Fluoroquinolones: are they essential to treat multidrug-resistant tuberculosis?

The excellent letter by HOLTZ and CEGIELSKI contributing to the current discussion on extensively drug-resistant (XDR)-tuberculosis (TB). Several publications have already demonstrated that resistance to fluoroquinolones (FQ) is independently associated with poor outcome and/or that the possibility of including FQ in regimens improves treatment outcomes of multidrug-resistant (MDR)-TB cases. This happened before the (recent) description of XDR-TB. We do not know how many of the patients with MDR-TB strains were, in fact, infected with XDR Mycobacterium tuberculosis. We wanted to establish the role of the different XDR-defining components (e.g. isoniazid and rifampicin, FQ and injectable second-line drugs) in determining poor treatment outcomes.