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. 2025 Oct;29(10):1400-1408.
doi: 10.1007/s10157-025-02708-6. Epub 2025 May 29.

cnm-positive Streptococcus mutans, a major pathogen in dental caries, may exacerbate IgA nephropathy via the tonsils

Seigo Ito  1 , Taro Misaki  2   3 , Shuhei Naka  4 , Daiki Matsuoka  4 , Kana Suehara  4 , Yuto Suehiro  5 , Yasuyuki Nagasawa  6 , Ryota Nomura  7 , Michiyo Matsumoto-Nakano  4 , Kazuhiko Nakano  5
Affiliations

cnm-positive Streptococcus mutans, a major pathogen in dental caries, may exacerbate IgA nephropathy via the tonsils

Seigo Ito et al. Clin Exp Nephrol. 2025 Oct.

Abstract

Background: Streptococcus mutans is a major pathogen in dental caries. This organism, which expresses Cnm protein encoded by the cnm gene, has been associated with the pathogenesis of IgA nephropathy (IgAN). Although tonsillectomy is used to treat IgAN, its efficacy is presently unclear in patients with IgAN who harbor cnm-positive S. mutans.

Methods: The presence of cnm-positive S. mutans in saliva specimens from 158 patients with IgAN was determined by polymerase chain reaction assay. The patients were divided according to the results of cnm-positive S. mutans detection and history of tonsillectomy into those who were cnm-positive S. mutans (-), tonsillectomy (-) (group A, n = 57); cnm-positive S. mutans (-), tonsillectomy ( +) (group B, n = 62); cnm-positive S. mutans ( +), tonsillectomy (-) (group C, n = 19); and cnm-positive S. mutans ( +), tonsillectomy ( +) (group D, n = 20). The patients' clinical data were compared between the four groups.

Results: The proportions of patients with proteinuria > 2 + and an estimated glomerular filtration rate < 60 mL/min/1.73 m2 were significantly greater in group C than in the other groups (p < 0.0083). Moreover, the proportion of patients with a serum IgA concentration of > 347 mg/dL was significantly higher in group C than in the other groups (p < 0.05).

Conclusions: These findings suggest that exacerbation of IgAN by cnm-positive S. mutans is possibly mediated by the tonsils and that tonsillectomy may be particularly effective in patients with IgAN and cnm-positive S. mutans in the oral cavity.

Keywords: Cnm-positive S. mutans; Dental caries; IgA nephropathy; Tonsillectomy.

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Conflict of interest statement

Declarations. Conflict of interest: The authors have no competing interests to declare. Ethical approval: The study protocol was approved by the ethics committees of Seirei Hamamatsu General Hospital (approval number 2354 20200925) and Osaka University Graduate School of Dentistry (approval number H29-E9) and conducted in full compliance with the Declaration of Helsinki (64 th WMA General Assembly, Fortaleza, Brazil, 2013). All participants had been informed of the study protocol and provided written consent before enrollment in the study.

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