Infect Chemother.  2017 Mar;49(1):62-67. 10.3947/ic.2017.49.1.62.

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

• Park KH
• Chong YP
• Kim SH
• Lee SO
• Lee MS
• Sung H
• Kim MN
• Kim YS
• Woo JH
• Choi SH

• KMID: 2375101
• DOI: http://doi.org/10.3947/ic.2017.49.1.62

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, and Morganella morganii. The 2011 CLSI criteria for cefotaxime and ceftazidime reduced the rates of susceptibility by 2.9% and 5.9%, 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 by 2.8%, 14.8%, and 53.6%, respectively. The proportion of ESBL phenotype among BSC-susceptible isolates was low (0.9% for cefotaxime, 3.0% for ceftazidime, and 3.3% for cefepime). In summary, implementation of new CLSI criteria led to little change in susceptibility to cefotaxime and ceftazidime but a substantial change in susceptibility to cefepime. The recognition of revised CLSI criteria for BSC and SDD will help clinicians to select the optimal antibiotic and dosing regimen.

Keyword

Cephalosporin; Susceptibility; Enterobacteriaceae

MeSH Terms

Cefotaxime
Ceftazidime
Cephalosporins
Citrobacter freundii
Enterobacter
Enterobacteriaceae*
Morganella morganii
Phenotype
Serratia marcescens
Cefotaxime
Ceftazidime
Cephalosporins

Figure

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  Figure 1 Distribution of zone of diameters around the cefotaxime (A), ceftazidime (B), and cefepime (C). ESBL, extended-spectrum ß-lactamase; CLSI, clinical and laboratory standards institute; SDD, susceptible-dose dependent.

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