Antibacterial effect of trans-cinnamaldehyde, eugenol, carvacrol, and thymol on salmonella enteritidis and Campylobacter jejuni in chicken cecal contents in vitro

Salmonella enterica serovar Enteritidis and Campylobacter jejuni are 2 major foodborne pathogens transmitted through poultry products. These pathogens colonize the chicken cecum, leading to contamination of carcasses during slaughter and subsequent processing operations. We investigated the antimicrobial efficacy of 4 GRAS (generally recognized as safe) status plant-derived molecules, namely, trans-cinnamaldehyde, eugenol, carvacrol, and thymol, against Salmonella Enteritidis and C. jejuni in chicken cecal contents in vitro. The plant molecules were added at different concentrations (ranging from 10 to 75 mM for Salmonella Enteritidis and 10 to 30 mM for C. jejuni) to autoclaved chicken cecal contents inoculated with approximately 7.0 log₁₀ cfu/mL of Salmonella Enteritidis or approximately 5.0 log₁₀ cfu/mL of C. jejuni. The pathogen populations in the cecal contents after 15 s, 8 h, and 24 h of incubation at 40°C were determined. Duplicate samples of treatments and the control were included, and the study was replicated 3 times. Campylobacter jejuni was more sensitive to all the molecules than Salmonella Enteritidis (P ≤ 0.05). All molecules were highly bactericidal, with the lowest concentration of trans-cinnamaldehyde (10 mM) reducing (P ≤ 0.05) Salmonella Enteritidis populations by approximately 6.0 log₁₀ cfu/mL after 8 h and >8.0 log₁₀ cfu/mL after 24 h of in- cubation. Trans-cinnamaldehyde at 25 mM eliminated detectable (P ≤ 0.05) Salmonella Enteritidis counts by 8 h of incubation. In addition, trans-cinnamaldehyde at all tested concentrations (10, 20, and 30 mM) reduced C. jejuni counts to <1.0 log₁₀ cfu/mL after 8 and 24 h of incubation. Carvacrol and eugenol decreased (P ≤ 0.05) Salmonella Enteritidis and C. jejuni counts to <1.0 log₁₀ cfu/mL at 50 and 75 mM and 20 and 30 mM, respectively. Although not as effective as other molecules, thymol also reduced the counts of both pathogens. We conclude that the aforementioned molecules could potentially be used to reduce Salmonella Enteritidis and C. jejuni in chicken ceca. Follow-up in vivo studies are planned to evaluate these possibilities.