Aerococcus urinae - A potent biofilm builder in endocarditis

PLoS One. 2020 Apr 23;15(4):e0231827. doi: 10.1371/journal.pone.0231827. eCollection 2020.


The diagnosis of infective endocarditis (IE) remains a challenge. One of the rare bacterial species recently associated with biofilms and negative cultures in infective endocarditis is Aerococcus urinae. Whether the low number of reported cases might be due to lack of awareness and misidentification, mainly as streptococci, is currently being discussed. To verify the relevance and biofilm potential of Aerococcus in endocarditis, we used fluorescence in situ hybridization to visualize the microorganisms within the heart valve tissue. We designed and optimized a specific FISH probe (AURI) for in situ visualization and identification of A. urinae in sections of heart valves from two IE patients whose 16S rRNA gene sequencing had deteced A. urinae. Both patients had a history of urinary tract infections. FISH visualized impressive in vivo grown biofilms in IE, thus confirming the potential of A. urinae as a biofilm pathogen. In both cases, FISH/PCR was the only method to unequivocally identify A. urinae as the only causative pathogen for IE. The specific FISH assay for A. urinae is now available for further application in research and diagnostics. A. urinae should be considered in endocarditis patients with a history of urinary tract infections. These findings support the biofilm potential of A. urinae as a virulence factor and are meant to raise the awareness of this pathogen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aerococcus / isolation & purification*
  • Aerococcus / physiology
  • Aged
  • Aged, 80 and over
  • Biofilms*
  • Endocarditis, Bacterial / diagnosis*
  • Endocarditis, Bacterial / microbiology*
  • Female
  • Heart Valves / microbiology*
  • Humans
  • In Situ Hybridization, Fluorescence / methods
  • Male
  • Urinary Tract Infections / microbiology
  • Urinary Tract Infections / pathology

Supplementary concepts

  • Aerococcus urinae

Grant support

This study was supported by Bundesministerium für Bildung und Forschung (13N14917) and Freunde und Förderer des Deutschen Herzzentrums Berlin. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.