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.