Microbial Infections of the GI Tract

Question 1

What is Helicobacter pylori and what does it mainly cause?

Answer 1

• a gram-negative, spiral-shaped bacterium with a flagellum that colonizes the gastric epithelium
• main cause of chronic gastritis and is linked to peptic ulcer disease (PUD), gastric cancer, and MALT lymphoma.

Question 2

How common is H. pylori infection worldwide?

Answer 2

• About two-thirds of the world’s population harbors H. pylori
• prevalence varies with age, ethnicity, geography, and hygiene

Question 3

How is H. pylori transmitted?

Answer 3

Person-to-person transmission is common, especially oral-oral via saliva
- It’s often transmitted within families

Question 4

What is chronic gastritis and what can it lead to?

Answer 4

• A long-lasting inflammation of the stomach lining due to H. pylori that affects 80% of infected individuals, often without symptoms
• can lead to atrophic gastritis; thinning of the stomach lining

Question 5

What is Peptic Ulcer Disease (PUD)?

Answer 5

• an acid-induced lesion that affects 1 in 12 people in the U.S
• Risk is higher with NSAIDs and H. pylori coinfection

Question 6

What are the symptoms of PUD?

Answer 6

• Dull/burning pain in the stomach, nausea, vomiting, dark stools, weight loss, and bloating
• Perforation and sepsis can occur

Question 7

What conditions cause blood in stool?

Answer 7

GI conditions such as gastric ulcers, gastric cancer, ulcerative colitis, and infectious colitis

Question 8

How does H. pylori affect oral health?

Answer 8

may cause oral sores, tongue discoloration, low salivary pH, and increase the risk of oral infections and cancer

Question 9

What are the major virulence factors of H. pylori?

Answer 9

• Urease - for colonization
• motility - for entry and replication
• adhesion - to gastric epithelial cells
• LPS - activates inflammation
• VacA toxin - inhibits B/T cell proliferation
• Cagall - induces inflammation

Question 10

What is the role of the cag pathogenicity island?

Answer 10

It encodes a secretion system that delivers CagA into gastric cells, disrupting signaling and increasing cancer risk

Question 11

How is H. pylori linked to gastric cancer?

Answer 11

• causes about 90% of gastric cancers
• Gastric cancer is the 5th most common malignancy globally, especially in East Asia

Question 12

What are extra-gastric diseases linked to H. pylori?

Answer 12

• Iron-deficiency anemia
• vitamin B12 deficiency
• Idiopathic thrombocytopenic purpura (ITP)
• MALT lymphoma

Question 13

What is the inverse association of H. pylori infection?

Answer 13

Infection is linked to reduced risk of asthma, GERD, Barrett’s esophagus, and esophageal adenocarcinoma

Question 14

How is H. pylori diagnosed?

Answer 14

Diagnosis can be
- invasive: endoscopy with biopsy, rapid urease test, histology, culture
- noninvasive: urea breath test, stool antigen, serology
- All patients with peptic ulcers should be tested

Question 15

Which diagnostic test for H. pylori is not affected by PPI or antibiotic use?

Answer 15

Serologic testing is the only method not influenced by PPI or antibiotic use, but it cannot confirm cure

Question 16

What is the most accurate noninvasive test for confirming H. pylori cure?

Answer 16

The urea breath test and stool antigen testing both have over 94% sensitivity and specificity for confirming cure

Question 17

What is the first-line treatment for H. pylori in patients under 60 with dyspepsia?

Answer 17

Proton pump inhibitor (PPI), clarithromycin, and amoxicillin or metronidazole

Question 18

What therapy is used for H. pylori eradication in patients ≥60 or with alarm symptoms?

Answer 18

Bismuth quadruple therapy: PPI, bismuth, tetracycline, and metronidazole

Question 19

How should H. pylori treatment be approached in NSAID users?

Answer 19

Eradication of H. pylori or switching to NSAIDs like celecoxib can reduce peptic ulcer risk by half