Wound infection rates following preoperative versus intraoperative commencement of antibiotic prophylaxis.

The effect of antibiotic prophylaxis initiated one hour prior to contamination or at the time of contamination was evaluated in a randomized blind study using a guinea pig model of surgical wound infection. Would infection, defined as accumulation of pus draining spontaneously or after opening of the wound, developed in 135 guinea pigs after intraincisional contamination before wound closure with 10(7) Escherichia coli plus 10(8) Bacteroides fragilis. Antibiotic prophylaxis with gentamicin plus clindamycin significantly reduced the wound sepsis rate from 82% in the control group of 61 animals to 19% in the two treated groups of 68 and 67 animals (p less than 0.001). However, the timing of antibiotic prophylaxis did not influence wound sepsis rates, rectal temperature during the postoperative period, or bacterial recovery from wound infections.