How H. Pylori Survives in Your Stomach Acid
Your stomach produces hydrochloric acid strong enough to dissolve metal — pH 1 to 3. For decades, scientists believed no bacteria could survive there. H. pylori proved them wrong. It produces urease, an enzyme converting urea into ammonia that creates a protective alkaline cloud around itself. It then burrows into the mucus layer protecting the stomach lining, where pH is more neutral. Once embedded, it can persist for decades.
H. pylori infects roughly half the world's population — making it one of the most common infections on earth. Spread person-to-person (oral-oral or fecal-oral routes), usually in childhood within families. Prevalence exceeds 80 percent in developing countries with crowded conditions and limited sanitation. In developed countries: 20-40 percent.
What It Does to Your Stomach
H. pylori triggers chronic inflammation (chronic gastritis). In most infected people — 80-90 percent — this inflammation is mild and causes no symptoms. The bacteria and immune system reach a stalemate that persists for life.
In 10-20 percent, chronic inflammation leads to peptic ulcers — open sores in the stomach or duodenum. Symptoms: burning stomach pain when the stomach is empty, bloating, nausea, loss of appetite, unintentional weight loss. In 1-2 percent, decades of inflammation can lead to stomach cancer (gastric adenocarcinoma) or MALT lymphoma. H. pylori is classified as a Group 1 carcinogen by the WHO. A study found that eradicating the infection reduces cancer risk, particularly when treated before precancerous changes develop.
The discovery that a bacterium causes ulcers — by Barry Marshall and Robin Warren, who won the Nobel Prize in 2005 — revolutionized gastroenterology. Before their work, ulcers were blamed on stress and treated with antacids indefinitely rather than being cured with antibiotics.
Testing and Treatment
Testing: Urea breath test (most common non-invasive — drink carbon-labeled urea, H. pylori's urease breaks it down, labeled CO2 measured in breath). Stool antigen test (equally reliable). Blood antibody tests detect prior exposure but cannot distinguish active from past infection. Important: PPIs, bismuth, and antibiotics must be stopped 2-4 weeks before breath or stool testing (they cause false negatives).
Treatment: Triple therapy — PPI (omeprazole) + 2 antibiotics (typically clarithromycin + amoxicillin) for 14 days. Quadruple therapy when resistance is suspected — PPI + bismuth + metronidazole + tetracycline for 14 days. Antibiotic resistance (particularly clarithromycin >15 percent in many regions) is a growing problem.
Treatment adherence is critical — missing doses promotes resistance and treatment failure. Common side effects: metallic taste, nausea, diarrhea, darkened stools from bismuth. After completing treatment, retest in 4-6 weeks with breath or stool test (not blood — antibodies persist long after clearance). First-treatment success rate: 70-85 percent. If first treatment fails, a different antibiotic combination is used.
Who Should Be Tested
Current guidelines recommend testing if you have: active peptic ulcer disease, history of peptic ulcers, uninvestigated persistent upper stomach discomfort, MALT lymphoma, family history of stomach cancer, or if starting long-term NSAID or aspirin therapy. A study in Gut found that test-and-treat strategies for H. pylori in dyspeptic patients were more cost-effective than empiric acid suppression.
Population screening is debated. In high stomach cancer regions, screening and treating all adults may reduce cancer. In lower-risk populations, benefit must be weighed against antibiotic resistance. If you have risk factors or persistent digestive symptoms, discuss testing with your doctor.
