- Detected with silver stain
- Motile rod
- Curved shape
- Contains multiple flagella
- Growth and culture:
- Complex growth requirements (special transport media required)
- Oxidase-positive, catalase-positive
- Urease-positive production: creates alkaline environment that permits survival of bacteria in acidic mucosa
Helicobacter genus contains about 35 species, with H. pylori being the most well known.
- Ubiquitous organism
- Humans are the primary reservoir.
- Acquired by:
- Oral–oral transmission: bacteria regurgitated with gastric content and temporarily colonize oral cavity
- Fecal–oral transmission: contaminated food and water supplies (poor sanitation)
- Person-to-person contact: clusters of infection noted in families
- Prevalence of infection:
- Low during childhood
- 40%–50% in older adults
- Highest in developing countries
Pathogenic features of Helicobacter pylori
- Urease-positive organism that produces ammonia:
- Neutralizes gastric acid → hypochloridia → stimulates gastrin production → increased gastric acid → mucosal damage
- Initial neutralization of gastric acid allows for mucosal colonization.
- Multiple flagella allow for rapid penetration of the mucosa.
- Contains mucinase and cytotoxins:
- Produces local tissue damage
- Acts as chemoattractant and activates host inflammatory response
- Effects: gastritis, development of ulcer(s), gastric carcinoma and gastric MALT lymphomas
- Increased production of stomach acid or damage of the gastric mucosal barrier → irritate the sensitive stomach lining → gastritis
- H. pylori infection is one of the most common etiologies.
- May be asymptomatic, or symptoms may include burning abdominal pain, dyspepsia, nausea, and vomiting
- Management of H. pylori infection: proton pump inhibitors with antibiotics
Gastric and duodenal ulcers
- Two most common types of peptic ulcers:
- Gastric ulcers:
- Located in the stomach
- Classically associated with pain that is worse when eating
- Duodenal ulcers:
- Located in the duodenum
- Typically have improvement in the level of pain while eating, followed by worsening of pain after the conclusion of the meal.
- Gastric ulcers:
- Most common etiologies include H. pylori infection and prolonged use of NSAIDs.
- H. pylori eradication (antibiotics and proton pump inhibitors)
- Eliminating risk factors
- Gastric cancer is the formation of malignant neoplasms of the stomach lining.
- Second most common cancer of the GI tract
- Chronic H. pylori infection: associated with an increased risk of gastric adenocarcinoma
Iron deficiency anemia and vitamin B12 deficiency
In H. pylori infection:
- ↓ Absorption of iron in the GI tract is observed, as uptake of iron requires an acidic environment.
- Chronic gastritis creates inflammatory damage to acid-producing cells → loss of acid production → reduced iron absorption
- Ongoing inflammation likewise leads to loss of parietal cells from which intrinsic factor is produced.
- Without intrinsic factor, vitamin B12 deficiency develops.
- Jensen P. J., Feldman M. (2020). Acute and chronic gastritis due to Helicobacter pylori. Retrieved 20 April 2021, from https://www.uptodate.com/contents/acute-and-chronic-gastritis-due-to-helicobacter-pylori
- Kusters J. G., van Vliet A. H. M., Kuipers E. J. (2006). Pathogenesis of Helicobacter pylori infection. Clinical Microbiology Reviews 19:449–490.
- Riedel S., Hobden J. A., Miller S., et al. (Eds.). (2019). Jawetz, Melnick, & Adelberg’s Medical Microbiology, 28th ed. McGraw-Hill.
- Lamont, J. T., Feldman M. (2020). Bacteriology and epidemiology of Helicobacter pylori infection. Retrieved 20 April 2021, from https://www.uptodate.com/contents/bacteriology-and-epidemiology-of-helicobacter-pylori-infection