Bacterial meningitis empirical antibiotic choice — dexamethasone timing and LP before CT dilemma?

25M presents to ED with fever 39.8°C, severe headache, neck stiffness, and photophobia for 6 hours. GCS 14 (E3V5M6). No focal neurological deficits. Petechial rash on trunk and lower limbs. CT head urgently done — normal, no mass lesion, no midline shift. Per IDSA 2023 bacterial meningitis guidelines: Should LP be done before or after starting antibiotics? Should dexamethasone be given before or with the first antibiotic dose? What is the empirical antibiotic regimen of choice for community-acquired bacterial meningitis in an immunocompetent adult?