What do systematic reviews say?

Combined oral and intravenous vs oral or intravenous alone

Combined oral and intravenous leads to lower surgical wound infection: oral + iv versus iv alone compared with oral or intravenous alone (high certainty).

• Antimicrobial prophylaxis for colorectal surgery 2014 · Cochrane Headline outcomes only
  RR 0.55 [0.43, 0.71]
  15 studies · 2929 participants
  High
• Antimicrobial prophylaxis for colorectal surgery 2014 · Cochrane Headline outcomes only
  RR 0.52 [0.35, 0.76]
  9 studies · 1880 participants
  High