SMOX and cystic fibrosis: Given the clear distinctions between PAO1 and FRD1 tolerance to RNI, we hypothesized that other chronic CF isolates would be uniquely sensitive to RNI compared to acute non-CF and environmental isolates of P. aeruginosa. To test this hypothesis, competition assays were performed where P. aeruginosa isolates were spotted next to S. parasanguinis in the presence or absence of nitrite.