Phage cocktail SalmoFREE® reduces Salmonella on a commercial broiler farm

Abstract

According to the World Health Organization, Salmonella is one of the most important zoonotic foodborne pathogens. Poultry products are thought to be the main source of Salmonella, which means that it is necessary to control Salmonella at the pre-harvest stage. Bacteriophages, acting as host-specific parasites of bacterial cells, represent one of the alternatives to antibiotics that can contribute to food safety and security. The present study evaluated the effectiveness of the bacteriophage cocktail SalmoFREE® to control Salmonella on a commercial broiler farm. We assessed the relationship between the use of SalmoFREE® and productivity parameters (feed conversion, weight gain, homogeneity). Two field trials (trial 1 n = 34,986; trial 2 n = 34,680) were carried out under commercial rearing conditions on a Colombian broiler farm with a record of Salmonella presence. Each trial comprised 2 control chicken houses and 2 experimental ones. SalmoFREE® and a control suspension were delivered in the drinking water at 3 time points in the production cycle, and the presence of Salmonella was assessed in cloacal swabs the day before and after the treatments. Results revealed that SalmoFREE® controls the incidence of Salmonella and does not affect the animals nor the production parameters, demonstrating its efficacy and innocuity at the production scale. We detected phage-specific genes in samples of total DNA extracted from ceca after the treatment with SalmoFREE®, and tested for the appearance of cocktail-resistant Salmonella, which showed to be an uncommon event. These results contribute relevant information to the adoption of phage therapy as an alternative to growth-promoter antibiotics on poultry farms.

Salmonella Phage cocktail, its effects and benefits on the gut of chickens in a commercial farm.

“…Besides the ceca samples, individual cloacal swaps samples were taken in order to detect Salmonella using a genus-speci c PCR as described in Clavijo et al, 2019 [34]. Each individual swab corresponded to the same individual chicken sacri ced for cecum extraction.…”

“…Treated ocks were separated from the controls by a distance of 300 m approximately. Information about houses' size, breed line, sex, and antimicrobial therapy per house and trial are presented in detail in Clavijo et al, 2019 [34]. Houses 1, 2, 3 and 4 correspond to 4, 8, 9 and 10 respectively in Clavijo et al, 2019.…”

“…The phages present in the cocktail have been characterized by host range, infection assays, stability in chlorine, transmission electron microscopy, genome sequencing and a safety assessment in broilers kept in cage batteries [33]. We have recently demonstrated the effectiveness of the cocktail to reduce the presence of Salmonella in a commercial farm [34], without affecting animals nor the production parameters, thus demonstrating its innocuity at the productive scale.…”

“…In order to further characterize, the behaviour of phages and its effect on the commensal microbial community, we studied the effect of SalmoFree ® in the cecum microbiota of broilers in a commercial farm, when phages were incorporated in the drinking water. This study is based on the same experimental set up recently published [34], and extended the analysis through the use of 16S rRNA gene amplicon sequencing. Altogether, this work expands the knowledge about the effect of phage therapy in the microbiota in broiler chickens and will help to reveal the performance of phages in the commercial farming conditions.…”

“…Additionally, this work is the rst study to characterize the composition of broilers microbiota at the growth stage of broilers under farming conditions. Two eld trials under commercial rearing conditions were carried out in a commercial broiler farm in Colombia [34]. This farm belongs to an integrated poultry company that typically handles the entire production and processing cycle of a chicken (hatching, feed, production, processing, and marketing).…”