Pseudomonas aeruginosa is an opportunistic human pathogen that is especially adept at forming surface-associated biofilms. P. aeruginosa causes catheter-associated urinary tract infections (CAUTI) through biofilm formation on the surface of indwelling catheters.
P. aeruginosa encodes for three extracellular polysaccharides, PEL, PSL and alginate, and utilizes PEL and PSL polysaccharides to form biofilms in vitro; however, the requirement of these polysaccharides during in vivo infections is not well understood. Here we show in a murine model of CAUTI that PAO1, a strain harboring both pel and psl genes, and PA14, a strain harboring only pel genes, form biofilms on the implanted catheters. To determine the requirement of exopolysaccharide during in vivo biofilm infections, we tested isogenic mutants lacking the pel, psl, and alg operons 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 induce the ΔpelD mutant to form biofilm, we tested mouse, human and artificial urine and show that urine can induce biofilm formation by the PA14 ΔpelD mutant. By testing the major constituents of urine, we show that urea can induce a pel-, psl-, and alg-independent biofilm. These pel-, psl-, and alg-independent biofilms are mediated by the release of extracellular DNA. Treatment of biofilms formed in urea with DNase I reduced the biofilm indicating extracellular DNA supports biofilm formation. Our results indicate that the opportunistic pathogen P. aeruginosa utilizes a distinct program to form biofilms that are independent of exopolysaccharides during CAUTI.
Cole SJ, Records AR, Orr MW, Linden SB, Lee VT Are you the author?
Department of Cell Biology and Molecular Genetics, Maryland Pathogen Research Institute, University of Maryland at College Park, College Park, MD, USA.
Reference: Infect Immun. 2014 Mar 4. (Epub ahead of print)