The inhibitory effect of garlic (Allium sativum L.) essential oil nanoliposomes on Shiga-toxin 2 expression in Escherichia coli O157:H7

Foodborne diseases are considered as one of the main problems of public health. Escherichia coli O157H7 are responsible for major outbreaks of bloody diarrhea and hemolytic uremic syndrome (HUS) throughout the world. The mortality is originated from the production of a Shiga toxin (Stx) by these bacteria. Garlic essential oil (GEO) has antibacterial effects on many food-borne pathogens. Therefore, this study was aimed to evaluate the antibacterial activity of the Allium sativum L. EO and its nanoliposomal form on the virulence of E. coli O157:H7. Reverse passive latex agglutination test was used to detect Shiga toxin2 (Stx2) production after exposure to sub-inhibitory concentrations of free and nanoencapsulated EO. Also, the effect of sub-inhibitory concentrations of free and nanoliposomal form of GEO was evaluated on Stx2 gene expression and the relative transcriptional level of Stx2 gene was determined by real-time PCR. It was found that the sub-inhibitory concentrations of liposomal form of EO (50 and 75%) had a significantly higher inhibitory effect on Stx2 titer than its free form (p<0.05). Also, increasing the concentration of EO and nanoencapsulated EO significantly reduced Shiga toxin 2 gene expression according to control. Using 75% sub-inhibitory value of free and nanoliposome GEO, the relative transcriptional level of Stx2A gene was reduced from 0.938 to 0.667 and 0.931 to 0.659, respectively. Based on our findings, different methods of nanoencapsulation should future study to improve nanoliposome efficacy to suppress toxin production on expression level.