Streptobacillus moniliformis mitral valve endocarditis and septic arthritis: the challenges of diagnosing rat-bite fever endocarditis.

Streptobacillus moniliformis, the cause of rat-bite fever (RBF) in the United States, has rarely been reported as a cause of infectious endocarditis. In the majority of previously reported cases, the diagnosis was clinically- based in patients with underlying valvular abnormalities in the setting of positive blood culture for Streptobacillus moniliformis. We report a case of native valve endocarditis secondary to Streptobacillus moniliformis in a woman with a mitral valve vegetation but negative blood cultures where the diagnosis was established using molecular diagnostics on the valvular tissue.