Eikenella corrodens is a gram negative bacteria that grows in environments that are rich in carbon dioxide without any regard for oxygen levels. It is found in the mouth and upper respiratory tract and is usually harmless. In rare cases, it can cause an infection, typically in cancers of the head and neck, in bite wounds, or when intravenous drug users lick a needle before using it. It can also spread when a patient has very poor oral hygiene. It's most common complication is endocarditis, although it is not a common cause of that condition.