meropenem + piperacillin-tazobactam + ticarcillin-clavulanate

This is a combination regimen of three broad-spectrum beta-lactam antibiotics, each with distinct but overlapping spectra of activity.

• Meropenem is a carbapenem antibiotic with very broad-spectrum activity against gram-positive, gram-negative, and anaerobic bacteria. It is highly effective against many resistant organisms, including extended-spectrum beta-lactamase (ESBL) producers and Pseudomonas aeruginosa.
• Piperacillin-tazobactam combines an antipseudomonal penicillin with the beta-lactamase inhibitor tazobactam to extend its spectrum to include many beta-lactamase-producing organisms and anaerobes.
• Ticarcillin-clavulanate pairs another antipseudomonal penicillin with clavulanic acid, also a beta-lactamase inhibitor, providing similar coverage for resistant gram-negatives and anaerobic bacteria.

These agents are used in severe or high-risk infections where multidrug-resistant organisms are suspected or confirmed—such as complicated intra-abdominal infections or hospital-acquired pneumonia—though their combined use together as a single regimen is not standard clinical practice due to overlapping spectra and increased risk of toxicity/resistance. Each component acts by inhibiting bacterial cell wall synthesis via binding to penicillin-binding proteins; the inhibitors block destruction by bacterial beta-lactamases.