V4-2004: Management strategies and control of Salmonella Infantis infections in broiler flocks (CRP project ARRS)

Duration of the project:

1. 11. 2020 – 31. 10. 2023

Lead partner:

University of Ljubljana, Faculty of Veterinary Medicine

Project partners:

University of Primorska, Faculty of Health Sciences
National Institute of Chemistry

Principal investigator / researcher:

Prof. Olga Zorman Rojs

Sodelujoči na UP FVZ:

Prof. Darja Barlič Maganja (SICRIS, ResearchGate)
Assist. Katja Bezek (SICRIS, ResearchGate)


In Europe, S. Infantis is the most commonly isolated Salmonella serotype in broilers and accounts for more than half of all Salmonella isolates from broiler flocks and meat. This serotype also predominates in Slovenian flocks, fresh meat and broiler meat preparations. Salmonella can enter any stage of the poultry farming process in a variety of ways; therefore, the knowledge of critical entry points and the mechanisms of bacterial persistence in the environment are extremely important for effective prevention of recurrent infections. S. Infantis is often recurrently isolated on the same holdings and in the same facilities, indicating the exceptional environmental persistence of this serotype and its high ability to spread in broiler farms. We will identify critical points for the introduction and spread of S. Infantis in broiler farms. Several sites in and around poultry farms including insects, rodents, means of transport and other possible contaminants will be sampled. The routes of transmission of S. Infantis strains within the same facilities and between different farms will be determined based on the results of microbiological investigation of the presence of S. Infantis and the identified critical points throughout the farm. WGS will be used for typing of selected isolates.

Outside the host, biofilm represents one of the key risk factors for bacterial resistance and survival.

Biofilm is the community of bacterial cells embedded within extracellular matrix structure of polysaccharides, showing greater resistance against negative environmental conditions including biocides. Despite cleaning and disinfection, S. Infantis is often recurrently isolated from the same location indicating its biofilm-forming ability. Within the framework of this project, the effectiveness of existing cleaning methods for prevention of residual impurities in poultry houses will be tested. Susceptibility of biofilms of genetically diverse S. Infantis isolates to different biocides will be evaluated. Based on the results of in vitro test, the suitability and effectiveness of biocides for the farm remediation will be tested.

In addition to biosecurity measures, preventive vaccinations are a feasible method for prevention of poultry infection with pathogenic microorganisms. The method of vaccine application is an extremely important factor for intensive poultry farming. Currently, no S. Infantis vaccine for broiler chickens is available on the market that could be used for commercial mass application. Production and oral administration of specific antibodies derived from chicken eggs represents a cost-effective alternative for prevention and treatment of S. Infantis infection. In this project, we will try to increase resistance of chicken to infection with S. Infantis by oral administration of encapsulated IgY. The antibodies will be obtained from an egg yolk of egg-laying hens previously immunized against S. Infantis. With this in mind an in vitro method for determination of efficacy and specificity of IgY antibodies in cell cultures will be developed.

Antimicrobial resistance of S. Infantis isolates will be determined. If the emergence ESBL producing S. Infantis is detected, additional biosecurity measures will be proposed for prevention for spreading of these strains. S. Infantis isolates will be compared with previously typed S. Infantis isolates from flocks of broilers  from the collection of the Slovenian National Reference Laboratory for Salmonella, and with isolates of poultry and human origin typed within the research program P4-0092 (Animal health, environment and safe food). The comparisons will be used for the risk assessment of S. infantis transmission through meat and meat preparation to humans. The isolates will be typed by WGS.

Guidelines for effective contamination management of farms before, during and after the housing of broiler flocks will be developed. Educations of breeders and veterinarians about the S. infantis contamination control will be organized.

The authors acknowledge the project “V4-2004: Management strategies and control of Salmonella Infantis infections in broiler flocks” is finacially supported by the Slovenian Research Agency.