Systemic Infection Facilitates Transmission of Pseudomonas aeruginosa

Health care-associated infections such as Pseudomonas aeruginosa (PA) bacteremia pose a major clinical risk for hospitalized patients, and efforts to limit them are a priority. The fitness pressures accounting for PA virulence factors that facilitate bloodstream infections are unclear, as these infections are presumed to be a \"dead-end\" and have no impact on transmission. Here, we used a mouse model to show that PA spreads from the bloodstream to the gallbladder, where it replicates to extremely high numbers. Bacteria in the gallbladder then seed the intestines and feces, leading to transmission to uninfected cage-mate mice. The findings demonstrate that the gallbladder is critical for spread of PA from the bloodstream to the feces during bacteremia, a process that promotes transmission.