistant Salmonella serovars isolated from broilers in Egypt. The most prevalent Salmonella serovars were S. typhimurium, S. enteritidis, and S. kentucky. All these Salmonella serovars were found to be resistant to more than two of the ten antimicrobial agents tested. Only S. kentucky was found to be resistant to seven antimicrobial agents. Examination of these phage particles by transmission electron microscopy (TEM), demonstrated that two phages (Salmacey1, Salmacey2) were found to belong to family Siphoviridae, and Salmacey3 was assigned to the family Myoviridae. The results of host range assay revealed that these bacteriophages were polyvalent and thus capable of infecting four strains of Salmonella serovars and Citrobacter freundii. Moreover, the two phages (Salmacey1, Salmacey2) had a lytic effect on Enterobacter cloacae and Salmacey3 was able to infect E. coli. All phages could not infect S. para Typhi, Staphylococus aureus and Bacillus cereus. One-step growth curves of bacteriophages revealed that siphovirus phages (Salmacey1, Salmacey2) have burst size (80 and 90pfu per infected cell with latent period 35min and 40min respectively), and for the myovirus Salmacey3 had a burst size 110pfu per infected cell with latent period 60min. Molecular analyses indicated that these phages contained double-stranded DNA genomes. The lytic activity of the phages against the most multidrug resistant serovars S. kentucky as host strain was evaluated. The result showed that these bacteriophages were able to completely stop the growth of S. kentucky in vitro. These results suggest that phages have a high potential for phage application to control Salmonella serovars isolated from broilers in Egypt.

Bacteriophage therapy to combat bacterial infections in poultry

Infections in poultry are an economic and health problem in Europe and worldwide. The most common infections are associated with salmonellosis, colibacillosis, campylobacteriosis, and others. The prevalence of Campylobacter-positive poultry flocks in European countries varies from 18% to 90%. In the United States, the prevalence of infected flocks is nearly 90%. A similar percentage of infection has been noted for salmonellosis (about 75-90%) and E. coli (90-95%). The occurence of Clostridium perfringens is a major problem for the poultry industry, with some estimates suggesting colonization of as many as 95% of chickens, resulting in clinical or subclinical infections. In the US, annual economic losses due to Salmonella infections run from $1.188 billion to over $11.588 billion, based on an estimated 1.92 million cases. Similar costs are observed in the case of other types of infections. In 2005 economic losses in the the poultry industry due to mortalities reached 1,000,000 USD.Infections caused by these pathogens, often through poultry products, are also a serious public health issue.The progressive increase in the number of multi-drug resistant bacteria and the complete ban on the use of antibiotics in livestock feed in the EU, as well as the partial ban in the US, have led to the growth of research on the use of bacteriophages to combat bacterial infections in humans and animals.The high success rate and safety of phage therapy in comparison with antibiotics are partly due to their specificity for selected bacteria and the ability to infect only one species, serotype or strain. This mechanism does not cause the destruction of commensal bacterial flora. Phages are currently being used with success in humans and animals in targeted therapies for slow-healing infections. They have also found application in the US in eliminating pathogens from the surface of foods of animal and plant origin. At a time of growing antibiotic resistance in bacteria and the resulting restrictions on the use of antibiotics, bacteriophages can provide an alternative means of eliminating pathogens.

Complete genome sequence of the salmonella enterica serovar enteritidis bacteriophages fSE1C and fSE4C isolated from food matrices

Salmonella enterica serovar Enteritidis is one of the most common causes of Salmonellosis worldwide. Utilization of bacteriophages as prophylactic agents is a practical solution to prevent Salmonellosis in ready-to-eat products. Shelf stability is one of the desirable properties for prophylactic bacteriophages. Here, we describe the phenotype, genome, and phylogeny of fSE1C and fSE4S Salmonella bacteriophages. fSE1C and fSE4S were previously isolated from pickle sauce and ground beef respectively and selected for their significant shelf stability. fSE1C and fSE4S showed a broad S. enterica serovar range, infecting several Salmonella serovars. The viral particles showed an icosahedral head structure and flexible tail, a typical morphology of the Siphoviridae family. fSE1C and fSE4C genomes consists of dsDNA of 41,720 bp and 41,768 bp with 49.73% and 49.78% G + C, respectively. Comparative genomic analysis reveals a mosaic relationship between S. enterica serovar Enteritidis phages isolated from Valparaiso, Chile.

Introduction to Preharvest Food Safety

This introductory article provides an overview of preharvest food safety activities and initiatives for the past 15 years. The section on traditional areas of preharvest food safety focuses on significant scientific advancements that are a culmination of collaborative efforts (both public health and agriculture) and significant research results. The highlighted advancements provide the foundation for exploring future preharvest areas and for improving and focusing on more specific intervention/control/prevention strategies. Examples include Escherichia coli and cattle, Salmonella and Campylobacter in poultry, and interventions and prevention and control programs. The section on "nontraditional" preharvest food safety areas brings attention to potential emerging food safety issues and to future food safety research directions. These include organic production, the FDA's Produce Rule (water and manure), genomic sequencing, antimicrobial resistance, and performance metrics. The concluding section emphasizes important themes such as strategic planning, coordination, epidemiology, and the need for understanding food safety production as a continuum. Food safety research, whether at the pre- or postharvest level, will continue to be a fascinating complex web of foodborne pathogens, risk factors, and scientific and policy interactions. Food safety priorities and research must continue to evolve with emerging global issues, emerging technologies, and methods but remain grounded in a multidisciplinary, collaborative, and systematic approach.

Evaluation of the efficacy of chitosan nanoparticles loaded ΦKAZ14 bacteriophage in the biological control of colibacillosis in chickens

Disease inflicted by avian pathogenic Escherichia coli (APEC) causes economic losses and burden to the poultry industry worldwide. In this study, the efficacy of chitosan nanoparticles loaded ΦKAZ14 (C-ΦKAZ14 NPs) as an oral biological therapy for Colibacillosis was evaluated. C-ΦKAZ14 NPs containing 10⁷ PFU/ml of ΦKAZ14 (Myoviridae; T4-like coliphage) bacteriophage were used to treat experimentally APEC-infected COBB 500 broiler chicks. C-ΦKAZ14 NPs and ΦKAZ14 bacteriophage were administered orally in a single dose. The clinical symptoms, mortality, and pathology in the infected birds were recorded and compared with those of control birds that did not receive C-ΦKAZ14 NPs or naked ΦKAZ14 bacteriophage. The results showed that C-ΦKAZ14 NP intervention decreased mortality from 58.33 to 16.7% with an increase in the protection rate from 42.00 to 83.33%. The bacterial colonization of the intestines of infected birds was significantly higher in the untreated control than in the C-ΦKAZ14 NP-treated group (2.30×10⁹ ± 0.02 and 0.79×10³ ± 0.10 CFU/mL, respectively) (P ≤ 0.05). Similarly, a significant difference in the fecal shedding of Escherichia coli was observed on d 7 post challenge between the untreated control and the C-ΦKAZ14 NP-treated group (2.35×10⁹ ± 0.05 and 1.58×10³ ± 0.06 CFU/mL, respectively) (P ≤ 0.05). Similar trends were observed from d 14 until d 21 when the experiment was terminated. Treatment with C-ΦKAZ14 NPs improved the body weights of the infected chicks. A difference in body weight on d 7 post challenge was observed between the untreated control and the C-ΦKAZ14 NP-treated group (140 ± 20 g and 160 ± 20 g, respectively). The increase was significant (P ≤ 0.05) on d 21 between the 2 groups (240 ± 30 g and 600 ± 80 g, respectively). Consequently, the clinical signs and symptoms were ameliorated upon treatment with C-ΦKAZ14 NPs compared with infected untreated birds. In all, based on the results, it can be concluded that the encapsulation of bacteriophage could enhance bacteriophage therapy and is a valuable approach for controlling APEC infections in poultry.

Bacteriophage Therapy: Advances in Formulation Strategies and Human Clinical Trials

Recently, a number of phage therapy phase I and II safety trials have been concluded, showing no notable safety concerns associated with the use of phage. Though hurdles for efficient treatment remain, these trials hold promise for future phase III clinical trials. Interestingly, most phage formulations used in these clinical trials are straightforward phage suspensions, and not much research has focused on the processing of phage cocktails in specific pharmaceutical dosage forms. Additional research on formulation strategies and the stability of phage-based drugs will be of key importance, especially with phage therapy advancing toward phase III clinical trials.

Bacteriophage-induced reduction in Salmonella Enteritidis counts in the crop of broiler chickens undergoing preslaughter feed withdrawal

Salmonella food poisoning is a public health problem. Feed withdrawal from broiler chickens before slaughter can favor the multiplication of Salmonella in the cecum and crop of contaminated animals and subsequently lead to contamination of carcasses in the processing plant. In the present study, a cocktail of lytic bacteriophages isolated from sewage water was orally administered to 45-d-old broiler chickens 1 h after they received an oral dose of 10(7) cfu/mL Salmonella enterica subspecies enterica serotype Enteritidis. Immediately after phage administration and 30 min, 1, 3, 6, and 12 h thereafter, groups of chicken were killed. Ceca and crops were analyzed for the presence of Salmonella. At 3 h posttreatment, there were 10(3) cfu/g and 10(1) cfu/g of cecal and crop suspension, respectively. At 6 h after treatment, the number of Salmonella was 10(3) cfu/g in the cecal suspension, but below the detection limit in the crops. Our results suggest that bacteriophage therapy may be able to reduce the contamination of chicken carcasses by reducing the preslaughter load of Salmonella in the birds.

Reducing Salmonella horizontal transmission during egg incubation by phage therapy

Salmonella is a serious problem for both animal production and public health worldwide. Contaminated poultry is the main vehicle of Salmonella and the most important serotype is Salmonella enterica serovar Enteritidis. In order to test the efficiency of bacteriophages to treat Salmonella enterica serovar Enteritidis infections in poultry, a cocktail of two phages, F1055S and F12013S, isolated from chicken litter was applied by aerosol spray on fertile eggs challenged with Salmonella Enteritidis. To the best of our knowledge, this is the first experiment in which phages were applied by spray on fertile eggs. Two groups of eggs were challenged with Salmonella (3×10(8) colony-forming units [CFU]/mL) and one of them was treated with the phage suspension (2×10(6) plaque-forming units [PFU]/mL). A third group was used as nonchallenged and nontreated control. The phage treatment of challenged Salmonella eggs reduced the disease symptoms in the chicks. The arthritis and pasting after 8 days in the challenged and treated group were similar to those normally occurring in chicks (nonchallenged and nontreated chick control group) (p=1.000 and p=0.828, respectively, for arthritis and pasting) and were significantly lower than the challenged but nontreated ones (p=0.017 and p=0.002 for arthritis and pasting, respectively). The phage-treated group did not lose weight, showing an average weight similar to that of the nonchallenged control group and higher than that of the challenged nontreated group. The results of this study suggest that the application of phages by aerosol spray during the transfer of the eggs from incubators to hatchers may be an effective and inexpensive approach for reducing the horizontal transfer of Salmonella in poultry.

wksl3, a New biocontrol agent for Salmonella enterica serovars enteritidis and typhimurium in foods: characterization, application, sequence analysis, and oral acute toxicity study

Of the Salmonella enterica serovars, S. Enteritidis and S. Typhimurium are responsible for most of the Salmonella outbreaks implicated in the consumption of contaminated foods in the Republic of Korea. Because of the widespread occurrence of antimicrobial-resistant Salmonella in foods and food processing environments, bacteriophages have recently surfaced as an alternative biocontrol tool. In this study, we isolated a virulent bacteriophage (wksl3) that could specifically infect S. Enteritidis, S. Typhimurium, and several additional serovars. Transmission electron microscopy revealed that phage wksl3 belongs to the family Siphoviridae. Complete genome sequence analysis and bioinformatic analysis revealed that the DNA of phage wksl3 is composed of 42,766 bp with 64 open reading frames. Since it does not encode any phage lysogeny factors, toxins, pathogen-related genes, or food-borne allergens, phage wksl3 may be considered a virulent phage with no side effects. Analysis of genetic similarities between phage wksl3 and four of its relatives (SS3e, vB_SenS-Ent1, SE2, and SETP3) allowed wksl3 to be categorized as a SETP3-like phage. A single-dose test of oral toxicity with BALB/c mice resulted in no abnormal clinical observations. Moreover, phage application to chicken skin at 8°C resulted in an about 2.5-log reduction in the number of Salmonella bacteria during the test period. The strong, stable lytic activity, the significant reduction of the number of S. Enteritidis bacteria after application to food, and the lack of clinical symptoms of this phage suggest that wksl3 may be a useful agent for the protection of foods against S. Enteritidis and S. Typhimurium contamination.

Characterization of a T5-like coliphage, SPC35, and differential development of resistance to SPC35 in Salmonella enterica serovar typhimurium and Escherichia coli

The potential of bacteriophage as an alternative biocontrol agent has recently been revisited due to the widespread occurrence of antibiotic-resistant bacteria. We isolated a virulent bacteriophage, SPC35, that can infect both Salmonella enterica serovar Typhimurium and Escherichia coli. Morphological analysis by transmission electron microscopy and analysis of its 118,351-bp genome revealed that SPC35 is a T5 group phage belonging to the family Siphoviridae. BtuB, the outer membrane protein for vitamin B(12) uptake, was found to be a host receptor for SPC35. Interestingly, resistant mutants of both E. coli and S. Typhimurium developed faster than our expectation when the cultures were infected with SPC35. Investigation of the btuB gene revealed that it was disrupted by the IS2 insertion sequence element in most of the resistant E. coli isolates. In contrast, we could not detect any btuB gene mutations in the resistant S. Typhimurium isolates; these isolates easily regained sensitivity to SPC35 in its absence, suggesting phase-variable phage resistance/sensitivity. These results indicate that a cocktail of phages that target different receptors on the pathogen should be more effective for successful biocontrol.