喹诺酮信号分子对铜绿假单胞菌毒力的影响

摘要

目的 探讨喹诺酮信号分子(PQS)对铜绿假单胞菌(PA)毒力的影响.方法 选择PAO1作为实验菌,分为PQS组、PQS与抑制剂组、抑制剂组以及正常组.QPCR方法检测Ⅲ型分泌系统(T3SS)的调节基因ExsA和毒力蛋白基因ExoS的转录水平；分光光度计检测绿脓素生成量；作用肺泡上皮细胞A549,用平板计数法比较PAO1粘附和侵袭力；构建小鼠腹膜炎模型,观察PQS对小鼠存活时间的影响.结果 PQS增多和减少不影响PAO1的成长情况.与正常组相比,PQS组的ExsA与其调控表达的ExoS毒力蛋白基因转录水平均显著升高(P＜0.01);PQS组PAO1产生的绿脓素也明显升高,抑制组却明显下降(P＜0.01)；与A549细胞作用时,抑制剂组PAO1的粘附和侵袭力均显著降低；腹膜炎模型小鼠PQS组存活时间也降低明显(P均＜0.01).抑制剂组Exos的转录水平有降低,差异有统计学意义(P＜0.05).与正常组比较,抑制剂组的ExsA转录水平无明显差异,PQS组PAO1的粘附力和侵袭力没有改变(Jp均＞0.05).结论 在PA感染宿主的整个过程中,PQS能维持粘附和侵袭能力,PQS的浓度与绿脓素的产生有正相关关系,从而最终使宿主的存活时间成负相关.%Objective To investigate the effect of Pseudomonas quinolone signal (PQS) on the virulence of Pseudomonas aeruginosa. Methods Pseudomonas aeruginosa strain PAO1 was treated with PQS alone, PQS plus farnesol, or farnesol alone. The transcriptional levels of the regulator gene ExsA and virulence protein gene ExoS of type III secretion system were examined using quantitative real-time PCR, and spectrophotometry was employed to detect pyocyanin production in the bacteria. The adhesion and invasiveness of the treated PAO1 in cultured alveolar epithelial cells A549 were assessed on plate count agar, and their effects on the survival of a mouse model of peritonitis was compared. Results The increase or decrease of PQS did not affect the growth of PAO1. Compared with the untreated bacteria, PQS-treated PAO1 showed obviously increased transcription levels of ExsA and ExoS (P<0.01) and pyocyanin production, which was significantly lowered by farnesol (P< 0.01). In A549 cell cultures, farnesol-treated PAO1 exhibited significantly lowered adhesion and invasiveness, while PQS-treated PAO1 caused a significantly decreased survival time of mice with peritonitis (P<0.01). Farnesol treatment did not obviously affected ExsA transcription (P>0.05) but caused a significant reduction in the transcriptional level of Exos (P<0.05) in PAO1. PQS showed no significant effect on the adhesion and invasiveness of PAO1 (P>0.05). Conclusion PQS can maintain the adhesion and invasiveness of Pseudomonas aeruginosa, and in the hosts of the bacteria, PQS concentration is positively correlated with pyocyanin production and hence negatively with the survival time of the hosts.