Phenotypic and genotypic characterization of Streptococcus mutans present in endodontic infections

Author(s)

Augusto Rodrigues Lima

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2021-05-21

Examining board members

Brenda Paula Figueiredo de Almeida Gomes; Felipe Nogueira Anacleto; Flaviana Bombarda de Andrade Ferreira; Caio Cezar Randi Ferraz; Marina Angélica Marciano

• Advisor: Brenda Paula Figueiredo de Almeida Gomes

Abstract

Streptococcus mutans plays an important role in the etiology of caries and, eventually, in systemic infections. In addition, it is often found in different types of endodontic infection. However, the pathophysiological characteristics of S. mutans found in this microenvironment with specific characteristics are still unknown. Therefore, this study aimed to detect and characterize S. mutans present in different types of endodontic infections, whether chronic or acute, primary or secondary in nature. Methods: Bacterial DNA was extracted from samples collected from 10 patients with pulp necrosis associated with radiographic evidence of apical periodontitis and 10 patients who required endodontic therapy due to the presence of pulp necrosis and acute apical abscess. The control group consisted of 10 patients with teeth with normal vital pulp and in need of endodontic treatment for prosthetic reasons. The presence of S. mutans was detected by quantitative real-time PCR (qPCR) using species-specific primers. The samples that housed S. mutans were also evaluated for the presence of the cnm / cbm genes by qPCR (article 1). In the second article, 14 strains were isolated and analyzed from microbiological collections from 10 patients with primary endodontic infection and 10 patients with secondary / persistent endodontic infection. The identification of S. mutans was done through PCR and sequencing of the complete genome, tests for growth and survival against oxidative stress and low pH were also analysed, in addition, tests for antibiotic protection and infection by G. mellonella (article 2). Results: All studied sites had a high prevalence of S. mutans (60 to 70%), except the control group. The cnm gene was detected only in the root canal samples of necrotic teeth from asymptomatic patients associated with radiographic periapical lesions (66.6%) (article 1). In the second article clinical isolates were hypersensitive to hydrogen peroxide. Notably, all 14 strains harbored and expressed Cbm, showing increased collagen binding, increased systemic virulence in G. mellonella and the ability to invade human coronary artery endothelial cells and dental pulp fibroblasts (article 2). Conclusion: The cnm gene was detected in chronic primary infections, using qPCR. In addition, it was possible to isolate S. mutans from primary and secondary endodontic infections, virulent strains of S. mutans (Cbm-positive) (AU)

• FAPESP's process: 16/23950-2 - Monitoring of infectious contents, endotoxic and gene presence of resistance to antibiotics of symptomatic and asymptomatic primary infections during endodontic therapy
• Grantee: Augusto Rodrigues Lima
• Support Opportunities: Scholarships in Brazil - Doctorate