Marcia Barinaga's News & Comment article "New test catches drug-resistant TB in the spotlight" (7 May, p. 750) did not mention that the idea of using reporter phages as indicators of bacterial growth was first suggested in a 1987 publication by Shimon Ulitzur and Jonathan Kuhn of the Israel Institute of Technology. What was technically new in the publication discussed in Barinaga's article was the engineering of mycobacteria phages as vectors to carry the firefly luciferase gene into mycobacteria, which include the bacteria that cause tuberculosis.