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 β-lactam-β-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.