colistin + polymyxin B + meropenem

A combination therapy consisting of **colistin**, **polymyxin B**, and **meropenem** represents an aggressive, multi-agent approach to treat infections by multidrug-resistant Gram-negative bacteria, particularly those producing carbapenemases such as KPC and NDM. - **Colistin** (also known as polymyxin E) and **polymyxin B** are polymyxin-class antibiotics that disrupt the outer membrane of Gram-negative bacteria by binding to lipopolysaccharides, leading to increased membrane permeability and cell death. - **Meropenem** is a broad-spectrum carbapenem antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), primarily PBP2, PBP3, and PBP4, resulting in cell lysis. - The rationale for this triple combination is to maximize bactericidal activity and minimize the emergence of resistance, particularly in the context of pan-resistant organisms such as *Acinetobacter baumannii*, *Klebsiella pneumoniae*, and other Enterobacteriaceae. - Evidence from in vitro and dynamic infection models shows that triple therapy with these agents can achieve synergistic killing, suppress regrowth, and delay or prevent resistance more effectively than monotherapy or double combinations, particularly for isolates resistant to most other treatment options[5][4]. - This combination is not standard and is typically reserved for critical, last-line settings due to limited clinical data, risk of toxicity (notably nephrotoxicity and neurotoxicity), and the potential for additive adverse effects[5][4]. - No unique brand name or single product for this exact triple combination exists; each drug is administered individually, often intravenously, at carefully adjusted dosages.