Abstract
Listeria monocytogenes, which causes serious foodborne infections and public health problems worldwide, is one of the most important foodborne pathogens. Linalool has been identified as an antimicrobial agent against some microorganism, but its mechanism of action is currently unclear. Here, we investigated the efficacy of linalool against L. monocytogenes while planktonic and as a biofilm and explored potential mechanisms of action. Linalool exhibited strong anti-listeria activity in the planktonic stage. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed seven stages were classified of cells at microscopic level. Mesosome-like structures were observed for the first time in L. monocytogenes after linalool treatment. Linalool also showed significant anti-biofilm activity through both dispersal and killing of cells in the biofilm based on confocal scanning laser microscopy (CLSM) and SEM imaging, crystal violet staining, XTT and COMSTAT assays. Moreover, comparative transcriptome analysis demonstrated many potential mechanisms of action for linalool and some important pathways were screened out through the analysis of GO enrichment and KEGG. Our study provides evidence that linalool exhibits a strong antimicrobial activity against both the planktonic and biofilm forms of L. monocytogenes and gives insight into its mechanism of action.
Highlights
Listeria monocytogenes (L. monocytogenes) is a Gram-positive pathogen that is able to survive under a variety of adverse environmental conditions such as refrigeration temperatures, low pH, hyperosmotic and high salt environments (Gandhi and Chikindas, 2007)
The in vitro antibacterial efficacy of linalool against planktonic L. monocytogenes cells was evaluated in our previous study (Guo et al, 2018)
Our study demonstrated that linalool is an effective and promising anti-listeria agent against both planktonic cells and biofilms
Summary
Listeria monocytogenes (L. monocytogenes) is a Gram-positive pathogen that is able to survive under a variety of adverse environmental conditions such as refrigeration temperatures, low pH, hyperosmotic and high salt environments (Gandhi and Chikindas, 2007). It is widely distributed in nature and can cause listeriosis, a severe food-borne zoonosis by contaminating ready-toeat food, dairy products, undercooked food and food processing equipment (Buchanan et al, 2017). L. monocytogenes biofilms are more difficult to eradicate from contaminated food than planktonic cells and have a greater potential to infect humans and lead to listeriosis than planktonic cells. Multipronged strategies are needed to prevent or eradicate L. monocytogenes biofilm
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