Meningoencephalitis with Streptococcus equi Subspecies equi Leading to a Dural Arteriovenous Fistula

Invasive infection with Lancefield group C streptococci in humans is extremely rare, with the vast majority of clinical isolates belonging to Streptococcus dysgalactiae subsp. equisimilis. We report a case of meningoencephalitis in a 69-year-old man caused by Streptococcus equi subsp. equi, a microbe that causes strangles in Equus caballus (i.e., the horse). This is only the fourth infection with this subtype of the central nervous system (CNS) reported in humans. The invasiveness of these bacteria, known to be capable of releasing strongly immunogenic exotoxins, is illustrated by white matter lesions that are present in the acute phase. This patient initially recovered well after treatment with antibiotics and glucocorticoids. However, the patient was readmitted 5 months later with multiple intraparenchymatous cerebral haemorrhages. Cerebral angiography confirmed the presence of a suspected superficial dural arteriovenous fistula (DAVF), which is seldom reported after CNS infection. The invasiveness of these bacteria was illustrated by white matter lesions present in the acute phase and the occurrence of a de novo dural arteriovenous fistula in the follow-up period.