Stool samples will be collected from two groups of neutropenic patients in the case that a therapy with either meropenem or piperacillin/tazobactam is needed due to a suspected infection. The intestinal resistome will be determined and quantified using shotgun metagenomics. Based on this, regression models will be used to determine the actual selection pressure caused by these drugs, and both selective forces will be compared. The results will reveal if there is a drug that causes a lower selection pressure compared to the other. The study aims to generate knowledge that is required to design effective antibiotic stewardship programs.