Not long ago, we were talking about the capabilities of service dogs. Here's a story about a dog trained to identify clostridium difficile:
http://www.foxnews.com/health/2012/12/14/dog-trained-to-sniff-out-deadly-c-difficile-superbug/?intcmp=features
http://www.foxnews.com/health/2012/12/14/dog-trained-to-sniff-out-deadly-c-difficile-superbug/?intcmp=features