Carvacrol and Cinnamaldehyde Inactivate Antibiotic-Resistant Salmonella enterica in Buffer and on Celery and Oysters

The emergence of antibiotic-resistant Salmonella is of concern to food processors. The objective of this research was to identity antimicrobial activities of cinnamaldehyde and carvacrol against antibiotic-resistant Salmonella enterica in phosphate-buffered saline (PBS) and oil celery and oysters. Twenty-three isolates were screened for resistance to seven antibiotics. Two resistant and two susceptible strains were chosen for the study. S. enterica cultures (1055 CFU/ml) were added to different concentrations of cinnamaldehyde and carvacrol (0.1, 0.2, 0.3, and 0.4% [vol/vol]) in PBS, mixed, and incubated at 37 degrees C. Samples were taken at 0, 1 5, and 24 h for enumeration. Celery and oysters were inoculated with S. enterica (10(6-7) CFU/ml), treated with 1% cinnamaldehyde or 1% carvacrol, incubated at 4 degrees C, and then sampled for enumeration oil days 0 and 3. Both anti microbials induced complete inactivation of S. enterica in PBS at 0.3 and 0.4% Oil exposure, and on 0.2% in 1 h. Exposure to cinnamaldehyde at 0.1% inactivated all pathogens at 1 h, and survivors were observed only for Salmonella Newport with 0.1% carvacrol at 1 h. In celery, 1% carvacrol reduced S. enterica populations to below detection oil day 0, while 1% cinnamaldehyde reduced populations by 1 and 2.3 log oil day 0 and day 3, respectively. In oysters, both antimicrobials caused about 5-log reductions on day 3. These results show the potential antimicrobial effects of carvacrol and cinnamaldehyde against antibiotic-resistant S. enterica in vitro and in foods.