Extracellular biofilm matrix leads to microbial dysbiosis and reduces biofilm susceptibility to antimicrobials on titanium biomaterial: An in vitro and in situ study

Objectives: To test the role of exopolysaccharide (EPS) polymers matrix to modulate the composition/virulence of biofilms growing on titanium (Ti) surfaces, the effect on antibiotic susceptibility, and whether a dual-targeting therapy approach for disrupted EPS matrix could improve the antimicrobial effect. Materials and Methods: A microcosm biofilm model using human saliva as inoculum was used, and the microbial composition was assessed by checkerboard DNA-DNA hybridization. EPS-enriched biofilms virulence was tested using fibroblast monolayer. Povidone-iodine (PI) was used as EPS-targeting agent followed by amoxicillin + metronidazole antibiotic to reduce bacterial biomass using an in situ model. Results: An EPS-enriched environment, obtained by sucrose exposure, promoted bacterial accumulation and led to a dysbiosis on biofilms, favoring the growth ofStreptococcus, Fusobacterium,andCampylobacterspecies and even strict anaerobic species related to peri-implant infections, such asPorphyromonas gingivalisandTannerella forsythia(similar to 3-fold increase). EPS-enriched biofilm transitioned from a commensal aerobic to a pathogenic anaerobic profile. EPS increased biofilm virulence promoting higher host cell damage and reduced antimicrobial susceptibility, but the use of a dual-targeting approach with PI pre-treatment disrupted EPS matrix scaffold, increasing antibiotic effect on in situ biofilms. Conclusion: Altogether, our data provide new insights of how EPS matrix creates an environment that favors putative pathogens growth and shed light to a promising approach that uses matrix disruption as initial step to potentially improve implant-related infections treatment.