Definition: A Disease-Causing Organism is a micro-organism that can make you sick if you eat it, inhale it, or come into contact with it (get it on your skin, or in your ears, etc).Standards for disease-causing organisms in Louisiana are based on a group of bacteria called fecal coliform bacteria.These bacteria are used for detecting the level of disease-causing organisms and untreated sewage in water. Fecal coliform bacteria come from intestines of warm-blooded animals.isease-causing organisms get into the water from untreated sewage. When people go to the bathroom they create waste called sewage. Every home, school, and business is required by law to have some way of treating its sewage or transporting it to a sewage treatment system.