||Caption: Bacteroides sp. - rod shaped, obligately anaerobic, gram-negative, saccharolytic bacterium. Bacteroides is the most common bacteria found in the human colon / intestinal tract. The main by-products of their anaerobic respiration are acetic acid, iso-valeric acid, and succinic acid. They are involved in many important metabolic activities in the human flora of the colon, including fermentation of carbohydrates, utilization of nitrogenous substances, and biotransformation of bile acids and other steroids. When Bacteroides escape the colon, they are responsible for many types of infections and abscesses that can occur all over the body including the upper body, chest, abdomen, pelvis, the skin, the soft tissues and central nervous system. Bacteroides fragilis, is responsible for many clinical infections. Bacteroides are known to be involved in cases of meningitis and shunt infections, especially in children. Bacteriodes often become resistant to antibiotics. B. fragilis, along with B. distasonis, B. ovalus, B. thetaiotaomicron, and B. vulgatus are almost universally resistant to penicillin. These bacteria are prevalent in the gastrointestinal tract and are responsible for most intra-abdominal infections, such as perirectal abscesses and decubitus ulcers.