What is Helicobacter pylori (H. pylori)?

Helicobacter pylori (H. pylori)

Helicobacter pylori is a gram-negative, microaerophilic bacterium that colonizes the human stomach, causing chronic gastritis and significantly increasing the risk of peptic ulcer disease, gastric cancer, and gastric MALT lymphoma. 1, 2, 3

Epidemiology and Characteristics

• H. pylori infects approximately 50% of the world's population, making it the most common bacterial infection worldwide 2
• Prevalence varies by region:
  • 70-90% in developing countries
  • Lower rates in developed countries 4
• Transmission occurs through:
  • Oral-oral route
  • Fecal-oral route
  • Iatrogenic spread 4
• The human stomach is the primary reservoir for H. pylori 4

Pathophysiology and Disease Associations

Gastrointestinal Manifestations

• Chronic gastritis: H. pylori causes inflammation that can progress through a cascade of:
  • Chronic gastritis → Atrophic gastritis → Intestinal metaplasia → Dysplasia → Gastric cancer 5
• Peptic ulcer disease: H. pylori infection significantly increases risk of both gastric and duodenal ulcers 1
• Gastric cancer: H. pylori is present in 71-95% of all gastric cancers 5
• MALT lymphoma: H. pylori eradication is first-line treatment for low-grade gastric MALT lymphoma, with cure rates of 60-80% in early-stage disease 1

Extra-gastric Associations

• Hematologic disorders: Strong evidence links H. pylori to:
  • Iron-deficiency anemia (Evidence level 1a)
  • Idiopathic thrombocytopenic purpura (Evidence level 1b)
  • Vitamin B12 deficiency (Evidence level 3b) 1
• Drug absorption: H. pylori infection can impair absorption of certain medications including:
  • Thyroxine
  • L-dopa 1

Diagnosis

Multiple testing methods are available, divided into invasive (requiring endoscopy) and non-invasive approaches:

Invasive Tests (Endoscopy Required)

• Histology: 90-95% sensitivity, 95-98% specificity
  • Improved by taking multiple biopsies from both antrum and body
  • Various staining methods available (modified Giemsa recommended for routine use) 1
• Rapid urease test: 80-95% sensitivity, 95-100% specificity
  • Based on H. pylori's urease enzyme activity
  • Requires approximately 10⁴ organisms for positive result 1
• Culture and PCR of gastric tissue 1

Non-invasive Tests

• Urea breath tests: High sensitivity and specificity
• Serological tests: Detect antibodies to H. pylori
• Stool antigen tests 1, 4

Treatment Implications

• Eradication therapy is recommended for:

  • Peptic ulcer disease
  • Low-grade MALT lymphoma
  • Atrophic gastritis
  • After resection of early gastric cancer
  • Unexplained iron deficiency anemia, ITP, or vitamin B12 deficiency 1

• First-line treatment when antibiotic susceptibility is unknown:

  • Bismuth quadruple therapy (BQT) for 14 days 6

• Special considerations:

  • H. pylori eradication is mandatory before starting NSAID treatment in patients with history of peptic ulcers 1
  • Testing for H. pylori should be performed in aspirin users with history of gastroduodenal ulcers 1
  • Eradication of H. pylori in patients on long-term PPI therapy prevents progression to atrophic gastritis 1

Prevention of Gastric Cancer

• Early eradication of H. pylori is most effective before development of preneoplastic conditions 5
• Target populations for screening and eradication include:
  • First-degree relatives of gastric cancer patients
  • Patients with previous gastric neoplasia
  • Patients with atrophic gastritis or intestinal metaplasia
  • Individuals from high-risk regions 5

Challenges in Management

• Increasing antibiotic resistance is a major global challenge 1, 6
• Successful eradication is critical for reducing gastric cancer risk 1, 5
• Research continues for effective vaccines against H. pylori 1, 7

Key Pitfalls to Avoid

• Failing to test for H. pylori in patients with unexplained iron deficiency anemia, ITP, or vitamin B12 deficiency
• Not eradicating H. pylori before starting long-term NSAID therapy in patients with history of peptic ulcers
• Inadequate follow-up after treatment to confirm eradication
• Using clarithromycin-based regimens in areas with high clarithromycin resistance without susceptibility testing