Antimicrobial peptides disrupting the bacterial membrane reduce Salmonella colonization in chickens

Salmonella is a significant food safety and public health concern. Poultry products have been considered the main vehicles of Salmonella infections in humans. Salmonella being present in visually healthy poultry is suggested as the preeminent human transmission risk factor, allowing bacteria to easily transmit from eggs and poultry to humans. Antimicrobial peptides (AMPs) have been suggested as promising alternatives to current antibiotics because of their low propensity for resistance development. In this study, we tested the efficacy of Lactobacillus rhamnosus GG (LGG)-derived small peptides (P1-NPSRQERR, P2- PDENK, and P4-MLNERVK) against Salmonella Typhimurium (ST) and Salmonella Enteritidis (SE) both in vitro and in chickens. Peptides inhibited ST, SE, and other public health-relevant Salmonella serovars in vitro. The antibacterial activity of peptides is likely due to their effect on Salmonella membranes. Importantly, P1 and P2 effectively reduced the colonization of ST by 2.2 and 1.8 logs, respectively, in chickens at 7 days post-infection. P1, P2, and P4 possessed no adverse effect on chicken cecum microbial community, but chickens not treated and challenged with Salmonella showed a difference in microbial richness and evenness compared to the unchallenged chickens. Furthermore, peptides retain their activity upon exposure to heat and protease treatments-characteristics necessary for the use of antimicrobial products in the poultry industry. In summary, these small peptides can provide a promising approach to develop novel strategies for controlling Salmonella infections in chickens.IMPORTANCESalmonella is the most frequently reported bacterial cause of foodborne illness in the United States. Poultry products (eggs and poultry meat) have been considered the main vehicles of Salmonella infections in humans. There is a need for developing and implementing effective antibiotic alternatives to reduce Salmonella in chickens, minimize human exposures, and simultaneously contribute to alleviating antibiotic resistance. AMPs have been suggested as promising alternatives to current antibiotics because of their low propensity for resistance development. Our study showed that LGG-derived peptides (P1-NPSRQERR, P2-PDENK, and P4-MLNERVK) significantly inhibit ST, SE and other Salmonella serovars in vitro and in chickens. Overall, our results demonstrate that small peptides can facilitate the development of promising approaches to control Salmonella infections in poultry, thus contributing to improved food safety and public health.