Impact of Revised Broad-Spectrum Cephalosporin Clinical and Laboratory Standards Institute Breakpoints on Susceptibility in Enterobacteriaceae Producing AmpC β-Lactamase

다국어 초록 (Multilingual Abstract)

We evaluated the impact of revised Clinical and Laboratory Standards Institute (CLSI) breakpoints for broad-spectrum cephalosporins(BSCs) on the susceptibilities of 1,742 isolates of Enterobacter species, Serratia marcescens, Citrobacter freundii, andMorganella morganii. The 2011 CLSI criteria for cefotaxime and ceftazidime reduced the rates of susceptibility by 2.9% and5.9%, respectively. The 2014 CLSI criteria for cefepime reduced the rate of susceptibility by 13.9%, and categorized 11.8%isolates as susceptible-dose dependent (SDD) for cefepime. Among 183 isolates with extended-spectrum ß-lactamase (ESBL)phenotype, implementation of the new criteria reduced the rates of susceptibility to cefotaxime, ceftazidime, and cefepime by2.8%, 14.8%, and 53.6%, respectively. The proportion of ESBL phenotype among BSC-susceptible isolates was low (0.9% forcefotaxime, 3.0% for ceftazidime, and 3.3% for cefepime). In summary, implementation of new CLSI criteria led to little changein susceptibility to cefotaxime and ceftazidime but a substantial change in susceptibility to cefepime. The recognition of revisedCLSI criteria for BSC and SDD will help clinicians to select the optimal antibiotic and dosing regimen.

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