Describes probiotics and their relationship to bacteria, yeasts, parasites, and viruses. Discusses how probiotics affect the healthy immune system. Explains antibiotics and antibiotic resistance. Describes how probiotics can be helpful in preventing and treating certain diseases and conditions. Identify good food sources of probiotics and prebiotics. Identify how to select probiotic supplements considering their risks and benefits. Describes how healthcare professionals can use this information to improve patient education and outcomes.