Antibiotic prophylaxis and the risk of Clostridium difficile-associated diarrhoea.

To test the hypothesis that extended antibiotic prophylaxis increases the risk of Clostridium difficile -associated diarrhoea (CDAD), we conducted a retrospective cohort study of 2641 patients under-going cardiovascular surgery. Main outcome measures were the duration of prophylaxis (< 48 h vs. > 48 h) and the occurrence of CDAD. CDAD occurred in 31 patients (1.2%), who were significantly older (70 +/- 9 y vs. 66 +/- 10 y; P = 0.03), received more therapeutic antibiotics (2.2 +/- 1.9 vs. 0.4 +/- 0.9; P = 0.001) and had a longer postoperative hospital stay (26 +/- 19 d vs. 9 +/- 8 d; P < 0.001) than non-cases. After adjusting for confounding, we did not observe an association between prolonged prophylaxis and CDAD [adjusted odds ratio (AOR), 0.8; CI, 0.4-1.8]. In contrast, three independent predictors were identified: increasing length of hospital stay (AOR per one-day-increment, 1.03; CI, 1.01-1.05), and treatment with third generation cephalosporins (AOR, 5.9; CI, 2.2-16.0) or beta-lactam-beta-lactamase inhibitor combinations (AOR, 4.6; CI, 1.7-12.3). Our results did not confirm that extended prophylaxis after clean surgery increases the risk of CDAD, which remains an uncommon postoperative complication, associated even with short antibiotic exposure. Copyright 2001 The Hospital Infection Society.