'Stealth bomb’ antibiotic vanquishes drug-resistant bacteria

A targeted antibiotic can eliminate infections caused by microbes that are resistant to most drugs, experiments in mouse cells suggest.

A team at biotechnology company Genentech in South San Francisco, California, borrowed a concept used in cancer treatment, in which an antibody – a protein designed to attach to particular cells – is connected to a cancer-fighting drug. Such 'antibody-drug conjugates' include Genentech’s Kadcyla (trastuzumab emtansine), which docks onto breast-cancer cells before deploying its cancer-killing payload.

Sanjeev Mariathasan, an immunologist at Genentech, and a large team of co-workers adapted this strategy – which they tested in mouse cells – by gluing an antibody against Staphylococcus aureus (Staph) bacteria to an antibiotic, a modified version of the drug rifampin, which is used to treat tuberculosis. More than 80,000 people in the United States are infected each year with methicillin-resistant S. aureus (MRSA), which is untreatable with most commonly used antibiotics, and more than 11,000 people of them die. MRSA is thought to be so deadly in part because after Staph invades the body, it quickly enters cells, where it becomes hard to kill with antibiotics.