Most E. coli strains are harmless, but some, such as serotype O157:H7, can cause serious foodpoisoning in humans.2. E. coli bacteria have been commonly found in recreational waters and its presence is used toindicate the presence of recent fecal contamination.3. But E. coli presence may not be indicative of human waste. E. coli are harbored in all warm blooded animals: birds and mammals alike.4. E. coli bacteria have also been found in fish and turtles.5. Sediment, sand and soil also harbor E. coli bacteria.