cid和lrg基因表达与表皮葡萄球菌临床株生物被膜形成关系的研究

Study on relationships between the expressions of cidA and lrgA and biofilm formation of Staphylococcus epidermidis clinical isolates

目的 cid和lrg操纵子是细菌程序性死亡和溶解的重要调控基因,本研究旨在探究表皮葡萄球菌临床株cidA和lrgA基因及其mRNA表达水平与生物被膜形成的关系.方法 前期收集的表皮葡萄球菌（来源于血液、尿液、痰、分泌物及导管等生物材料表面）临床株39株,通过黏附试验和icaA基因扩增将其分为生物被膜形成菌株20株,非生物被膜形成菌株19株,PCR扩增表皮葡萄球菌cidA和lrgA基因片段,半定量RT-PCR检测cidA和lrgA mRNA水平,计算cid/lrg mRNA比率.结果 39株表皮葡萄球菌临床株均可扩增出cidA和lrgA的基因片段.随机选取生物被膜形成菌株表皮葡萄球菌Y36和非生物被膜形成菌株表皮葡萄球菌Y26检测培养2、4、6、8、10 h的cidA和lrgA的表达水平,两株菌cidA mRNA均在培养4 h后达峰,lrgA mRNA均在培养6 h后达峰.39株表皮葡萄球菌培养4 h后,生物被膜形成菌株与非生物被膜形成菌株,菌株中cidA基因相对表达水平分别为0.340±0.250和0.406±0.408（P=0.541）,lrgA基因相对表达水平为0.325±0.218和0.253±0.211（P=0.299）,两组相比差异均无统计学意义.cid/lrg mRNA比率,生物被膜形成菌株为1.067±0.529,非生物被膜形成菌株为1.958±1.877,两组总体分布差异有统计学意义（P=0.001）.结论 表皮葡萄球菌临床株cidA和lrgA基因表达可能具有一定的时限性,cidA和lrgA基因在生物被膜形成菌株与非生物被膜形成菌株表皮葡萄球菌的表达没有明显差异,cid/lrg mRNA比率可能具有一定生物学意义.

Objective To investigate the relationships between the expressions of cidA and lrgA and the biofilm formation of Staphylococcus epidermidis clinical isolates. Methods Thirty-nine S. epidermidis clinical isolates were divided into biofilm formation group and non-biofilm formation group according to adhesion assays and icaA amplification, 20 strains for biofilm formation group and 19 strains for another group respectively. Amplify cidA and lrgA fragment with PCR, detect mRNA levels of cidA and lrgA with RT-PCR and then calculate the ratios of cid/lrg mRNA. Results All of the 39 isolates of S. epidermidis existed cidA and lrgA gene.Select 2 strains of S. epidermidis, Y36 and Y26, at random for detecting the cidA and lrgA mRNA levels of different phases, the highest level of cidA mRNA shows on 4 h＇s culture while lrgA shows on6 h. The relative expression levels of cidA of 39 isolates of S. epidermidis were 0.340 ＋ 0.250 in biofilm formation group and 0. 406 ＋0. 408（ P =0. 541 ） in non-biofilm formation group for 4 h culture, while the relative expression levels of lrgA were 0.325 ± 0.218 and 0.253 ± 0.211 respectively （ P = 0. 299）. There were no significant differences between these two groups. The ratios of cid/lrg mRNA were 1.067 ±0.529 and 1.958 ±1.877 respectively, the difference of population distribution was significant（ P = 0.001 ）. Conclusion The expressions of cidA and lrgA of S. epidermidis clinical isolates may be time-limited. There were no significant differeces of expressions of cidA and lrgA between biofilm formation group and non-biofilm formation group. The ratios of cid/lrg mRNA maybe have some biological significance.