Connecting to another database – security question

I’m working on a project that requires me to connect to another WordPress database on the same server. This seems to be easy enough to do by setting up a new wpdb class:

$wpdb2 = new wpdb('database_user', 'password', 'database_name', 'localhost');

However, I’m curious about the security ramifications of putting all that database connection info in, say, functions.php. What would be the best way to handle this?