Helicobacter pylori

Helicobacter pylori

Organism

Helicobacter is a gram-negative spiral-shaped bacterium with polar flagella.
Microaerophilic (def).

Habitat

The human gastrointestinal tract is the primary source.

Source

Person-to-person spread by the fecal-oral route.

Epidemiology

In developing countries, 70%-90% of individuals are colonized by the age of 10; in developed countries, colonization is low during children but increases to around 45% in older adults.
Between 70% and 90% of people with gastritis, peptic ulcers, or doedonal ulcers are infected with H. pylori.

Clinical Disease

Appears as gastritis (def), peptic ulcers (def), gastric adenocarcinoma (def), and certain B-cell lymphomas (def).
Chronic gastritis is a risk factor for gastric carcinoma.

Pathogenesis

Flagella enable the bacterium to penetrate the gastric mucous layer (see Fig. 1).
Urease can neutralize gastric acid, chemotactically attract phagocytes to the infected site, and stimulate the production of inflammatory cytokines (def).
Acid-inhibitory protein blocks acid secretion from parietal cells in the stomach.
Various cell wall adhesins (def) enable H. pylori to adhere to host gastrointestinal epithelial cells (see Fig. 1).
Mucinase and phospholipase disrupt the gastric mucosa.
Superoxide dismutase and catalase prevent phagocytic killing by neutralizing toxic oxygen molecules.
Vacuolating cytotoxin stimulates the migration of neutrophils into mucosa (see Fig. 1).

Treatment

Various treatment regimes are available including a combination of tetracycline, metronidazole, bismuth, and omeprazole* (see antibiotic table).

*Drugs may change with time.

For a more detailed article on Helicobacter pylori infections, see Helicobacter pylori Infection, by Luigi Santacroce, MD, Assistant Professor, Department of Dentistry and Surgery, Section of General Surgery, Medical and Dentistry School, State University at Bari, Italy and Giuseppe Miragliotta, MD, Chairman, Professor, Section of Microbiology, University Hospital of Bari, Italy; Manoop S Bhutani, MD, Associate Professor of Medicine, Division of Gastroenterology, University of Texas Medical Branch at Galveston