Pseudomonas aeruginosa hijacks the murine nitric oxide metabolic pathway to evade killing by neutrophils in the lung

Neutrophils play a critical role in the eradication of Pseudomonas aeruginosa, a major pathogen causing lung infection. However, the mechanisms used by the pathogen to evade neutrophil-mediated killing remain poorly understood. Using a high-density transposon screen, we find that P. aeruginosa colonization in the lung is promoted by pathogen nitrite reductase nirD. nirD is required for ammonia production from nitrite, a metabolite derived from nitrogen oxide (NO) generated by inducible NO synthetase (iNOS) in phagocytes. P. aeruginosa deficient in nirD exhibit reduced survival in wild-type neutrophils but not in iNOS-deficient neutrophils. Mechanistically, nirD enhances P. aeruginosa survival in neutrophils by inhibiting the localization of the pathogen in late phagosomes. P. aeruginosa deficient in nirD show impaired lung colonization after infection in wild-type mice but not in mice with selective iNos deficiency in neutrophils. Thus, P. aeruginosa uses neutrophil iNOS-mediated NO production to limit neutrophil pathogen killing and to promote its colonization in the lung. [Display omitted] •P. aeruginosa nirD promotes pathogen colonization in the lung•nirD uses neutrophil iNOS-generated nitric oxide to produce ammonium from nitrite•Ammonium generated via nirD inhibits pathogen localization in the late phagosome Nakatsuka et al. identified P. aeruginosa nirD as a factor that enhances pathogen lung colonization. P. aeruginosa uses neutrophil iNOS-mediated NO production to generate ammonium via nirD, which inhibits pathogen localization in the late phagosome. Thus, the pathogen uses the host NO to evade killing by neutrophils in the lung.