Selection and assessment of bacteriophages against salmonella spp. In the poultry industry
- Autores: Sandra Sevilla Navarro
- Directores de la Tesis: Pablo Catalá Gregori (dir. tes.), Clara Marín Orenga (dir. tes.)
- Lectura: En la Universitat Politècnica de València ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: Natàlia Majó i Masferrer (presid.), Manuel Laínez Andrés (secret.), Joan Colom Comas (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia y Tecnología de la Producción Animal por la Universitat Politècnica de València
- Materias:
- Enlaces
- Tesis en acceso abierto en: RiuNet
- Resumen
Millions of human salmonellosis cases are reported worldwide every year, and the disease results in thousands of deaths. In 2018, a total of 94,203 confirmed cases in humans were reported in Europe of which 8,730 were in Spain. The main source of infection is poultry products as eggs and chicken meat. National Salmonella Control Programmes have succeeded in reducing the prevalence of the bacteria at the field level. However, new cases of salmonellosis in humans continue to emerge every year and the presence of the bacterium continues to be detected in poultry farms. Therefore, new alternatives continue to be sought in the fight against the bacteria, such as the use of bacteriophages.
Bacteriophages or phages are ubiquitous viruses in the environment and are widely distributed in nature. They are microorganisms that specifically attack bacteria, altering them until they are destroyed. These characteristics make phages a very promising tool for the elimination of Salmonella in poultry farms as a complementary tool for cleaning and disinfection, and as another control tool to be included in good hygiene practices at field level.
Thus, in this doctoral thesis, we have focused our studies on determining the phage diversity in poultry farms and studying the application of phage therapy for the control of Salmonella as a complementary measure to cleaning and disinfection.
To this end, three experiments were carried out during the period from January 2017 to December 2019, where phages were isolated, purified, and multiplied from different samples taken from poultry farms and their epidemiology was studied.
The objective of the first experiment was to assess Salmonella-phage prevalence in commercial poultry farms in terms of the production livestock type: layers or broilers. The results of this study indicated that poultry farms could represent an important source of Salmonella phages. Moreover, we have shown a close relationship between Salmonella phage prevalence and Salmonella serovar prevalence in poultry farms, suggesting that phages co-exist within their serovar.
The purpose of the second experiment was to assess the effect of phages against Salmonella Infantis and Salmonella Enteritidis on farm surfaces and evaluate phage application procedure as sanitiser against Salmonella in field conditions. Results showed S. Infantis and S. Enteritidis decreased by 4.55 log10 CFU/mL and 3.85 log10 CFU/mL, respectively; the maximum reduction in Salmonella was on the 5th day, after 108 PFU/mL and 103 PFU/mL phage application. These results highlight phages as a promising tool together with cleansing and disinfection. However, more studies are needed to demonstrate their efficacy as sanitisers in poultry farms.
Finally, the aim of the third experiment was to assess the application of autophages for the control of S. Enteritidis in a naturally contaminated laying hen farm. This study shows that autophages could be used not only as a measure to reduce the excretion of Salmonella by infected animals but also as a complementary measure in the cleaning and disinfection of the facilities. In addition, the fact that autophages eliminated the Salmonella from the environment, even with the animals inside the facility, could avoid horizontal transmission of Salmonella among infected and non-infected animals.
The most relevant results obtained from this doctoral thesis are that the poultry sector has a promising, economic and ecological tool, as phage therapy, able to significantly reduce the prevalence of Salmonella when current measures cannot eliminate it from poultry farms.
