Abstract
Enterococcus faecalis, a member of the human gastrointestinal microbiota, is an opportunistic pathogen associated with hospital-acquired wound, bloodstream, and urinary tract infections. E. faecalis can subvert or evade immune-mediated clearance, although the mechanisms are poorly understood. In this study, we examined E. faecalis-mediated subversion of macrophage activation. We observed that E. faecalis actively prevents NF-κB signaling in mouse RAW264.7 macrophages in the presence of Toll-like receptor agonists and during polymicrobial infection with Escherichia coli. E. faecalis and E. coli co-infection in a mouse model of catheter-associated urinary tract infection (CAUTI) resulted in a suppressed macrophage transcriptional response in the bladder compared to E. coli infection alone. Finally, we demonstrated that co-inoculation of E. faecalis with E. coli into catheterized bladders significantly augmented E. coli CAUTI. Taken together, these results support that E. faecalis suppression of NF-κB-driven responses in macrophages promotes polymicrobial CAUTI pathogenesis.
Author Summary Synergistic polymicrobial infections can contribute to both disease severity and persistence. Enterococcus faecalis and Escherichia coli are frequently co-isolated from polymicrobial urinary tract infections. Immunomodulation by co-infecting microbes can result in a more permissive environment for pathogens to establish infection. Presently, we do not yet understand how these microbes overcome host immunity to establish polymicrobial infections. To address this, we investigated how the immunosuppressive function of E. faecalis can contribute to acute infection. We defined that E. faecalis is able to suppress macrophages in vitro, despite the presence of E. coli. We also demonstrated E. faecalis’ ability to augment E. coli titers in vivo to establish kidney infection. Our findings raise the prospect that E. faecalis can alter host immunity to increase susceptibility to other uropathogens.
