Globally, tuberculosis is the most common bacterial infectious disease leading to death. The pathogen causing tuberculosis, Mycobacterium tuberculosis, has a number of peculiarities. One is that it is growing very slowly. While other typical pathogens, such as pneumococcal and pseudomonads, can already be identified by their growth in the microbiological laboratory in the first 72 hours, several weeks usually pass before tuberculosis bacteria grow in the lab. Thus it often takes one to two months before the efficacy of individual medicines can be tested.
However, these efficacy tests are essential for the effective treatment of multidrug-resistant tuberculosis (MDR-TB), which is becoming increasingly common. In these cases, the pathogen has become resistant, i.e. insensitive, to the best tuberculosis drugs, rifampicin and isoniazid. This is due to changes in the genome, so-called mutations, which almost always occur at the same points in the genome. Treatment of MDR-TB is protracted, costly and frequently associated with side effects.
For the selection of antibiotics in a combination therapy, doctors have so far depended on the results of the drug test after cultivation. “Currently, 15 drugs are available for second-line therapy, of which at least four are used in combination,” explains Prof. Christoph Lange, coordinator of the clinical study at the Research Center Borstel.
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Clinical Infectious Diseases. Study Paper:
A typical bacterium
Non TB Mycobacterial infection 
