Prevention and Treatment

Preventive measures include handwashing, pasteurization of drinks, and thorough cooking of food. Treatment of E. coli gastroenteritis includes replacing the fluid lost from vomiting and diarrhea. In addition, infants may require antibiotics such as gen-tamicin or polymyxin for a few days. Traveler's diarrhea can be

Table 24.7 Characteristics of Diarrhea-Causing Escherichia coli

Designation

Characteristic Features

Clinical Picture

Enterotoxigenic E. coli (ETEC)

Can release two kinds of toxin, one similar to cholera toxin; small intestinal location

Nausea, vomiting, abdominal cramps, massive watery diarrhea leading to dehydration

Enteroinvasive E. coli (EIEC)

Entry into and growth in intestinal epithelium, with cell destruction; large intestinal location

Fever, cramps, blood and pus in the feces

Enteropathogenic E. coli (EPEC)

Attachment of the bacterium is followed by loss of microvilli and formation of a platform or pedestal of actin fibrils under the bacterium; small intestinal location

Fever, vomiting, watery diarrhea containing mucus; associated with a limited number of serotypes

Enterohemorrhagic E. coli (EHEC)

Same as above, except large intestine location and release of Shigalike toxin

Fever, abdominal cramps, bloody diarrhea without pus; 2% to 7% develop hemolytic uremic syndrome; most cases due to serotype O157:H7

616 Chapter 24 Alimentary System Infections

Table 24.8 Escherichia coli Gastroenteritis

(T) Pathogenic strain of E. coli enters the body by the fecal-oral route, usually with contaminated food or beverage

(2) Most strains colonize the small intestine and produce watery diarrhea

® Others invade the large intestine and cause dysentery

@ Some strains produce Shiga toxin which is absorbed by the bloodstream and causes hemolytic-uremic syndrome with damage to red blood cells and the kidneys

(5) The bacteria exit the body with feces ft

Symptoms

Incubation period Causative agent Pathogenesis

Epidemiology

Prevention and treatment

Vomiting and diarrhea; sometimes dysentery

2 hours to 6 days

Escherichia coli, certain strains

Various mechanisms; attachment to small intestinal cells allows colonization; some strains produce one or more enterotoxins; some strains, resembling shigellas, invade large intestinal epithelium; others cause host cell membrane thickening and loss of microvilli, and may produce Shiga toxin

Common in travelers; can be foodborne or waterborne; fecal-oral route transmission, sometimes animal source

Sanitary precautions including careful handwashing; pasteurization of drinks, thorough cooking of meats; replacement of fluid loss, antibiotics and bismuth compounds for treatment prevented with bismuth preparations (such as Pepto-Bismol) or an antibacterial medication such as fluoroquinolone if the E. coli strains in the geographic area visited are sensitive to the antibiotic. The widespread use of an antibiotic to prevent diarrhea, however, promotes the appearance of resistant strains by fostering the spread of R plasmids, and thus antibiotics should not be used routinely.

Some features of E. coli gastroenteritis are summarized in table 24.8.

Salmonellosis

Salmonellosis, a disease caused by bacteria of the Salmonella genus, can be contracted from many animal sources. On the average, roughly 47,500 cases are reported per year in the United States, but most cases go unreported, and the actual number is estimated at well over 2,000,000 per year.

Humans are the only source for a few Salmonella strains, which are now rare in the United States. These human strains generally cause severe symptoms, as in typhoid fever.

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