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Stomach bugs’ bad acid trip: Scientists find tools H. pylori uses to sense organ’s wicked secretions

The stomach is one of the human body's most extreme environments, pumping out about 1.5 liters of strong acid daily. So it's no wonder that omeprazole (Prilosec) and similar compounds known as proton-pump inhibitors (or PPIs), which block stomach-acid production, rank among the world's most commonly used drugs. Stanford microbiologist Manuel Amieva, MD, tells me annual worldwide PPI sales exceed $13 billion.

Amieva pays attention to this sort of thing because he studies Helicobacter pylori -- a corkscrew-shaped bacterium that happily inhabits half of all human stomachs on Earth. While H. pylori can cause stomach ulcers and, less frequently, highly lethal stomach cancer, it co-exists peacefully with four out of five infected people, causing no symptoms at all.

You have to wonder: How does this bug manage to survive, hanging out in a churning vat of hydrochloric acid that kills most microorganisms and dissolves pretty much everything we normally eat except for corn kernels?  Amieva and his team have busted their share of laboratory glassware puzzling this out, along with determining how H. pylori makes trouble when it does make trouble.

Truth be told, H. pylori hates acid and constantly swims away from it, hiding out by burrowing into the mucus lining that protects the stomach's surface. Some swim farther, through fissures and channels, eventually snuggling deep within secretory glands dotting the stomach. It's in these glands that H. pylori may pose the most cancer risk, because they induce inflammation and emit toxins that can irritate stomach stem cells residing there, launching them into rounds of overdrive replication.

In a new study in PLoS Pathogens, Amieva and his colleagues identified receptors H. pylori uses to detect and flee the detested acidity of its chosen sanctuary. They also observed that blocking acid production in the stomach of experimental animals with omeprazole (now available over the counter) allowed H. pylori to spread more freely within the stomach, extending its range to infect more glands in regions of the organ that are ordinarily bacteria-free.

That's somewhat disconcerting, as it suggests that PPI use could inadvertently increase stomach-cancer risk in H. pylori-infected people -- although there's no solid direct evidence to that effect yet. That worry is amplified -- at least for me -- by findings in a 2015 study that tied PPI use to elevated heart-attach risk. Maybe it's time to put that over-the-counter rating under the microscope.

On a lighter note, you can watch the video displayed here and judge for yourself how H. pylori feel about stomach acid. The almost-linear object that suddenly appears at the left is a microscopic needle the researchers used to drip acid into lab dishes in which unsuspecting H. pylori had been gaily frolicking. The clip is, in fact, a composite of two superimposed movies: One shows the movements of green bacteria (they aren't usually green, it's just stage makeup) that get exposed to a relatively high concentration of acid, while the other captures the peregrinations of red ones (same species, different dye) that get exposed to a lower acid concentration. The dramatic closing shot represents one-second segments of each movie compressed into a single image and overlaid on one another.

Previously: When bacteria swarm: H. pylori home in on our stomach cells, Widely prescribed heartburn drugs may heighten heart attack risk and Ulcer-causing bacteria manipulate stomach stem cells to their own ends
Video courtesy of Manuel Amieva

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