Carvacrol Selective Pressure Allows the Occurrence of Genetic Resistant Variants of Listeria monocytogenes EGD-e

• Published in: Foods Vol. 11; no. 20; p. 3282
• Main Authors: Berdejo, Daniel, Gayán, Elisa, Pagán, Elisa, Merino, Natalia, Campillo, Raúl, Pagán, Rafael, García-Gonzalo, Diego
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 20.10.2022; MDPI
• Subjects: Ampicillin; antibiotic resistance; Antibiotics; Antiinfectives and antibacterials; Antimicrobial agents; Carvacrol; Cross-resistance; Drug dosages; Essential oils; evolution assays; Exposure; Food; Food preservation; Food safety; Food science; Gene sequencing; Genomes; Gram-positive bacteria; Heat treatment; Heat treatments; Listeria; Listeria monocytogenes; Long-term effects; Mode of action; Mutation; Nucleotides; Preservatives; resistant variants; Veterinary medicine; Whole genome sequencing; Germany; antibiotic resistance; whole-genome sequencing; Listeria monocytogenes; evolution assays; carvacrol; resistant variants; heat treatments
• ISSN: 2304-8158; 2304-8158
• DOI: 10.3390/foods11203282

Essential oils and their constituents, such as carvacrol, are potential food preservatives because of their great antimicrobial properties. However, the long-term effects of these compounds are unknown and raise the question of whether resistance to these antimicrobials could emerge. This work aims to evaluate the occurrence of genetic resistant variants (RVs) in EGD-e by exposure to carvacrol. Two protocols were performed for the RVs selection: (a) by continuous exposure to sublethal doses, where LmSCar was isolated, and (b) by reiterative exposure to short lethal treatments of carvacrol, where LmLCar was isolated. Both RVs showed an increase in carvacrol resistance. Moreover, LmLCar revealed an increased cross-resistance to heat treatments at acid conditions and to ampicillin. Whole-genome sequencing identified two single nucleotide variations in LmSCar and three non-silent mutations in LmLCar. Among them, those located in the genes encoding the transcriptional regulators RsbT (in LmSCar) and ManR (in LmLCar) could contribute to their increased carvacrol resistance. These results provide information regarding the mode of action of this antimicrobial and support the importance of knowing how RVs appear. Further studies are required to determine the emergence of RVs in food matrices and their impact on food safety.