Evidence of Bacteroides fragilis protection from Bartonella henselae-induced damage

PLoS One. 2012;7(11):e49653. doi: 10.1371/journal.pone.0049653. Epub 2012 Nov 15.


Bartonella henselae is able to internalize endothelial progenitor cells (EPCs), which are resistant to the infection of other common pathogens. Bacteroides fragilis is a gram-negative anaerobe belonging to the gut microflora. It protects from experimental colitis induced by Helicobacter hepaticus through the polysaccharide A (PSA). The aim of our study was to establish: 1) whether B. fragilis colonization could protect from B. henselae infection; if this event may have beneficial effects on EPCs, vascular system and tissues. Our in vitro results establish for the first time that B. fragilis can internalize EPCs and competes with B. henselae during coinfection. We observed a marked activation of the inflammatory response by Real-time PCR and ELISA in coinfected cells compared to B. henselae-infected cells (63 vs 23 up-regulated genes), and after EPCs infection with mutant B. fragilis ΔPSA (≅90% up-regulated genes) compared to B. fragilis. Interestingly, in a mouse model of coinfection, morphological and ultrastructural analyses by hematoxylin-eosin staining and electron microscopy on murine tissues revealed that damages induced by B. henselae can be prevented in the coinfection with B. fragilis but not with its mutant B. fragilis ΔPSA. Moreover, immunohistochemistry analysis with anti-Bartonella showed that the number of positive cells per field decreased of at least 50% in the liver (20±4 vs 50±8), aorta (5±1 vs 10±2) and spleen (25±3 vs 40±6) sections of mice coinfected compared to mice infected only with B. henselae. This decrease was less evident in the coinfection with ΔPSA strain (35±6 in the liver, 5±1 in the aorta and 30±5 in the spleen). Finally, B. fragilis colonization was also able to restore the EPC decrease observed in mice infected with B. henselae (0.65 vs 0.06 media). Thus, our data establish that B. fragilis colonization is able to prevent B. henselae damages through PSA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiomatosis, Bacillary / genetics
  • Angiomatosis, Bacillary / microbiology*
  • Angiomatosis, Bacillary / pathology
  • Animals
  • Antibiosis*
  • Bacteroides Infections / genetics
  • Bacteroides Infections / microbiology*
  • Bacteroides Infections / pathology
  • Bacteroides fragilis / physiology*
  • Bartonella henselae / physiology*
  • Cluster Analysis
  • Coinfection
  • Cytokines / genetics
  • Disease Models, Animal
  • Endothelial Cells / microbiology
  • Female
  • Gene Expression Profiling
  • Host-Pathogen Interactions
  • Humans
  • Inflammation / genetics
  • Inflammation / microbiology
  • Mice
  • Polysaccharides, Bacterial
  • Stem Cells / microbiology


  • Cytokines
  • Polysaccharides, Bacterial

Grant support

This work was supported by a grant from the “Progetto di Rilevante Interesse Nazionale Ministero Italiano dell’Istruzione dell’Università e della Ricerca” 2006 [Code 0622153_002 “Meccanismi fisiopatologici di danno vascolare/trombotico ed angiogenesis”] and 2008 [Code T85HLH_002 “Regolazione dell'espressione genica della via SIRT/Foxo1- dipendente in cellule endoteliali progenitrici nella nicchia vascolare] to the Second University of Naples for CN; by a grant from “Programmi di Rilevante Interesse Nazionale Ministero Italiano dell’Istruzione dell’Università e della Ricerca” 2008 [prot. 2008232P4H_002 “Patogenicità batterica e sviluppo di vaccini”] for PS, CP and R. Colicchio. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.