Heat, acid, and salt tolerance of leucocin-resistant Listeria monocytogenes

The stress tolerance of wild type and leucocin-resistant (leu R) Listeria monocytogenes ATCC 15313, CDC 7762, and FS 15 was studied in high temperature (60°C), low pH (acetic acid, pH = 3.6), and saline (8% NaCl) conditions. Heat tolerance of leuR variants of L. monocytogenes was the same as the wild type strains, except for one leuR variant of L. monocytogenes FS 15 (FS15L2) that had increased thermotolerance. A decrease in acid tolerance was observed for leuR variants of L. monocytogenes ATCC 15313 and CDC 7762, but the acid tolerance of leuR L. monocytogenes FS 15 was the same as that of the wild type strain. There was no difference in the salt tolerance of wild type and leuR L. monocytogenes. Restriction fragment differential display-PCR and confirmatory dot blot analysis did not identify any differentially expressed genes.