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

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.