ch. 20 infectious diseases of the GI tract

micro bio

1. Describe the defenses and the parts of the GI tract.

• Saliva – contains enzymes and antimicrobial properties.

• Mucus + IgA – traps microbes, IgA provides immune defense.

• Peristalsis – movement pushes microbes out.

• Stomach acid – kills most pathogens.

• GALT (Gut-associated lymphoid tissue) – immune surveillance.

• Tonsils & Peyer’s Patches – lymphoid tissues that detect invaders.

what are the organisms in the GI tract

-Salmonella

-Shigella

-Vibrio cholerae

-Campylobacter jejuni

-Clostridium difficile

-E. coli O157:H7 (STEC)

-Rotavirus

-Norovirus

what is salmonella

• symptoms

• transmission

• prevention/treatment

-Salmonella

• Symptoms: Fever, septicemia, vomiting, diarrhea (2–5 days).

• Transmission: Fecal-oral (human feces), zoonotic (chickens, reptiles, cattle).

• Prevention/Treatment: Food safety, hygiene; severe cases → electrolyte replacement + ciprofloxacin.

what is shigella

• symptoms

• transmission

• prevention/treatment

• virulence

-Shigella

• Symptoms: Dysentery (bloody diarrhea), fever, intense abdominal pain, vomiting.

• Transmission: Fecal-oral from infected persons.

• Prevention/Treatment: Hygiene, sanitation; supportive care, antibiotics in severe cases.

• Virulence: Shiga toxin → intestinal/systemic damage.

what is vibrio cholerae

• symptoms

• transmission

• prevention/treatment

-Vibrio cholerae

• Symptoms: “Rice-water” stool, dehydration, muscle cramps, sunken eyes, shock.

• Transmission: Contaminated water/food (esp. in underdeveloped countries).

• Prevention/Treatment: Safe water, sanitation; rapid rehydration therapy (oral/IV electrolytes).

what is Campylobacter jejuni

• symptoms

• transmission

• complication

• prevention/treatment

-Campylobacter jejuni

• Symptoms: Watery diarrhea, fever, vomiting, headache, abdominal pain.

• Transmission: Undercooked poultry, contaminated water, contact with pet feces.

• Complication: Guillain-Barré Syndrome (temporary paralysis).

• Prevention/Treatment: Proper cooking, hygiene; supportive care.

what is Clostridium difficile

• symptoms

• transmission

• prevention/treatment

-Clostridium difficile

• Symptoms: Antibiotic-associated colitis, abdominal pain, leukocytosis, watery diarrhea, rapid heart rate.

• Transmission: Healthcare-associated, spread patient-to-patient.

• Prevention/Treatment: Limit unnecessary antibiotics, hygiene; treat with metronidazole/vancomycin, probiotics, fecal transplant in severe cases.

what is E. coli O157:H7 (STEC)

• symptoms

• transmission

• prevention/treatment

-E. coli O157:H7 (STEC)

• Symptoms: Bloody diarrhea, fever; severe complication → HUS (kidney failure, blindness, seizures, stroke).

• Transmission: Contaminated food (esp. beef), cattle reservoir.

• Prevention/Treatment: Food safety, hygiene; supportive care (no antibiotics—can worsen HUS).

what is rotavirus

• symptoms

• transmission

• prevention/treatment

-Rotavirus

• Symptoms: Watery diarrhea, fever, vomiting, dehydration (esp. infants).

• Transmission: Fecal-oral via food, water, fomites.

• Prevention/Treatment: Vaccination, hygiene; supportive care with fluids.

what is norovirus

• symptoms

• transmission

• prevention/treatment

-Norovirus

• Symptoms: Profuse watery diarrhea, vomiting, lasts 3–5 days.

• Transmission: Fecal-oral, contaminated food/water.

• Prevention/Treatment: Hygiene, sanitation; supportive care.

List the 3 main causes for food poisoning,

• staphylococcus aureus

• bacillus cereus

• clostridium perfringens

what is staphylococcus aureus

• associated foods:

  • foods handled by people

  • saftey/sugary foods

• contamination: skin of food handler, unrefrigerated

• symptoms:

  • Cramping

  • nausea

  • vomiting

  • diarrhea (24 hrs)

what is bacillus cereus

• associated foods: Rice/pasta (emetic toxin), meats/veggies (diarrheal toxin)

• contamination: Spores survive cooking

• symptoms: Vomiting (rice), diarrhea (meats/veggies), lasts 24 hrs

what is clostridium perfringens

• associated foods: Undercooked beans/meats

• contamination: Heat-labile exotoxin, improper reheating

• symptoms: Abdominal pain, nausea, diarrhea (24 hrs)

list the best treatment for acute diarrhea.

• rehydration therapy (oral/IV electrolytes)

• hand hygiene and food safety: to prevent spread

• Avoid untreated water.

• Antibiotics only in severe bacterial cases

  • e.g., ciprofloxacin for Salmonella, vancomycin for C. difficile