Carvacrol and cinnamaldehyde inactivate antibiotic-resistant salmonella entérica in buffer and on celery and oysters

The emergence of antibiotic-resistant Salmonella is of concern to food processors. The objective or this research was to identify antimicrobial activities of cinnamaldehyde and carvacrol against antibiotic-resistant Salmonella enterica in phosphatebuffered saline (PBS) and on 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 (10⁵ 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°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°C, and then sampled for enumeration on days 0 and 3. Both antimicrobials induced complete inuctivution of S. enterica in PBS at 0.3 and 0.4% on exposure, and on 0.2% in I 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 on day 0, while 1% cinnamaldehyde reduced populations by 1 and 2.3 log on 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 antibioticresistant S. enterica in vitro and in foods.