Digestive System Infections Overview

Digestive System Infections - Learning Outcomes

• Describe the functions of the upper and lower digestive tract.
• Compare dental caries, periodontal disease, and acute necrotizing ulcerative gingivitis.
• Describe Helicobacter pylori gastritis and its relation to gastric ulcers and stomach cancer.
• Compare and contrast herpes simplex (cold sores) and mumps.
• Compare and contrast cholera, shigellosis, E. coli gastroenteritis, and Clostridium difficile infection.
• Identify characteristics of diseases caused by rotaviruses and noroviruses.
• Understand the transmission and characteristics of giardiasis.

Digestive System Anatomy and Function

• The main function is converting food into usable energy and raw materials for growth.
• Two main components are the digestive tract and accessory organs.
• The digestive tract is one of the body's major boundaries with the environment.
• It has a rich microbial community; however, balance is delicate.

Infectious Diseases of the Upper Digestive System

• Bacterial diseases of the mouth: Dental caries, periodontal disease, acute necrotizing ulcerative gingivitis.
• Bacterial diseases of the stomach: Helicobacter pylori gastritis.
• Viral diseases of the mouth: Oral herpes, mumps.

Infectious Diseases of the Lower Digestive System

• Bacterial diseases: Cholera, shigellosis, E. coli gastroenteritis, Salmonella gastroenteritis, Enteric fever (typhoid and paratyphoid), Campylobacteriosis, Clostridium difficile infection.
• Viral diseases: Rotavirus, norovirus, Hepatitis.
• Protozoan diseases: Giardiasis, Cryptosporidiosis, Cyclospora, Amebiasis.

Dental Caries

• A chronic biofilm-mediated disease damaging tooth enamel.
• Causative agent: Streptococcus mutans (or related species).
• Pathogenicity: Bacteria attach, ferment sugars, produce acids leading to tooth decay.
• Treatment: Restoration (drilling and filling cavities) and control through restricting sucrose.
• Symptoms: Initially tooth sensitivity, progressing to discoloration and severe throbbing pain.

Periodontal Disease

• A bacterial disease of the gums.
• Pathogenicity: Plaque accumulation near the gum line triggers inflammation and tissue damage.
• Signs and Symptoms: Tender gums that bleed easily, bad breath; red, bleeding gums; bone loss (loosened teeth).
• Causative Agent: Typically anaerobic bacteria, different from plaque associated with dental caries.
• Treatment: Cleaning inflamed gums and removing plaque. In severe cases minor surgery.

Acute Necrotizing Ulcerative Gingivitis (ANUG)

• A severe bacterial infection of the gums.
• Pathogenicity: Spirochetes, other anaerobes invade tissue, causing necrosis and ulcerations.
• Epidemiology: Called "trench mouth" (common in soldiers).
• Symptoms: Bleeding, painful ulcers, sometimes necrotic lesions, bad breath, sometimes metallic taste. Fever, malaise and swollen lymph nodes.
• Causative Agent: Polymicrobial infections (like periodontal disease), associated with heavy growth of anaerobes at the gum line.
• Treatment: Mouthwash, pain medication, necrotic tissue debridement, antibiotics (if systemic symptoms), daily brushing, flossing, regular professional cleaning.

Helicobacter pylori Gastritis

• Causative agent: short, curved, Gram-negative, microaerophilic bacterium with multiple polar flagella.
• Epidemiology: Present in many people; 35% of adults in the U.S. are infected, incidence rising with age.
• Symptoms: Often asymptomatic, but can cause belching, bloating, loss of appetite, nausea, vomiting. Peptic ulcers (abdominal pain and tenderness, bleeding in stool).
• Pathogenesis: Produces urease that neutralizes stomach acidity.
• Treatment: combination of antibiotics and medication inhibiting stomach acid production to clear gastritis and heal ulcers.

Viral Diseases of the Digestive Tract

• Viral diseases of the mouth: Herpes simplex viruses (HSV) and mumps.
• Viral diseases of the intestinal tract: Rotavirus, norovirus (viral gastroenteritis).
• Viral diseases of the liver: Hepatitis A, B, C, D, E.

Protozoan Diseases of the Lower Digestive System

• Giardiasis. Cryptosporidiosis, Cyclosporiasis, and Amebiasis.

Cholera

• Causative agent: Vibrio cholera (curved Gram-negative rod).
• Signs/Symptoms: Abrupt onset of severe watery diarrhea, vomiting and muscle cramps.
• Pathogenesis: Bacteria adhere to intestinal cells, secrete toxin leading to severe fluid loss.
• Epidemiology: Primarily in regions with inadequate sanitation and contaminated water.
• Treatment/Prevention: Rapid fluid and electrolyte replacement, sanitation, and safe water supply crucial.

Shigellosis

• Causative agent: Shigella bacteria (Gram-negative rods).
• Symptoms/Dysentery: Bloody diarrhea, abdominal cramps, fever and other symptoms.
• Pathogenesis: Bacteria enter intestinal cells, multiply and cause cell death, intense inflammation. "actin tail" to spread to other cells.
• Epidemiology: Primarily in overcrowded areas with contaminated food or water.
• Treatment/Prevention: Antimicrobial medications (in severe cases), good sanitation crucial.

Escherichia coli Gastroenteritis

• Causative agent: Escherichia coli (Gram-negative rod).
• Symptoms: Varying depending on the strain but often watery diarrhea.
• Pathogenesis: Most strains are harmless but some produce virulence factors. Can produce toxins. May attach or invade intestinal epithelial cells.
• Epidemiology: Frequently foodborne; contaminated water/foods (unpasteurized milk, contaminated beef).
• Treatment/Prevention: Typically self-limiting. Fluid replacement and good sanitation/food handling.

Giardiasis

• Causative agent: Giardia lamblia (flagellated pear-shaped protozoan).
• Symptoms: Mild to severe diarrhea, abdominal cramps, weight loss, nausea, vomiting, and intestinal gas.
• Pathogenesis: Ingested cysts develop into trophozoites in the small intestine impairing nutrient absorption and causing symptoms.
• Epidemiology: Fecal-oral transmission via contaminated water/food/person-to-person.
• Treatment/Prevention: Antimicrobial medications, clean water with proper filtering/boiling.

Review Questions

• Questions related to the identifying the body parts of the digestive system, the mechanisms behind diseases, pathogenesis, epidemiology, treatment, and prevention are included in the document. These are specific disease questions.