Surgical site infections are frequently occurring iatrogenic infections and therefore should be avoided through the use of antibiotic prophylaxis. These SSIs are most commonly caused by commensal flora of the skin and gut (such as staphylococci and E. coli respectively) and as such, the choice of antibiotics for surgical prophylaxis must cover a broad spectrum of these microbes Beta-lactams cephalosporins (particularly the first-generation cephalosporin cefazolin) are the most commonly used antibiotics for prophylaxis as they cover a broad range of the commensal skin flora. If a person has a B-lactam allergy, they may take metronidazole + aminoglycoside or fluoroquinolone, vancomycin + aminoglycoside, aztreonam, or fluoroquinolone, or clindamycin + aminoglycoside. Adults should receive prophylactic intravenous doses of metronidazole 500 mg, gentamycin 5 mg/kg body weight, and amikacin 15 mg/kg body weight one hour prior to the incision.