Previous studies have shown that P. aeruginosa altered its quorum sensing systems and cell wall component (lasR, mpl) to reduce its virulence during adaptation in the airway of VAP patients[16]; while this bacterium slowly adapts to the airway of CF patients by genetic mutations in its mucA, algU, vgrG and etc. genes for chronic infection [17, 38]. This evidence concerns the gene MPL and ventilator-associated pneumonia.