A 38-year-old man from rural Maharashtra presents with a 4-month history of progressive back pain and low-grade fever. On examination, he has kyphotic deformity of the thoracic spine and a palpable paravertebral abscess. Plain radiographs show anterior vertebral body erosion with loss of disc space at T5–T6. MRI reveals marrow edema in two adjacent vertebral bodies with epidural extension and cord compression. Serum ESR is 78 mm/hr and CRP is 12 mg/dL. Sputum smear microscopy is negative, but GeneXpert MTB/RIF is positive. What is the most appropriate next step in management?