Antimicrobial Activity and Action Mechanism of Thymoquinone against and Its Spores.

In this study, thymoquinone (TQ), a natural active substance, was investigated for its antibacterial activity against , and its inhibitory effect on in reconstituted infant formula (RIF) was evaluated. In addition, the inhibitory effect of TQ on spore germination was explored. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of TQ against eight strains ranged from 4.0 to 8.0 μg/mL, whereas treated with TQ displayed a longer lag phase than the untreated control. TQ exerted a good bactericidal effect on in Luria-Bertani broth. In addition, TQ obviously reduced the intracellular ATP concentration of , which caused depolarization of the cell membrane, increased the intracellular reactive oxygen species level, impaired the cell morphology, and destroyed proteins or inhibited proteins synthesis. This provides a mechanism for its bacteriostatic effect. TQ also inactivated growth in RIF. Moreover, reverse transcription-quantitative polymerase chain reaction illustrated that TQ downregulated the transcription of genes related to hemolysin, non-hemolytic enterotoxin, enterotoxin, and cytotoxin K. Meanwhile, TQ displayed the ability to inhibit the germination of spores. These findings indicate that TQ, as an effective natural antimicrobial preservative, has potential applications in controlling food contamination and foodborne diseases caused by .