Dear David Shadick:
I saw your query, and it reminded me of a paper given by Dr. Don Woods at
a local CSM meeting in Calgary a few years back. They were working with
ciprofloxacin treatment of cystic fibrosis patients. Although some strains of
Pseudomonas aeruginosa became ciprofloxacin resistant, once treatment was
stopped there was a strong reversal for these strains to become
ciprofloxacin sensitive. It seems that because the antibiotic deals with DNA
gyrase, the bug isn't happy in being resistant as it has to
compromise a lot in its DNA synthetic mechanism. Once the selective advantage
of being ciprofloxacin resistant is remove, there is a selective advantage of
normal sensitive strains over abnormal resistant strains.
Hope this helps...John
