You do know that MySQL users are not the same as system users? You can't use system user accounts to commect to the MySQL server. You need to create these users in MySQL and then assign their privilidges to each database that you want them to access.
Your error message:
ERROR 1227 (42000): Access denied; you need (at least one of) the CREATE USER privilege(s) for this operation
That's a MySQL user error - not a system user error.
