title: Impact of Revised Broad-Spectrum Cephalosporin Clinical and Laboratory Standards Institute Breakpoints on Susceptibility in Enterobacteriaceae Producing AmpC β-Lactamase.
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 β-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.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea.
authors.forename: Ki Ho
authors.initials: KH
authors.lastname: Park
authors.affiliation: Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Yong Pil
authors.initials: YP
authors.lastname: Chong
authors.affiliation: Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Sung Han
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Sang Oh
authors.initials: SO
authors.lastname: Lee
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea.
authors.forename: Mi Suk
authors.initials: MS
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Heungsup
authors.initials: H
authors.lastname: Sung
authors.affiliation: Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Mi Na
authors.initials: MN
authors.lastname: Kim
authors.affiliation: Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Yang Soo
authors.initials: YS
authors.lastname: Kim
authors.affiliation: Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jun Hee
authors.initials: JH
authors.lastname: Woo
authors.affiliation: Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. sangho@amc.seoul.kr.
authors.forename: Sang Ho
authors.initials: SH
authors.lastname: Choi
keywords: Cephalosporin; Enterobacteriaceae; Susceptibility