This is a randomized, controlled, parallel study to determine the efficiency of oral antibiotics in reduction of surgical site infection (SSI) in rectal cancer surgery.

Patients undergoing rectal cancer surgery in a single centre will assigned randomly to combined preoperative oral antibiotics (metronidazole and erythromycin) and perioperative intravenous antibiotics (cefmetazole) (oral+intravenous group) or to perioperative intravenous antibiotics (cefmetazole) alone (intravenous group). The primary endpoint is the overall rate of SSI.

Inclusion Criteria:

• Have a planned of resection of rectum
• Have signed approved informed consent form for the study.

Exclusion Criteria:

• Significant simultaneous surgical procedure (e.g., liver resection of metastasis)
• Bacterial infection at the time of surgery or antimicrobial therapy up to 4 weeks before surgery
• Preoperative severe impairment in renal function (creatinine clearance (MDRD) < 30 ml/min)
• Allergy on the study drugs .