Infectious diarrhea

Infectious diarrhea is an extremely common illness that affects millions of Americans annually. For most patients, the illness is a self-limited one. Its major risk is dehydration. However, for some patients, diarrhea can lead to severe dehydration or be associated with bacteremia and metastatic infection. Patients with these conditions require prompt treatment. A large number of organisms have been associated with diarrhea in humans, and most laboratories routinely screen for Salmonella, Shigella, and Campylobacter. Other bacteria, parasites, and viruses account for a significant percentage of diarrhea cases and frequently go undetected. This article summarizes many of these pathogens and describes the settings in which they can be acquired. Food distribution networks have made the delivery of previously rare foods to remote areas a commonplace occurrence; this has also led to new challenges in the diagnosis and prevention of food-borne illnesses. Outbreaks of diarrhea now frequently extend across many states. The identification of a rare strain of a bacterial pathogen or changes in the isolation rate of common pathogens may be early clues to the cause of such an ongoing outbreak. Most enteric pathogens cause disease by either stimulating the secretion of fluids at the level of the small bowel or by irritating and invading the colon. Organisms that cause disease by the latter mechanism have the potential to invade the blood stream and spread to other parts of the body, including the bones and the central nervous system. Several organisms have been associated with specific postinfectious syndromes that are responsible for additional morbidity and mortality. The antibiotic resistance of bacterial pathogens has been increasing, and this has a limiting effect on the empiric treatment choices available for suspected bacterial diarrhea. Careful attention to local sensitivity patterns and appropriate testing of the patient's isolate are among the important factors that lead to successful treatment decisions.