A 45 yr old male presents with fever, cough, and anorexia. Sputum is positive for AFB. He is staed on isoniazid, rifampicin, pyrazinamide and ethambutol. What is the reason for administering multidrug therapy in tuberculosis?

The reason for administering muti-drug therapy in tuberculosis is to prevent develompment of resistance. Resistance to individual drugs in Mycobacterium tuberculosis occurs by spontaneous point mutations that occur at a low but predictable rate (10 to 10 ). The development of drug-resistant tuberculosis (TB) is almost invariably the result of monotherapy, i.e., the failure of the health care provider to prescribe at least 2 drugs to which the tubercle bacilli are susceptible. Hence, multi-drug therapy is recommended for tuberculosis. Common point mutations in M.tuberculosis which cause drug resistance Rifampin : rpoB gene Isoniazid : katG gene & inhA Pyrazinamide : pncA gene Ethambutol : embB gene Aminoglycosides : rrs gene fluoroquinolones : gyrA-gyrB genes Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition