Effect of dietary bacteriophage supplementation on internal organs, fecal excretion, and ileal immune response in laying hens challenged by Salmonella Enteritidis

A review of bacteriophage and their application in domestic animals in a post-antibiotic era

Bacteriophages (phages for short) are the most abundant biological entities on Earth and are natural enemies of bacteria. Genomics and molecular biology have identified subtle and complex relationships among phages, bacteria and their animal hosts. This review covers composition, diversity and factors affecting gut phage, their lifecycle in the body, and interactions with bacteria and hosts. In addition, research regarding phage in poultry, aquaculture and livestock are summarized, and application of phages in antibiotic substitution, phage therapy and food safety are reviewed.

Effects of Long-Term Coated Sodium Butyrate Supplementation on the Intestinal Health and Colonization of Cecal Salmonella of Laying Hens Infected with Salmonella enteritidis

Salmonella enterica ser. Enteritidis (S. Enteritidis) is widely found in chickens and eggs, and it can potentially induce human illness. The investigation in this study centers on the impacts of long-term dietary supplementation with coated sodium butyrate (CSB) on intestinal well-being and the colonization of cecum Salmonella in laying hens infected with S. Enteritidis. We segregated a total of 120 Lohmann laying hens aged 51 weeks into four treatment categories: 0 (CON), 300 (CSB1), 500 (CSB2), and 800 (CSB3) mg/kg of CSB, supplemented with CSB from the first day of the experiment. A 24-week observation process was carried out for each laying hen. The S. Enteritidis was orally administered to all chickens on the morning of the first and third days of week 22 of the trial. After the S. Enteritidis challenge, egg production decreased the most in the CON group. Compared to the CON group, the three doses of CSB significantly improved egg production after the S. Enteritidis challenge (PANOVA < 0.05). S. Enteritidis challenge increased plasma DAO activity, but CSB supplementation reduced plasma DAO activity (Plinear < 0.05). The S. Enteritidis challenge disrupted intestinal villi morphology; compared to the CON group, the three dosages of CSB resulted in an increase in villus height (VH) and the ratio of villus height to crypt depth (V/C) in the duodenum, jejunum, and ileum of infected laying hens (Plinear < 0.05), with a significant increase in jejunal villus height (PANOVA < 0.05). A decrease in ileal crypt depth was also observed (Plinear < 0.05). CSB2 and CSB3 markedly increased the content of butyric acid in the cecum (PANOVA < 0.05). Additionally, in contrast to those in the CON group, the propionic acid content in the CSB supplementation group increased (Plinear < 0.05). Compared with those in the CON group, mRNA relative expression of the IL-6 and IL-1β in jejunum (Plinear < 0.05) and mRNA relative expression of the IL-1β in ileum (PANOVA < 0.05) were significantly lower, and mRNA relative expression of the IL-10 in ileum (Plinear < 0.05) were significantly higher in the CSB group. In addition, in contrast to the CON group, the CSB supplementation group significantly upregulated mRNA relative expression of the ZO-1 and CLDN1 (PANOVA < 0.05). Additionally, CSB supplementation reduced the number of Salmonella and increased the number of Lactobacilli in the cecum (Plinear < 0.05) and tended to increase the total bacteria count (Plinear = 0.069) and reduce the E. coli count (Plinear = 0.081). In conclusion, long-term dietary supplementation with coated sodium butyrate can alleviate intestinal injury and the colonization of cecum Salmonella in laying hens infected with S. Enteritidis.

Coccidiosis in Egg-Laying Hens and Potential Nutritional Strategies to Modulate Performance, Gut Health, and Immune Response

Avian coccidiosis, despite advancements in management, nutrition, genetics, and immunology, still remains the most impactful disease, imposing substantial economic losses to the poultry industry. Coccidiosis may strike any avian species, and it may be mild to severe, depending on the pathogenicity of Eimeria spp. and the number of oocysts ingested by the bird. Unlike broilers, low emphasis has been given to laying hens. Coccidiosis in laying hens damages the gastrointestinal tract and causes physiological changes, including oxidative stress, immunosuppression, and inflammatory changes, leading to reduced feed intake and a drastic drop in egg production. Several countries around the world have large numbers of hens raised in cage-free/free-range facilities, and coccidiosis has already become one of the many problems that producers have to face in the future. However, limited research has been conducted on egg-laying hens, and our understanding of the physiological changes following coccidiosis in hens relies heavily on studies conducted on broilers. The aim of this review is to summarize the effect of coccidiosis in laying hens to an extent and correlate it with the physiological changes that occur in broilers following coccidiosis. Additionally, this review tries to explore the nutritional strategies successfully used in broilers to mitigate the negative effects of coccidiosis in improving the gut health and performance of broilers and if they can be used in laying hens.

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.

Salmonella in reptiles: a review of occurrence, interactions, shedding and risk factors for human infections

Salmonella are considered a part of the normal reptile gut microbiota, but have also been associated with disease in reptiles. Reptile-associated salmonellosis (RAS) can pose a serious health threat to humans, especially children, and an estimated 6% of human sporadic salmonellosis cases have been attributed to direct or indirect contact with reptiles, although the exact number is not known. Two literature searches were conducted for this review. The first evaluated reports of the prevalence of Salmonella in the intestinal tracts of healthy reptiles. Salmonella were most commonly detected in snakes (56.0% overall), followed by lizards (36.9%) and tortoises (34.2%), with lower detection rates reported for turtles (18.6%) and crocodilians (9%). Reptiles in captivity were significantly more likely to shed Salmonella than those sampled in the wild. The majority of Salmonella strains described in reptiles belonged to subspecies I (70.3%), followed by subspecies IIIb (29.7%) and subspecies II (19.6%). The second literature search focused on reports of RAS, revealing that the highest number of cases was associated with contact with turtles (35.3%), followed by lizards (27.1%) and snakes (20.0%). Reptiles associated with RAS therefore did not directly reflect prevalence of Salmonella reported in healthy representatives of a given reptile group. Clinical symptoms associated with RAS predominantly involved the gastrointestinal tract, but also included fever, central nervous symptoms, problems with circulation, respiratory symptoms and others. Disease caused by Salmonella in reptiles appears to be dependent on additional factors, including stress, inadequate husbandry and hygiene, and other infectious agents. While it has been suggested that reptile serovars may cause more severe disease than human-derived strains, and some data is available on invasiveness of individual strains in cell culture, limited information is available on potential mechanisms influencing invasiveness and immune evasion in reptiles and in RAS. Strategies to mitigate the spread of Salmonella through reptiles and to reduce RAS focus mostly on education and hygiene, and have often been met with some success, but additional efforts are needed. Many aspects regarding Salmonella in reptiles remain poorly understood, including the mechanisms by which Salmonella persist in reptile hosts without causing disease.

Effects of bacteriophage on Salmonella Enteritidis infection in broilers

Bacteriophages (BP) are viruses that can infect bacteria. The present study evaluated the effect of BP on Salmonella infected broilers. A number of 150 day-old broilers were used in a completely randomized design with five treatments that included: (1) basal diet from day 0 to 28; (2) basal diet + 0.3 g/kg of colistin from day 0 to 28; (3) basal diet from day 1 to 13, and basal diet + 0.4 g/kg of colistin from day 14 to 28; (4) basal diet + 1 g/kg of BP from day 0 to 28; (5) basal diet + 1.5 g/kg of BP from day 0 to 28. On day 13, 15 chickens from each treatment were challenged by Salmonella Enteritidis (SE), while fifteen from each treatment were not; instead, they were kept in the same cage with the challenged chickens (exposed chickens). At 7 and 14 days post-challenge, the number of SE and coliform bacteria in the cecum and liver of colistin and BP-fed birds was lower than the control treatment. In exposed and challenged chickens, the height and surface area of villus were greater in the BP and colistin-supplemented groups. Serum concentrations of aspartate aminotransferase and alanine transaminase were greater, while serum albumin and triglycerides concentrations were lower in the control treatment. The liver of the challenged chickens had more pathological lesions than exposed birds. BP significantly decreased PPARγ gene expression in exposed chickens. In the challenged and exposed chickens, TLR4 gene expression was lower in BP and colistin-treated birds as compared to the control. In conclusion, adding BP to the diet from the day of age prevents the spread of Salmonella.

Natural Killers: Opportunities and Challenges for the Use of Bacteriophages in Microbial Food Safety from the One Health Perspective

Ingestion of food or water contaminated with pathogenic bacteria may cause serious diseases. The One Health approach may help to ensure food safety by anticipating, preventing, detecting, and controlling diseases that spread between animals, humans, and the environment. This concept pays special attention to the increasing spread and dissemination of antibiotic-resistant bacteria, which are considered one of the most important environment-related human and animal health hazards. In this context, the development of innovative, versatile, and effective alternatives to control bacterial infections in order to assure comprehensive food microbial safety is becoming an urgent issue. Bacteriophages (phages), viruses of bacteria, have gained significance in the last years due to the request for new effective antimicrobials for the treatment of bacterial diseases, along with many other applications, including biotechnology and food safety. This manuscript reviews the application of phages in order to prevent food- and water-borne diseases from a One Health perspective. Regarding the necessary decrease in the use of antibiotics, results taken from the literature indicate that phages are also promising tools to help to address this issue. To assist future phage-based real applications, the pending issues and main challenges to be addressed shortly by future studies are also taken into account.

The targeted anti-Salmonella bacteriophage attenuated the inflammatory response of laying hens challenged with Salmonella Gallinarum

Fowl typhoid is a severe disease caused by Salmonella Gallinarum with considerable mortality and morbidity in laying hen farms. The current study has focused on controlling the infection in laying hens using anti-Salmonella spp. bacteriophage. The treatments included, PC, without challenge; NC, S. Gallinarum challenged (SGC); B5, 5 mg bacteriophage/kg + SGC; B10, 10 mg bacteriophage/kg + SGC. The Salmonella shedding, inflammatory responses, and gene expression of pro-inflammatory cytokines, toll-like receptor (TLR), and heat shock protein (HSP) in the jejunum, liver, and thigh muscle were tested in laying hens. Supplementation of bacteriophage reduced the abundance of S. Gallinarum in the excreta at d 3, 7, and 14. The abundance of S. Gallinarum was lower in the B10 than the B5 at d 7. Supplementation of bacteriophage decreased the abundance of S. Gallinarum in the oviduct, spleen, and cecum at d 14. The laying hens in the NC group showed an increased relative spleen weight compared with the PC and B10 treatments. Among the SGC treatments, the NC treatment showed higher gene expressions of IL-4 compared with the B5, higher gene expressions of interferon (IFNγ), TLR4, and tumor necrosis factor-α (TNF-α) compared with the B5 and B10, and higher gene expressions of HSP27 compared with the B10 in the jejunum. Dietary supplementation of B10 decreased the mRNA expressions of TLR4 and TNF-α compared with the B5 treatment in the jejunum. The NC treatment showed the highest gene expressions of HSP27, TLR4, and TNF-α in the liver. Dietary supplementation of B10 showed lower mRNA expressions of HSP27 compared with the B5 treatment in the liver. Moreover, the IFNγ and HSP27 were upregulated in the NC treatment compared with the B5 and B10 in the muscle. In conclusion, it can be suggested that bacteriophage is an effective supplement to control S. Gallinarum infection in laying hens and possibly lower horizontal contaminations in laying hen flocks.

Effects of bacteriophage supplement on the growth performance, microbial population, and PGC-1α and TLR4 gene expressions of broiler chickens

Bacteriophages (BP) are viruses that invade bacteria and propagate inside them, leading to the lysis of the bacterial cells. The aim of this study was to investigate the effect of adding BP to the broiler's diet and its effect on the performance, morphology and bacterial population of the gut, some immune responses and expression of some intestinal genes. Accordingly, dietary treatments were as follows: basal diet (control), and control + 0.3 g/kg colistin or 0.5, 1 and 1.5 g BP/kg of diet. BP increased the body weight gain and reduced the feed conversion ratio (FCR), as compared to the colistin treatment, in the finisher and overall period (P < 0.05). European efficiency factor was significantly higher in 1.5 g BP-fed birds, as compared to the control and colistin treatments. meanwhile, bacteriophage and colistin-fed birds had higher Lactobacillus and lowered coliform bacteria counts, as compared to the control treatment (P < 0.05). Cecal concentrations of propionate in the 1.5 g BP-fed birds were higher than those in the control treatment (P < 0.05). BP-fed birds had a significantly increased villus height to crypt depth ratio, as compared to the control treatment. BP increased the serum concentrations of the total antibody, immunoglobulin (Ig) M, and IgG, as compared to the control treatment (P < 0.05). In the ileum, the expression of the Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) gene was decreased by dietary BP supplementation (P < 0.05). Furthermore, Toll-like receptor 4 (TLR4) gene expression was down-regulated in the BP-fed birds, whereas Interleukin 10 (IL-10) gene expression was up-regulated (P < 0.05). Overall, the use of BP may be a promising alternative to growth-promoting antibiotics in broilers by altering the gastrointestinal tract microbiota, enhancing immunological responses and improving the gut's morphology.

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.

Gastrointestinal Dynamics of Non-Encapsulated and Microencapsulated Salmonella Bacteriophages in Broiler Production

Simple Summary

Bacteriophages are viruses that kill targeted bacteria and could be used as a therapy against multidrug-resistant bacteria in animal production. Gastrointestinal tract conditions throughout the broiler production cycle might compromise the efficacy of bacteriophage oral administration against Salmonella. Microencapsulation of phages could protect and prevent the premature release of the bacteriophage, thereby allowing targeted delivery to the colonization site of Salmonella, the caecum. This study was designed to assess the optimal timing of the phage intervention over a 42-day production cycle and to compare microencapsulated (delivered in animal feed) and non-encapsulated phages (delivered through the drinking water) delivery along the gastrointestinal tract. Results of this study suggest that microencapsulation of the phages in a Eudragit^® L100 pH-responsive formulation allowed targeted delivery of the phage to the chicken caecum. Microencapsulation of phages administered orally through animal feed could be a promising method to control Salmonella in the field at any time during the animal rearing period.

Abstract

Bacteriophage therapy is being considered as a promising tool to control Salmonella in poultry. Nevertheless, changes in gastrointestinal tract environmental conditions throughout the production cycle could compromise the efficacy of phages administered orally. The main objectives of this study were to assess the optimal timing of the phage administration over a 42-day production cycle and to compare microencapsulated and non-encapsulated phages and the spatial and temporal dynamics of the phage delivery along the gastrointestinal tract. Phage FGS011 was encapsulated in the pH-responsive polymer Eudragit^® L100 using the process of spray drying. At different weeks of the chicken rearing period, 15 broilers were divided into three groups. Over a period of 24 h, group 1 received non-encapsulated phages (delivered through drinking water), group 2 received microencapsulated phages (incorporated in animal feed), and group 3 did not receive any phages. Microencapsulation was shown to enable efficient delivery of the bacteriophages to the animal gut and cecum throughout the animal rearing period. During the six weeks of application, the crop displayed the highest phage concentration for both phage delivery methods. The L100 based encapsulation offered significant protection to the phages from the harsh environmental conditions in the PV-Gizzard (not seen with phages administered in drinking water) which may help in the delivery of high phage doses to the cecum. Future Salmonella challenge studies are necessary to demonstrate the benefits of microencapsulation of phages using L100 formulation on phage therapy in field studies during the rearing period.

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.

In Vitro and In Vivo Gastrointestinal Survival of Non-Encapsulated and Microencapsulated Salmonella Bacteriophages: Implications for Bacteriophage Therapy in Poultry

The therapeutic use of bacteriophages is recognized as a viable method to control Salmonella. Microencapsulation of phages in oral dosage forms may protect phages from inherent challenges of the gastrointestinal tract in chickens. Therefore, the main objective of this study was to assess the survival of Salmonella BP FGS011 (non-encapsulated and microencapsulated) through the gastrointestinal tract under in vitro as well as in vivo conditions after oral administration to 1-day-old chicks. To this end, the phage FGS011 was encapsulated in two different pH-responsive formulations with polymers Eudragit^® L100, and Eudragit^® S100 using the process of spray drying. Phages encapsulated in either of the two formulations were able to survive exposure to the proventriculus-gizzard in vitro conditions whereas free phages did not. Moreover, phages formulated in polymer Eudragit^® S100 would be better suited to deliver phage to the caeca in chickens. In the in vivo assay, no statistically significant differences were observed in the phage concentrations across the gastrointestinal tract for either the free phage or the encapsulated phage given to chicks. This suggested that the pH of the proventriculus/gizzard in young chicks is not sufficiently acidic to cause differential phage titre reductions, thereby allowing free phage survival in vivo.

Impacts of Microbial based Therapy on Growth Performance, Intestinal Health, Carcass Traits and Economic Efficiency of Clostridium perfringens-Infected Cobb and Arbor Acres Broilers

The poultry farms need a safe and effective alternative for antibiotics that can counteract the negative impacts of necrotic enteritis (NE), which causes severe mortalities and economic losses. The current study was aimed to examine the influence of antibiotic (Flagymox) and the microbial‐based administration on carcass traits in Clostridium(C.)perfringens‐infected Cobb and Arbor Acres broilers. A total number of 360 Cobb and Arbor Acres broiler chicks (180 numbers per breed) were allocated to four groups; negative control group (without any treatments); positive control group (administration of C. perfringens at the rate of 1 × 10⁹cfu/bird via crop gavage twice daily from day 16 to 18 post‐hatch); C. perfringens challenge plus antibiotic (Flagymox^®) group, and Clostridiumperfringens challenge plus microbial‐based treatment (Big‐lactoα^®) group. The results indicated that the Flagymox and Big‐lactoα treated Cobb breed group achieved a significant increase in their body weight (BW) than the positive control group at the third week post‐infection. Also, the Arbor Acres breed gained significantly higher weight compared to the Cobb breed at the third week. Total weight gain (TWG) from 0 to the fifth week in the Cobb and Arbor Acres breeds were higher in the groups treated with Flagymox and Big‐lactoα compared to the birds challenged with C. perfringens without any treatment, thus, increasing the total return (TR) in the treated groups. Economic efficiency showed no significant differences (p < .05) between the treatment groups of both the breeds. Although the treatment cost of Flagymox is higher than the microbial‐based treatment (0.86 versus 0.35 LE), there were no mortalities reported in the microbial‐based groups in both the breeds resulting in significantly low losses compared to the Flagymox treated groups. The groups treated with the microbial‐based products in both breeds were superior in dressing percentage (75.16 and 77.06% for Cobb and Arbor Acres, respectively) compared to that of the other groups. In conclusion, microbial‐based therapy improved the growth rate, carcass traits, survival rate, and economic efficiency in necrotic enteritis induced in Cobb and Arbor Acres broilers.

Influence of Salmonella specific bacteriophages (O1; S16) on the shedding of naturally occurring Salmonella and an orally applied Salmonella Eastbourne strain in bearded dragons (Pogona vitticeps)

This study determined the passage time and phage propagation time of salmonella specific phages, Felix O1 and S16, in 10 bearded dragons, based on re‐isolation from cloacal swabs and faecal samples following oral administration, as a possible tool for reducing salmonella shedding. In Study 1, Felix O1 was administered orally for 12 consecutive days. Over 60 days, swabs were taken from the oral cavity and cloaca and qualitative Salmonella detection as well as salmonella quantification from faecal samples were performed. In Study 2, a phage cocktail (Felix O1 and S16) was administered to half of the tested animals. Salmonella (S.) Eastbourne was also given orally to all animals. Oral and cloacal swabs were tested as in Study 1, and faecal samples were collected for phage quantification. Various Salmonella serovars were detectable at the beginning of the study. The numbers of serovars detected declined over the course of the study. S. Kisarawe was most commonly detected. Salmonella titres ranged from 10² to 10⁷ cfu/g faeces. The phages (Felix O1 and S16) were detectable for up to 20 days after the last administration. The initial phage titres ranged from 10³ to 10⁷ pfu/ml. The study shows that the phages were able to replicate in the intestine, and were shed for a prolonged period and therefore could contribute to a reduction of Salmonella shedding.

Impact of an anti-Salmonella. Typhimurium Bacteriophage on intestinal microbiota and immunity status of laying hens

Typhoid is a distinct gastrointestinal disease that largely affects the public by consumption of inadequately or partially cooked eggs from contaminated laying hen farms. This has led the research on laying hens to focus on controlling the contamination by an effective anti-Salmonella spp. agent in the intestine. The treatments included, control, without challenge; PC, Salmonella typhimurium challenged (STC); BP5, 5 ppm bacteriophage/kg + STC; BP10, 10 ppm bacteriophage/kg + STC, on Salmonella shedding, body organs inflammatory reactions, and expression of toll-like receptor (TLR), pro-inflammatory cytokines, and heat shock protein (HSP) in the jejunum, liver,and thigh muscle in the STC laying hens. The RT-PCR method was used to enumerate the number of Salmonella typhimurium in the organs. The birds in the STC groups exhibited the increased population of Salmonella spp. in the excreta (p < .01). In the STC groups, the BP5 and BP10 laying hens exhibited a lower (p < .01) population of Salmonella spp. in the excreta at d 7 after STC. Supplementation of bacteriophage significantly decreased (p < .01) the colonization of S. Typhimurium in the spleen, oviduct, caecum and excreta. Among the STC treatments, the BP10 laying hens showed lower (p < .01) mRNA expression of interferon-γ (IFNγ) and TLR-4 in the jejunum compared with the PC treatment. After the STC, dietary supplementation with BP5 or BP10 decreased (p < .01) the mRNA expressions of IFNγ, HSP-27 and tumour necrosis factor-α in the liver compared with the PC treatment. These results suggest that bacteriophage can be used as an effective agent to decrease S. Typhimurium contamination in laying hens and possibly lower S. Typhimurium transfer to foods.

Salmonella Infantis and Salmonella Enteritidis specific bacteriophages isolated form poultry faeces as a complementary tool for cleaning and disinfection against Salmonella

Salmonellosis represents an important public health concern. Several authors point out the inefficiency of the cleaning and disinfection protocols to remove the bacteria from the field. For this reason, innovative techniques, as bacteriophages, could be implemented to control the bacteria. The main objectives of this study were to assess the effect of bacteriophages against Salmonella Infantis and Salmonella Enteritidis on farm surfaces, and to evaluate bacteriophage procedure application as sanitiser against Salmonella in field conditions. Thus, most prevalent serovars in poultry production were selected (Salmonella Infantis and Salmonella Enteritidis) to contaminate farm facilities. Then, two specific bacteriophages isolated from poultry faeces were applied against them. Results showed Salmonella Infantis and Salmonella Enteritidis decreased of 4.55 log₁₀CFU/mL and 3.85 log₁₀CFU/mL, respectively; the maximum reduction in Salmonella was the 5^th day, after 10⁸ PFU/mL and 10³ PFU/mL bacteriophage application. These results highlight bacteriophages as a promising tool together with cleaning and disinfection.

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.