colistin + fosfomycin

Colistin + fosfomycin is a combination of two antibiotics used primarily for the treatment of infections caused by multidrug-resistant Gram-negative bacteria, including carbapenem-resistant Enterobacterales and Acinetobacter baumannii. Colistin (also known as polymyxin E) is a cationic polypeptide antibiotic that disrupts the bacterial outer cell membrane by binding to lipid A in lipopolysaccharides, leading to increased membrane permeability and cell death[1][4]. Fosfomycin is a small molecule antibiotic that irreversibly inhibits UDP-N-acetylglucosamine enolpyruvyl transferase (MurA), an enzyme involved in the first step of peptidoglycan biosynthesis, thereby blocking bacterial cell wall formation[5][6][7]. The combination has shown synergistic antibacterial effects against various multidrug-resistant pathogens in vitro and in vivo, making it a promising option when other treatments are limited due to resistance[2][3].