Microbiology: A Systems Approach, 2nd 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