  Extending the ideal MHD stability code MISHKA, a new code, MISHKA-A, is
developed to study the impact of pressure anisotropy on plasma stability. Based
on full anisotropic equilibrium and geometry, the code can provide normal mode
analysis with three fluid closure models: the single adiabatic model (SA), the
double adiabatic model (CGL) and the incompressible model. A study on the
plasma continuous spectrum shows that in low beta, large aspect ratio plasma,
the main impact of anisotropy lies in the modification of the BAE gap and the
sound frequency, if the q profile is conserved. The SA model preserves the BAE
gap structure as ideal MHD, while in CGL the lowest frequency branch does not
touch zero frequency at the resonant flux surface where $m+nq=0$, inducing a
gap at very low frequency. Also, the BAE gap frequency with bi-Maxwellian
distribution in both model becomes higher if $p_\perp > p_\parallel$ with a q
profile dependency. As a benchmark of the code, we study the m/n=1/1 internal
kink mode. Numerical calculation of the marginal stability boundary with
bi-Maxwellian distribution shows a good agreement with the generalized
incompressible Bussac criterion [A. B. Mikhailovskii, Sov. J. Plasma Phys 9,
190 (1983)]: the mode is stabilized(destabilized) if $p_\parallel < p_\perp
(p_\parallel > p_\perp)$.
