If a patient falls ill with multi-resistant tuberculosis (MDR-TB), it must be clarified which drugs the pathogens still respond to. So far, doctors have required results of drug testing after culturing the bacteria. The problem: Mycobacterium tuberculosis grows very slowly. It can take several weeks for the bacteria to grow in the laboratory, and it often takes a month or two before the effectiveness of the individual drugs can be tested. As a result, the start of an effective therapy is delayed.