Phage therapy strategies to fight salmonella in the poultry sector under the one health framework
- Autores: Jan Torres Boncompte
- Directores de la Tesis: Pablo Catalá Gregori (dir. tes.), José Miguel Soriano del Castillo (codir. tes.), Sandra Sevilla Navarro (codir. tes.)
- Lectura: En la Universitat de València ( España ) en 2025
- Idioma: inglés
- Número de páginas: 274
- Tribunal Calificador de la Tesis: Pilar García Suárez (presid.), Mónica Gozalbo Monfort (secret.), Davide Giovanardi (voc.)
- Programa de doctorado: Programa Oficial de Doctorado en Medicina
- Materias:
- Enlaces
- Resumen
According to the World Health Organization, Salmonella ranks among the four leading causes of infectious gastrointestinal diseases worldwide. Each year, it accounts for approximately 550 million cases, including 220 million in children, with an estimated loss of 33 million healthy life years. In the European Union alone, the annual healthcare cost is estimated at 330 million euros, and in 2023, 77,486 cases were reported, 14,801 required hospitalization, and 88 resulted in death.
Non-typhoidal Salmonella, a gram-negative enterobacterium widely distributed in domestic animals, particularly poultry and pigs, is primarily transmitted to humans through contaminated food. Although only two species exist, S. enterica and S. bongori, S. enterica subsp. enterica comprises over 2,500 serotypes pathogenic to humans. Most infections cause mild gastrointestinal symptoms; however, infants and elderly individuals are more vulnerable to severe, potentially life-threatening disease.
Since 2007, the Spanish poultry sector has implemented National Control Programs for Salmonella based on regular sampling, official inspections, vaccination, and strict biosecurity measures targeting priority serotypes (S. Typhimurium, S. Enteritidis, S. Infantis, S. Virchow, and S. Hadar). Nevertheless, the emergence of antimicrobial resistance, including to fluoroquinolones, has exacerbated the public health concern.
In this context, bacteriophages, or phages, viruses that specifically infect bacterial cells, have re-emerged as plausible alternatives to conventional antimicrobial substances. Because phages require bacterial hosts for replication and must lyse them to complete their life cycle, they can be employed as antimicrobial agents on contaminated surfaces or in infected animals, a strategy known as phage therapy. Between 2021 and 2025, this doctoral thesis conducted four studies aimed at developing and optimizing phage therapy strategies for the poultry industry under the One Health approach.
In the first study, the ISO 6579:2017 protocol was evaluated for Salmonella phage isolation from MSRV agar plates. In experimental trials, phages were detected in 95.7% of treated plates, and in field tests (159 samples, 1,440 analyses) isolation rates ranged from 80–90%. The findings confirmed the protocol’s suitability for simultaneous pathogen–phage recovery, thus reducing intervention time.
In the second study, five phage candidates isolated from livestock were characterized against the most prevalent Salmonella serotypes in the EU. They exhibited lytic activity against 10 of 12 serotypes, stability across wide pH and temperature ranges, and morphologies compatible with Myoviridae, Siphoviridae, and Podoviridae as observed by transmission electron microscopy. Genomic analysis confirmed strictly lytic cycles and the absence of virulence or antibiotic-resistance genes, while all genomes contained depolymerase-associated genes. These results identified the phages as strong candidates for therapeutic application.
The third study assessed the lytic efficacy of phages against S. Infantis biofilms under farm-relevant environmental conditions (aerobic and microaerobic, 25 °C and 37 °C). Variable reductions in extracellular polymeric substances and viable cell counts were observed depending on environmental conditions, corroborated by scanning electron microscopy. The study highlighted the importance of appropriate phage selection based on biofilm phenotype for effective field application.Overall, the thesis provides an integrated perspective on the development of phage therapy strategies tailored to the poultry industry. The results support the inclusion of bacteriophages as a promising tool to enhance food safety, reduce economic losses, and mitigate the public health risks associated with Salmonella.
