Microorganisms interaction in oral biofilms and effect of surface treatment on titanium to reduce microbial accumulation

Author(s)

João Gabriel Silva Souza

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2019-08-23

Examining board members

Valentim Adelino Ricardo Barão; Jaime Aparecido Cury; Magda Feres; Livia Maria Andaló Tenuta; Marlise Inêz Klein

• Advisor: Valentim Adelino Ricardo Barão

Abstract

Biofilm formation on dental implant surface made of titanium (Ti) is the main etiologic factor to trigger oral infection that lead to rehabilitation treatment failure. Among initial colonizers on oral cavity Streptococcus from mitis group (S. mitis, S. gordonii, S. sanguinis and S. oralis) interacts and form biofilms with C. albicans, the main opportunistic fungus on oral environment. However, the interaction among these organisms on Ti surface and its effect on tissue destruction has not been evaluated. (1) Then, the first study evaluated by in vitro model the ability of Streptococcus and C. albicans to form single-specie biofilm (72h) and to Interact on Ti surface. Moreover, the pathogenic potential of these interaction on tissue destruction was evaluated using a 3D-tissue model. The results showed that C. albicans presence favored biofilm formation on Ti (p<0.05), promoting bacteria growth, mainly for S. oralis. Synergistic effect was found for this interaction, since bacteria up-regulated genes related to Candida virulence expression. Additionally, this interaction led to a higher tissue destruction. (2) The interaction between Candida and streptococcus is also mediate by glucan polymers synthesized by glucosyltranferase (gtf) enzyme. S. oralis which Interact with C. albicans in biofilm state and has a single gene of gtf (gtfR), has not been evaluated in relation the role of gtfR on cross-kingdom interaction with Candida. Therefore, second study used S. oralis wild type (WT) strain and mutant strain lacking gtfR gene to evaluate the interaction with C. albicans on biofilms formed on plastic, surface, Ti and 3D-tissue. The results showed that gtfR and glucans synthesized increased S. oralis biofilm biomass due the effect on biofilm matrix. On Candida presence, mixed biofilms with WT showed higher bacteria count, compared to mutant strain on biofilms formed on all surfaces. However, this interaction was modulated by surface where biofilm is growing, since Candida up-regulated gtfR expression by S. oralis on Ti. (3) Considering that Ti surface is also substrate for microbial adhesion by oral pathogens, as well the role of biofilm on peri-implant disease, the third study aimed to develop a superhydrophobic surface coating on Ti using low pressure glow discharge plasma. Surface coating showed biocompatibility, promoted corrosion resistance and reduced bacteria and Candida adhesion and, consequently, multi-specie biofilm formation on Ti. In conclusion, Streptococcus from mitis group interacts with C. albicans on biofilms formed on Ti surface, promoting bacteria growth and its pathogenic potential. The interaction between S. oralis and Candida is mediated by extracellular polymers and modulated by surface where the biofilms is growing. To reduce microbial adhesion and biofilm formation on Ti surface the superhydrophobic coating developed is a promising strategy (AU)

• FAPESP's process: 15/23118-2 - Antibacterial effect and biocompatibility evaluation of glow discharge plasma treatment on titanium surface: in vitro and in situ study
• Grantee: João Gabriel Silva Souza
• Support Opportunities: Scholarships in Brazil - Doctorate