ceftriaxone + metronidazole + ampicillin + gentamicin + metronidazole

This is a combination of four antibiotics: **ceftriaxone** (a third-generation cephalosporin), **metronidazole** (a nitroimidazole), **ampicillin** (a beta-lactam penicillin), and **gentamicin** (an aminoglycoside). This combination is not a standard or branded fixed-dose formulation but may be used in clinical practice for severe or complicated intra-abdominal infections, especially in children and neonates, as part of empirical or tailored therapy. Each component provides coverage against different classes of bacteria: - ceftriaxone for broad-spectrum Gram-negative and some Gram-positive bacteria, - metronidazole for anaerobes, - ampicillin for additional Gram-positive and some Gram-negative organisms (notably Enterococcus spp.), - gentamicin for aerobic Gram-negative organisms. Mechanistically, each drug acts via inhibition of bacterial cell wall synthesis or protein synthesis, or by disrupting DNA synthesis (metronidazole). The combination seeks comprehensive coverage for mixed aerobic/anaerobic, Gram-positive, and Gram-negative bacterial infections.