Serotype and distribution of adhesion genes in Streptococcus mutans isolated from people with Parkinson's disease

The delicate balance of the oral cavity is disrupted by changes in hygiene and diet, leading to caries. The virulence of Streptococcus mutans, a key caries pathogen, is partly explained by its rhamnose-glucose polysaccharide (RGP) and its sucrose-dependent and -independent adhesion mechanisms. Given their role in comorbidities, this study investigates the diversity of S. mutans through analysis of RGP and sucrose-independent adhesion proteins (SpaP, WapA, Cnm, Cbm) in Parkinson's disease patients. In the PARKIDENT clinical trial, strains were isolated from saliva samples of Parkinson's patients at baseline and during a follow-up visit. Strains were preanalyzed by multiplex PCR for serotype and collagen-binding proteins, followed by high-throughput sequencing and bioinformatics analysis using RAST® and BLAST®. Phylogenetic analyses and protein modeling were also conducted. Of 40 patients in the Parkident clinical trial, only 24 had Streptococcus mutans strains isolable from salivary swabs. Serotyping revealed that over 80% of the 44 strains isolated were serotype c, in line with prevalence data in the literature. Furthermore, only SpaP types A and B were identified in the strains. The low variability observed for the WapA protein underlines its functional importance. Finally, the cbm gene was not found in any strain, and only 5 strains possessed the cnm gene, all of them serotype c. The study of these 44 Streptococcus mutans strains showed characteristics similar to other populations. Serotype c predominates, with minimal peptide sequence variability in adhesion proteins (SpaP, WapA). Collagen-binding proteins Cnm and Cbm are rare or absent. Further research is essential to better characterize strain distribution in the Parkinson's-affected population due to S. mutans' growing role in extra-oral pathologies. Trial registry: ClinicalTrials.gov ID NCT03827551, First submitted: 2019-01-25.