Growth kinetics of Listeria innocua and Listeria monocytogenes under exposure to carvacrol and the occurrence of sublethal damage

Abstract

The aim of this work was to compare the growth kinetics of Listeria innocua and Listeria monocytogenes serovar 4b exposed to carvacrol, considering two initial inoculum sizes, and the occurrence of sublethal damage in these cell populations, by plating them in selective and non-selective medium. Bacteria were grown in TSB supplemented with carvacrol: 0.0 μL/mL (control), 0.100 μL/mL and 0.175 μL/mL. The increase in carvacrol concentration resulted in an extended lag phase and lower maximum growth rate in comparison with the untreated cells (p ≤ 0.05). In the presence of carvacrol, the lower inoculum size showed an increased growth rate and relatively longer lag phase compared to the higher inoculum size (p ≤ 0.05). The cells of L. innocua and L. monocytogenes had a greater extension of lag time, slower growth rate and higher percentage of injured cells when treated with carvacrol (p ≤ 0.05). Results also indicated that L. monocytogenes grows faster than L. innocua when treated with carvacrol, this scenery could compromise the use of L. innocua as a surrogate for L. monocytogenes serovar 4b for this antimicrobial substance. Finally, it was shown that good growth control of Listeria was achieved with 0.175 μL/mL of carvacrol.