Cooperativity between Stenotrophomonas maltophilia and Pseudomonas aeruginosa during Polymicrobial Airway Infections.

is a Gram-negative bacterium found ubiquitously in the environment that has historically been regarded as nonpathogenic. is increasingly observed in patient sputa in cystic fibrosis (CF), and while existing epidemiology indicates that patients with have poorer diagnoses, its clinical significance remains unclear. Moreover, as multidrug resistance is common among isolates, treatment options for these infections may be limited. Here, we investigated the pathogenicity of alone and during polymicrobial infection with Colonization, persistence, and virulence of were assessed in experimental respiratory infections of mice. The results of this study indicate that transiently colonizes the lung accompanied by significant weight loss and immune cell infiltration and the expression of early inflammatory markers, including interleukin 6 (IL-6), IL-1α, and tumor necrosis factor alpha (TNF-α). Importantly, polymicrobial infection with elicited significantly higher counts in bronchoalveolar lavages and lung tissue homogenates. This increase in bacterial load was directly correlated with the density of the population and required viable bacteria. Microscopic analysis of biofilms formed revealed that formed well-integrated biofilms with , and these organisms colocalize in the lung during dual-species infection. Based on these results, we conclude that active cellular processes by afford a significant benefit to during polymicrobial infections. Furthermore, these results indicate that may have clinical significance in respiratory infections.