Escherichia coli is an organism that is a Gram negative bacillus when viewed microscopically after Gram’s stain. This organism is a universal colonizer of every person’s gastrointestinal tract. However, some strains may be acquired from ingesting contaminated food or water resulting in diarrhea. Some of these strains are common causes of traveler’s diarrhea, while others can result in complications such as hemolytic-uremic syndrome, a kidney disease affecting children. E. coli is the most common cause of urinary tract infection. It may also cause peritonitis and some other infections.