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Cronobacter sakazakii is a foodborne pathogen associated with fatal forms of necrotizing enterocolitis, meningitis and sepsis in neonates and infants. The aim of this study was to determine whether citral, a major component of lemongrass oil, could suppress putative virulence factors of C. sakazakii that contribute to infection. Sub-inhibitory concentrations of citral significantly decreased motility, quorum sensing, biofilm formation and endotoxin production. Citral substantially reduced the adhesion and invasion of C. sakazakii to Caco-2 cells and decreased bacterial survival and replication within the RAW 264.7 macrophage cells. Citral also repressed the expression of eighteen genes involved in the virulence. These findings suggest that citral has potential to be developed as an alternative or supplemental agent to mitigate the infections caused by C. sakazakii.

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This study aimed to determine the antimicrobial activity of thymoquinone (TQ) against Listeria monocytogenes , and to examine its inhibitory effects on biofilm formation, motility, hemolysin production, and attachment-invasion of host cells. The minimum inhibitory concentrations (MICs) of TQ against eight different L. monocytogenes strains ranged from 6.25—12.50 μg/mL. Crystal violet staining showed that TQ clearly reduced biofilm biomass at sub-MICs in a dose-dependent manner. Scanning electron microscopy suggested that TQ inhibited biofilm formation on glass slides and induced an apparent collapse of biofilm architecture. At sub-MICs, TQ effectively inhibited the motility of L. monocytogenes ATCC 19115, and significantly impacted adhesion to and invasion of human colon adenocarcinoma cells as well as the secretion of listeriolysin O. Supporting these findings, real-time quantitative polymerase chain reaction analysis revealed that TQ down-regulated the transcription of genes associated with motility, biofilm formation, hemolysin secretion, and attachment-invasion in host cells. Overall, these findings confirm that TQ has the potential to be used to combat L. monocytogenes infection.