The Yersinia pestis GTPase BipA Promotes Pathogenesis of Primary Pneumonic Plague.

is a highly virulent pathogen and the causative agent of bubonic, septicemic, and pneumonic plague. Primary pneumonic plague caused by inhalation of respiratory droplets contaminated with is nearly 100% lethal within 4 to 7 days without antibiotic intervention. Pneumonic plague progresses in two phases, beginning with extensive bacterial replication in the lung with minimal host responsiveness, followed by the abrupt onset of a lethal proinflammatory response. The precise mechanisms by which is able to colonize the lung and survive two very distinct disease phases remain largely unknown. To date, a few bacterial virulence factors, including the Ysc type 3 secretion system, are known to contribute to the pathogenesis of primary pneumonic plague. The bacterial GTPase BipA has been shown to regulate expression of virulence factors in a number of Gram-negative bacteria, including , , and serovar Typhi. However, the role of BipA in has yet to be investigated. Here, we show that BipA is a virulence factor that promotes defense against early neutrophil-mediated bacterial killing in the lung. This work identifies a novel virulence factor and highlights the importance of early bacterial/neutrophil interactions in the lung during primary pneumonic plague.