BSAC standardized disc susceptibility testing method (version 3)

Received 2 September 2003; accepted 16 December 2003 Since the Journal of Antimicrobial Chemotherapy Supplement containing the BSAC standardized disc susceptibility testing method was published in 2001, there have been various changes to the recommendations and these have been posted on the BSAC website (http://www.bsac.org.uk). Two major organizational changes have been made to the interpretative tables. First is the separation of the acceptable ranges for the control strains from the interpretative criteria. The Working Party felt that it was appropriate to do this, as the control ranges are a tool for controlling the performance of the test and are not used for interpreting susceptibility. Second, in line with the European consensus, the presentation of MIC breakpoints (mg/L) has been amended as follows: MIC ≤ (as previously) MIC breakpoint concentration = organism-susceptible MIC > (previously ≥) MIC breakpoint concentration = organism-resistant. In practice, this does not make any changes to breakpoint systems based on two-fold dilutions, but it avoids the theoretical ‘gap’ inherent in the previous system. However, the appearance of the tables will change, e.g. R ≥ 16, S ≤ 8 will change to R > 8, S ≤ 8.