Computer illustration of Bacteroides sp. bacteria. These are rod shaped, obligate anaerobic, Gram-negative, saccharolytic bacteria. Bacteroides are the most common bacteria found in the human intestinal tract. 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, skin, soft tissues and central nervous system. Bacteroides are known to be involved in cases of meningitis and shunt infections, especially in children. Bacteroides often become resistant to antibiotics.