Day 1 is when patients are started on SDD which consists of colistin 100 mg, gentamicin 80mg, and nystatin 2 million/U in 23mL. It is given every 6 hour via a nasogastric tube with the nasogastric tube then clamped for 1 hour. Stool will be collected once a day at baseline (pre administration of SDD), and then days 4, 7 and 14 for quantitative culture of resistant pathogens in the stool. VRE, MRSA and Pseudomonas aeruginosa will be sought. An endotracheal aspirate once a day will also be collected on these days (baseline, 1, 4, 7, and 14) for qualitative culture for the presence of MRSA and Pseudomonas aeruginosa. If there are no bowel movements on the days that stool is to be collected, no samples will be obtained. In addition, if the endotracheal tube is pulled, no further endotracheal aspirates will be obtained. Samples will only be obtained if available.