| Staphylococcus aureus is one of the most common pathogen in suppulative infection, and food poisoning caused by its enterotoxin is a globle health problem. Sublancin, a bacteriocin of the Bacillus subtilis, exerts powerful antibacterial activity against a broad spectrum of gram-positive bacteria including S. aureus. We have developed a highly efficient expression system using Bacillus subtilis800in order to obtain large amounts. To investigate the effect of sublancin on S. aureus and possible antibacterial mechanism, methicillin susceptible S. aureus CVCC1882and methicillin resistant S. aureus ATCC43300were used.(1) The minimal inhibitory concentrations of sublancin for the two stains are3.75and60mg/L, and exert powerful antibacterial activity.(2) In order to identify the intracellular target site. ATCC43300cells were incubated with sublancin and electron micrographs and proteomic analysis were done. Electron micrographs results confirmed that S. aureus cells division was interrupted. The differentially expressed S. aureus proteins involve in energy metabolism, amino acid metabolism and response to stress.(3) The effect of sublancin on S. aureus in vivo. The experiments were done using the two stains, respectively. A total of160, four week old mice were randomly assigned to1of8treatments. Mice in the control group were injected intraperitoneally with0.5mL of0.9%saline. Mice in the other seven groups were given an intraperitoneal injection of0.5mL saline containing1.0×1010CFU/mL S. aureus. Six hours after inoculation, mice in the control group were again injected with0.5mL of0.9%saline. Mice in the other seven groups were injected intraperitoneally with0.5mL of0.9%saline containing0,0.5,1.0,2.0or4.0mg/kg BW sublancin or1.0or2.0mg/kg BW ampicillin. The results showed that sublancin significantly reduced mice mortality. The height and the number of proliferated cells from the intestinal villi in the sublancin treated mice were higher than in the control. Sublancin also downregulated inflammatory cytokines, the NF-κB and iNOS in the intestine of mice. Sublancin also reduced the number of apoptosis cells and increased number of the CD8cells in spleen. ATCC43300express enterotoxins while CVCC1882doesn’t, and enterotoxins sharply stimulate lymphocyte (especially CD4cells). Thus, the ratio of white pulp and the number of CD4cells in the spleen of mice increased significantly. After sublancin treatment, the ratio of white pulp and the number of CD4cells in the spleen of ATCC43300infected mice significantly decreased. In conclusion, sublancin powerfully inhibited S. aureus growth through inhibiting the energy metabolism and thus inhibiting the cell division. Sublancin also showed antibacterial effects in vivo and protect the intestine and spleen injury. |
