Phenotypic characterization and genomic analysis of a Salmonella phage L223 for biocontrol of Salmonella spp. in poultry.

The escalating incidence of foodborne salmonellosis poses a significant global threat to food safety and public health. As antibiotic resistance in Salmonella continues to rise, there is growing interest in bacteriophages as potential alternatives. In this study, we isolated, characterized, and evaluated the biocontrol efficacy of lytic phage L223 in chicken meat. Phage L223 demonstrated robust stability across a broad range of temperatures (20-70 °C) and pH levels (2-11) and exhibited a restricted host range targeting Salmonella spp., notably Salmonella Typhimurium and Salmonella Enteritidis. Characterization of L223 revealed a short latent period of 30 min and a substantial burst size of 515 PFU/cell. Genomic analysis classified L223 within the Caudoviricetes class, Guernseyvirinae subfamily and Jerseyvirus genus, with a dsDNA genome size of 44,321 bp and 47.9% GC content, featuring 72 coding sequences devoid of antimicrobial resistance, virulence factors, toxins, and tRNA genes. Application of L223 significantly (p < 0.005) reduced Salmonella Typhimurium ATCC 14,028 counts by 1.24, 2.17, and 1.55 log CFU/piece after 2, 4, and 6 h of incubation, respectively, in experimentally contaminated chicken breast samples. These findings highlight the potential of Salmonella phage L223 as a promising biocontrol agent for mitigating Salmonella contamination in food products, emphasizing its relevance for enhancing food safety protocols.

Isolation, whole genome sequencing and application of a broad-spectrum Salmonella phage.

Salmonella is considered as one of the most common zoonotic /foodborne pathogens in the world. The application of bacteriophages as novel antibacterial agents in food substrates has become an emerging strategy. Bacteriophages have the potential to control Salmonella contamination.We have isolated and characterized a broad-spectrum Salmonella phage, SP154, which can lyse 9 serotypes, including S. Enteritidis, S. Typhimurium, S. Pullorum, S. Arizonae, S. Dublin, S. Cholerasuis, S. Chester, S. 1, 4, [5], 12: i: -, and S. Derby, accounting for 81.9% of 144 isolates. SP154 showed a short latent period (40 min) and a high burst size (with the first rapid burst size at 107 PFUs/cell and the second rapid burst size at approximately 40 PFUs/cell). Furthermore, SP154 activity has higher survival rates across various environmental conditions, including pH 4.0-12.0 and temperatures ranging from 4 to 50 °C for 60 min, making it suitable for diverse food processing and storage applications. Significant reductions in live Salmonella were observed in different foods matrices such as milk and chicken meat, with a decrease of up to 1.9 log10 CFU/mL in milk contamination and a 1 log10 CFU/mL reduction in chicken meat. Whole genome sequencing analysis revealed that SP154 belongs to the genus Ithacavirus, subfamily Humphriesvirinae, within the family Schitoviridae. Phylogenetic analysis based on the terminase large subunit supported this classification, although an alternate tree using the tail spike protein gene suggested affiliation with the genus Kuttervirus, underscoring the limitations of relying on a single gene for phylogenetic inference. Importantly, no virulence or antibiotic resistance genes were detected in SP154. Our research highlights the potential of using SP154 for biocontrol of Salmonella in the food industry.

Characterization of vB_SalS_PSa2, a T5-like Demerecviridae bacteriophage, and its potential use in food matrices.

This study characterizes a newly isolated Demerecviridae phage, named vB_SalS_PSa2, belonging to the phage T5 group. The main variations between vB_SalS_PSa2 and T5 concern structural proteins related to morphology and host recognition. vB_SalS_PSa2 is infective to 19 out of the 25 tested Salmonella enterica (including the rare "Sendai" and "Equine" serotypes) and Escherichia coli isolates, most of them being multidrug resistant. vB_SalS_PSa2 displayed good thermal stability (4-60 °C) and broad pH stability (4.0-12.0). It also exhibited antibacterial activity against S. enterica sv. Paratyphi A Enb50 at 4 °C in milk during the whole tested period (5 d), and for 3-6 h at both 25 and 37 °C. Furthermore, vB_SalS_PSa2 was able to inhibit biofilm formation and to show degradation activity on mature biofilms of E. coli K12 and S. enterica sv. Paratyphi Enb50 in both LB and milk. Altogether, these results indicate that phage vB_SalS_PSa2 is a valuable candidate for controlling foodborne S. enterica and E. coli pathogens.

Post-harvest biocontrol of Salmonella Enteritidis on Chicken breast meat and Shell eggs using multiphage cocktail.

The study aimed to evaluate the efficacy of a phage cocktail to reduce Salmonella Enteritidis contamination on perishable food items viz. chicken breast meat and shell eggs using different concentrations. Initially, four bacteriophages €P54, €P59, €P66, and €P72 were isolated from sewage water using Salmonella Enteritidis as a target strain. €P54 and €P66 were found to be Myoviruses while €P59 and €P72 belonged to the Siphoviridae family. A phage cocktail was applied at a concentration of 100 and 10,000 multiplicity of infection (MOI) after artificially contaminating both food items with Salmonella Enteritidis. Results showed that, phage cocktail significantly (p ≤ 0.05) reduced Salmonella Enteritidis count at both concentrations. However, the increased reduction was witnessed at 10,000 MOI. In comparison to untreated control, on chicken breast meat bacterial count was reduced to 1.94 and 3.17 Log10 cfu/g at 100 and 10,000 MOI respectively at 4oC. Similarly, on shell eggs, the bacterial count was reduced to 3.09 and 2.81 Log10 cfu/mL at 10,000 MOI at 4°C and 25°C respectively, while at 100 MOI there was less drop in bacterial count at both 4°C and 25°C. The results showed a better reduction at 4°C as compared to 25°C. Our data showed that the phage cocktail is an effective alternative and additional measure compared to conventional bacterial control methods for meat and eggs.

Genome Analysis and Therapeutic Evaluation of a Novel Lytic Bacteriophage of Salmonella Typhimurium: Suggestive of a New Genus in the Subfamily Vequintavirinae.

Salmonella Typhimurium, a foodborne pathogen, is a major concern for food safety. Its MDR serovars of animal origin pose a serious threat to the human population. Phage therapy can be an alternative for the treatment of such MDR Salmonella serovars. In this study, we report on detailed genome analyses of a novel Salmonella phage (Salmonella-Phage-SSBI34) and evaluate its therapeutic potential. The phage was evaluated for latent time, burst size, host range, and bacterial growth reduction in liquid cultures. The phage stability was examined at various pH levels and temperatures. The genome analysis (141.095 Kb) indicated that its nucleotide sequence is novel, as it exhibited only 1-7% DNA coverage. The phage genome features 44% GC content, and 234 putative open reading frames were predicted. The genome was predicted to encode for 28 structural proteins and 40 enzymes related to nucleotide metabolism, DNA modification, and protein synthesis. Further, the genome features 11 tRNA genes for 10 different amino acids, indicating alternate codon usage, and hosts a unique hydrolase for bacterial lysis. This study provides new insights into the subfamily Vequintavirinae, of which SSBI34 may represent a new genus.

Isolation, characterization and application of bacteriophage PSDA-2 against Salmonella Typhimurium in chilled mutton.

Salmonella is a common foodborne pathogen, especially in meat and meat products. Lytic phages are promising alternatives to conventional methods for Salmonella biocontrol in food and food processing. In this study, a virulent bacteriophage (PSDA-2) against Salmonella enterica serovar Typhimurium was isolated from the sewage and it was found that PSDA-2 belongs to Cornellvirus genus of Siphoviridae family by morphological and phylogenetic analysis. Based on the one-step growth curve, PSDA-2 has a short latent period (10 min) and a high burst size (120 PFU/cell). The stability test in vitro reveals that PSDA-2 is stable at 30-70°C and pH 3-10. Bioinformatics analysis show that PSDA-2 genome consists of 40,062 bp with a GC content of 50.21% and encodes 63 open reading frames (ORFs); no tRNA genes, lysogenic genes, drug resistance genes and virulence genes were identified in the genome. Moreover, the capacity for PSDA-2 to control Salmonella Typhimurium in chilled mutton was investigated. The results show that incubation of PSDA-2 at 4°C reduced recoverable Salmonella by 1.7 log CFU/mL and 2.1 log CFU/mL at multiplicity of infection (MOI) of 100 and 10,000 respectively, as relative to the phage-excluded control. The features of phage PSDA-2 suggest that it has the potential to be an agent to control Salmonella.

Isolation, identification and some characteristics of two lytic bacteriophages against Salmonella enterica serovar Paratyphi B and S. enterica serovar Typhimurium from various food sources.

Salmonellosis is an important worldwide food-borne disease. Increasing resistance to Salmonella spp. has been reported in recent years, and now the prevalence of multidrug-resistant Salmonella spp. is a worldwide problem. This necessitates alternative approaches like phage therapy. This study aimed to isolate bacteriophages specific for Salmonella enterica serovar Paratyphi B and S. enterica serovar Typhimurium isolated from different sources (chicken meat, beef and eggshells). The antibiotic resistance profiles of the bacteria were determined by phenotypic and genotypic methods. The prevalence of extended-spectrum ß-lactamase genes was examined by polymerase chain reaction. In total, 75% of the isolated Salmonella strains were resistant to tetracycline, whereas 70% of them were resistant to azithromycin. All of the isolates from beef were resistant to nalidixic acid. The most common extended-spectrum ß-lactamase genes among the isolates were blaSHV (15%) followed by blaTEM (10%) and blaCTX (5%). Two specific bacteriophages were isolated and characterized. The host range for vB_SparS-ui was Salmonella Paratyphi B, S. enterica serovar Paratyphi A and S. enterica, while that for vB_StyS-sam phage was Salmonella Typhimurium and S. enterica serovar Enteritidis. The characteristics of the isolated phages indicate that they are proper candidates to be used to control some foodstuff contaminations and also phage therapy of infected animals.

Genome analysis of Salmonella phage vB_SalM_8-19 (genus Rosemountvirus).

This work describes the characterization and genome annotation of Salmonella phage vB_SalM_8-19 (referred to as 8-19) isolated from sewage samples collected in a pig farm in Jilin, China. This phage was capable of infecting 60% Salmonella strains in our lab stock. The genome of phage 8-19 is composed of linear double-stranded DNA that is 52,648 bp in length with a G + C content of 46.02%; containing 74 ORFs and no tRNA genes. In October 2019, phylogenetic analyses indicated that phage 8-19 might belong to a novel cluster among the other similar phages which have not been specifically classified within some new genus in family Myoviridae. Recently, the International Committee on Taxonomy of Viruses (ICTV) defined phage 8-19 and its related phages as genus Rosemountvirus, family Myoviridae. This new genus, known as Rosemountvirus, is rarely reported in the literature.

Isolation and Characterization of Salmonella Jumbo-Phage pSal-SNUABM-04.

The increasing emergence of antimicrobial resistance has become a global issue. Therefore, many researchers have attempted to develop alternative antibiotics. One promising alternative is bacteriophage. In this study, we focused on a jumbo-phage infecting Salmonella isolated from exotic pet markets. Using a Salmonella strain isolated from reptiles as a host, we isolated and characterized the novel jumbo-bacteriophage pSal-SNUABM-04. This phage was investigated in terms of its morphology, host infectivity, growth and lysis kinetics, and genome. The phage was classified as Myoviridae based on its morphological traits and showed a comparatively wide host range. The lysis efficacy test showed that the phage can inhibit bacterial growth in the planktonic state. Genetic analysis revealed that the phage possesses a 239,626-base pair genome with 280 putative open reading frames, 76 of which have a predicted function and 195 of which have none. By genome comparison with other jumbo phages, the phage was designated as a novel member of Machinavirus composed of Erwnina phages.

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

Salmonella is one of the most common agents of foodborne disease worldwide. As natural alternatives to traditional antimicrobial agents, bacteriophages (phages) are emerging as highly effective biocontrol agents against Salmonella and other foodborne bacteria. Due to the high diversity within the Salmonella genus and emergence of drug resistant strains, improved efforts are necessary to find broad range and strictly lytic Salmonella phages for use in food biocontrol. Here, we describe the isolation and characterization of two Salmonella phages: ST-W77 isolated on S. Typhimurium and SE-W109 isolated on S. Enteritidis with extraordinary Salmonella specificity. Whole genome sequencing identified ST-W77 as a Myovirus within the Viunalikevirus genus and SE-W109 as a Siphovirus within the Jerseylikevirus genus. Infectivity studies using a panel of S. Typhimurium cell wall mutants revealed both phages require the lipopolysaccharide O-antigen, with SE-W109 also recognizing the flagella, during infection of Salmonella. A combination of both phages was capable of prolonged (one-week) antibacterial activity when added to milk or chicken meat contaminated with Salmonella. Due to their broad host ranges, strictly lytic lifestyles and lack of lysogeny-related genes or virulence genes in their genomes, ST-W77 and SE-W109 are ideal phages for further development as Salmonella biocontrol agents for food production.

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

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

Isolation and Characterization of a Lytic Salmonella paratyphi Phage and Its Antibiofilm Activity Individually or Collaborative with Kanamycin Sulfate.

Salmonella is among the most serious of foodborne pathogens worldwide and distributed widely in the natural environment; in addition, it has caused severe medical problems and foodborne diseases. Bacterial biofilm was the multicellular community of microorganisms that attached to nonbiological and biological surfaces. Phages and their derivatives are ideal candidates for replacing and compensating antibiotic resistance problems in the future. In this study, a virulent phage of KM15 was isolated from pig slaughterhouse sump samples in Kunming, China. It belonged to the Siphoviridae family, and optimal growth temperature was 42°C, the pH of optimal preservation buffer was 6-7, optimal multiplicity of infection was 0.0001, and the genome size was 41,869 bp. The Salmonella paratyphi A and Salmonella paratyphi B have a broad spectrum of antibiotic resistance and were isolated from clinical patients in the First People's Hospital of Yunnan Province; fortunately, most of them can be lysed by phage KM15. Collaboration of phage KM15 and kanamycin sulfate has a better antibiofilm effect than KM15 and kanamycin sulfate alone, in low-concentration bacterial culture; KM15 has better antibiofilm effect than kanamycin sulfate in high-concentration bacterial culture. The data of this study provided a strong evidence of application of phage to reduce the growth of Salmonella biofilm, which was important for public health.

The complete genome of lytic Salmonella phage vB_SenM-PA13076 and therapeutic potency in the treatment of lethal Salmonella Enteritidis infections in mice.

S. Enteritidis continues to be the most common pathogen of farm animals and a major public health burden worldwide. Using bacteriophages is a potential alternative to antibiotics against S. Enteritidis infection. In this study, the genome analysis of the lytic phage vB_SenM-PA13076 (PA13076) infecting S. Enteritidis revealed a linear, double-stranded DNA genome, which comprised of 52,474 bp and contained 69 ORFs. It belongs to the order Caudovirales; family Myoviridae, genus unclassified. The genes coded for DNA packaging, phage structural proteins, lysis components, DNA recombination, regulation, modification, and replication. No bacterial virulence or drug-resistance genes were detected. The phage PA13076 protected mice from a lethal dose of S. Enteritidis 13076Amp (5 × 108 CFU) by reducing the concentration of bacterial cells in blood, intestine, liver, spleen, and kidney. The phage PA13076 achieved at least 2.5 log reductions of S. Enteritidis cells in infected mice within 24 h (P < 0.05) when compared to the organs of control mice. The data also indicated that phage PA13076 could rapidly enter the blood and four organs of infected mice, remaining therein at concentrations of>104 PFU/g for at least 72 h. These results show that phage PA13076 has definite potential as an antibacterial therapeutic agent for attenuating S. Enteritidis infections.

A broad-spectrum phage controls multidrug-resistant Salmonella in liquid eggs.

Salmonella is a foodborne pathogen constantly threating public health. The widespread use of antibiotics and globalization of the food industry result in rapid growth of drug-resistance. Eggs contaminated by multidrug-resistant (MDR) Salmonella are one of the riskiest factors of salmonellosis, which are frequently associated with outbreaks worldwide. Thus, there are increasing needs for the development of new technologies in controlling MDR pathogens and for the confirmation of their practical efficiency in target food matrices. In this study, 43 Salmonella phages were isolated from environmental resources and among them, phage D1-2 was selected since it exhibited the most potent lytic ability and the broadest host spectrum against tested Salmonella strains. Further study demonstrated that D1-2 shows high pH and thermal tolerances and a short latent period, together with a low frequency of emergence of phage resistance. D1-2 effectively inhibited the growth of two MDR Salmonella strains in liquid egg white and egg yolk at both 4 °C and 25 °C. Morphology and phylogeny indicated that D1-2 belongs to the Myoviridae family. Genome analysis of D1-2 revealed a linear dsDNA sequence with no homology to virulence or antibiotic-resistance associated genes, presenting D1-2 is a promising candidate for the biocontrol of MDR Salmonella in highly risky foods.

Bacteriophage ZCSE2 is a Potent Antimicrobial Against Salmonella enterica Serovars: Ultrastructure, Genomics and Efficacy.

Developing novel antimicrobials capable of controlling multidrug-resistant bacterial pathogens is essential to restrict the use of antibiotics. Bacteriophages (phages) constitute a major resource that can be harnessed as an alternative to traditional antimicrobial therapies. Phage ZCSE2 was isolated among several others from raw sewage but was distinguished by broad-spectrum activity against Salmonella serovars considered pathogenic to humans and animals. Lytic profiles of ZCSE2 against a panel of Salmonella were determined together with low temperature activity and pH stability. The morphological features of the phage and host infection processes were characterized using a combination of transmission electron and atomic force microscopies. Whole genome sequencing of ZCSE2 produced a complete DNA sequence of 53,965 bp. No known virulence genes were identified in the sequence data, making ZCSE2 a good candidate for phage-mediated biological control purposes. ZCSE2 was further tested against S. Enteritidis in liquid culture and was observed to reduce the target bacterium to below the limits of detection from initial concentrations of 107-108 Colony Forming Units (CFU)/mL. With a broad host-range against pathogenic Salmonella serovars, phage ZCSE2 constitutes a potential tool against a major cause of human and animal disease.

Characterization and whole-genome sequencing of broad-host-range Salmonella-specific bacteriophages for bio-control.

Salmonella Enteritidis (S. Enteritidis), which could cause human disease and death by consuming the contaminated food, is an important zoonotic pathogen. With the rapid increase of antibiotic resistance all over the world, bacteriophage-based bio-control has gradually attracted public attention widely. In order to find a suitable phage treating S. Enteritidis infection, four phages infecting S. Enteritidis were isolated from poultry fecal samples. Host range showed that four phages had a broad-host-range to Salmonella isolates. The morphological analysis illustrated that all of those phages were classified as the Myoviridae family. The one-step growth curve indicated that bacteriophage BPSELC-1 has a short latent period of about 10 min and a large burst size of 500 pfu/cell in comparison to the other three phages. Then phage BPSELC-1 was sequenced and conducted in vitro experiment. The genome of phage BPSELC-1 is 86,996 bp in size and has 140 putative genes containing structure proteins-encoding genes, tRNA genes and DNA replication or nucleotide metabolism genes. Importantly, no known virulence-associated, antibiotic and lysogeny-related genes were identified in the genome of BPSELC-1. In vitro experiment of phage treatment pointed out that the number of viable S. Enteritidis ATCC 13076 was reduced by 5.9×log10 at MOI of 102 after 4 h. To the best of our knowledge, the phage BPSELC-1 exhibited higher efficiency in S. Enteritidis treatment compared to previous studies. Moreover, it is promising to be used as a broad-spectrum candidate against Salmonella infections in commercial owing to its broad-host-range.

Characterization of Salmonella spp.-specific bacteriophages and their biocontrol application in chicken breast meat.

Chicken breast meat is considered as the main source of Salmonella infection in humans. The aim of this study was to isolate lytic bacteriophages specific for Salmonella enterica serovars Enteritidis and examine their efficacy in a cocktail for the biocontrol of Salmonella spp. in raw chicken breast meat. Four lytic phages belonging to the Myoviridae and Siphoviridae families were isolated from a river proximate to a duck farm. They exhibited broad lytic activities against 11 strains of S. Enteritidis, 11 strains of S. Typhimurium, and one each of S. Paratyphi A, S. San Diego, and S. Typhi. The phages were determined to be stable, exhibited similar degrees of resistance to heat and pH, and had latent periods ranging from 5 to 30 min. In addition, the phage particles were 100% adsorbed within 18 to 40 min. Viable cell counts of bacteria were significantly reduced in raw chicken breast samples (P < 0.05) when treated with a cocktail of all four bacteriophages at 4 °C for 7 days (multiplicities of infection were from 104 to 106 ). These results indicate the potential efficacy of the bacteriophage cocktail as a biological agent against S. Enteritidis in raw chicken breast meat. PRACTICAL APPLICATION: Our findings demonstrate that the phages could be effective in reducing the viability of Salmonella spp. bacteria in chicken breast meat. Therefore, the phage cocktail is a potential bactericidal agent for the biocontrol of Salmonella spp. in raw chicken breast meat and could be used use in various poultry industries in the future.

Characterization of Salmonella bacteriophages and their potential use in dishwashing materials.

AIMS: The aims of this study were to isolate and characterize novel Salmonella phages and to evaluate the effectiveness of phage cocktails used as antibacterial agents in dishwashing materials. METHODS AND RESULTS: The effective phages, vB_STy-RN5i1 and vB_STy-RN29, were isolated from drain water samples collected from open markets using Salmonella Typhimurium as the host strain. These phages were identified as members of Podoviridae and Siphoviridae, respectively. Both phages infected at least six Salmonella serovars and rapidly lysed their host within one hour. They were stable at 4-45°C and at pH 6-9 for at least an hour while being evaluated in this study. The phage application results indicated that bacterial cells were reduced by 3⋅1 and 2⋅7 log CFU per ml at room temperature when they encountered the phage cocktail on scouring pads (SPs) and dishwashing sponges (DSs), respectively. CONCLUSIONS: The isolated Salmonella phages, vB_STy-RN5i1 and vB_STy-RN29, had potential against Salm. Typhimurium and could reduce the occurrence of bacterial-cross-contamination from dishwashing materials, which have been reported to be a source of bacteria, to other kitchen utensils and food. SIGNIFICANCE AND IMPACT OF THE STUDY: The successful reduction of bacterial contamination in dishwashing materials by the phage cocktail consisting of vB_STy-RN5i1 and vB_STy-RN29 reveals its potential to be an alternative antimicrobial agent for SPs and DSs.

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 5th day, after 108 PFU/mL and 103 PFU/mL bacteriophage application. These results highlight bacteriophages as a promising tool together with cleaning and disinfection.

The flagellotropic bacteriophage YSD1 targets Salmonella Typhi with a Chi-like protein tail fibre.

The discovery of a Salmonella-targeting phage from the waterways of the United Kingdom provided an opportunity to address the mechanism by which Chi-like bacteriophage (phage) engages with bacterial flagellae. The long tail fibre seen on Chi-like phages has been proposed to assist the phage particle in docking to a host cell flagellum, but the identity of the protein that generates this fibre was unknown. We present the results from genome sequencing of this phage, YSD1, confirming its close relationship to the original Chi phage and suggesting candidate proteins to form the tail structure. Immunogold labelling in electron micrographs revealed that YSD1_22 forms the main shaft of the tail tube, while YSD1_25 forms the distal part contributing to the tail spike complex. The long curling tail fibre is formed by the protein YSD1_29, and treatment of phage with the antibodies that bind YSD1_29 inhibits phage infection of Salmonella. The host range for YSD1 across Salmonella serovars is broad, but not comprehensive, being limited by antigenic features of the flagellin subunits that make up the Salmonella flagellum, with which YSD1_29 engages to initiate infection.