I saw Night of the Creeps years ago on VHS and since acquired it on DVD, and I played through RE0 when my friend let me borrow his Gamecube and copy of the game (I never actually owned one). Although I see the connection, there are a handful of slug-based horror movies out there, like Shivers, Slither and Slugs. There could be doubted that RE0 was influenced by NotC, but considering it's the best film of the ones I mentioned I'd give it the benefit of the doubt.
Then again, it could have been influenced by Splatterhouse.
The left call me a fascist
The right call me a communist