The prediction of abdominal surgical wound infection: the value of an enrichment broth for initial culture of operative parietal swabs.

At the conclusion of 817 abdominal operations, duplicate swabs were taken from the subcutaneous tissues for microbiological examination; one swab was transported to the laboratory in Stuart's thioglycollate medium and the other immediately incubated in Robertson's cooked meat broth. The latter method resulted in significantly more isolations of potentially pathogenic bacteria than the former, (31% compared with 17%, P less than 0.001). Immediate culture in broth with subsequent subculture allowed more accurate prediction of patients at risk of wound infection; using this method we found a 1:3 likelihood of wound infection with a 5% chance of severe infection when a single pathogenic species was cultured, and a 1:2 likelihood of wound infection with a 10% chance of severe infection when two or more pathogenic species were cultured. Transport of swabs in thioglycollate medium, in contrast, detected fewer patients with parietal contamination and showed a 1:5 likelihood of wound infection when the swab was sterile and a 1:2 chance when one or more than one pathogenic species was cultured.