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

Background: Cerebral microbleeds (CMBs) influence long term prognoses of stroke patients. Streptococcus mutans expressing the collagen-binding protein Cnm induces cerebrovascular inflammation, impairing blood brain barrier integrity and causing cerebral bleeding. Here, we examine the association of Cnm-positive S. mutans with CMBs.Methods: Acute stroke patients were selected from a single-center registry database. Oral carriage of Cnm-positive or Cnm-negative S. mutans was determined using polymerase chain reaction assays. The associations of Cnm-positive S. mutans with CMB number and specifically the presence of > 10 CMBs were examined using quasi-Poisson and logistic regression models, respectively.Results: This study included 3154 stroke patients, of which 428 patients (median [inter quartile range] age, 73.0 [63.0- 81.0] years; 269 men [62.9%]) underwent oral bacterial examinations. In total, 326 patients harbored S. mutans. After excluding four patients without imaging data, we compared patients with Cnm-positive (n = 72) and Cnm-negative (n = 250) S. mutans. Harboring Cnm-positive S. mutans was independently associated with the presence of > 10 CMBs (adjusted odds ratio 2.20 [1.18- 4.10]) and higher numbers of deep and lobar CMBs (adjusted risk ratio 1.61 [1.14- 2.27] for deep; 5.14 [2.78- 9.51] for lobar), but not infratentorial CMBs, after adjusting for age, sex, hypertension, stroke type, National Institutes of Health Stroke Scale score, and cerebral amyloid angiopathy.Conclusions: Harboring Cnm-positive S. mutans was independently associated with a higher number of CMBs in deep and lobar locations. Reducing Cnm-positive S. mutans in the oral cavity may serve as a novel therapeutic approach for stroke.