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Questions and Answers
What organism is most likely to be visualized on histologic evaluation of a gastric biopsy specimen?
Helicobacter pylori
Besides microscopy, what other test provides rapid detection of Helicobacter pylori?
Urease test
What two factors facilitate Helicobacter pylori's ability to colonize the stomach?
What is the morphology of Helicobacter pylori?
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H. pylori infection is present in 70%-90% of persons with duodenal ulcers.
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What laboratory test is used to identify the biochemical characteristics of Helicobacter species?
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Study Notes
Case Presentation
- A 48-year-old man presents with a 2-month history of upper abdominal pain, associated with nausea.
- Symptoms are exacerbated by coffee, soda, or alcohol consumption.
- Antacids provide temporary relief.
- Patient has a history of smoking for 20 years, occasional alcohol use, and frequent NSAID use.
- Physical examination and vital signs are normal.
- Abdominal examination reveals epigastric tenderness.
- CBC shows mild hypochromic, microcytic anemia.
- Upper GI endoscopy reveals diffuse gastritis and a gastric ulcer.
Helicobacter pylori
- Helicobacter pylori is a spiral, Gram-negative bacterium, measuring 3 x 0.5-0.9 µm.
- Possesses a single polar tuft of flagella for motility.
- Requires microaerophilic conditions for growth: 10% CO2, 5% O2, 85% N2.
- Does not grow anaerobically.
- Grows optimally at 37°C.
- Requires high humidity and 5-10% CO2 for growth.
- Isolates can be grown on specialized media, including Butzler's medium, Skirrow's medium (similar to chocolate agar), and other media containing antibiotics like cefazolin, bacitracin, nalidixic acid, and amphotericin.
- Colonies are typically small, translucent, gray, 1-2 mm in diameter, and weakly β-hemolytic.
- Most H. pylori strains take 3-7 days to grow in culture.
Biochemical Characteristics of Helicobacter pylori
- Positive for catalase and oxidase.
- Weakly positive for H2S production.
- Positive for urease activity.
- Susceptible to cephalotin (30 µg) and resistant to nalidixic acid (30 µg).
H. pylori Pathogenesis
- Considered the primary risk factor for peptic ulceration, gastric adenocarcinoma, and gastric MALT (mucosa-associated lymphoid tissue) lymphoma.
- Colonizes the stomach of approximately 50% of the global population.
- Infection is present in 70%-90% of individuals with duodenal ulcers and approximately 70% of those with gastric ulcers.
- Antibiotic treatment of H. pylori infection promotes healing of ulcers and reduces their recurrence.
Virulence Factors
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H. pylori has several virulence factors that facilitate colonization of the stomach:
- Acid-inhibitory protein: Blocks acid production.
- Urease: Neutralizes stomach acid by producing ammonia.
Diagnosis
- Microscopy: Visualizing H. pylori on a gastric biopsy specimen.
- Rapid urease test: Detect urease activity, indicating H. pylori presence.
Other Helicobacter Species Associated with Human Disease
- H. heilmannii: Associated with gastritis.
- H. cinaedi and H. fennelliae: Associated with gastroenteritis, septicemia, and proctocolitis.
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Description
Explore the clinical presentation and diagnosis of a gastric ulcer caused by Helicobacter pylori in this informative quiz. The case details involve a middle-aged man experiencing upper abdominal pain exacerbated by certain foods and beverages. Test your knowledge on H. pylori characteristics and its implications in gastrointestinal health.
