Try the Comprehensive Antibiotic Resistance Database: http://arpcard.mcmaster.ca/

Interesting question, this was the best that I have found. http://ardb.cbcb.umd.edu/. It is not huge and not maintained since 2009.

Old post, but here is a tool I want to share VRprofile/ It's a tool for in silico profiling of virulence and antibiotic resistance traits encoded within genome sequences of pathogenic bacteria. Efficient to detect bacterial drug resistance

A nice up-to-date collection of databases is available in abricate: https://github.com/tseemann/abricate

Otherwise, it's mostly blasting against databases for every such tool.