title: Klebsiella pneumoniae translocates across the intestinal epithelium via Rho GTPase- and phosphatidylinositol 3-kinase/Akt-dependent cell invasion.
abstract: Klebsiella pneumoniae is an important pathogen that causes hospital-acquired septicemia and is associated with the recent emergence of community-acquired pyogenic liver abscess (PLA). Clinical typing suggests that K. pneumoniae infections originate from the gastrointestinal reservoir. However, the underlying mechanism remains unknown. Here, we have sought to determine how K. pneumoniae penetrates the intestinal barrier. We identified that bacteremia and PLA clinical isolates adhered to and invaded intestinal epithelial cells. Internalization of K. pneumoniae in three different human colonic cell lines was visualized by confocal microscopy and three-dimensional (3D) imaging. Using a Transwell system, we demonstrated that these K. pneumoniae isolates translocated across a polarized Caco-2 monolayer. No disruptions of transepithelial electrical resistance and altered distribution of tight junction protein ZO-1 or occludin were observed. Therefore, K. pneumoniae appeared to penetrate the intestinal epithelium via a transcellular pathway. Using specific inhibitors, we characterized the host signaling pathways involved. Inhibition by cytochalasin D and nocodazole suggested that actin and microtubule cytoskeleton were both important for K. pneumoniae invasion. A Rho inhibitor, ML141, LY294002, and an Akt1/2 inhibitor diminished K. pneumoniae invasion in a dose-dependent manner, indicating that Rho family GTPases and phosphatidylinositol 3-kinase (PI3K)/Akt signaling were required. By a mouse model of gastrointestinal colonization, in vivo invasion of K. pneumoniae into colonic epithelial cells was demonstrated. Our results present evidence to describe a possible mechanism of gastrointestinal translocation for K. pneumoniae. Cell invasion by manipulating host machinery provides a pathway for gut-colonized K. pneumoniae cells to penetrate the intestinal barrier and access extraintestinal locations to cause disease.
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Chun-Ru
authors.initials: CR
authors.lastname: Hsu
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Yi-Jiun
authors.initials: YJ
authors.lastname: Pan
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Ju-Yun
authors.initials: JY
authors.lastname: Liu
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Chun-Tang
authors.initials: CT
authors.lastname: Chen
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Tzu-Lung
authors.initials: TL
authors.lastname: Lin
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan wangjt@ntu.edu.tw.
authors.forename: Jin-Town
authors.initials: JT
authors.lastname: Wang
mesh_terms: D008841:Actin Cytoskeleton; D000818:Animals; D016470:Bacteremia / Q000276:immunology / Q000382:microbiology; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology*; D007710:Klebsiella Infections / Q000276:immunology / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000276:immunology / Q000472:pathogenicity*; D051379:Mice; D008807:Mice, Inbred BALB C; D008870:Microtubules; D009025:Morpholines / Q000494:pharmacology; D015739:Nocodazole / Q000494:pharmacology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D062793:Occludin / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000502:physiology*; D015398:Signal Transduction; D019108:Tight Junctions / Q000276:immunology / Q000382:microbiology; D050257:Tubulin Modulators / Q000494:pharmacology; D062826:Zonula Occludens-1 Protein / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D002867:Chromones; D009025:Morpholines; D019384:Nucleic Acid Synthesis Inhibitors; D062793:Occludin; C568986:Ocln protein, mouse; D000081082:Phosphoinositide-3 Kinase Inhibitors; C569043:Tjp1 protein, mouse; D050257:Tubulin Modulators; D062826:Zonula Occludens-1 Protein; D015638:Cytochalasin D; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D051057:Proto-Oncogene Proteins c-akt; D020741:rho GTP-Binding Proteins; D015739:Nocodazole