Saline wound irrigation reduces the postoperative infection rate in guinea pigs

Wound irrigation with saline is widely used alone or together with systemic antibiotic prophylaxis to prevent postoperative wound infection. This study was aimed to investigate the effect of saline irrigation upon the bacterial load on wound surfaces and on the wound infection rate in an animal model. In 16 guinea pigs, two wounds were contaminated with Bacteroides fragilis and Escherichia coli. One wound was irrigated with saline, while the other received no prophylaxis. Quantitative wound cultures were performed before and after irrigation. The wound infection rate was determined at 10 days. Saline irrigation reduced the aerobic and anaerobic bacterial counts in wound margins. The infection rate was also reduced (15/16 nonirrigated vs 6/16 irrigated, P < 0.001). High bacterial counts at the end of operation were associated with wound infection (P < 0.001). At skin closure, wounds which later became infected harbored fourfold more bacteria than noninfected wounds [8.7 (6.4- 1 1.0) vs 2.3 (0.8-3.7) colony-forming units x 10(3) of E. coli/cm2; P < 0.005]. Saline wound irrigation diminishes infection rate in experimental animals by means of a significant reduction of the bacterial inoculum present at the time of skin closure.