Clin. Infect. Dis. 49, 869–875 (2009)

Antibiotic resistance in pathogens can be reversed by rolling back the total amount of the drug consumed, but it increases as soon as consumption rises again.

During a seven-month period in 2001–02, the use of ciprofloxacin, a popular antibiotic, was restricted in Israel because supplies were being stockpiled in case of a bioterrorist attack. Michal Chowers and her colleagues at Tel Aviv University in Israel measured the ciprofloxacin sensitivity of the bacterium Escherichia coli from urine samples before, during and after this period.

A near 50% drop in ciprofloxacin use reduced the percentage of samples containing resistant bacteria from 12% to 9%. But resistance surged as soon as people started popping the pills again.