Postoperative wound infection after appendicectomy. Evaluation of infection risk with qualitative and quantitative...

The predictive value for postoperative infection of incisional wound cultures obtained at wound closure was studied in two series of appendicectomies, comprising 404 patients studied with qualitative swab cultures, and 491 patients studied with quantitative velvet pad imprint cultures. 17% and 19%, respectively, of the patients in the two series yielded cultures positive with Gram-negative enterobacteria. The postoperative wound infection rate among contaminated cases was 36.1% and 26.9%, respectively, which was a significantly higher rate (p less than 0.001) as compared to operations yielding negative cultures. Using quantitative culture technique, 63% of all infections was shown to occur in the 15% of all patients whose culture yielded two or more colonies of enterobacteria. Of these high risk patients, those who were given antibiotics at operation had an infection rate of 25%, and those not given antibiotics had a rate of 48%. The remaining 85% of the patients had an infection rate of less than 5%.