Addition of lime juice and NaCl to minced seafood may stimulate the expression of Listeria monocytogenes virulence, adhesion, and stress response genes.

Listeria monocytogenes is a ubiquitous opportunistic bacterium responsible for deadly listeriosis outbreaks. This pathogen has been recognized as a significant food-borne pathogen in seafood products. The present study aimed to investigate the transcript levels of virulence, adhesion, and stress response genes of L .  monocytogenes upon exposure to sublethal levels of lime juice and NaCl in shrimp matrix. For this purpose, minced and broth shrimp samples (control, 2% NaCl, 5% NaCl, 25 μL/mL lime, and 50 μL/mL lime, as well as 2% NaCl+25 μL/mL lime) were inoculated with approximately 10 7  CFU/g or ml of L .  monocytogenes , and subsequently, the samples were stored at 12°C or 37°C. For the minced samples, the transcription of one stress-related ( sigB ), two adhesion ( imo1634 and imo1847 ), and four virulence ( hly , prf , intA , and plc ) genes was assessed by RT-qPCR after different storage times (0 and 48 h). Results showed that the transcript levels of sigB , imo1847 , and imo1634 genes increased with increasing storage temperatures of shrimp broth (12°C to 37°C). At the beginning, the transcription of the studied genes decreased in all treatments of minced shrimp; however, after 48 h of storage at 12°C, the transcript levels of hly , prf , imo1847 , imo1634 , and intA genes were significantly upregulated up to 0.5-9 log 2 fold-change in all treatments compared to the control group ( p  < .05). These results highlight that the survived L .  monocytogenes after exposure to moderate salt content or lime juice could represent enhanced virulence and adhesion capabilities, posing a significant public health risk.