Dairy-cow manure that is spread on farmland could also be spreading a wide variety of genes encoding antimicrobial resistance, reports a Connecticut-based team.

Jo Handelsman at Yale University in New Haven and her team analysed DNA from five samples of manure from dairy cows (pictured) and found 80 genes from a variety of bacteria that encode proteins for resistance to a wide range of antibiotics. Among them was a new group of genes that are specific to cow manure and confer resistance to the antibiotic chloramphenicol, which is used clinically. The protein sequences deduced from the 80 genes were, on average, only 50–60% identical to known amino-acid sequences.

Credit: Claudius Thiriet/Biosphoto/Ardea

Cow manure is commonly used as a crop fertilizer, and this could be one way in which resistance genes disperse beyond the dairy farm, the team suggests.

mBio 5, e01017-13 (2014)