铜绿假单胞菌lasR rhlR基因缺陷对大鼠慢性肺部感染的影响

Effects of lasR rhlR defects on chronic Pseudomonas aeruginosa lung infection in rats

目的观察铜绿假单胞菌（Pseudomonas aeruginosa，Pa）PAO1野生型及群体感应（quorum sensing，QS）系统的lasR rhlR基因缺陷型Pα菌株人工生物被膜致病性的差异，及QS系统的lasR rhlR基因在Pα生物被膜感染致病过程中的地位。方法从大鼠支气管内直接予以Pα（菌种为PAO1野生型和PAO1 lasR rhlR基因缺陷型）海藻酸盐微菌粒悬液（10^9CFU／ml）攻击，建立PAO1野生型及QS系统的lasR rhlR基因缺陷型菌株人工生物被膜肺部感染动物模型。分别于感染1周和2周后评估各组大鼠的肺部病理学、细菌学及细胞因子（IL-4、IL-10）反应的变化。结果感染1周和2周后，PAO1野生型组的肺部病理学改变和细菌学改变均明显重于PAO1 lasR rhlR基因缺陷组（P〈0．001）；感染1周后PAO1野生型组肺部的IL-4、IL-10水平都高于PAO1 lasR rhlR基因缺陷组（P〈0．01，P〈0．05）；2周后PAO1野生型组肺部IL-10水平进一步升高（P〈0．01），明显高于PAO1 lasR rhlR基因缺陷组（P〈0．001）。结论PAO1野生型组在病程中引起持久和严重的肺部感染，激发了TH2样免疫反应，而PAO1 lasR rhlR基因缺陷组的肺部病变明显轻于PAO1组，说明QS系统的lasR rhlR基因在Pα肺部感染的建立及慢性化发展过程中发挥着重要作用。

Objective To tmderstand the importance of quorum sensing （QS） system in Pseudomonas aeruginosa （Pα） biofilm lung infection, the pathogenic effects of the wild-type Pa PAO1 in vivo were compared with QS double mutant PAO1 lasR rhlR. Methods Rats were challenged intratracheally with alginate embedded strain PAO1 and the mutant of QS in the concentration of 10^9 CFU/ml. One and two weeks after intratracheal challenge with Pa, parameters were evaluated. Results One week after challenge, significantly milder microscopic and macroscopic lung pathology （ P 〈 0.001） and lower lung bacterial load （ P 〈 0. 001） with lower IL-4 （ P 〈 0.01）, IL-10 （ P 〈0.05） production in the lungs were found in the lasR rhlR mutant group compared with the wild type PAO1. In the PAO1 group, the lung IL-10 level in week 2 was higher than that in the mutant group （ P 〈0.001） and also higher than that in week 1 （P〈0.01）. Conclusion The wild type PAO1 could cause persistent and acute lung infection, which induced a TH2-like cytokine response. The pathogenic effects of the lasR rhlR mutant were obviously milder than that of the wild type PAO1 in the animal models. So the functional lasR and rhlR genes of Pa play an important role in the establishment and persistence of the chronic lung infection.