In this paper, numerical studies for the mathematical model of tuberculosis (TB), that incorporates three
strains, i.e., drug - sensitive, emerging multi - drug resistant(MDR) and extensively drug - resistant
(XDR), are presented. Special class of numerical methods, known as nonstandard finite difference method
(NSFDM) is introduced to solve this model. Numerical stability analysis of fixed points are studied. The
obtained results by NSFDM are compared with other known numerical methods such as implicit Euler
method and fourth-order Runge–Kutta method (RK4). It is concluded that NSFD scheme preserves the
positivity of the solution and numerical stability in larger region than the other methods