There are keratin media described in the literature - one observes clearing of the insoluble keratin associated with colonies of keratinolytic activity.  One can also use   dye-associated keratin  and follow the release of dye as keratin is hydrolyzed.  You can make your own fairly simply - but do qualify with controls isolates.  Here are a couple of cites: 

http://scialert.net/abstract/?doi=ijps.2010.482.489

http://individual.utoronto.ca/jscott/publications/keratin_azure.pdf