Metabolic cross-talk promotes persistence of Enterococcus in a model of polymicrobial catheter-associated urinary tract infection

Catheter-associated urinary tract infections (CAUTI) account for 70%∼80% of urinary tract infections (UTI) and can lead to adverse outcomes. Most CAUTIs are polymicrobial with resilient communities maintaining a consistent composition of species over time, despite antibiotic treatment and catheter replacement. However, the mechanisms promoting persistence are poorly understood. Here we examine how a chemical interaction between Gram-positive Enterococcus faecalis and Gram-negative Klebsiella pneumoniae can explain their high rate of co-occurrence on long-term indwelling urinary catheters. Sequence analyses of longitudinal isolates from several human patients co-infected with E. faecalis and K. pneumoniae revealed that despite frequent replacement, catheters became re-colonized with the same or a nearly identical consortium of strains throughout the study collection period. Using artificial urine medium (AUM), monoculture revealed that the K. pneumoniae isolates grew robustly and formed biofilm, while the E. faecalis isolates grew poorly and did not form biofilm. However, co-culture of paired isolates resulted in enhanced E. faecalis growth and biofilm, which could be reproduced by supplementing E. faecalis with cell-free K. pneumoniae conditioned AUM supernatant (KpAUMSup). Analyses using comparative transcriptomics, mutant strains and chemical inhibitors with cell culture and murine CAUTI models revealed that: i) KpAUMSup, but not AUM, stimulated expression of the E. faecalis Fsr quorum-sensing system; ii) Fsr was required for E. faecalis to respond to KpAUMSup; iii) E. faecalis cultured in KpAUMSup was more efficient in initiating CAUTI; and iv) Disruption of Fsr inhibited initiation of CAUTI. This interspecies signaling may help explain the high rate of co-colonization of these CAUTI pathogens and highlights new therapeutic strategies to treat polymicrobial CAUTI.