Enterotoxigenic Escherichia coli: traveler's diarrhea comes home.

The article in this issue of Clinical Infectious Diseases by Beatty et al. [1] on an outbreak of diarrhea due to enterotoxi-genic Escherichia coli (ETEC) further documents the emergence of ETEC as a significant diarrheal pathogen in the United States. The main contribution of the article by Beatty and colleagues is that it describes one of the largest foodborne outbreaks ever reported in the United States (an estimated 3600 persons became ill). ETEC is the most common cause of traveler's diarrhea, which is often related to travel to developing countries (commonly referred to as " Montezuma's revenge, " " Bali belly, " " Ti-juana trot, " and " Turista "). Recent data, however , suggest that Americans no longer have to travel to developing countries to become exposed to this toxin-mediated, cholera-like infection [2, 3]. ETEC was first recognized as a cause of human illness in the 1960s [4]. The non-invasive organism colonizes the small intestine without causing mucosal damage. ETEC causes acute, self-limited, secretory diarrhea mediated through the action of heat-stable and heat-labile enterotoxins. The duration of illness is typically 3–5 days, and the illness usually resolves without antimicrobial treatment, but symptoms can persist for 2–3 weeks without complications or sequelae [5–7]. Contaminated water and food have been implicated as vehicles for transmission of ETEC infection [2, 3, 8]. Food sources reported for ETEC-related diarrhea include fresh fruits and vegetables (especially lettuce), parsley, basil, scallops, shrimp, crab meat, tuna paste, prepared salads, and soft cheeses. ETEC infections, as was reported in this outbreak, are always associated with poor hygiene and sanitation. Contaminated seafood and salads are frequently implicated as vehicles of infection in outbreaks of ETEC infection. In this outbreak, multiple prepared salads (potato, macaroni, and egg) were implicated as vehicles of infections, although the exact route of contamination was never determined. Unlike E. coli O157:H7, ETEC is uncommonly found in meat products. To cause infection, a high infective dose of 110 8 colony-forming units is required [9]; therefore, food and water must be heavily contaminated for outbreaks to occur. Waterborne outbreaks attributed to ETEC have been particularly problematic on cruise ships. In one series of outbreaks reported on cruise ships, contaminated water and ice cubes caused thousands of infections because of a failure to adequately chlorinate water after bun-kering [10]. Because it is difficult to detect and isolate this organism, ETEC infections in the United States are often …