Raw milk can do more harm than good

Raw or unpasteurized cow’s milk from US retail stores may contain a large number of antimicrobial-resistant genes if left at room temperature, according to a new study by researchers at the University of California, Davis. The study also found that bacteria harboring antimicrobial-resistant genes can transfer them to other bacteria, which could spread resistance if consumed. The study was published in the journal. Microbiome.

“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 developing bacteria with antibiotic-resistant genes,” said lead author Jinxin Liu, a postdoctoral researcher at the Department of Food Science and Technology at UC Davis.

Lack of probiotics

An estimated 3 percent of the US population consumes unpasteurized or raw milk, which has not been heated to kill pathogens and extend shelf life. Raw milk is often touted as a plentiful supply of healthy bacteria or probiotics by consumers compared to pasteurized milk. UC Davis investigators did not find that to be the case.

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

Bacteria with antimicrobial resistant genes, if passed on to a pathogen, have the potential to become “superbugs,” so pharmaceuticals to treat infections or diseases no longer work. Each year, nearly 3 million people contract an antibiotic-resistant infection, and more than 35,000 people die, according to the Centers for Disease Control.

The longer you sit, the worse it gets

UC Davis researchers analyzed more than 2,000 samples of retail milk from five states, including raw milk and pasteurized milk in different ways. The study found that raw milk had the highest prevalence of antibiotic-resistant microbes when left at room temperature.

“Our study shows that with any abuse of temperature in raw milk, whether intentional or not, these bacteria can grow with antimicrobial resistance genes,” said co-author Michele Jay-Russell, research microbiologist and manager of the Food Center. UC Davis Western Center. Safety. “It won’t just go bad. It’s a really high risk if it’s not handled properly.”

Some consumers are intentionally letting raw milk sit outside the refrigerator at room temperature for fermentation in order to do what is known as a clabber. Dairy Food Science Chair Peter J. Shields co-author and chair David Mills said that if consumers eat raw milk, they are likely adding a large number of antimicrobial resistant genes to their intestines.

“It could be flooding your gastrointestinal tract with these genes,” said Mills. “We no longer live in a world free of antibiotics. These genes are everywhere, and we need to do everything we can to stop that flow in our bodies.”

While more work is needed to fully understand whether antibiotic-resistant genes in raw milk translate into human health risks, Mills suggests that consumers use a starter culture if they want to ferment raw milk, which carries strains specific bacteria to inoculate milk. .