Reduction of Salmonella enterica Serovar Enteritidis Colonization in 20-Day-Old Broiler Chickens by the Plant-Derived Compounds trans -Cinnamaldehyde and Eugenol

Abstract

ABSTRACT The efficacies of trans -cinnamaldehyde (TC) and eugenol (EG) for reducing Salmonella enterica serovar Enteritidis colonization in broiler chickens were investigated. In three experiments for each compound, 1-day-old chicks ( n = 75/experiment) were randomly assigned to five treatment groups ( n = 15/treatment group): negative control (-ve S . Enteritidis, -ve TC, or EG), compound control (-ve S . Enteritidis, +ve 0.75% [vol/wt] TC or 1% [vol/wt] EG), positive control (+ve S . Enteritidis, -ve TC, or EG), low-dose treatment (+ve S . Enteritidis, +ve 0.5% TC, or 0.75% EG), and high-dose treatment (+ve S . Enteritidis, +ve 0.75% TC, or 1% EG). On day 0, birds were tested for the presence of any inherent Salmonella ( n = 5/experiment). On day 8, birds were inoculated with ∼8.0 log 10 CFU S . Enteritidis, and cecal colonization by S . Enteritidis was ascertained ( n = 10 chicks/experiment) after 24 h (day 9). Six birds from each treatment group were euthanized on days 7 and 10 after inoculation, and cecal S . Enteritidis numbers were determined. TC at 0.5 or 0.75% and EG at 0.75 or 1% consistently reduced ( P < 0.05) S . Enteritidis in the cecum (≥3 log 10 CFU/g) after 10 days of infection in all experiments. Feed intake and body weight were not different for TC treatments ( P > 0.05); however, EG supplementation led to significantly lower ( P < 0.05) body weights. Follow-up in vitro experiments revealed that the subinhibitory concentrations (SICs, the concentrations that did not inhibit Salmonella growth) of TC and EG reduced the motility and invasive abilities of S . Enteritidis and downregulated expression of the motility genes flhC and motA and invasion genes hilA , hilD , and invF . The results suggest that supplementation with TC and EG through feed can reduce S . Enteritidis colonization in chickens.