Harboring Cnm‐expressing Streptococcus mutans in the oral cavity relates to both deep and lobar cerebral microbleeds

Streptococcus mutans, a major cariogenic bacterium, expressing the collagen-binding protein Cnm induces cerebrovascular inflammation, resulting in the impairment of blood brain barrier integrity followed by cerebral bleeding. We here examined the association of Cnm-positive S. mutans with cerebral microbleeds (CMBs) in acute stroke patients selected from a single-center registry database. Of 428 patients who received oral bacterial examinations among 3154 stroke patients, 326 patients who harbored S. mutans were identified. After excluding four patients without imaging data, we compared 72 patients with Cnm-positive S. mutans and 250 with Cnm-negative S. mutans. Deep, lobar and infratentorial CMBs were observed in 46 (63.9%), 36 (50.0%), 25 (34.7%) patients with Cnm-positive S. mutans and 144 (57.6%), 114 (45.6%), 101 (40.4%) with Cnm-negative S. mutans. Possession of Cnm-positive S. mutans was related to higher numbers of both deep and lobar, but not infratentorial, CMBs (risk ratios 1.57 [1.07‒2.30], deep; 5.44 [2.50‒11.85], lobar). Statistical significance persisted after adjusting for age, sex, hypertension, stroke type, National Institutes of Health Stroke Scale score, and cerebral amyloid angiopathy (risk ratios 1.61 [1.14‒2.27], deep; 5.14 [2.78‒9.51], lobar). Our study indicated that reduction of Cnm-positive S. mutans may serve as a therapeutic approach for improving the prognosis of stroke patients.