Helicobacter pylori (General properties, pathogenesis, lab diagnosis and treatment)

General properties:

  • Man appears to be the sole reservoir of H.pylori and it colonizes the gastric mucosa of almost one in four of the adult population
  • It is found to be associated with peptic ulceration.
  • It is transmitted from person to person presumably by the oral-oral route or possibly faecal-oral  route.
  • Nosocomial infection from inadequately sterilized endoscopes are  also reported.
  • H.pylori are spiral or curved bacilli (2-4×0.5-1µm).
  • Gram negative, non-sporing rods which may be spheroid or coccoid on prolonged culture.
  • Usually motile with multiple monopolar sheathed flagella (other Helicobacter have multiple bipolar sheathed flagella).
  • Inhabit the gastro-intestinal tract of mammals and birds
  • Gastric helicobacters (pylori, H.heilmannii, H.mustelae) primarily inhabit the stomach whereas enteric helicobacters (H.canis, H.cinaedi, H.pullorum etc.) inhabit the lower GI tract (small intestine, colon, rectum etc.) and hepatobiliary tract.

Culture characteristics:

  • Strictly micro-aerophilic (requires 5-10% CO2 and humidity for growth)
  • Grow on Campylobacter media at 370C in 3-5 days (but not at 430C).
  • Colonies are circular, convex and translucent and less than 2mm in diameter.

Biochemical activity:

  • Produces oxidase, catalase, DNA-ase, alkaline phosphatase and glutamyl aminopeptidase.
  • H.pylori also produces urease in significant amount (about 100 times more powerful than that of Proteus vulgaris).
  • Turns Christensens’s urea broth to pink color in a few minutes.
  • Helicobacters inhabiting the stomach produce urease unlike in the helicobacters found in the intestines.

Virulence factors:

  • H.pylori possesses multiple potential virulence factors
    1. Cytotoxin and other enzymes:
      • It is the most important virulent factor and produces vacuolating cytotoxin.
      • This cytotoxin induces localized cell damage together with urease, urease by-products, mucinase and lipopolysaccharide leading to inflammatory response.
    2. Urease activity: Ammonia produced from bacterial urease activity neutralizes gastric acidity facilitating initial colonization of the organism.
    3. Motility: The actively motile bacteria can easily pass through the gastric mucosa and adhere to the epithelial cells, after colonization.
    4. Autoimmune response: The bacterial antigens cross react with antral gastric antigens stimulating an autoimmune response.
    5. Protease: Protease produced by the organism degrades gastric mucosa.
    6. H.pylori infected patients show hypergastinaemia that upsets gastrin-HCl homeostasis.

Pathogenesis and clinical syndrome:

  • In man, it is believed to be transmitted from person to person (cases clustered in families).
  • Gastric antrum is the most favoured site although any part of stomach may become colonized.
  • The bacteria are present in large number in the gastric mucosa and deep in gastric glands.
  • There is a superficial infiltration of polymorphonuclear leucocytes (characteristic of superficial or chronic gastritis).
  • H.pylori has been detected from 77% and 66% cases of duodenal and gastric ulcers respectively, collectively known as peptic ulcers.
  • H.pylori is associated with chronic active or type B gastritis.
  • Aetiological agent in most cases of gastric and duodenal ulcers.
  • Long standing infections are associated with risk of developing gastric adenocarcinomas.

Laboratory diagnosis:

  • The gold standard approach to the diagnosis of H.pylori infection involves gastric intubation, endoscopy and biopsy.
  • Endoscopy reveals the pathological changes.
  • Biopsy provides mucosa to be used for detection of H.pylori by:

a. Invasive tests:

  • Rapid urease test:
    • A portion of biopsied tissue is placed into a small quantity of urea-containing broth (added with a pH indicator).
    • If H.pylori present, urease produced by it will breakdown urea and generate ammonia gas within few minutes to few hours (to change the color).
  • Gram/Giemsa stain analysis (Microscopy):
    • Histological sections and impression smears of the gastric mucosa are prepared by Gram or Giemsa stain and Warthin-Starry silver stain and observed under the microscope.
  • Culture:
    • Specimen can be cultured in selective media used for Camplylobacter within 2 hours of collection, which is not normally done for diagnosis.
  • Molecular tests: DNA hybridization with PCR have been developed but not yet widely employed.

b. Non-invasive tests:

  • Serology: ELISA technique can be used to detect the humoral antibody produced against H.pylori.
  • Urea broth test:
  • Urine test:
  • Histological examination: It is more sensitive than culture.
  • Antigen detection: Direct faecal antigen detection can be done using commercial kit available.


  • Treatment is done with combination of antacids and one of two broad spectrum antibiotics.
    1. Antacids: Omeprazole (preferred for 2-3 wks)
    2. Antibiotics: Metronidazole, Clarithromycin, tetracycline (usually doxycycline), Amoxycillin
    3. Bismuth subsalicylate-metronidazole-tetracycline for 14 days (triple therapy).

*The most successful treatment regimen include the use of triple drug therapy (metronidazole-omeprazole-clarithromycini) for 7 to 14 days that eliminates H.pylori infection in over 90% infection.

Helicobacter pylori (General properties, pathogenesis, lab diagnosis and treatment)