Impact of changed co-amoxiclav susceptibility testing formats on apparent resistance rates for bloodstream Escherichia coli in a long-term surveillance

Rosy Reynolds, Shazad Mushtaq, Michael K. Allen, Carolyne Horner, Christopher Longshaw, David M. Livermore

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Until 2014 the BSAC advocated that co-amoxiclav MICs should be determined using a 2:1 gravimetric ratio of amoxicillin and clavulanate. Subsequently, following adoption of EUCAST breakpoints, this advice changed to using clavulanate at a fixed concentration of 2 mg/L. The effect was to lower the breakpoint for Enterobacterales from systemic infections from 8 + 4 to 8 + 2 mg/L. We report on the consequences for apparent resistance prevalence among Escherichia coli as recorded in the BSAC Bacteraemia Antimicrobial Resistance Surveillance Programme.
Original languageEnglish
Pages (from-to)1206–1208
Number of pages3
JournalJournal of Antimicrobial Chemotherapy
Issue number4
Early online date19 Jan 2022
Publication statusPublished - Apr 2022

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