Transcriptomic analysis of Listeria monocytogenes strains linked to fresh produce outbreaks in response to commercial sanitizers

Several fresh produce outbreaks have been associated with Listeria monocytogenes contamination during postharvest processing. Sanitation practices are among the most critical measures for controlling and minimizing bacterial growth. Thus, the aim of this research was to evaluate the transcriptomic response of a cocktail of four L. monocytogenes strains associated with the 2011 cantaloupe and 2014 caramel apple listeriosis outbreaks. Differentially expressed genes (DEGs) were evaluated after exposure to sublethal concentrations of four sanitizer treatments including chlorine (Cl) and peracetic acid (PAA) at 5 ppm, lactic acid 0.2% (v/v) (LA), and silver dihydrogen citrate 50% (v/v) (SDC) which contained 2.43% citric acid and 0.0015% silver ions, during 70 s exposure via RNA-sequencing (n=4). SDC exposure resulted in the greatest number of DEGs, followed by LA, Cl, and PAA. Non-coding RNAs ranked among the most significant DEGs across treatments. From those, one unique gene lmos88 , associated with S-Adenosyl Methionine (SAM) synthesis, was significantly upregulated across all sanitizers. Both SDC and LA had significant overlap in gene responses. Only Cl treatment caused significant downregulated pathways including tRNA charging (Q=0.00263), aminoacyl-tRNA biosynthesis (Q=0.00328), and other related metabolic clusters (Q=0.00355). Upregulated gene ontology (GO) terms were observed only after SDC application and were related to membrane-associated functions (Q=0.00034). These findings underscore how commercially available sanitizers affect L. monocytogenes transcriptomic profile, and the potential key role non-coding RNA genes play in response to sanitizers.