Is oral Streptococcus mutans with collagen-binding protein a risk factor for intracranial aneurysm rupture or formation?

Objective: Streptococcus mutans (SM) with the collagen-binding protein Cnm is a unique member of the oral resident flora because it causes hemorrhagic vascular disorders. In the multicenter study, we examined the relationship between Cnm-positive SM (CP-SM) and intracranial aneurysm (IA) rupture, which remains unknown.

Methods: Between May 2013 and June 2018, we collected whole saliva samples from 431 patients with ruptured IAs (RIAs) and 470 patients with unruptured IAs (UIAs). Data were collected on age, sex, smoking and drinking habits, family history of subarachnoid hemorrhage, aneurysm size, number of teeth, and comorbidities of lifestyle disease.

Results: There was no difference in the positivity rate of patients with CP-SM between the patients with RIAs (17.2%) and those with UIAs (19.4%). The rate of positivity for CP-SM was significantly higher in all IAs <5 mm than in those ≥10 mm in diameter (P=0.0304). In the entire cohort, the rate of positivity for CP-SM was lower in larger aneurysms than in smaller aneurysms (P=0.0393).

Conclusions: The rate of positivity for CP-SM was lower among patients with large UIAs. These findings are consistent with the hypothesis that CP-SM plays a role in the formation of vulnerable IAs that tend to rupture before becoming larger.