H. pylori Virulence Factors: Treat or Watch

A large share of the world carries H. pylori and most of them will never have a problem from it. So a positive result is the beginning of the question, not the answer — and the virulence factors underneath it are where the answer actually lives.

Presence is not the question

H. pylori is one of the most widely carried organisms in human beings. Estimates vary by region and by population, but across the world it is carried by a very large number of people, most of whom never develop an ulcer, a cancer or a symptom.

That single fact should change how a positive reads. If carriage were sufficient to cause disease, the disease would be far more common than it is.

There is also a genuine argument — not a fringe one — that the relationship is more complicated than purely adversarial. Declining H. pylori prevalence in developed countries has coincided with rising rates of reflux disease, Barrett's oesophagus and oesophageal adenocarcinoma, and there is an active literature examining whether carriage is protective against some of those outcomes. That does not mean it is harmless. It means the organism is not a simple villain, and reflexive eradication of every positive is not obviously correct.

So the useful question is never is it there. It is is this strain, in this patient, doing harm — and the GI Map gives you more to answer that with than most practitioners use.

What the virulence factors tell you

Strains differ, and the genes they carry are what separate a quiet coloniser from one causing damage.

Factor	What it does
cagA	The best-studied of them. Injects a protein into gastric epithelial cells, driving inflammation. Associated with peptic ulcer disease and with gastric cancer risk
vacA	A vacuolating toxin that damages epithelial cells. Different alleles carry different pathogenic weight
babA	An adhesin. Binds the organism to gastric epithelium, raising colonisation density and, with cagA, clinical significance
dupA	Associated with duodenal ulceration
iceA, oipA, virB, hopQ	Further markers of inflammatory and adhesive capacity; weigh them as part of the picture rather than individually

The practical reading:

Positive with no virulence factors, in an asymptomatic patient, is a colonised patient. That is information about terrain, not a treatment plan.

Positive with cagA, vacA or several factors together, in a symptomatic patient, is a different proposition entirely and deserves acting on.

The report gives you both pieces. Reading only the top line of it — positive, negative — throws away the half that decides what you do.

The acid paradox

Here is the part that explains why two patients with the same organism present as opposites.

Where the colonisation sits in the stomach changes what it does to acid.

Antral-predominant. The antrum is where gastrin-producing cells live. Inflammation there disrupts the local feedback, gastrin rises, and acid output goes up. These are the patients with duodenal ulcer and a high-acid picture.

Corpus-predominant. The corpus is where the acid-producing parietal cells live. Inflammation there damages them, and over time can progress to atrophy. Acid output goes down. This is the pattern associated with gastric ulcer and, over years, with gastric cancer risk.

So H. pylori can raise acid or lower it, and the patient with a positive result and low stomach acid is not a contradiction — they are a different distribution of the same infection.

This matters for a specific and common mistake. If you reach for betaine HCl in a patient with active H. pylori and gastritis, you are adding acid to inflamed, possibly eroded tissue. Establish what you are dealing with before supporting acid in anyone with a positive result or symptoms suggesting active gastritis.

Treat, watch, or refer

Refer, before anything else, if there are alarm features. Unintentional weight loss, difficulty swallowing, persistent vomiting, GI bleeding or anaemia, a palpable mass, new symptoms in an older patient, or a family history of gastric cancer. These need medical assessment and often endoscopy, and a stool test is not the instrument for them.

Act where the organism is present with meaningful virulence factors in a symptomatic patient, or where there is a history of ulcer disease, or a family history of gastric cancer. Eradication is a medical decision and standard regimens exist for a reason — work with the patient's physician rather than around them. Where your role is supportive, it is supportive of a process someone else is directing.

Watch, and work on terrain, where a positive sits with no virulence factors in a patient who is asymptomatic or whose symptoms have a better explanation elsewhere on the report. Pursuing eradication here can cost you more than it returns — antimicrobial exposure, disruption of the rest of the microbiome, and a patient treated for something that was not their problem.

The judgement being asked for is not can I clear this. It is should this be cleared, and by whom.

Testing pitfalls

Most false negatives are produced by the test conditions rather than by the organism being absent.

Acid suppression. PPIs suppress H. pylori enough to turn stool antigen and urea breath tests negative in a patient who is carrying it. They generally need to be stopped roughly two weeks before testing — which is awkward, because the patient on a PPI is exactly the patient you want to test. Plan the sequence rather than discovering it afterwards.

Recent antimicrobials. Antibiotics and bismuth do the same thing. A course finished recently makes a negative uninterpretable.

Serology cannot date an infection. Antibodies persist after successful eradication, sometimes for years. A positive serology tells you the patient met the organism at some point in their life, not that they have it now. It is the wrong test for the question nearly every time it gets used for it.

Retesting too early. Confirming eradication requires a gap after treatment finishes, or you are testing the treatment rather than the outcome.

If you take one thing: ask what the patient has taken in the last month before you believe a negative.

Where to start

1. Screen for alarm features first. If any are present, that decides the next step and it is not yours to make.

2. Read the virulence factors, not just the positive. They are the difference between a coloniser and a problem.

3. Work out what it is doing to acid. Antral or corpus, high or low — and do not support acid in active gastritis.

4. Check what they have taken. PPIs and recent antimicrobials make a negative meaningless.

5. Decide treat, watch or refer — and if treat, do it alongside the prescriber rather than in parallel to them.

6. Look at the rest of the report. H. pylori rarely arrives alone, and the overgrowth or low elastase sitting beneath it may be doing more of the symptom work than the organism everyone is focused on.

The GHT Academy Gut Guide covers H. pylori in full — virulence factors marker by marker, protocols with specific supplements, dosing and timelines, and video walkthroughs of real-time H. pylori and GI Map interpretation. It is the reference I built for my own team.