Hydroquinone derivatives attenuate biofilm formation and virulence factor production in Vibrio spp

Gram-negative Vibrio parahaemolyticus is a halophilic human pathogen known to be the leading cause of food poisoning associated with consuming uncooked or undercooked seafood. The increasing presence and contamination of seafood have caused serious safety concerns in food facilities. Notably, it can form biofilms on food surfaces that confer resistance to antimicrobial treatments. Therefore, in the present study, the antibacterial, antibiofilm, and antivirulence activities of hydroquinone (HQ) and its 16 derivatives were investigated against V. parahaemolyticus and V. harveyi. Representative active antibacterial and antibiofilm compounds, 2,3-dimethylhydroquinone (2,3-DMHQ) and 2,5-ditert-butylhydroquinone (DBHQ), were further examined using a crystal violet assay, biochemical reactions, live cell imaging, and scanning electron microscopy. 2,3-DMHQ with a minimum inhibitory concentration (MIC) of 20 μg/mL completely inhibited biofilm formation at a sub-MIC of 15 μg/mL. And, DBHQ with an MIC of ˃1000 μg/mL reduced biofilm formation by 70 % at sub-MIC of 25 μg/mL. Both 2,3-DMHQ and DBHQ inhibited protease and indole production as well as motility phenotypes. 2,3-DMHQ decreased fimbriae production and hydrophobicity whereas DBHQ did not. Transcriptomic studies revealed that genes related to biofilm, quorum sensing (QS), and hemolysin were downregulated. In addition, 2,3-DMHQ and DBHQ prevented biofilm formation of V. parahaemolyticus on squid surfaces and 2,3-DMHQ reduced the presence of V. parahaemolyticus in a boiled shrimp model. Toxicity assays using the Caenorhabditis elegans and seed germinations models showed that they were non-to-mildly toxic. These results suggest that 2,3-DMHQ and DBHQ possess the antimicrobial properties required to control V. parahaemolyticus planktonic and biofilm states in food production facilities.