Helicobacter pylori is a bacteria found only in the gastrointestinal tracts of humans and closely related primates. When I say in the stomach, I mean in the stomach. H. pylori burrows into the mucous coating your stomach and touches the epithelial cells.
Fun fact: in the presence of acid, the gastic mucous hardens in an almost solid shell, which H. pylori cannot penetrate. It works around this by preferentially seeking out high pH areas within the stomach, and by releasing ammonia to neutralize the acid. So H. pylori can be both a cause and consequence of low gastic acid. This fits in with my general view on physical processes and life in general: everything either stops on its own or is part of a self-reinforcing loop.
H. pylori is most famous for causing gastric ulcers. This was especially important because it was a beautiful example of something previously considered a “lifestyle” disease having a distinct, exogenous cause. I use it as a go-to example of medical science not respecting its limitations. Alas, my example was itself oversimplified not respecting its limitations: only 60% of ulcers are caused by H. pylori. Half the remainder (20% of the total) are caused by NSAIDs, and other half are caused by “Other”. I do wonder how they’re determining presence. I had two different H. pylori tests done (both on a stool sample), and only one cam back positive. Putting this on the list to investigate further.
The coolest cause I found was Zollinger-Ellison syndrome, in which tumors made of gastrin-secreting cells cause an overproduction of gastrin. This is how I learned they can test for gastrin levels directly, which I am curious about given its likely contribution to my digestive issues.
H. pylori also raises your lifetime risk of stomach cancer, but only by 0.6 percentage points.
Despite that scary sounding list, 80-85% of infected people show no symptoms. That may be due to genetic differences in the bacteria infecting them. There is also research suggests that H. pylori is, or at least was, mutualistic with humans, and that lack of it increases a person’s risk for gastrointestinal issues. If that is true, the question becomes: is this pathogenicity -causing-strain new, or has it always been present, and only recently became dangerous?
H. pylori treatment protocols commonly include proton pump inhibitors , which make the stomach less acidic. This struck me as a rather interesting choice for fighting a pathogen that prefers high-pH environments: apparently the goal is to coax the bacteria into areas more easily reached by antibiotics.
Confession: I thought that the stomach had a thriving bacterial ecosystem, of which H. pylori was an unwanted guest. It turns out I was thinking of the large intestine. Almost nothing survives in the stomach, and of the things that do, it’s unclear that establish permanent residence, much less are mutually beneficial.