You are describing oral inflammation (stomatitis) and gingvitis.  This
is common in cats, but not common in ferrets.  Since there was bacteria
then it is time to treat him with clavamox drops for the oral infection.
Chlorhexidine rinses can also be used (with clavamox) to control the
infection.  Additional immunosuppresive drugs may also be needed.  It
is time to have a dental cleaning to remove any tatar too.
 
Hope that helps,
Jerry Murray, DVM
 
PS In cats, sometimes we have to pull teeth to limit the inflammation of
   the gums.
[Posted in FML issue 3493]