Catheter-Associated Urinary Tract Infection by Pseudomonas aeruginosa Is Mediated by Exopolysaccharide-Independent Biofilms

Abstract

ABSTRACTPseudomonas aeruginosais an opportunistic human pathogen that is especially adept at forming surface-associated biofilms.P. aeruginosacauses catheter-associated urinary tract infections (CAUTIs) through biofilm formation on the surface of indwelling catheters.P. aeruginosaencodes three extracellular polysaccharides, PEL, PSL, and alginate, and utilizes the PEL and PSL polysaccharides to form biofilmsin vitro; however, the requirement of these polysaccharides duringin vivoinfections is not well understood. Here we show in a murine model of CAUTI that PAO1, a strain harboringpel,psl, andalggenes, and PA14, a strain harboringpelandalggenes, form biofilms on the implanted catheters. To determine the requirement of exopolysaccharide duringin vivobiofilm infections, we tested isogenic mutants lacking thepel,psl, andalgoperons and showed that PA14 mutants lacking these operons can successfully form biofilms on catheters in the CAUTI model. To determine the host factor(s) that induces the ΔpelDmutant to form biofilm, we tested mouse, human, and artificial urine and show that urine can induce biofilm formation by the PA14 ΔpelDmutant. By testing the major constituents of urine, we show that urea can induce apel-,psl-, andalg-independent biofilm. Thesepel-,psl-, andalg-independent biofilms are mediated by the release of extracellular DNA. Treatment of biofilms formed in urea with DNase I reduced the biofilm, indicating that extracellular DNA supports biofilm formation. Our results indicate that the opportunistic pathogenP. aeruginosautilizes a distinct program to form biofilms that are independent of exopolysaccharides during CAUTI.