  We provide evidences for the duality between ${\cal N}=6$ $U(M)_{4} \times
U(N)_{-4}$ Chern-Simons matter theory and ${\cal N}=5$ $O(\hat{M})_{2} \times
USp(2\hat{N})_{-1}$ theory for a suitable $\hat{M},\hat{N}$ by working out the
superconformal index, which shows perfect matching. For ${\cal N}=5$ theories,
we show that supersymmetry is enhanced to ${\cal N}=6$ by explicitly
constructing monopole operators filling in $SO(6)_R$ $R$-currents. Finally we
work out the large $N$ index of $O(2N)_{2k} \times USp(2N)_{-k}$ and show that
it exactly matches with the gravity index on $AdS_4 \times S^7/D_k$, which
further provides additional evidence for the duality between the ${\cal N}=5$
and ${\cal N}=6$ theory for $k=1$
