The Gastrointestinal Tract and Its Defenses Lecture Two

1. The Gastrointestinal Tract and Its Defenses Lecture Two

2. Acute Diarrhea Caused by E.coli O157:H7 (EHEC) • Most virulent strain of E. coli • EnterohemorrhagicE. coli • Symptoms range from mild gastroenteritis with fever to bloody diarrhea • About 10% of patients develop hemolytic uremic syndrome (can cause kidney damage and failure) • Can also cause neurological symptoms such as blindness, seizure, and stroke

3. Acute Diarrhea Caused by Other E. coli • Four other categories: • Enterotoxigenic • Enteroinvasive • Enteropathogenic • Enteroaggregative

4. Enterotoxigenic E. coli (ETEC) • Presentation varies depending on which type of E. coli is causing the disease • Traveler’s diarrhea: watery diarrhea, low-grade fever, nausea, and vomiting

5. Enteroinvasive E. coli (EIEC) • Cause a disease similar to Shigella dysentery • Invade gut mucosa and cause widespread destruction • Blood and pus found in stool • Significant fever

6. Enteropathogenic E. coli (EPEC) • Profuse, watery diarrhea • Fever and vomiting also common • Produce effacement of gut surfaces

7. Enteroaggregative E. coli (EAEC) • Can cause chronic diarrhea in young children and in AIDS patients

8. Acute Diarrhea Caused by Campylobacter • Most common bacterial cause of diarrhea in the U.S. • Frequent watery stools, fever, vomiting, headaches, and severe abdominal pain • Symptoms may last beyond 2 weeks • Symptoms may subside then recur over a period of weeks • In a small number of cases, can lead to a serious neuromuscular paralysis called Guillain-Barré syndrome (GBS)

9. Acute Diarrhea Caused by Yersinia Species • Y. enterocolitica and Y. pseudotuberculosis • Uncommon in U.S. • Inflammation of the ileum and mesenteric lymph nodes gives rise to severe abdominal pain • Infection occasionally spreads to the bloodstream

10. Acute Diarrhea Caused by Clostridium difficile • Causes pseudomembranous colitis • Major cause of diarrhea in hospitals • Able to superinfect the large intestine when drugs have disrupted the normal biota • Produces two enterotoxins (toxins A and B) that cause areas of necrosis in the wall of the intestine • Diarrhea • Severe cases exhibit abdominal cramps, fever, and leukocytosis

11. Acute Diarrhea Caused by Vibrio cholera • Incubation period of a few hours to a few days • Symptoms begin abruptly with vomiting • Followed by copious watery feces called secretory diarrhea • Can lose up to 1 liter of fluid an hour in severe cases

12. Acute Diarrhea Caused by Cryptosporidium • Headache, sweating, vomiting, severe abdominal cramps, and diarrhea • In AIDS patients may develop into chronic persistent cryptosporidial diarrhea

13. Acute Diarrhea Caused by Rotavirus • Effects of infection vary with age, nutritional state, general health, and living conditions of the patient

14. Acute Diarrhea Caused by Other Viruses • Many other viruses can cause gastroenteritis • For example adenoviruses, noroviruses, and astroviruses • Common in the U.S. and around the world • Profuse, water diarrhea of 3 to 5 days duration

17. Acute Diarrhea with Vomiting (Food Poisoning) • Symptoms in the gut that are caused by a preformed toxin of some sort • If the symptoms are violent and the incubation period is very short, intoxication rather than infection should be considered

18. Food Poisoning by StaphylococusaureusExotoxin • Associated with food such as custards, sauces, cream pastries, processed meats, chicken salad, potatoe salad, or ham that have been contaminated and then left unrefrigerated for a few hours • Toxins do not noticeably alter the food’s taste or smell • Heating the food after toxin production may not prevent disease • Symptoms: cramping, nausea, vomiting, and diarrhea • Rapid recovery- usually within 24 hours

19. Food Poisoning by Bacillus cereusExotoxin • Two exotoxins: one causes diarrheal-type disease, the other cause an emetic disease • The type of disease that takes place is influenced by the type of food that is contaminated • Emetic form frequently linked to fried rice, especially when cooked and kept warm for long periods of time • Diarrheal form associated with carbohydrate dishes, cook meats or vegetables that are held at a warm temperature for long periods of time

20. Food Poisoning by ClostridumperfringensExotoxin • Animal flesh and vegetables such as beans that have not been cooked thoroughly enough to destroy endospores • Acute abdominal pain, diarrhea, and nausea in 8 to 16 hours • Rapid recovery

22. Chronic Diarrhea by Cyclospora • Incubation period of about 1 week • Watery diarrhea, stomach cramps, bloating, fever, and muscle aches • If prolonged, also experience anorexia and weight loss

23. Chronic Diarrhea by Giardia • Diarrhea of long duration, abdominal pain, and flatulence • Stools have a greasy, malodorous quality • Fever usually not present

24. Chronic Diarrhea by Entamoeba • Clinical amoebiasis exists in intestinal and extraintestinal forms • Intestinal targets: ceacum, appendix, colon, and rectum • Secretes enzymes that dissolve tissues • Leaves erosive ulcerations as it penetrates deeper layer of mucosa • Dysentery, abdominal pain, fever, diarrhea, weight loss • Can also manifest hemorrhage, perforation, appendicitis, and amoebomas • Extraintestinal: common target is the liver • Amoebic hepatitis • Rarer complication- pulmonary amoebiasis