title: Impact of revised susceptibility breakpoints on bacteremia of Klebsiella pneumoniae: Minimum inhibitory concentration of cefazolin and clinical outcomes.
abstract: BACKGROUND
  The Clinical and Laboratory Standards Institute (CLSI) revised the susceptibility breakpoints of cephalosporins for Enterobacteriaceae in 2010 and 2011. However, there is a lack of clinical data about the correlation of minimum inhibitory concentrations (MICs) and clinical outcome. Data for the distribution of MICs and clinical outcomes were analyzed in this study to evaluate the impact of changes in the CLSI breakpoints on the treatment of Klebsiella pneumoniae bacteremia.
  
  
  METHODS
  Ninety-seven bacteremic K. pneumoniae isolates from Taichung Veterans General Hospital, Taichung, Taiwan were collected for study during the period 2009-2011. The cefazolin MIC was determined by the broth microdilution method according to the recommendations of the CLSI. The MIC distribution of cefazolin and the clinical responses to definitive cefazolin treatment were analyzed.
  
  
  RESULTS
  The modal cefazolin MIC among the 97 isolates was 1 μg/mL and accounted for 73 (75.3%) isolates. There were 18 (18.6%) isolates with a cefazolin MIC of 2 μg/mL. The conventional dosage regimens of cefazolin (1 g every 6 hours or 8 hours) achieved a clinical cure in 70 (97.2%) of 72 patients in the group with a cefazolin MIC ≤1 μg/mL and in 14 (87.5%) of 16 patients in the group with a cefazolin MIC of 2 μg/mL. With the conventional dose, the cumulative clinical cure rate for K. pneumoniae bacteremia with cefazolin MIC ≤2 μg/mL was 95.5% (84/88 patients).
  
  
  CONCLUSIONS
  The conventional cefazolin dose still can result in satisfactory clinical cure rates for bacteremic episodes due to K. pneumoniae with cefazolin MIC ≤2 μg/mL, the revised susceptible breakpoint of CLSI 2011.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Chia-Hui
authors.initials: CH
authors.lastname: Chuang
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Meei-Fang
authors.initials: MF
authors.lastname: Liu
authors.affiliation: Microbiology Section of the Medical Laboratory, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Chin-Fu
authors.initials: CF
authors.lastname: Lin
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: zyshi@vghtc.gov.tw.
authors.forename: Zhi-Yuan
authors.initials: ZY
authors.lastname: Shi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D016470:Bacteremia / Q000188:drug therapy*; D002437:Cefazolin / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007710:Klebsiella Infections / Q000188:drug therapy*; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D013624:Taiwan; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D002437:Cefazolin
keywords: Klebsiella pneumoniae; breakpoint; cefazolin; minimum inhibitory concentration