Substantially reducing the use of antibiotics such as ciprofloxacin stopped an outbreak of severe diarrhea caused by Clostridium difficile in the United Kingdom (Lancet Infect Dis [Epub Jan 24, 2017]).
Inappropriate use and widespread overprescribing of fluoroquinolone antibiotics such as ciprofloxacin allowed resistant C. difficile to thrive, because nonresistant bugs in the gut were killed off by the antibiotic, leaving the way clear for rapid growth of resistant C. difficile.