Application of ΦSP-1 and ΦSP-3 as a therapeutic strategy against Salmonella Enteritidis infection using Caenorhabditis elegans as model organism

Characterization and efficacy of Salmonella phage cocktail PHA46 in the control of Salmonella Newport and Typhimurium internalized into cherry tomatoes

Non-typhoid Salmonella enterica causes salmonellosis illness, and this bacterium can contaminate food throughout the production chain, including those that are consumed as raw products. Salmonella enterica can adhere to and internalize into fresh produce such as cherry tomatoes. It has been reported that lytic bacteriophages (phages) can be used as a biocontrol agent in the agricultural field, being an alternative for the control of Salmonella in red meat, fish, lettuce, and cabbage. The aim of this study was to characterize the two phages present in the PHA46 cocktail to determine their morphology, genome, host range, and resistance to different temperatures and pHs values; and later evaluate their lytic activity to reduce the adherence to and internalization of Salmonella enterica serovars Newport and Typhimurium into cherry tomatoes. In addition, in this work, we also explored the effect of the PHA46 cocktail on the virulence of S. Newport-45 and S. Typhimurium SL1344, recovered from the interior of cherry tomatoes, on the lifespan of the animal model Caenorhabditis elegans. The nematode C. elegans, recently has been used to test the virulence of Salmonella and it is easy to maintain and work with in the laboratory. The results revealed that the morphology obtained by Transmission Electron Microscopy of two phages from the PHA46 cocktail correspond to a myovirus, the analyses of their genomes sequences did not report virulence or antimicrobial resistance genes. The PHA46 sample is specific for 33 different serovars from different Salmonella strains and shows stability at 7 °C and pH 6. Also, the PHA46 cocktail was effective in reducing the adherence of S. Newport-45 and S. Typhimurium SL1344 to cherry tomatoes, at an average of 0.9 log10, respectively. Regarding internalized bacteria, the reduction was at an average of 1.2 log10, of the serovars mentioned above. The lifespan experiments in C. elegans showed by itself, that the PHA46 cocktail was harmless to the nematode, and the virulence from both Salmonella strains grown in vitro is diminished in the presence of the PHA46 cocktail. In conclusion, these results showed that the PHA46 cocktail could be a good candidate to be used as a biocontrol agent against Salmonella enterica.

The applications of animal models in phage therapy: An update

The rapid increase in antibiotic resistance presents a dire situation necessitating the need for alternative therapeutic agents. Among the current alternative therapies, phage therapy (PT) is promising. This review extensively summarizes preclinical PT approaches in various in-vivo models. PT has been evaluated in several recent clinical trials. However, there are still several unanswered concerns due to a lack of appropriate regulation and pharmacokinetic data regarding the application of phages in human therapeutic procedures. In this review, we also presented the current state of PT and considered how animal models can be used to adapt these therapies for humans. The development of realistic solutions to circumvent these constraints is critical for advancing this technology.

Animal Models of Phage Therapy

Amidst the rising tide of antibiotic resistance, phage therapy holds promise as an alternative to antibiotics. Most well-designed studies on phage therapy exist in animal models. In order to progress to human clinical trials, it is important to understand what these models have accomplished and determine how to improve upon them. Here we provide a review of the animal models of phage therapy in Western literature and outline what can be learned from them in order to bring phage therapy closer to becoming a feasible alternative to antibiotics in clinical practice.

Animal Models to Translate Phage Therapy to Human Medicine

Phagotherapy, the use of bacteriophages to fight bacterial infections as an alternative to antibiotic treatments, has become of increasing interest in the last years. This is mainly due to the diffusion of multi-drug resistant (MDR) bacterial infections that constitute a serious issue for public health. Phage therapy is gaining favor due to its success in agriculture and veterinary treatments and its extensive utilization for human therapeutic protocols in the Eastern world. In the last decades, some clinical trials and compassionate treatments have also been performed in the Western world, indicating that phage therapy is getting closer to its introduction in standard therapy protocols. However, several questions concerning the use of phages in human therapeutic treatments are still present and need to be addressed. In this review, we illustrate the state of art of phage therapy and examine the role of animal models to translate these treatments to humans.

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.

Therapeutic bacteriophages as a rescue treatment for drug-resistant infections - an in vivo studies overview

Bacteriophages, highly prevalent in all environments, have found their use in medicine as an alternative or complement to antibiotics. The therapeutic use of bacteriophages was particularly popular in the 1920s and 1930s, until the discovery and introduction of antibiotics. Due to the dynamic growth of antibiotic resistance among bacterial strains, numerous international institutions (such as the FDA) have declared the search for novel treatment modalities to be of the highest priority. To date, bacteriophage therapy has not been registered for general use in Western countries. The regulation of biological medicinal products (within medicinal product regulation) does not contain a specific documentation frame for bacteriophages (only for vaccines, blood derived products, etc.) which, as active substances, need to meet specific requirements. Recently, the FDA allowed bacteriophage therapy to be used in the United States, via the Emergency Investigational New Drug scheme; clinical trials to compare the safety and efficacy of bacteriophage therapy are also permitted. To date, several therapeutic products of this type have made it to phase I or II; some clinical programmes have also been completed. This article cites numerous animal model studies and registered clinical trials, showing the safety and effectiveness of bacteriophage therapy, including infections caused by bacterial strains resistant to antibiotic treatment.

Isolation and characterization of a broad-spectrum phage of multiple drug resistant Salmonella and its therapeutic utility in mice

Salmonella are causes of livestock, poultry, and other animal diseases but they also have the potential to infect people. Currently, antibiotics are the first choice for treatment of Salmonella infections. Thus, the utility of phage has become the research focus for scientists for several reasons. There are efficient, non-toxic, ubiquitous, easy to prepare and can result in the lysis of host bacteria. In this study, a broad spectrum bacteriophage of Salmonella was isolated from the fecal samples of a poultryfarm and we studied the morphological aspects, thermal stability, pH stability, optimal multiplicity of infection (MOI), and one-step growth curve of this phage. This phage was named Salmonella phage SaFB14 and lysed 54.12%(105/194)Salmonella spp. SaFB14 belongs to the Siphoviridae and has a polyhedron head with a diameter approximating 60 × 60 nm and a tail approximating 140 nm. The optimum growth temperature was 37 °C and maintained high activity over a widepH range(pH3-10) with an optimum of pH 7.0. The optimal MOI was 0.1. A one-step growth curve showed that its latency time was 10 min, burst time was 70 min, and burst was 23 particles. In order to study the therapeutic effect of phage SaFB14 in infected mice, mice were challenged with 2 × 10⁹ CFU/mouse Salmonella (cs20130523-001-1). Each mouse was injected to 2 × 10¹⁰ PFU SaFB14 1 h later. SaFB14 protected 40% of mice from infection. Then, the same dose of phage was given to mice for 3 days continuously. After 3 days treatment, the survival rate increased to 60%.In conclusion, phage SaFB14 showed wide host range and good activity in vivo, it is promising against diseases caused by Salmonella.