Chapter 22b - Lecture Outline
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Chapter 22b - Lecture Outline






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Chapter 22b - Lecture Outline Chapter 22b - Lecture Outline Presentation Transcript

  • Microbiology: A Systems Approach, 2 nd ed. Chapter 22: The Gastrointestinal Tract and Its Defenses
  • Acute Diarrhea Caused by E.coli O157:H7 (EHEC)
    • Most virulent strain of E. coli
    • Enterohemorrhagic E. 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
  • Figure 22.12
  • Acute Diarrhea Caused by Other E. coli
      • Four other categories:
        • Enterotoxigenic
        • Enteroinvasive
        • Enteropathogenic
        • Enteroaggregative
  • 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
  • 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
  • Enteropathogenic E. coli (EPEC)
    • Profuse, watery diarrhea
    • Fever and vomiting also common
    • Produce effacement of gut surfaces
  • Enteroaggregative E. coli (EAEC)
        • Can cause chronic diarrhea in young children and in AIDS patients
  • 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)
  • Figure 22.13
  • 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
  • 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
  • Figure 22.14
  • 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
  • Figure 22.15
  • Acute Diarrhea Caused by Cryptosporidium
    • Headache, sweating, vomiting, severe abdominal cramps, and diarrhea
    • In AIDS patients may develop into chronic persistent cryptosporidial diarrhea
  • Figure 22.16
  • Figure 22.17
  • Acute Diarrhea Caused by Rotavirus
      • Effects of infection vary with age, nutritional state, general health, and living conditions of the patient
  • Figure 22.18
  • 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
  • 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
  • Food Poisoning by Staphylococus aureus Exotoxin
    • Associated with food such as custards, sauces, cream pastries, processed meats, chcken 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
  • Food Poisoning by Bacillus cereus Exotoxin
    • 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 cook mats or vegetables that are held at a warm temperature for long periods of time
  • Food Poisoning by Clostridum perfringens Exotoxin
    • 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