Should antimicrobial prophylaxis in colorectal surgery include agents effective against both anaerobic and aerobic...

It is now well demonstrated that a mixed flora of aerobic and anaerobic microorganisms will be found in wound abscesses and peritonitis after bowel surgery. An impressive reduction in infectious complications caused by anaerobic microorganisms can be achieved with nitroimidazole prophylaxis, but considerable uncertainty about the role of agents active against aerobic microorganisms in such prophylaxis still exists. We have earlier reported that a single dose of tinidazole and doxycycline significantly reduces postoperative infections and is superior to doxycycline alone. The effect of an agent active only against anaerobic microorganisms was tested in a double-blind study of 267 patients who underwent elective colorectal surgery. The patients received either tinidazole (1600 mg) and placebo or tinidazole (1600 mg) and doxycycline (400 mg) as a single preoperative infusion. Patients who received tinidazole and doxycycline had significantly fewer infectious complications, reoperations, additional use of antibiotics, and a shorter hospital stay. Microbiologic studies demonstrated that tinidazole alone gave effective protection against anaerobic organisms but did not protect the patients from aerobic gram-negative infectious complications. A single preoperative dose of antimicrobial agents effective against both anaerobic and aerobic bowel organisms seems to be the preferred prophylaxis for patients undergoing colorectal surgery.