Metabolic interplay betweenProteus mirabilisandEnterococcus faecalisfacilitates polymicrobial biofilm formation and invasive disease

Abstract

Catheter-associated urinary tract infections (CAUTI) account for 40% of all nosocomial infections and can lead to significant life-threatening complications such as bacteremia. Microbial biofilms play an important role in the development and pathogenesis of CAUTI, and these biofilms are often polymicrobial. Proteus mirabilis and Enterococcus faecalis are two of the most common causes of CAUTI, and they often persistently co-colonize the catheterized urinary tract. We previously demonstrated that co-culture of E. faecalis with P. mirabilis increased biofilm biomass, antimicrobial resistance, and disease severity. In this study, we uncover the metabolic interplay that drives biofilm enhancement and examine the contribution of this polymicrobial interaction to CAUTI severity. Though compositional and proteomic biofilm analyses, we determined that the increase in biofilm biomass stems from an increase in the protein fraction of the polymicrobial biofilm. We further observed an enrichment in proteins associated with ornithine and arginine metabolism in polymicrobial biofilms compared to single-species biofilms. By testing mutants of E. faecalis and P. mirabilis, we found that L-ornithine secreted by the E. faecalis ArcD antiporter promotes L-arginine biosynthesis in P. mirabilis via ArgF, which ultimately fuels production of proteins that facilitate contact-dependent interactions to enhance biofilm biomass. We further demonstrate that ArcD and ArgF are not important for urinary tract colonization by either species when alone, but ornithine/arginine interplay is critical for the increased disease severity that occurs during coinfection. This study provides deeper insight into the polymicrobial interactions occurring during CAUTI and highlights how these interactions can have significant impacts on pathogenesis and bacterial persistence.

Characterizing arginine, ornithine, and putrescine pathways in enteric pathobionts

“…Our data indicates that E. faecalis ATCC 29212, K. pneumoniae ATCC 9101, and S. epidermidis ATCC 51025 consumed the most arginine and generated the highest amounts of ornithine. Previous work has demonstrated that E. faecalis generated ornithine promotes other pathobionts (Hunt et al, 2023;Keogh et al, 2016;Smith et al, 2022). L-ornithine was found to stimulate enterobactin production and iron transfer in E. faecalis and uropathogenic E. coli polymicrobial biofilms (Keogh et al, 2016).…”

“…Ornithine was specifically found to facilitate E. coli biosynthesis of the enterobactin siderophore, allowing E. coli growth and biofilm formation in iron‐limiting conditions that would otherwise restrict its growth. E. faecalis generated ornithine was also found to promote arginine biosynthesis in another gut pathobiont Proteus mirabilis (Hunt et al, 2023 ). To date, no studies have examined the cross‐talk of ornithine from K. pneumoniae or S. epidermidis on other bacteria, but studies in the future would be valuable.…”

The Role of Metabolomics and Microbiology in Urinary Tract Infection

“…Secondly, changes in the microbiome and metabolome can influence the severity of UTIs and the recovery process [ 22 , 100 ]. For instance, l-ornithine secretion by E. faecalis increases arginine production in P. mirabilis , a metabolic interaction that significantly reduces infection severity [ 125 ]. Microbial biofilms are critical in the origin and pathophysiology of catheter-associated UTIs.…”