Acid suppressants inhibit the secretion of stomach acid and alter the composition of the intestinal microbiome. A systematic review and meta-analysis were conducted to determine whether use of these widely used agents is associated with an increased risk of intestinal colonization with multidrug-resistant microorganisms.

Of 26 clinical and observational studies that met the selection criteria, 12 studies including 22,305 participants provided adjusted risk estimates. Approximately 38% of participants in these studies used acid suppressants. Acid suppression was associated with increased odds of intestinal carriage of both multidrug-resistant microorganisms of the Enterobacterales order and vancomycin-resistant enterococci. The association was found in a primary analysis of the 12 studies that provided adjusted odds ratios as well as a secondary analysis of all 26 studies.

The authors note that while the association between acid suppression and increased risk of multidrug-resistant microorganism colonization is biologically plausible, the results should be regarded with caution, because observational studies can't prove causation. They advise that acid suppressants should be used when needed, but unnecessary use should be avoided.