Procedures involving only simple ostomy closures 2. Known allergy to cefazolin or metronidazole or an antibiotic preferred and routinely used by the surgeon 3. Persons less than 18 years old 4. Emergency operation as designated by the surgeon will be included only with the appropriate approval by the institutional IRB at an individual research site 5. Pregnant or breast-feeding women 6. A known bleeding/hemorrhagic/thrombotic disorder is exclusionary unless there is a written clearance chart-note or clearance letter from a primary care physician or hematologist 7. Significant psychiatric problems which might impair ability to give truly informed consent or which may impair follow-up communication with the surgeon and staff 8. Clinically significant cardiac arrhythmias are exclusionary unless there is a written clearance chart-note or clearance letter from a cardiologist 9. Heart/liver/kidney disease, neuropsychiatric disease classifying patient as ≥ ASA V 10. Major concomitant infections such as pneumonia or sepsis 11. In non-emergency surgery, pre-existing active bacterial skin infection at the time of the surgical incision; however, pre-existing bacterial infections are not exclusionary in burn or trauma patients.