Non-Invasive Enteritis and Food Poisoning

1. Non-Invasive Enteritis and Food Poisoning

2. FOODBORNE ILLNESS (Bacterial) • Foodborne illness results from eating food contaminated with organisms or toxins • Foodborne illness tends to occur at picnics, school cafeterias, and large social functions • These are commonly situations in which food may be left unrefrigerated or food preparation techniques are insufficiently safe • Foodborne illness often occurs from undercooked meats or dairy products that have remained at room temperature for extended periods

3. In patients with foodborne illness, fluid consumption is important to avoid dehydration • Solid foods should not be eaten until the diarrhea has passed, and dairy should be avoided, as it can worsen diarrhea temporarily • Intravenous fluid may be indicated in patients with severe diarrhea who are unable to drink fluids • for example, caused by nausea or vomiting

4. Most patients spontaneously recover from the most common types of foodborne illness within a couple of days • Antibiotic therapy is usually not indicated, except in cases of severe illness • Infants and elderly people have the greatest risk for foodborne illness • It is estimated that foodborne gastroenteritis causes 48 million illnesses, 127,000 hospitalizations, and 3,000 deaths in the United States annually

5. VIBRIO • Members of the genus Vibrio are short, curved, rod-shaped organisms • Vibrios are closely related to the family Enterobacteriaceae • They are rapidly motile by means of a single polar flagellum • Vibriosare facultative anaerobes

6. Pathogenic vibrios include • 1) Vibrio cholerae, serogroup O1 strains that are associated with epidemic cholera • 2) non-O1 V. cholerae and related strains that cause sporadic cases of choleralike and other illnesses • 3) Vibrio parahaemolyticus and other halophilic vibrios, which cause gastroenteritis and extraintestinalinfections

7. A. Epidemiology • V. cholerae is transmitted to humans by contaminated water and food • Among humans, long-term carriage is considered uncommon • Outbreaks have been associated with raw or undercooked seafood harvested from contaminated waters • Natural (and even man-made) disasters are often followed by cholera outbreaks

8. B. Pathogenesis • Following ingestion, V. cholerae infects the small intestine • Adhesion factor(s) are important for colonization and virulence • The organism is noninvasive but adheres to the epithelium by expression of pili called Tcp, or toxin-coregulated pili • These pili are coordinately expressed along with cholera toxin, which is an enterotoxin that initiates an outpouring of fluid • This, in turn, causes an outflowing of ions and water to the lumen of the intestine

9. C. Clinical significance • Full-blown cholera is characterized by massive loss of fluid and electrolytes from the body • After an incubation period ranging from hours to a few days, profuse watery diarrhea (“rice-water” stools) begins • Untreated, death from severe dehydration causing hypovolemic shock may occur in hours to days, and the death rate may exceed 50 percent • Appropriate treatment reduces the death rate to less than 1 percent • Patients with suspected cholera need to be treated prior to laboratory confirmation, because death by dehydration can occur within hours

10. D. Laboratory identification • V. cholerae grows on standard media such as blood and Mac-Conkey agars • The organism is oxidase positive, but further biochemical testing is necessary for specific identification of V. cholerae

11. E. Treatment and prevention • Replacement of fluids and electrolytes is crucial in preventing shock and does not require bacteriologic diagnosis • Antibiotics (doxycycline is the drug of choice) can shorten the duration of diarrhea and excretion of the organism • Prevention relies primarily on public health measures that reduce fecal contamination of water supplies and food • Adequate cooking of foods can minimize transmission • Vaccines that are only modestly protective are available in many other countries but not in the United States

12. ESCHERICHIA COLI • Escherichia coli is part of the normal flora of the colon in humans and other animals but can be pathogenic both within and outside of the GI tract • E. coli has pili that are important for adherence to host mucosal surfaces, and different strains of the organism may be motile or nonmotile • Most strains can ferment lactose in contrast to the major intestinal pathogens • E. coli produces both acid and gas during fermentation of carbohydrates

13. A. Structure and physiology • E. coli shares many properties with the other Enterobacteriaceae • They are all facultative anaerobes, they all ferment glucose, and they all can generate energy by aerobic or anaerobic respiration

14. B. Clinical significance: intestinal disease • Transmission of intestinal disease is commonly by the fecal–oral route • contaminated food and water serving as vehicles for transmission • E. coli infection should be suspected in all patients with acute bloody diarrhea • particularly if associated with abdominal tenderness and absence of fever

15. C. Clinical significance: extraintestinal disease • The source of infection for extraintestinal disease is frequently the patient's own flora, in which the individual’s own E. coli is nonpathogenic in the intestine • However, it causes disease in that individual when the organism is found, for example, in the bladder or bloodstream (normally sterile sites)

16. D. Laboratory identification • 1. Intestinal disease • Because E. coli is normally part of the intestinal flora, detection in stool cultures of disease-causing strains is generally difficult • Current molecular techniques, such as polymerase chain reaction, may be employed to identify E. coli strains

17. 2. Extraintestinal disease • Isolation of E. coli from normally sterile body sites is diagnostically significant • Specimens may be cultured on MacConkeyagar • Strains of E. coli can be further characterized on the basis of serologic tests

18. E. Prevention and treatment • Intestinal disease can best be prevented by care in selection, preparation, and consumption of food and water • Maintenance of fluid and electrolyte balance is of primary importance in treatment • Antibiotics may shorten duration of symptoms, but resistance is nevertheless widespread • Extraintestinal diseases require antibiotic treatment • Antibiotic sensitivity testing of isolates is necessary to determine the appropriate choice of drugs