Inhibition effect of tea tree oil on Listeria monocytogenes growth and exotoxin proteins listeriolysin O and p60 secretion.

Listeria monocytogenes (L.monocytogenes) is a Gram-positive bacterium that causes infections in humans. In this study, the effects of tea tree oil (TTO) at subinhibitory concentrations on L.monocytogenes growth and two important exotoxin proteins secreted by L.monocytogenes were researched. Treatment with half of minimal inhibitory concentration of TTO demonstrated very little or no reduction in numbers of viable ATCC 19115 cells. Listeriolysin O (LLO) and p60, were investigated. A listeriolysin assay was used to investigate the hemolytic activities of L.monocytogenes exposed to TTO, and the secretion of LLO and p60 was detected by immunoblot analysis. Additionally, real-time RT-PCR was used to analyse the influence of TTO on the transcription of LLO and p60 encoded genes hly and iap respectively. According to our experimental results, we propose that TTO could be used as a promising natural compound against L.monocytogenes and its virulence factors.