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Chapter 22b - Lecture Outline

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