Metagenomic Next-Generation Sequencing Diagnosis of Streptococcus agalactiae Meningitis in a Diabetic Patient

<i>Streptococcus agalactiae </i>meningitis is primarily observed among neonates and is uncommon in adults. We present a rare case of <i>Streptococcus agalactiae </i>meningitis in an adult. The patient was a 74-year-old male with a history of gastric perforation surgery, chemotherapy for neck lymphoma, and hypertension. He presented to the emergency department with an 11-day history of neck pain, one day of limited mouth opening and dysphagia, and eight hours of altered consciousness. On examination, he exhibited impaired consciousness (Glasgow Coma Scale score: 8) and cervical rigidity. He was intubated and received oxygen therapy. Laboratory findings revealed elevated infection markers and turbid cerebrospinal fluid (CSF). Metagenomic next-generation sequencing (mNGS) of the CSF detected <i>Streptococcus agalactiae</i>. Enhanced MRI of the head and neck showed a small subdural effusion, spinal cord edema at C5-C6, thickening and enhancement of the anterior and posterior longitudinal ligaments and meninges at the skull base, suggestive of <i>Streptococcus agalactiae</i> infection. After 10 days of anti-infective treatment with ceftriaxone, the patient's condition improved, and he was transferred to a local hospital for continued management.