New Insights into the Enterococcus faecium and Streptococcus gallolyticus subsp. gallolyticus Host Interaction Mechanisms

PLoS One. 2016 Jul 27;11(7):e0159159. doi: 10.1371/journal.pone.0159159. eCollection 2016.

Abstract

Enterococcus faecium and Streptococcus gallolyticus subsp. gallolyticus (S. gallolyticus) were classically clustered into the Lancefield Group D streptococci and despite their taxonomic reclassification still share a similar genetic content and environment. Both species are considered as opportunistic pathogens. E. faecium is often associated with nosocomial bacteraemia, and S. gallolyticus is sporadically found in endocarditis of colorectal cancer patients. In both cases, the source of infection is commonly endogenous with a translocation process that launches through the intestinal barrier. To get new insights into the pathological processes preceding infection development of both organisms, we used an in vitro model with Caco-2 cells to study and compare the adhesion, invasion and translocation inherent abilities of 6 E. faecium and 4 S. gallolyticus well-characterized isolates. Additionally, biofilm formation on polystyrene, collagen I and IV was also explored. Overall results showed that E. faecium translocated more efficiently than S. gallolyticus, inducing a destabilization of the intestinal monolayer. Isolates Efm106, Efm121 and Efm113 (p < .001 compared to Ef222) exhibited the higher translocation ability and were able to adhere 2-3 times higher than S. gallolyticus isolates. Both species preferred the collagen IV coated surfaces to form biofilm but the S. gallolyticus structures were more compact (p = .01). These results may support a relationship between biofilm formation and vegetation establishment in S. gallolyticus endocarditis, whereas the high translocation ability of E. faecium high-risk clones might partially explain the increasing number of bacteraemia.

MeSH terms

  • Biofilms
  • Caco-2 Cells
  • Enterococcus faecium / physiology*
  • Host-Pathogen Interactions*
  • Humans
  • Streptococcus gallolyticus / physiology*

Grants and funding

This work was supported by The Ministerio de Economía y Competitividad, Instituto de Salud Carlos III (PS09/00825 and PI13/205) and co-financed by The European Regional Development Fund (ERDF) ‘A Way to Achieve Europe’, the Spanish Network for Research in Infectious Diseases (REIPI RD12/0015), and the European Commission (grant R-GNOSIS-FP7-HEALTH-F3-2011-282512). AMSD was contracted with European Union funds (MON4STRAT-FP7-HEALTH-2013-602906). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.