Raw or unpasteurized cows’ milk from U.S. retail stores can hold a huge amount of antimicrobial-resistant genes if left at room temperature, according to a new study.

«We don’t want to scare people, we want to educate them. If you want to keep drinking raw milk, keep it in your refrigerator to minimize the risk of it developing bacteria with antibiotic-resistant genes,» said lead author Jinxin Liu, a postdoctoral researcher in the Department of Food Science and Technology at UC Davis.

Lacking in Probiotics

An estimated 3 percent of the U.S. population consumes unpasteurized, or raw, milk, which has not been heated to kill pathogens and extend shelf life. Raw milk is often touted to consumers as having an abundant supply of probiotics, or healthy bacteria, compared with pasteurized milk. UC Davis researchers did not find that to be the case.

«Two things surprised us,» said Liu. «We didn’t find large quantities of beneficial bacteria in the raw milk samples, and if you leave raw milk at room temperature, it creates dramatically more antimicrobial-resistant genes than pasteurized milk.»

Bacteria with antimicrobial-resistant genes, if passed to a pathogen, have the potential to become «superbugs,» so that pharmaceuticals to treat infection or disease no longer work. Each year, almost 3 million people get an antibiotic-resistant infection, and more than 35,000 people die, according to the Centers for Disease Control.

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Materials provided by University of California — Davis. Original written by Amy Quinton. Note: Content may be edited for style and length.