# Aggregatibacter actinomycetemcomitans induces biofilm formation of Streptococcus sanguinis on titanium implants

## TL;DR

This study shows that Aggregatibacter actinomycetemcomitans boosts Streptococcus sanguinis biofilm formation on titanium implants, but surface roughness effects remain unclear.

## Contribution

The study reveals a novel synergistic interaction between two bacterial species in biofilm formation on implant surfaces.

## Key findings

- Dual-species biofilms of S. sanguinis and A. actinomycetemcomitans showed increased biofilm formation compared to single-species.
- Surface roughness of titanium implants did not conclusively affect biofilm formation.
- Fluorescence microscopy confirmed the efficiency of washing steps in biofilm analysis.

## Abstract

This study aims to investigate the distinct behaviors of single-species and dual-species biofilms formed by Streptococcus sanguinis and Aggregatibacter actinomycetemcomitans on different titanium and implant surfaces. Four types of surfaces were examined: two clinically used implant surfaces, a super-polished surface and a sand-blasted surface of grade 4 titanium.

Specimens were incubated with single- and dual-species biofilms for 24 h. Biofilm formation was determined based on the amount of total DNA extracted from the bacteria. In order to specifically determine the biofilm formation of Streptococcus sanguinis, qPCR experiments were carried out. Staining followed by fluorescence microscopy was employed to verify the efficiency of the washing steps.

Biofilm formation by single- and dual-species cultures was observed on all tested implant surfaces. However, a clear influence of surface characteristics on biofilm formation could not be conclusively demonstrated. Mixed cultures of S. sanguinis and A. actinomycetemcomitans (AAC) exhibited increased biofilm formation through the enhanced DNA amount of S. sanguinis. In contrast, this effect was not observed in dual-species cultures of Staphylococcus epidermidis and S. sanguinis.

AAC promotes biofilm formation of S. sanguinis, highlighting the significant role of AAC in enhancing biofilm development. Conversely, a definitive conclusion regarding the correlation between titanium implant surface roughness and biofilm formation was not possible. However, our results suggest a tendency that dual-species biofilm formation may be influenced by surface structure.