/usr/lib/x86_64-linux-gnu/libmysqlclient.so.18 is in libmysqlclient18 5.5.22-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18.0.0
/usr/lib/x86_64-linux-gnu/libmysqlclient.so.18.0.0