erythromycin + gentamicin + metronidazole + neomycin

This is a combination of four antibiotics—erythromycin, gentamicin, metronidazole, and neomycin—used together primarily for perioperative prophylaxis in colorectal surgery and other gastrointestinal procedures. Each component has a distinct mechanism of action:

• Erythromycin is a macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit.
• Gentamicin is an aminoglycoside antibiotic that binds to the 30S ribosomal subunit, causing misreading of mRNA and inhibiting protein synthesis.
• Metronidazole is a nitroimidazole antibiotic effective against anaerobic bacteria and protozoa; it disrupts DNA structure through reduction in anaerobic cells.
• Neomycin is another aminoglycoside that also inhibits bacterial protein synthesis at the 30S ribosomal subunit.

This combination targets both aerobic and anaerobic bacteria commonly found in the gut flora. It may be used as part of bowel preparation regimens before colorectal surgery to reduce surgical site infections. The regimen can involve oral administration (neomycin, erythromycin or metronidazole) combined with intravenous gentamicin or metronidazole.