Are breakpoints for phenotypic susceptibility testing no longer needed?

Abstract

The European Committee on Antimicrobial Susceptibility Testing (EUCAST) was formed in 1997 to determine breakpoints and provide guidance on methods for phenotypic antimicrobial susceptibility testing (AST) in Europe. Up until 2008, when EUCAST completed the process of harmonizing breakpoints for the most widely used organism–agent combinations, laboratories in Europe used one of seven available breakpoint systems. Since 2002, EUCAST has served as an umbrella organization for the national breakpoint committees in Europe (France, Germany, Netherlands, Norway, Sweden and the UK) and today almost all European countries have agreed to use the EUCAST breakpoints and methods for phenotypic AST. Over the last few years, methods to detect resistance genes, and particularly whole genome sequencing, have made inroads—not for general AST but for characterizing resistance and for typing of bacteria for epidemiological purposes. Lately, it has been suggested that very soon we shall not need breakpoints and recommendations for phenotypic susceptibility testing as these will be replaced by genetic methods. This of course hinges on the ability of genetic methods to predict not only resistance but also susceptibility, and on their ability to quantify the degree of resistance. Such prediction is gradually becoming more difficult as multiple resistance mechanisms become more common, and more of a concern as extreme resistance and pan-drug resistance become a reality. In 2015 the EUCAST Steering Committee asked Neil Woodford and colleagues to form a EUCAST Subcommittee to evaluate the current knowledge regarding whole genome sequencing for prediction of antimicrobial susceptibility in a number of important bacterial species. The resulting report is published in Clinical Microbiology and Infection following a period of open consultation by EUCAST during 2016. In response to the consultation there were comments from ten other experts or groups of experts. In the tradition of EUCAST the comments and the responses from the EUCAST Subcommittee will be available on the EUCAST website (www.eucast.org). The findings of the Subcommittee were also presented and discussed with colleagues during the ECCMID 2016 in Amsterdam. The report will be reviewed and updated at intervals, the length of which will be decided by the pace of developments in the field. For EUCAST and CMI Editorial Note: not peer-reviewed