BACKGROUND: Streptococcus acidominimus, which belongs to the viridans streptococci group, is rarely considered pathogenic in humans. However, over the past 10 years, this bacterium has been reported to cause serious infections in humans, particularly among the critically ill. This article is the first case report of pyogenic ventriculitis (PV) and meningitis caused by S. acidominimus in North America.

CASE REPORT: A 49-year-old Asian male presented to the emergency department with complaints of a headache, fever greater than 37.8°C (100°F) and confusion, of approximately 3 days duration. He was unable to speak coherently or follow approximately half of the given commands. He appeared ill; an intracranial infection was suspected. Magnetic resonance imaging of the brain showed: 1) infected proteinaceous material and pus-like material throughout the cerebral sulci and in the occipital horns of both lateral ventricles, 2) ependymal signal abnormality of the posterolateral margin of the occipital horn of the left lateral ventricle, and 3) early hydrocephalus suggestive of ventriculitis and meningitis. The blood and cerebrospinal fluid cultures were positive for S. acidominimus. The patient improved with minimal deficits after 6 weeks of IV ceftriaxone without requiring a neurosurgical intervention, such as an intraventricular drain or neuroendoscopic surgery.

CONCLUSIONS: PV and meningitis caused by S. acidominimus are rare but potentially fatal intracranial infections. Therefore, despite the risk of generalizing, our case report suggests that PV and meningitis caused by S. acidominimus can be effectively treated with a prompt and prolonged course of IV ceftriaxone without neurosurgical intervention.

Keywords: Brain Diseases, Cerebral Ventriculitis, Diffusion Magnetic Resonance Imaging, Meningitis, Bacterial, Viridans Streptococci