Oral Presentation Australian Institute of Medical Scientists National Scientific Meeting 2013

BSAC to EUCAST - The Right Move (#9)

Michael Huysmans 1
  1. Alfred Hospital, Melbourne, VIC, Australia

In 2010, there were in effect just two antimicrobial susceptibility standards in routine use in diagnostic microbiology laboratories in Australia: the Clinical and Laboratory Standards Institute (CLSI) standard, and the Calibrated Dichotomous Sensitivity (CDS) standard. However, in December 2009, a new major contender, the European Committee on Antimicrobial Susceptibility Testing (EUCAST), published their first version of breakpoint tables for interpretation of MICs and zone diameters.

At the time of EUCAST publishing their first susceptibility standard, the Microbiology Department at the Alfred Hospital, Melbourne, Victoria, had been using the British Society for Antimicrobial Chemotherapy (BSAC) susceptibility standard for approx. 10 years. Following some informative presentations about EUCAST at the 2010 national meeting of the Australian Society for Antimicrobials (ASA), Alfred Microbiology decided to change over to EUCAST breakpoints for antimicrobial susceptibility testing. As the only laboratory in Australia using BSAC and since they were an integral part of EUCAST, it was felt to be the right move.

Some of the reasons for changeover included:
• Clinical breakpoint reviews based on pK, pD, MIC distributions and clinical trials
• Improved data (pK, pD, MIC, clinical trial) for new agents
• Use of the same medium as CLSI (Mueller-Hinton agar)
• Antimicrobial susceptibility standards provided free in the public domain

Implementation of the EUCAST standards took 6 months and involved the updating of laboratory manuals and instrument software, changes to quality control and regular communication with laboratory and medical staff. The new breakpoints produced a variable impact on overall susceptibility results, with the largest effect observed with the disc zone diameter breakpoints for Enterobacteriaceae and Streptococci.