Do acid blockers let microbes reach the colon?

Suppressing stomach acid while taking antibiotics may allow antibiotic-resistant bacteria to colonize the intestines, a study shows.

Researchers had previously linked stomach-acid suppression to pneumonia (SN: 10/30/04, p. 277). To test the effect of acid-suppressing drugs on bacteria passing through the stomach to the intestines, researchers gave mice two kinds of live, resistant bacteria via a feeding tube over 3 days. The animals then received an acid-suppressing drug, the antibiotic clindamycin, or both. The acid blocker was a proton-pump inhibitor called pantoprazole.

The bacteria colonized the intestines of the mice receiving both the acid blocker and the antibiotic more than three times as often as they did the intestines of mice receiving the antibiotic alone, says Curtis J. Donskey, an infectious-disease physician at the Louis Stokes Cleveland Veterans Affairs Medical Center in Ohio. He presented the findings at the 46th Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco last month.

Both factors--acid suppression and an antibiotic--were needed to make the intestines a welcoming home to the resistant microbes. By reducing acid concentrations in the animals' stomachs, pantoprazole provided "free passage through the stomach" for the microbes, Donskey says. In the intestines, the antibiotic suppressed natural, protective microbes, while the invading drug-resistant bacteria thrived, he says.