The aim of this study was to evaluate the effect of two antimicrobial substances, carvacrol and citral, on
Listeria monocytogenes and Listeria innocua cells, as well as possible virulence changes in injured cells,
using Caenorhabditis elegans as a model test. The results indicated that the percentage of sublethal
damage was higher in L. monocytogenes than in L. innocua. The results of the study carried out by using
C. elegans indicated that C. elegans fed in a lawn of L. monocytogenes previously treated with carvacrol
showed a loss in life span (p 0.05) as compared with L. monocytogenes treated with citral, Escherichia
coli OP50 as a negative control, and treated and untreated L. innocua. Egg laying was also affected: worms
fed in a lawn of treated and untreated L. monocytogenes laid fewer eggs than those fed in a lawn of
treated and untreated L. innocua or fed with OP50 as a negative control. Worms fed in a lawn of treated
and untreated L. innocua also laid fewer eggs than those fed with OP50 as a negative control. A
phenotype named bag of worms and an undescribed new one, “vulva inflammation”, were also observed.
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