Stability of sublethal acid stress adaptation and induced cross protection against lauric arginate in Listeria monocytogenes

The stability of acid stress adaptation in Listeria monocytogenes and its induced cross protection effect against GRAS (generally recognized as safe) antimicrobial compounds has never been investigated before. In the present study, the acid stress adaptation in L. monocytogenes was initially induced in pH 5.0 tryptic soy broth supplemented with 0.6% yeast extract (TSB-YE) at 37 degrees C. Subsequently, the stability of acid stress adaptation, which was defined as the capacity to maintain its acquired acid adaptation after induction in the absence of sublethal acid stress, was determined at 37 degrees C, 22 degrees C or 4 degrees C in broth and in different food substrates. Then, the acid stress adaptation induced cross protection against lauric arginate (LAE) and its stability was investigated in TSB-YE, milk and carrot juice. Our findings show that the acid stress adaptation was stable at 4 degrees C up to 24 h but was reversed at 37 degrees C or 22 degrees C within 2 h. In the cross protection assay with LAE, the acid stress adapted cells had approximately 2 log CFU/ml greater survival than non-adapted cells in broth at 22 degrees C or in milk and carrot juice at 4 degrees C. The acid adaptation induced cross protection against LAE in L monocytogenes was reversible within 1 h at 4 degrees C in the absence of sublethal acid stress. Our findings suggest that the stability of acid adaptation in L. monocytogenes under cold conditions should be taken into account when the risk analysis is performed during food processing. (C) 2015 Elsevier B.V. All rights reserved.