What is Helicobacter pylori (H. pylori)?
Helicobacter pylori is a gram-negative, spiral-shaped bacterium that colonizes the human stomach and is one of the world's most common infectious pathogens, infecting approximately 50-60% of the global population. 1, 2
Bacteriology and Characteristics
H. pylori is a microaerophilic, flagellated bacterium that uniquely survives in the acidic gastric environment by producing high levels of urease enzyme, which neutralizes stomach acid by converting urea to ammonia. 1, 3
The bacterium resides on the luminal surface of gastric epithelial cells, where it establishes chronic infection that can persist for decades if untreated. 3, 1
All fresh isolates express significant urease activity, which is essential for both survival and pathogenesis of the organism. 1
Clinical Significance and Disease Associations
H. pylori infection is the most consistent risk factor for gastric cancer and represents the most promising target for reducing gastric cancer incidence worldwide. 3
The infection causes chronic gastritis in all colonized individuals, though most infected persons remain asymptomatic throughout their lives. 4, 2
Primary disease manifestations include chronic gastritis, peptic ulcer disease (both gastric and duodenal), gastric MALT lymphoma, and gastric adenocarcinoma. 5, 4
H. pylori is strongly associated with gastric malignancies, ranking as the third most common cause of global cancer-related mortality. 6, 3
Less than 1% of infected individuals develop gastric cancer, but the infection increases risk substantially through progression from chronic gastritis to atrophic gastritis, intestinal metaplasia, and eventually adenocarcinoma. 3
Recognized Extragastric Manifestations
Iron-deficiency anemia is a confirmed extragastric manifestation (Evidence level 1a, Grade A recommendation), occurring through chronic occult blood loss from gastritis or ulcers. 5, 3
Idiopathic thrombocytopenic purpura (ITP) is recognized with Evidence level 1b and Grade A recommendation. 5, 3
Vitamin B12 deficiency is associated with H. pylori infection (Evidence level 3b, Grade B recommendation). 5, 3
The infection affects bioavailability of certain medications including thyroxine and L-dopa. 5
Transmission and Epidemiology
The only significant reservoir of H. pylori appears to be humans themselves, with no substantial animal or environmental reservoir identified. 1, 7
Transmission occurs primarily through oral-oral or fecal-oral routes, with childhood representing the major period of acquisition in developing countries. 3, 7
In developing countries, 70-90% of the population carries H. pylori, while prevalence is lower in developed nations. 1
Iatrogenic transmission can occur through inadequately sterilized endoscopes and pH probes. 7
Diagnostic Approaches
Infection can be diagnosed by both invasive (requiring endoscopy and biopsy) and noninvasive techniques. 3
Invasive Tests (Require Endoscopy)
Histological examination with special stains (modified Giemsa, immunohistochemistry) has 90-95% sensitivity when examining at least two samples from both antrum and body. 3
Rapid urease test (RUT) detects H. pylori urease activity with 80-95% sensitivity and 95-100% specificity in pretreatment settings. 3
Culture allows antibiotic susceptibility testing but is technically demanding. 3
Noninvasive Tests
Urea breath test has 88-95% sensitivity and is the preferred method for confirming eradication. 5, 8
Monoclonal stool antigen test has 94% sensitivity. 5
Serology detects antibodies but cannot distinguish active from past infection and should never be used to confirm eradication. 8
Critical Clinical Pitfalls
H. pylori does not cause diarrhea as a primary manifestation—patients with both diarrhea and H. pylori likely have separate conditions requiring independent evaluation. 5
The infection does not typically cause fever unless advanced gastric cancer with complications is present. 5
Testing should be performed at least 4 weeks after completing therapy and at least 2 weeks after discontinuing PPIs to avoid false-negative results. 8