In many cases these infections are nosocomial, which means that they can be acquired in the hospital. Klebsiella and Proteus sometimes cause pneumonia , ear and sinus infections, and urinary tract infections. Diarrhea caused by enterobacteria is a common problem in the United States. It is estimated that each person in the general population has an average of 1.5 episodes of diarrhea each year, with higher rates in children, institutionalized people, and Native Americans. This type of enterobacterial infection can range from a minor nuisance to a life-threatening disorder, especially in infants, elderly persons, AIDS patients, and malnourished people.
Enterobacterial infections are one of the two leading killers of children in developing countries.
They may be bacteria that are already present in the stomach and intestines, or they may be transmitted by contaminated food and water. Escherichia coli E. coli infections cause most of the enterobacterial infections in the United States. The organisms are categorized according to whether they are invasive or noninvasive. These subtypes invade the stomach tissues directly, causing tissue destruction and bloody stools. EHEC has become a growing problem in the United States because of outbreaks caused by contaminated food.