Could the pesticides being used to grow animal feed be making those same animals riskier to eat? The results of a new study out of Germany suggest that they might be.

Roundup, one of the most commonly used pesticides in the U.S., is frequently applied to corn and soy, the two crops that make up the bulk of factory-farmed chicken feed, and the study, published in the journal Current Microbiology, has found that the active ingredient in Roundup interferes with healthy bacteria in the guts of animals, possibly leading to stronger and more drug-resistant strains of unhealthy, disease-causing organisms.

The researchers looked at the effect of glyphosate, Roundup's main ingredient, on beneficial bacteria in the guts of chickens being raised for meat. They found that the levels of glyphosate commonly found in corn- and soy-based feeds did in fact interfere with the birds' gut flora. Healthy bacteria, they found, were easily killed by the herbicide chemical, while disease-causing bacteria appeared to be unaffected by it. It's often the healthy bacteria that keep bad bacteria, such as E. coli, Clostridium, Salmonella and Staphylococcus, in check, they write.

Furthermore, they found that three strains of Salmonella bacteria were resistant to glyphosate, which acts as an antibiotic in the chickens' guts, and that certain strains of Staphylococcus appeared to be able to develop resistance to the chemical, suggesting that glyphosate residues could be contributing to harder-to-treat strains of these harmful bacteria.

The widespread use of antibiotics in chicken feed is undoubtedly driving the proliferation of antibiotic-resistant bacteria in poultry farms, as well as in beef, dairy, and pork operations—the Food and Drug Administration estimates that 80 percent of all antibiotics sold in the U.S. are given to animals. But this study suggests that those virulent bugs could be getting some help from Roundup, which is now applied to 86 percent of U.S. corn crops and 93 percent of U.S. soy crops.

Genetically modified versions of corn and soy have been bred to withstand huge quantities of the herbicide, and Roundup's use has increased 7 percent since the crops were first introduce in 1996, according to a recent study in the journal Environmental Sciences Europe.

The bottom line: Buy organic meat. Not only are antibiotics banned in organic meat production, but so is feed containing genetically modified corn and soy.