[Effect of sodium houttuyfonate in combination with erythromycin on luxS, agr/RNAⅢ of Staphylococus epidermidis]

Quorum sensing of bacteria and its specific gene expression regulation have a very important role in bacterial biofilm formation. LuxS and agr are the key regulatory genes in quorum sensing of Staphylococcus epidermidis, and RNA Ⅲ is the effector molecule of agr system. In order to evaluate the effects of sodium houttuyfonate in combination with erythromycin on the transcription level of S. epidermidis, serial dilution method was used to determine the MIC of sodium houttuyfonate, erythromycin and vancomycin on S. epidermidis, and fluorescent quantitative PCR method was used to detect the transcription levels of luxS, agr/RNAⅢ in different time periods after treatment on S. epidermidis by sodium houttuyfonate in combination with erythromycin, vancomycin, and erythromycin alone. Our results showed that in treatment by 1/2MIC, 1/4MIC sodium houttuyfonate, 1/2MIC sodium houttuyfonate +1/2MIC erythromycin, 1/4MIC sodium houttuyfonate+1/4MIC erythromycin, and 1/8MIC sodium houttuyfonate+1/8MIC erythromycin for ATCC 35984, they could rapidly up-regulate the expression of luxS of S. epidermidis from the beginning as compared with negative control, with significant differences (P<0.05); furthermore, sodium houttuyfonate can still up-regulate the expression of luxS even after treatment for 6, 12 and 48 h. Sodium houttuyfonate in MIC and 1/2MIC concentration can significantly down-regulate the expression of agr (P<0.05); 1/2MIC sodium houttuyfonate+1/2MIC erythromycin, 1/4MIC sodium houttuyfonate+1/4MIC erythromycin, can also significantly down-regulate the expression of agr in 6 h, 12 h and 24 h(P<0.05). Sodium houttuyfonate in MIC, can significantly down-regulate the expression of RNA Ⅲ (P<0.05), and 1/2MIC sodium houttuyfonate+1/2MIC erythromycin can also significantly down-regulate the expression of RNAⅢ(P<0.05). Therefore, our presented results showed that sodium houttuyfonate in combination with erythromycin can rapidly up-regulate the transcription of luxS of S. epidermidis, and can down-regulate the expression of agr/RNA Ⅲ in certain concentrations, and suggested that sodium houttuyfonate in combination of erythromycin could inhibit mutual aggregation between S. epidermidis and biofilm bacteria, inhibit membrane nutrition and formation of water transport channels, prevent separation of bacterial cells in biofilm, and inhibit the formation of bacterial exotoxin of S. epidermidis.