A small molecule produced by bacteria living naturally in people can help to combat a pathogen that is resistant to many antibiotics.

Sean Brady at the Rockefeller University in New York City and his colleagues analysed the genomes of the human microbiota to identify genes predicted to encode molecules with antibiotic properties. They then synthesized these molecules and measured their antibacterial effects. One, humimycin A, was active against a strain of methicillin-resistant Staphylococcus aureus (MRSA) collected from patients. MRSA-infected mice treated with humimycin A and dicloxacillin, a commercially available antibiotic, all remained alive 48 hours after infection. By contrast, at least half of the animals died after treatment with either drug alone.

Improved bioinformatic and chemical-synthesis techniques could lead to the discovery of more compounds with therapeutic potential from the microbial world, the authors suggest.

Nature Chem. Biol. http://dx.doi.org/10.1038/nchembio.2207 (2016)