Nat. Biotechnol. 23, 445–451 (2005)

In the abstract on page 445, the quantities given for lysostaphin in the following sentences are incorrect: “To test the feasibility of protecting animals through genetic engineering, transgenic cows secreting lysostaphin at concentrations ranging from 0.9 to 14 mg/ml in their milk were produced” and “Protection against S. aureus mastitis appears to be achievable with as little as 3 mg/ml of lysostaphin in milk.” The correct quantities are 0.9 to 14 μg/ml and 3 μg/ml, respectively. The quantities are correct in the rest of the paper.