Effect on Physician Prescribing Practices of Changing from a Qualitative to a Quantitative Antimicrobial Susceptibility Test Reporting System

The use of disc diffusion susceptibility testing has been criticized because it often fails to take into consideration achievable levels of antimicrobial agents at the actual sites of infection. An increasing number of hospitals are converting from disc diffusion antimicrobial susceptibility testing to more quantitative susceptibility testing techniques. Advocates of these latter techniques have suggested that providing information beyond sensitive, intermediate, and resistant reporting will emphasize, more effectively, the importance of considering achievable antibiotic concentrations at the site of infection, when choosing an antimicrobial agent. This study examined whether providing more quantitative susceptibility test reports would affect physicians' antimicrobial prescribing practices.

Results obtained on the preeducation and posteducation questionnaires indicate success in improving the collective knowledge of physicians. In retrospective audits of the appropriateness of antimicrobial use, both before and after the educational program, physician usage of antimicrobial agents was categorized as inappropriate in more than ⅔ of the cases. The major reason for the negative outcome in this study is probably due to physicians' indifference to the results of urine culture and susceptibility test data. A change was made in antimicrobial therapy after return of the susceptibility report less than 20 percent of the time.

As more laboratories convert to quantitative antimicrobial susceptibility testing, there will be a need for a closer liaison among physicians, clinical pharmacists, microbiologists, and infectious disease specialists, to ensure optimum utilization of the additional susceptibility data provided.