<prompt> XDR-TB is defined as: March 2012Resistance to at least INH and rifampicin - other drugsResistance to any of the 3 first line drugsResistance to all 1st line drugs and any 3 second line injectable drugsResistance to at least INH and rifampicin any quinolones at least 1 injectable 2nd line drug  <response>: Ans: D i.e. Resistance to atleast INH and rifampicin any quinolones atleast 1 injectable 2nd line drug Terminology related to drug therapy of TB MDR Multi Drug Resistant TB is defined by resistance to at least rifampicin and isoniazid, with or without other drug resistance Drug resistant TB is defined by the presence of resistance to any first line agent Extensively drug resistant XDR TB is defined by resistance to at least rifampicin and isoniazind, in addition to any quinolone and at least one injectable second line agent 