Oral versus systemic antibiotic prophylaxis in elective colon surgery: a randomized study and meta-analysis send a message from the 1990s.

Objectives: To compare the efficacy of combined oral and systemic antibiotics (combined) versus systemic antibiotics (systemic) alone in preventing surgical site infection in elective surgery of the colon, and to perform a meta-analysis of randomized studies comparing combined versus systemic antibiotics in elective colon surgery. Design: A double-blind, placebo-controlled, randomized clinical trial. Setting: The Queen Elizabeth Hospital, Montreal, a university-affiliated community hospital. Participants: Two hundred and fifteen patients scheduled to undergo elective surgery of the colon. Interventions: Patients were randomized to receive neomycin and metronidazole orally (109 patients) or identical placebos (106 patients) on the final preoperative day. All were given amikacin and metronidazole intravenously just before operation. Thirteen randomized series comparing combined and systemic antibiotic prophylaxis in elective colon surgery were identified for meta-analysis. Outcome measures: Rates of postoperative surgical site infections: risk differences, risk ratios (RRs) and 95% confidence intervals (CIs); organisms found in the colon and wound fat at surgery, and in infected wounds. Results: Three patients in the systemic group, and 5 in the combined group were excluded. Wound infections occurred in 5 patients in the combined group but in 17 in the systemic group (p < 0.01, RR = 0.29, 95% CI 0.11‐0.75). Bacteria isolated from wound infections and wound fat were similar to those found in the colon. They were more frequent in the colon in the systemic group (p < 0.001) and occurred in wound fat in the systemic group twice as often as in the combined group (p < 0.001). By stepwise logistic regression, the presence of bacteria in wound fat at surgery was the strongest predictor of postoperative wound infection (p < 0.002). In the meta-analysis, the summary weighted risk difference in surgical site infections between groups (dw) and the summary RR both favoured combined prophylaxis (dw = 0.56, 95% CI 0.26‐0.86; RR = 0.51, 95% CI 0.24‐0.78; p < 0.001). Conclusions: In elective surgery of the colon combined oral and systemic antibiotics are superior to systemic antibiotics in preventing surgical site infections. Orally administered antibiotics add value by reducing bacterial loading of the colon and wound fat contamination, both associated with postoperative wound infection. Meta-analysis of randomized clinical trials reported from 1975 to 1995 supports these conclusions. Objectifs : Comparer l’efficacite d’antibiotiques oraux et systemiques combines (combines) a celle des antibiotiques systemiques (systemiques) seuls pour prevenir l’infection du site chirurgical en chirurgie elective du colon, et effectuer une meta-analyse d’etudes randomisees ayant compare des antibiotiques combines aux antibiotiques systemiques en chirurgie elective du colon. Conception : Etude clinique randomisee controlee par placebo et a double insu. Contexte : L’Hopital Reine-Elizabeth de Montreal, hopital communautaire affilie a une universite. Participants : Deux cent quinze patients devant subir une chirurgie elective du colon. Intervention : On a reparti les patients au hasard pour recevoir de la neomycine et du metronidazole par voie orale (109 patients) ou des placebos identiques (106 patients) la veille de l’intervention. Tous ont recu de l’amikacine et du metronidazole par voie intraveineuse immediatement avant l’intervention. On a trouve, pour la meta-analyse, 13 series randomisees ou l’on comparait la prophylaxie aux antibiotiques combines et systemiques en chirurgie elective du colon. Mesures de resultats : Taux d’infections postoperatoires du site chirurgical : risque differentiel, risque relatif (RR), intervalles de confiance (IC) a 95 %; micro-organismes decouverts dans le colon et les tissus