Effect of NaCl on Thermal Resistance, Antibiotic Resistance, and Human Epithelial Cell Invasion of Listeria monocytogenes

This study evaluated the effects of NaCl on heat resistance and Caco-2 cell invasion of Listeria monocytogenes in broth media and sausage. A 10-strain mixture of L. monocytogenes was inoculated in tryptic soy broth containing 0.6% yeast extract (TSBYE), and sausage formulated with 0, 2, 4, and 6% NaCl. The medium was stored at 7, 15, 20, and 25˚C for 3- 16 d, and medium samples were withdrawn at the appropriate time and challenged to 55, 60, and 63˚C to evaluate the thermal resistance of the pathogen. Sausage samples were stored at 7 and 25˚C, and they were exposed to 63˚C to evaluate thermal resistance. NaCl-habituated L. monocytogenes strains NCCP10811 and NCCP10943 were examined for 12 antibiotics and Caco-2 cell invasion assay (only L. monocytogenes NCCP10943). Bacterial populations of L. monocytogenes generally increased (p