How to grep and then fail an if-statement on specific output from grep?

Ok I need to find the output that a command gives, notely "gbak: ERROR" and then fail on it. I don't know if I'm going about it the right way, I tried to make if fail if the grep did an output to /dev/null but I couldn't get that working either (probably just poor syntax). I'm sure this is a simple one, please let me know.

The if statement I've got at the moment is:

if [ `sudo -u firebird $GBAK_COMMAND | grep "gbak: ERROR"` == *gbak: ERROR* ]; then
   echo "$DATE Unsucessful $1.gdb Gbak. Incorrect user/password" >> /var/log/messages
   echo "Failed"
   exit 1
else
   echo "pass"
fi