Impact of antibiotic administrative restrictions on trends in antibiotic resistance.

CONTEXT In March 2001, in response to concerns about increasing resistance to fluoroquinolone (FQ) antibiotics, the Ontario Drug Benefit (ODB) program limited reimbursement of FQs to ODB beneficiaries defined as high risk or in whom other therapies are not tolerated. OBJECTIVE To analyze the impact of the limited use (LU) policy changes on antibiotic resistance rates in Ontario, focussing on community-acquired pathogens. DESIGN Ontario data submitted to the Canadian Bacterial Surveillance Network (CBSN) between January 1, 1998 and June 30, 2002 were analyzed for rates of resistance in various pathogen-antibiotic combinations. The effect of the LU policy on the level and rate of change of antibiotic resistance was estimated using time series models. RESULTS Resistance rates for S. pneumoniae were 10-12% for penicillin, erythromycin and trimethoprim sulfamethoxazole (TMP/SMX) and less than 3% for amoxicillin and all three FQs tested. There was a statistically significant increasing trend in resistance rates of S. pneumoniae to amoxicillin and levofloxacin throughout the study period. Antibiotic resistance of S. pneumoniae to ciprofloxacin indicated a statistically significant decreasing trend over the study period with a statistically significant increase in the level of antibiotic resistance at the time of the LU policy implementation. No other indication of any statistically significant decrease in resistance rates associated with the LU policy was found. CONCLUSIONS Although no direct cause and effect can be proven with these observational data, there is no evidence that the limited use policy to restrict fluoroquinolones decreased antibiotic resistance in any of the pathogen-antibiotic combinations tested.