A new study conducted by researchers from Ohio State University and the University of Illinois Urbana-Champaign has demonstrated the efficacy of antimicrobial peptides for reducing Salmonella in poultry—potentially offering a novel, non-antibiotic intervention strategy that could help mitigate the rise of antimicrobial resistance (AMR) stemming from agricultural drug use.

According to the researchers, the peptides are not only effective at inactivating Salmonella, but can also kill other bacterial pathogens such as Escherichia coli, making them broadly valuable for food safety. The researchers say that their study could provide a framework for developing and using antimicrobial peptides to control Salmonella in chickens. In future projects, they will test the peptides in chickens on a large scale, seeking to optimize peptide delivery via water and/or feed, better understand how they kill Salmonella, and explore the usefulness of additional peptides.

The corresponding author on the study, published in Microbiology Spectrum, is cited as Gireesh Rajashekara, B.V.Sc., Ph.D. of the University of Illinois Urbana-Champaign’s College of Veterinary Medicine. Work conducted within Dr. Rajashekara’s lab was supported by a U.S. Department of Agriculture National Institute of Food and Agriculture (USDA-NIFA). The first author on the study is Gary Closs Jr., Ph.D. of the Department of Food Science and Technology at Ohio State University.

Efficacy of Antimicrobial Peptides Against Salmonella in Chickens, Under Processing Conditions

For their study, the researchers evaluated six Lactobacillus rhamnosus GG (LGG)-derived peptides (P1–P6) for their ability to inhibit Salmonella Typhimurium and Salmonella Enteritidis, both in vitro and in vivo.

Peptides P1 (NPSRQERR), P2 (PDENK), and P4 (MLNERVK) emerged as the most effective in vitro, demonstrating broad-spectrum activity against multiple Salmonella serovars, including S. Anatum, S. Heidelberg, and S. Newport.

Next, the researchers conducted a controlled in vitro study using layer chickens. They found that oral administration of P1 and P2 at 50 milligrams per kilogram of bodyweight (mg/kg bw) was able to significantly reduce S. Typhimurium colonization in the cecum by 2.2 and 1.8 logs, respectively, seven days post-infection. These reductions are considered epidemiologically relevant for lowering pathogen shedding and transmission.

Peptides also reduced S. Typhimurium presence in the liver by 30 percent without affecting body weight, indicating no adverse impact on bird health or performance.

Importantly, mimicking commercial poultry feed processing conditions, the peptides retained their antibacterial properties after exposure to heat and protease treatments, making them viable candidates for industry application.

Microbiota Preservation and Safety Profile

Unlike traditional antibiotics, which can disrupt gut microbiota and increase susceptibility to secondary infections, P1, P2, and P4 did not affect microbial richness or diversity in the chicken cecum. Metagenomic analysis confirmed that the peptides preserved beneficial gram-positive bacteria such as Lactobacillus and Bifidobacterium, while selectively inhibiting pathogenic gram-negative strains, including Escherichia coli.

Mechanism of Action and Resistance Studies

Confocal and transmission electron microscopy revealed that P1 and P2 likely exert their antibacterial effects by disrupting the outer membrane of Salmonella, a mechanism associated with reduced likelihood of resistance development. Supporting this, no resistance was observed in lethal or sub-lethal exposure assays over multiple passages.

Docking studies further confirmed strong binding affinities of P1 and P2 to outer membrane proteins OmpF and OmpC—chosen by the researchers to predict binding propensities because they are likely to function by affecting the outer membrane lipid asymmetry system in avian pathogenic E. coli—reinforcing the peptides’ membrane-targeting capabilities.

Implications for Poultry Industry and Food Safety

The study provides evidence that LGG-derived short peptides can serve as effective, non-antibiotic antimicrobial agents in poultry, without contributing to the growing public health threat that is AMR. The peptides’ stability under processing conditions, selective inhibition of pathogens, and preservation of gut microbiota position them as promising candidates for integration into poultry feeding strategies.

Further research is warranted to evaluate long-term efficacy, optimal dosing, and delivery methods in commercial settings. Nonetheless, the findings align with global antibiotic stewardship goals and offer a viable path forward for reducing Salmonella-related foodborne illnesses.