Microbiology of postoperative wound infection: a prospective study of 1770 wounds.

A prospective study of postoperative wound infection was carried out over a 12-month period. Intra-operative swabs from the patients' anterior nares, the opened viscus and parietes were cultured using standard bacteriological techniques. Of the 1770 wounds studied, 167 (9.4%) became infected. Wound infection rates, according to clinical wound types, were clean 5.9%, clean-contaminated 10.7%, contaminated 24.3% and dirty 52.9%. The figures according to microbiological wound types were clean 4.7%, and potentially, lightly and heavily contaminated 15.3%, 22.1% and 30.2% respectively. The commonest causative organisms were Staphylococcus aureus 23.7%, Escherichia coli 16.9%, Staphylococcus epidermidis 13.5% and Pseudomonas aeruginosa 13.0%. When isolated intra-operatively, Enterobacter spp., Proteus spp., Klebsiella spp. and P. aeruginosa appeared to have a high probability of causing postoperative wound infection, but the intra-operative isolation of Bacteroides sp. was a poor predictor of subsequent wound infection.