Department of Cell Biology and Molecular Genetics, Maryland Pathogen Research Institute, University of Maryland at College Park, College Park, Maryland, USA.
Infect Immun. 2014 May;82(5):2048-58. doi: 10.1128/IAI.01652-14. Epub 2014 Mar 4.
Pseudomonas aeruginosa is an opportunistic human pathogen that is especially adept at forming surface-associated biofilms. P. aeruginosa causes catheter-associated urinary tract infections (CAUTIs) through biofilm formation on the surface of indwelling catheters. P. aeruginosa encodes three extracellular polysaccharides, PEL, PSL, and alginate, and utilizes the 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 pel, psl, and alg genes, and PA14, a strain harboring pel and alg 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 induces 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 that 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.
铜绿假单胞菌是一种机会性人类病原体，特别擅长形成表面相关的生物膜。铜绿假单胞菌通过在留置导管表面形成生物膜引起导管相关尿路感染（CAUTI）。铜绿假单胞菌编码三种细胞外多糖，PEL、PSL 和藻酸盐，并利用 PEL 和 PSL 多糖在体外形成生物膜；然而，这些多糖在体内感染过程中的需求尚不清楚。在这里，我们在 CAUTI 的小鼠模型中表明，携带 pel、psl 和 alg 基因的 PAO1 菌株和携带 pel 和 alg 基因的 PA14 菌株在植入的导管上形成生物膜。为了确定外多糖在体内生物膜感染过程中的需求，我们测试了缺失 pel、psl 和 alg 操纵子的同基因突变体，并表明缺乏这些操纵子的 PA14 突变体可以在 CAUTI 模型中成功地在导管上形成生物膜。为了确定诱导ΔpelD 突变体形成生物膜的宿主因素，我们测试了小鼠、人类和人工尿液，并表明尿液可以诱导 PA14 ΔpelD 突变体形成生物膜。通过测试尿液的主要成分，我们表明尿素可以诱导一种不依赖于 pel、psl 和 alg 的生物膜。这些不依赖于 pel、psl 和 alg 的生物膜是由细胞外 DNA 的释放介导的。用 DNase I 处理尿素形成的生物膜减少了生物膜，表明细胞外 DNA 支持生物膜的形成。我们的结果表明，机会性病原体铜绿假单胞菌在 CAUTI 期间利用一种独特的程序形成不依赖于细胞外多糖的生物膜。
