I'm curious why you were given metronidazole: was it for Lyme disease or did you develop a C difficile infection from other antibiotics? I'm just curious because I'm a physician and have never heard of using metronidazole for Lyme disease.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3132871/
However, this study was done on petri dish cultures of borellia and didn't actually look at whether or not it improved symptoms in people (which I imagine is a difficult thing to study in this field).
When I searched for borrellia and metronidazole there was one more article for in vitro use from the 1990s: http://www.ncbi.nlm.nih.gov/pubmed/10379684