According to Dr. Jeff McCombs, Founder / CEO at McCombs Center For Health, "Studies have shown that a 5-day or 7-day course of antibiotics will wipe out the 100 trillion organisms/bacteria of the gut, leaving only a few antibiotic resistant strains. These antibiotic resistant strains will be the only ones present in the gut for up to a year and the composition of the intestinal bacteria will be permanently altered. As bacteria re-populate the gut, they will acquire antibiotic resistance from the few strains that survived the antibiotics. With altered intestinal flora, the entire function of the intestinal tract becomes altered and disease processes begin. Antibiotics have been associated with diabetes, obesity, inflammation, asthma, allergies, rapid aging, IBS, IBD, cancers, and life-threatening colitis. By altering the intestinal flora, every organ, tissue, and cell in the body becomes affected. This recent study, published in Science Daily, once again points out the connection of antibiotics to colon cancer and the chain of events that takes place"
http://www.sciencedaily.com/releases/2012/08/120816141527.htm.