The use of antibiotics disrupts the ecology of the microbiome in three important ways. First, antibiotic therapy can lead to secondary infection, as in antibiotic-associated diarrhea caused by Clostridium difficile infection. A second effect is an increase in levels of antibiotic resistance in the regrowth flora, which can be suppressed by administration of probiotics. A third effect is the development of certain diseases and syndromes, such as inflammatory bowel syndrome, several months after the use of antibiotics.