Antimicrobial formularies: can they minimize antimicrobial resistance?

The relationship between antimicrobial drug use and resistance rates and the implications for antimicrobial formularies are described. Efforts to restrict antimicrobial drug use to reduce resistance in certain microorganisms have been accompanied by increases in resistance in other microorganisms. Random cycling of a variety of antimicrobial agents to treat infections caused by the same microorganism in different patients within a health care institution has been advocated as a means to reduce antimicrobial resistance. Analysis of actual antimicrobial drug use and resistance data from a network of 40 hospitals revealed wide variability in antimicrobial use. The specific type and volume of antimicrobial agents used appear to play key roles in determining resistance rates. It may be feasible to optimize diversity in antimicrobial drug use and minimize resistance by making judicious changes to the antimicrobial formulary.