Multiple preclinical and clinical studies, including the investigators' published work and the ongoing SOLUTION series, have consistently demonstrated that intracalvariosseous (ICO) injection can markedly increase drug exposure within the central nervous system with acceptable safety. This trial is designed to further evaluate the efficacy and safety of antibiotic delivery via the ICO route in the treatment of bacterial meningitis, particularly in patients with moderate-to-severe disease who have shown an inadequate response to standard therapy.