Recent data link the incidence of intestinal GvHD (iGvHD) after allogeneic haematopoietic stem cell transplantation (aSCT) to exposure with piperacillin-tazobactam or imipenem-cilastatin. To assess relevance of timing, duration, sequence and combination of antibiotic treatment in this setting, we applied a time-dependent model to our aSCT cohort. Patients from the prospective Cologne Cohort of Neutropenic Patients (CoCoNut) undergoing aSCT from January 2007 to April 2013 were included into a time-dependent multivariate Cox proportional hazards regression model with backward-stepwise selection. In 399 eligible patients, cumulative antibiotic exposure (hazard ratio (HR) 2.46; 95% confidence interval (95% CI) 1.59-3.81; P<0.001) and exposure to sequential treatment with penicillin derivatives and carbapenems (HR 6.22, 95% CI 1.27-30.31), but not to the individual classes, were associated with iGvHD at day 100. Glycopeptides were assessed as a risk factor (HR 3.73, 95% CI 1.51-9.19), but not considered independent, since their use was dependent on previous exposure to penicillin derivatives and carbapenems. Patients with iGvHD presented with increased non-relapse mortality at day 365 (HR 3.51; 95% CI 2.10-5.89; P<0.001). We identified sequential exposure to penicillin derivatives and carbapenems as well as overall exposure to antibiotics as independent risk factors for iGVHD. Confirmation of these findings in larger, prospective cohorts is necessary.

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