Pseudomonas aeruginosa Induces Localized Immunosuppression During Pneumonia. Infection and immunity [Infect Immun] Journal article

Hospital-acquired bacterial pneumonia is a common and serious complication of modern medical care. Many aspects of these infections remain unclear, including the mechanisms by which invading pathogens resist clearance by the innate immune response and the propensity of these infections to be polymicrobial. Here, we use a mouse model of infection to show that Pseudomonas aeruginosa, a leading cause of hospital-acquired pneumonia, interferes with the ability of recruited phagocytic cells to eradicate bacteria from the lung. Early in infection, phagocytic cells, predominantly neutrophils, are recruited to the lungs but are incapacitated upon entering the airways by the P. aeruginosa toxin ExoU. The resulting paucity of functioning phagocytes allows the persistence of P. aeruginosa within the lungs and results in local immunosuppression that facilitates superinfection with less pathogenic bacteria. Together, our results provide explanations for prior reports linking ExoU-secreting P. aeruginosa with more severe pulmonary infections and for the predilection of hospital-acquired pneumonia to be polymicrobial.

Infection and immunity [Infect Immun]