新的细胞壁锚定蛋白SasX促进金黄色葡萄球菌黏附聚集和定植能力

The novel surface-anchored protein SasX promotes aggregation and colonization of Staphylococcus aureus

目的研究新的细胞壁锚定蛋白SasX对金黄色葡萄球菌黏附聚集和定植能力的影响。方法采用基因敲除及基因互补技术获得耐甲氧西林金黄色葡萄球菌（methicillin-resistant Staphylococcus aureus，MRSA）ST-239HS770sasX基因突变株及基因互补株。显微镜下直接观察sasX基因突变前后细菌自身的黏附聚集能力。通过黏附实验检测sasX基因突变前后对金黄色葡萄球菌黏附至人体鼻腔上皮细胞能力，并通过阻断实验检测表达纯化的SasX蛋白对金黄色葡萄球菌黏附至人体鼻腔上皮细胞的阻断能力，分析SasX蛋白对金黄色葡萄球菌定植能力的影响。结果与野生株相比，突变株HS770asasX自身的聚集能力明显减弱，而互补表达株HS770asasX（pRBsasX）的自身聚集能力与野生株无明显差异。与野生株相比，突变株HS770AsasX黏附至人体鼻腔上皮细胞能力明显减弱（P〈0．01），互补表达株HS770 asasX（pRBsasX）黏附能力明显增强（P〈0．01）。表达纯化的GST融合蛋白SasX和人体鼻腔上皮细胞预培养对于野生株HS770黏附至人体鼻腔上皮细胞的能力具有明显的抑制作用。结论新的细胞壁锚定蛋白SasX影响金黄色葡萄球菌黏附聚集和定植能力，金黄色葡萄球菌通过获得sasX基因更加容易定植到宿主易感部位，进而引发感染。

Objective To determine whether the novel surface-anchored protein SasX promotes aggregation of S. aureus and adherence of S. aureus to human nasal epithelial cells. Methods MRSA ST- 239 HS770 sasX gene mutant （ HS770 AsasX） and complement [ HS770 AsasX （pRBsasX） ] were gotten by gene knock-out and complement methods. The aggregation ability of S. aureus was observed through micro- scope. By adherence assay which was used for detection of the adherence ability of wild type and mutant to human nasal epithelial cells and blocking experiments which detected the ability of the purified recombinant SasX protein in blocking the adherence of S. aureus to human nasal epithelial cells, we investigated the influ- ence SasX on colonization of S. aureus. Results Compared to wild type, HS770 A sasX showed a reduction in cell aggregation, while the complement had no difference with wild type in aggregation. HS770 AsasX showed a significant reduction of adherence to human nasal epithelial cells compared to wild type （P 〈 0.01 ）, and the complement showed a very clear increasement of adherence to human nasal epithelial cells compared to wild type（P〈0.01 ）. Preineubation of nasal epithelial cells with the purified recombinant SasX protein inhibited S. aureus binding significantly. Conclusion SasX had an influence in aggregation of S. au- reus and its adherence to human nasal epithelial cells. By acquiring sasX, S. aureus colonized more easily to the susceptible sites of the host, and thus caused infection.