gentamicin + oxacillin + piperacillin

This is a combination of three antibiotics—gentamicin, oxacillin, and piperacillin—used together for the treatment of severe or mixed bacterial infections.

• Gentamicin is an aminoglycoside antibiotic that acts by binding to the 30S subunit of bacterial ribosomes, inhibiting protein synthesis and leading to cell death. It is particularly effective against aerobic gram-negative bacteria and shows synergistic effects when combined with beta-lactam antibiotics like penicillins.
• Oxacillin is a narrow-spectrum beta-lactam (penicillinase-resistant penicillin) antibiotic used primarily for infections caused by penicillinase-producing staphylococci (notably Staphylococcus aureus). It inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins.
• Piperacillin is an extended-spectrum ureidopenicillin that inhibits bacterial cell wall synthesis; it has broad activity against both gram-positive and gram-negative organisms, including Pseudomonas aeruginosa. Piperacillin may be used in combination with other agents for severe or hospital-acquired infections.

The rationale for combining these agents includes broadening antibacterial coverage (covering both gram-positive—including resistant staphylococci—and gram-negative pathogens), exploiting potential synergistic effects between aminoglycosides and beta-lactams, and targeting polymicrobial or high-risk hospital-acquired infections.