Notes on Infectious Diseases Affecting the Gastrointestinal Tract

The Human Digestive System

• Composed of two categories of organs:
  • Gastrointestinal (GI) tract
  • Accessory digestive organs

Microbiota of the Digestive System

• Millions of bacteria per ml of saliva
• Large numbers in large intestine
• 100 billion bacteria per gram of feces

Oral Cavity Diseases

Dental Caries (Tooth Decay)

• Caused by plaque build-up, dietary carbohydrates, acidogenic bacteria.
• Major contributor: Streptococcus mutans which ferments carbohydrates into acids.
• Prevention: Fluoride and dietary changes.

Stages of Tooth Decay

1. Healthy tooth with plaque
2. Decay in enamel
3. Advanced decay
4. Decay in dentin
5. Decay in pulp

Periodontal Disease

• Results from inflammation of periodontal tissue due to poor oral hygiene.
• Characterized by:
  • Ulcers and bleeding along the gingival margin.
  • Degradation of periodontal ligaments and bone.
  • Loosened or lost teeth.
• Stages:
  1. Healthy gingivae
  2. Gingivitis
  3. Periodontal pockets
  4. Periodontitis

Viral Infections

Mumps

• Spread easily through infected saliva.
• Characterized by enlarged jaw tissues due to swollen salivary glands.

Bacterial Diseases of the GI Tract

• Infection: Growth of a pathogen with incubation of 12 hours to 2 weeks, fever.
• Intoxication: Ingestion of toxins, symptoms appear 1 to 48 hours after ingestion, leading to gastroenteritis (diarrhea, dysentery).
• Treatment: Oral rehydration therapy.

Food and Water Contamination Routes

• Improper slaughtering of meat.
• Contaminated water used to wash fruits and vegetables.
• Fecal-oral route contamination from infected individuals.

Staphylococcal Food Poisoning

Pathogen: Staphylococcus aureus

• Symptoms: Nausea, vomiting, diarrhea.
• Mechanism:
  1. Cook protein food, killing bacteria.
  2. Contaminated by worker with Staphylococci.
  3. Food left at room temperature incubates toxins.
  4. Ingestion of toxin leads to intoxication 1-6 hours later.
• Prevention: Proper food handling, refrigeration, heating.

Major Bacterial Infections of the GI Tract

Vibrio Cholerae (Cholera)

• Caused by consumption of raw oysters and contaminated water.
• Requires large infectious dose to colonize intestines, often causing significant fluid loss.

Escherichia coli (E. coli) Gastroenteritis

• Pathogenic serotypes attach to intestinal cells, produce toxins.
• Symptoms: Watery diarrhea, dysentery, hemorrhagic colitis, hemolytic uremic syndrome.
• Diagnosis: Bacterial isolation and treatment with oral rehydration and antibiotics.

Shigellosis (Bacillary Dysentery)

• Pathogen: Shigella spp.
• Symptoms: Tissue damage and dysentery, causing severe diarrhea.
• Diagnosis and Treatment: Bacterial isolation, treatment with quinolones.

Salmonellosis

• Caused by Salmonella enterica, can lead to Typhoid Fever.
• Symptoms: Nausea, diarrhea, high fever.
• Treatment involves oral rehydration and antibiotics.

Helicobacter pylori and Gastric Ulcers

• Spread from person to person.
• Produces urease, which neutralizes stomach acid allowing survival.

Protozoan Diseases

Giardia lamblia

• Symptoms: Diarrhea, abdominal pain, greasy stools, usually no fever.
• Transmission: Ingesting cysts in contaminated food or water, infectious dose as few as 10-100 cysts.

Entamoeba histolytica

• Causes dysentery, abdominal pain, and weight loss.
• Can lead to severe complications like hemorrhage and appendicitis.

Helminthic Diseases (Worms)

Common Infections

• Nematodes: Enterobius vermicularis (pinworm).
• Cestodes: Taenia solium (tapeworm).
• Symptoms can include abdominal pain, diarrhea, and general distress.

Viral Diseases of the GI System

Viral Gastroenteritis

• Pathogens: Rotavirus and Norovirus.
• Symptoms: Vomiting, diarrhea, time-frame varies.

Hepatitis

• Inflammation of the liver that can stem from multiple viral infections.
• Types: A, B, C, D, E; each with varying transmission routes and chronic disease potential.

Mycotoxin Intoxications

Ergot Poisoning

• Caused by Claviceps purpurea affecting blood supply.

Aflatoxin Poisoning

• Caused by Aspergillus flavus, leading to liver cirrhosis and cancer.

Important Note

• The interplay of diet, hygiene, and microbial infections creates significant health implications in gastrointestinal diseases, necessitating understanding for prevention and treatment.