If at any point during the hospitalization or during the follow-up timeframe a patient receiving kefir displays signs or symptoms of an invasive bacterial, yeast, or fungal infection, blood cultures and other cultures as deemed clinically appropriate (urine culture, sputum culture, wound culture, etc.) will be obtained. Signs and symptoms of an invasive infection include, but are not limited to, the following: fever, chills, elevated WBC concentration, elevated serum C-reactive protein (CRP) and/or procalcitonin levels, and hypotension.