daptomycin + aztreonam

Daptomycin + aztreonam is a **fixed-dose combination** of two antibiotics with **distinct spectra and mechanisms of action**. - **Daptomycin** is a cyclic lipopeptide that acts by binding to bacterial cell membranes in a calcium-dependent manner, causing rapid depolarization, loss of membrane potential, and ultimately cell death; it is highly active against Gram-positive bacteria[2][4][5][10]. - **Aztreonam** is a monobactam beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding protein 3 (PBP3), leading to cell lysis; its activity is specific for Gram-negative bacteria[1]. The **combination** leverages synergy between Gram-positive (daptomycin) and Gram-negative (aztreonam) activity and may be employed for polymicrobial infections or in cases where broad-spectrum coverage is clinically indicated, such as complex intra-abdominal infections[3]. Neither daptomycin nor aztreonam is known to antagonize the other’s effect, and this combination is investigated or sometimes applied in clinical scenarios requiring broad empirical coverage.