Case Commentary: Intraventricular polymyxin B-small steps, big questions.

Carbapenem-resistant gram-negative ventriculitis is a life-threatening infection with limited treatment options. H. Jiang, Y. Hu, J. Cai, J. Zhang, et al. (Antimicrob Agents Chemother 70:e00943-25, 2026, https://doi.org/10.1128/aac.00943-25) describe two patients with this condition who were successfully treated with intraventricular polymyxin B. Their report highlights uneven antibiotic distribution within the ventricles, the influence of cerebrospinal fluid drainage on intraventricular drug concentrations, and cure with intraventricular polymyxin B alone. These findings raise important questions about optimal intraventricular antimicrobial dosing and whether concurrent intravenous therapy is needed in healthcare-associated ventriculitis.