Patients who consent to enter the study will receive the synbiotic mix, or a placebo, which comes in a powder that may be mixed with a drink, or washed down into the stomach through the NG tube if the patient is still on a ventilator. Dosing will be initiated within four hours of patient arrival in the Cardiac Surgery Intensive Care Unit and will continue on a twice daily basis for the duration of their admission days. Infection and diarrhea data will be monitored.