Study On The Inhibition Effect And Mechanism Of Subinhibitory Concentrations Of Cinnamaldehyde On The Productions Of α-toxin,Staphylococcal Enterotoxin A,B In Staphylococcus Aureus

Staphylococcal aureus can cause the food poisoning and infection of people and animals. With the abuse of antibiotics, more and more drug-resistant strains were found, from the penicillin resistant strain to methicillin and vancomycin resistant strains. These drug-resistant strains push the therapy of the infection caused by drug-resistant strains in an embarrassing place. As known to all, the virulence of the Staphylococcal aureus is depended on the production of the virulence factors, people now want to find drugs with new mechanisms that can reduce the virulence.MIC determination of the Cinnamaldehyde: 1 strardand strain ATCC 29213 and 6 strains separated from the clinic were used to detect the MICs of Cinnamaldehyde. The results showed that the MICs of Cinnamaldehyde for 7strains were 128mg/l-256mg/l.Bacteriostasis growth curve detection: ATCC 29213 was used to detect the growth curve under the Cinnamaldehyde at the concentrations of 256mg/l, 126mg/l, 64mg/l, 32mg/l, 16mg/l and 0mg/l, and measuring the OD600 every 15 min. The result showed that only 256mg/l and 128mg/l of Cinnamaldehyde remarkably inhibited the growth of the bacteria.Assay of the immunoblotting: ATCC 29213 and SA3629 were used to detect the productions ofα-toxin, Staphylococcal enterotoxin A and B. The strains were cultured at the concentrations of above (except 256mg/l) to OD600 of 2.5, then separated the bacterias and supernatants for the immunoblotting. The results showed that at the concentrations of 128mg/l and 64mg/l Cinnamaldehyde decreased the production ofα-toxin, Staphylococcal enterotoxin A and B remarkably, other concentrations were not notably.Detection of the expression of hla and agrA: The real-time Q-PCR was used to detect the expressions of hla and agrA genes of ATCC 29213 at subinhibitory Cinnamaldehyde. The results showed that the expressions of hla and agrA of all the 4 subinhibitory concentrations were less than the control group, and the reduction was depended on the concentration. The expressions of hla and agrA at the concentration of 128mg/l were only 6.33% and 12.11% compared to the control group.The present study showed that subinhibitory concentrations of Cinnamaldehyde could decreased the productions ofα-toxin, Staphylococcal enterotoxin A and B, and the mechanism of the inhibition was possible through the agr two-component regulatory systems.