SMOX and susceptibility to pneumonia measurement: To identify the role of AprA in the pathogenesis of P. aeruginosa, we developed a murine pneumonia model of bacterial infection through the intranasal inoculation of 5 × 106 c.f.u. of different strains of P. aeruginosa, including a wild-type parental PAO1 and an aprA deletion mutant PAOaprA−.