Journal of Hospital Infection (1988) 12, 207-214 A trial of mezlocillin versus cefriroxime with or without metronidazole for the prevention of wound sepsis after biliary and gastrointestinal surgery K. J. Cann, R. M. Watkins,* C. George,* J. Payne-James,* E. Crawfurd* and T. R. Rogers *Departments of Surgery and Medical Microbiology, Char&g Cross and Westminster Medical School, London SWlP 2AR Accepted for publication 24 March 1988 Summary: A randomized controlled trial was undertaken to compare the role of mezlocillin, as the sole prophylactic agent, with a combination of cefuroxime and metronidazole in patients undergoing biliary and gastrointes- tinal surgery. No difference in wound infection rates was seen in patients following appendicectomy, biliary or gastro-oesophageal surgery. A signifi- cantly higher wound infection rate was seen in patients undergoing colorectal surgery who received mezlocillin alone (30.2%) compared with those receiv- ing cefuroxime and metronidazole (11.5%): this rate was similar to that of historical placebo controls in other units. The wound infections seen in patients receiving mezlocillin alone were polymicrobial involving organisms of faecal origin, including non-sporing anaerobes which were predominantly sensitive to mezlocillin. Infections due to Staphylococcus aurats, resistant to mezlocillin, were more frequent in patients receiving mezlocillin and usually secondary in nature. We conclude that mezlocillin may be an effective sole prophylactic agent in appendicectomy but not in colorectal surgery; the possible reasons for failure to adequately prevent infection, following colo- rectal surgery, are discussed. Keywords: Mezlocillin; cefuroxime; metronidazole; prophylaxis; wound infection. Introduction Postoperative wound infection is a common complication of biliary and gastrointestinal surgery and causes considerable morbidity. The development of intra-abdominal abscess and septicaemia are associated with marked increases in mortality. The incidence of postoperative septic complications varies with the degree of bacterial contamination at surgery (Keighley & Burdon, 1979; Galland, 1982; Pollock, Evans & Parida, 1986) Correspondence to: Dr K. J. Cann 0195%6701/88/070207 +08 003.00/O 207