Determining Whether Phages are Good Detectives of Salmonella Diversity Using Different Animal Production Systems in Chile as a Model

Introduction: Salmonella is a widely distributed zoonotic pathogen that can be transmitted to humans through food or by animal contact. Salmonella has 2,600 serovars that show distinct distribution in different animals and geographic regions; a few serovars (e.g., Enteritidis) are globally distributed. For all animal production systems, Salmonella is a concern, as it can enter the production systems and from there, it can reach consumers. While isolating Salmonella from animals is, in some cases, difficult; bacteriophages are abundant and easily isolated and characterized in the laboratory. In Chile, animal production shows considerable diversity. From backyards to industries, mostly, poultry, pigs, and cows are raised.

Purpose: The purpose of this project was to study Salmonella phage, using different animal production systems in Chile as models.

Methods: A total of 7 study systems (backyard poultry and pigs (n=35), industrial pigs (n=36), backyard cattle (n=47), industrial cattle (n=160), wild bird in peri-urban locations (n=49), wild bird – wetland (n=271), and backyard – South American camelids (n=49)) in Chile were sampled for Salmonella spp. and phages. These systems are located from the north to the south of Chile, including Easter Island. Isolates representing the most common serovars (Enteritidis, Typhimurium, Infantis, and Heidelberg) were used to isolate phages. The isolated phages we tested for the host range using a set of 26 isolates, representing 23 Salmonella serovars.

Results: We have isolated three times more phages than Salmonella (93 Salmonella versus 322 phages). The host range was found to be different in the different systems, with widest host range found in backyard poultry. Clustering of phages based on host range, showed distinct profiles according to the animal system. For example, phages from cattle prefer to lyse Salmonella serovars Enteritidis, Javiana, Dublin, and Agona.

Significance: This was the first study that investigated Salmonella phage diversity in different animal production systems.