Bacterial density in laparotomy wounds during gastro-instestinal operations

Operation wounds were sampled quantitatively for aerobic bacteria in 56 patients by the velvet pad rinse technique in a prospective, randomised study of abdominal operations (1) truncal vagotomy and pyloroplasty, (2) gastric or (3) colo-rectal operations, and (4) exploratory laparotomy. On entering the peritoneal cavity and prior to incision of the gastro-intestinal tract the bacterial density in the wounds did not differ significantly between these four types of operations, the median being 5.4X10(-1) viable counts/cm2 (range 0.7-135.8). In all series of operations the median bacterial density was increased prior to closure of the wounds, significantly so after colo-retal operations, being 21.3X10(-1) viable counts/cm2 (range 1.1-144.4), caused by a rise in density of aerobic intestinal species, especially Escherichia coli. Regardless of type of operation, all wounds were contaminated during operation by aerobic commensals of the skin and mucous membranes of the upper respiratory tract, in particular by Staphylococcus epidermidis, this species not differing significiantly in density from the beginning to the end of operation. This same study revealed that within the operation wound, sites of low or even zero bacterial density were close to sites with a high density. It is suggested that postoperative wound infection is closely related to the density of the different species of bacteria present in the operation wound at closure.