All isolates were identified as members of the M. tuberculosis complex, using gene probes (ACCUProbe; Hologic, San Diego, CA, USA) or the GenoType MTBC assay (Hain Lifescience, Nehren, Germany). The differentiation between the species of the M. tuberculosis complex was based on genotyping data of each individual isolate [7 (link)–9 (link)]. Drug susceptibility testing was determined by means of the proportioning method on Löwenstein–Jensen medium and/or by means of the modified proportioning method with the BACTEC MGIT 960 system (Becton Dickinson Microbiology Systems, Cockeysville, MD, USA).