Determining the Antibacterial Effects of Trans-Cinnamaldehyde, the Major Component of Cinnamon Essential Oil, on Salmonella Heidelberg in Commercial Broiler Chickens

Abstract

Foodborne illness is a major cause of gastrointestinal diseases in humans, despite many efforts to control foodborne pathogens. In the United States, non-typhoidal Salmonella is one of the major pathogens that causes the most foodborne illnesses per year. Of these pathogens, Salmonella enterica serovar Heidelberg has become one of the most important pathogens implicated in Salmonella outbreaks, especially in poultry. Salmonella enterica serovar Heidelberg is known to be resistant to some common antibiotics such as gentamicin, streptomycin, tetracycline, and ampicillin. Poultry and poultry products are a significant source of Salmonella for humans. This is because poultry are a natural reservoir for Salmonella, as it colonizes in the gastrointestinal tract of the bird, and can be spread easily through feces, infecting the flock. Alternatives that are safe and environmentally sustainable are needed as antibiotics are being phased out of the agriculture industry due to the potential for development of antibiotic resistance in bacteria. Essential oils have received attention as alternatives because of their many functional benefits, including antimicrobial properties. One essential oil, trans-cinnamaldehyde, has been investigated for its use against Salmonella in both pre-harvest and post-harvest interventions. In this thesis project, we investigated the use of trans-cinnamaldehyde for both pre- and post-harvest control of the pathogens in poultry. We hypothesized that TC would be effective against the multidrug resistant S. Heidelberg in broiler chickens and on poultry products. Two objectives were used to test this hypothesis: 1) to determine the effect of trans-cinnamaldehyde on S. Heidelberg when used prophylactically and therapeutically, in broiler chickens and 2: to determine the effect of trans-cinnamaldehyde on S. Heidelberg on broiler meat and drumstick during the scalding step in poultry processing. HASH(0x40c9830) In the first objective, we determined the effect of trans-cinnamaldehyde on S. Heidelberg when delivered through feed and water in broiler chickens. Broiler chicks (5-week study – 3 broilers/group, two experiments; 7-week study – 3 broilers/group, two experiments) were divided into 4 groups: Negative control (NC), Positive Control (PC), Antibiotic Control (AB) and trans-cinnamaldehyde group (TC). In the 5-week study, the broilers in NC and PC groups were fed a standard diet from day 1 to week 5. The AB group received standard diet containing 50g/ton of bacitracin (BMD) for 5 weeks. The TC group was fed with a standard diet containing 0.5% TC for 4 weeks through feed and then after the pathogen challenge, 0.03% TC was supplemented through drinking water for the remaining 7 days. All groups except NC were challenged with S. Heidelberg (3.8 log10 CFU/bird) on week 4. The broilers were euthanized 7-days after the challenge. Cecum and cecal contents were collected for S. Heidelberg recovery. In the 7-week study, the NC or PC groups and AB group were fed with standard and bacitracin diets, respectively, through 7 weeks of age. The pathogen challenge (8.2 log10 CFU/bird) was conducted on week 6. Trans-cinnamaldehyde (0.03%) was provided as therapeutic supplementation to broilers in TC group through drinking water for 7 days after S. Heidelberg inoculation. Salmonella recovery was done 7 days after inoculation. The supplementation of 0.5% TC through feed and 0.03% TC in water resulted in ~2.0 log10 CFU/g reduction of S. Heidelberg from the cecum of 5-weeks old broilers whereas bacitracin reduced the pathogen to non-detectable levels (~3.7 log10 CFU/g reduction) (P<0.05). Conversely, bacitracin did not show significant reduction in S. Heidelberg colonization in 7-week old broilers. However, TC through water resulted in >90% reduction (~1.2 log10 CFU/g reduction) in S. Heidelberg colonization (P<0.05) without affecting body weights of broilers. HASH(0x40c82c8) In the second objective, we determined the effect of trans-cinnamaldehyde on S. Heidelberg during a simulated scalding treatment, and analyzed the effects on contaminated drumsticks during chilling and storage after the scalding treatment. Broiler chicken drumsticks were inoculated with either low (~3.0 log10 CFU/g) or high (~4.5 log10 CFU/g) concentrations of S. Heidelberg and were immersed in treatment water containing 0.5% TC, 1% TC, 0.05% peracetic acid (PAA), 0.5% TC + 0.05% PAA or 1% TC + 0.05% PAA at 54oC for 2 min (USDA-recommended time-temperature combination for scalding). The drumsticks inoculated with S. Heidelberg and without any antimicrobial treatment in scalding water served as the positive control (PC). After scalding, the drumsticks were homogenized in 350 mL Phosphate Buffered Saline for 30 s to obtain surviving S. Heidelberg populations. Also, the populations of S. Heidelberg on drumsticks and in the scalding water were enumerated by surface plating and enrichment methods. We also determined the efficacy of the scalding treatments against S. Heidelberg survival on drumsticks during chilled storage. For this study, the drumsticks were inoculated with 4.5 log10 CFU/g S. Heidelberg and immersed in scalding water containing 1% TC, 0.05% PAA or 1% TC + 0.05% PAA. After scalding, the drumsticks were immersed in chilling water without any antimicrobials for 30 min, packed and stored at 4oC for 48 h. The surviving S. Heidelberg populations were determined immediately after chilling and after 48 h of storage. Additionally, the effect of the treatments on the surface color of drumsticks was evaluated. All experiments were repeated six times and data were analyzed. Results revealed that PAA and its combination with TC (0.5 or 1%) resulted in the significant reduction of S. Heidelberg for low (1.7 to 2.4 log10 CFU/g reduction) and high inoculum (2.1 to 3.1 log10 CFU/g reduction) levels of S. Heidelberg (P<0.05). Moreover, the same treatments inactivated S. Heidelberg to non-detectable levels from the scalding water whereas 2.0- (low inoculum study) and 4.0- (high inoculum study) log10 CFU/ml S. Heidelberg survived in PC (P<0.05). The scalding treatments were also effective in inhibiting S. Heidelberg on the drumsticks compared to the respective controls during chilled storage. The treatments did not affect the surface color of the drumsticks (P>0.05). Both of these studies revealed that TC could be used as an effective alternative to antibiotics for S. Heidelberg control in the poultry industry.