Consequences of switching from a fixed 2 : 1 ratio of amoxicillin/clavulanate (CLSI) to a fixed concentration of clavulanate (EUCAST) for susceptibility testing of Escherichia coli

Abstract

EUCAST methodology resulted in higher co-amoxiclav E. coli resistance rates than CLSI methodology, but correlated better with clinical outcome. EUCAST-compliant microdilution and disc diffusion provided discrepant results.

Trends over time in Escherichia coli bloodstream infections, urinary tract infections, and antibiotic susceptibilities in Oxfordshire, UK, 1998–2016: a study of electronic health records

“…A limitation of surveillance studies such as this is that changes in the protocol for antimicrobial susceptibility testing can occur and these changes can affect results. 38,39 In our study, antimicrobial susceptibility testing protocol was updated in February, 2013, and, although changes in co-amoxiclav resistance were seen around this time, they occurred regardless of the method used (appendix p 31). Data 40 suggest that microbroth dilution and the gold standard agar dilution have high agreement; thus, the increasing incidence of co-amoxiclav-resistant (as defined by European Committee on Antimicrobial Susceptibility Testing breakpoints) E coli bloodstream infections and E coli UTIs seen in our study are probably correct.…”

National laboratory-based surveillance system for antimicrobial resistance: a successful tool to support the control of antimicrobial resistance in the Netherlands

“…Examples of research based on Dutch national surveillance data are studies on the impact the EUCAST breakpoint implementation in Dutch MMLs had on resistance levels in surveillance data [17,26], a review on the adequacy of the urinary tract infection treatment guideline in hospitalised patients [27], a trend analysis for AMR in hospitals where SDD/SOD is applied vs hospitals where this is not the case [28,29], trends in the proportion of E. coli and K. pneumoniae with an ESBL-producing gene [30], and detection and epidemiology of carbapenemase-producing Enterobacteriaceae in the Netherlands [31]. …”

Trends in Escherichia coli bloodstream infection, urinary tract infections and antibiotic susceptibilities in Oxfordshire, 1998-2016: an observational study

“…A limitation of surveillance studies is changes in antimicrobial susceptibility testing methodology (here in February 2013). Whilst the proportion of isolates classified as resistant can vary by testing protocol, 27,28 crucially changes in co-amoxiclav resistance around this time occurred regardless of method (Supplementary Figure 14). Recent data suggest that broth dilution (BD-Phoenix) and the gold standard agar dilution have high agreement; 29 thus, rising rates of co-amoxiclav-resistant (as defined by EUCAST breakpoints) EC-BSI/EC-UTI are likely correct.…”