  In this research, we prove analytically that a generic spherically symmetric
thin-shell wormhole (TSW) with its throat located at the innermost photonsphere
of the bulk asymptotically flat black hole and supported by a generic surface
barotropic perfect fluid is unstable against a radial linear perturbation. This
is the generalization of the instability of the Schwarzschild TSW (STSW) with
the throat's radius located at $a_{0}=3M$ that was revealed by Poisson and
Visser in their seminal work \cite{Poisson1995} where they studied the
mechanical stability of STSW. Our proof provides a link between the instability
of the null circular geodesics on the innermost photonsphere of a generic
static spherically symmetric asymptotically black hole and the TSW constructed
in the same bulk with $a_{0}=r_{c}$ where $% a_{0} $ and $r_{c}$ are the radius
of the TSW and the innermost photonsphere, respectively. For asymptotically
flat spherically symmetric black holes possessing more than one photonspheres,
the number of the photonspheres is odd and at least one photonsphere is stable
which implies the corresponding TSW with its throat identical with the stable
photonsphere is also stable.
