As per RNTCP guidelines, Multi drug resistance (MDR) TB is defined as resistance to:
Confirmed MDR-TB case: MDR-TB suspect is one who is sputum culture positive and whose TB is due to Mycobacterium tuberculosis that are resistant in-vitro to at least isoniazid and rifampicin (the culture and DST result being from an RNTCP accredited laboratory). Ref: Park 21st edition, page 178.
Rifampicin
Rifampicin and isoniazide
Rifampicin, isoniazide and ethambutol
None of the above