Streptococcus pneumoniae Serotype 23B Causing Asymptomatic Sinusitis Complicated by Endocarditis and Meningitis: Sequela of a Non-vaccine Serotype.

We describe a rare case of a  () infection causing mitral valve endocarditis and bacterial meningitis in a previously healthy young adult male in his 20s who presented with altered mentation. Though our patient did not endorse any respiratory issues, we suspected the paranasal sinuses to have been the cryptic primary source of disseminated infection into the respiratory system and meninges due to incidental mucosal thickening being found on imaging. Blood and cerebrospinal fluid analyses and cultures revealed the proliferation of  serotype 23B, despite our patient having previously received appropriate pneumococcal vaccinations in his childhood without delinquency. Ultimately, surgical replacement of the mitral valve, as well as a course of ceftriaxone, was indicated for this patient, in which full resolution of symptoms was achieved upon discharge.