Continued in vitro cefazolin susceptibility in methicillin-susceptible Staphylococcus aureus

Benjamin H. Gern, Alexander L. Greninger, Scott J. Weissman, Jennifer R. Stapp, Yue Tao, Xuan Qin

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Objectives: In vitro trends of cefazolin and ceftriaxone susceptibilities from pediatric clinical isolates of methicillin-susceptible Staphylococcus aureus (MSSA) between 2011 and 2016 were analyzed for surveillance. Methods: Our laboratory continues to use agar disk diffusion for staphylococcal susceptibilities applying Clinical Laboratory Standard Institute's 2012 breakpoints. Results: A total of 3992 MSSA clinical isolates in the last 6 years were analyzed for their in vitro cefazolin and ceftriaxone susceptibilities. While all MSSA isolates exhibited cefazolin susceptibilities within the "susceptible" zone range, there have been a proportion of isolates with ceftriaxone susceptibilities falling in "intermediate" zones, ranging from 2.6% in 2011 to 8.3% in 2016. Conclusions: Cefazolin continues to be the recommended agent for MSSA treatment at our institution, reflected by the finding that only 2% (6/321) of patients who received ceftriaxone as definitive therapy for MSSA bacteremia during the study period. We have confirmed the cefoxitin-predicted MSSA susceptibility to cefazolin, but have found concerning drifts in ceftriaxone susceptibilities by continued in vitro monitoring over the last 6 years.

Original languageEnglish (US)
Article number5
JournalAnnals of Clinical Microbiology and Antimicrobials
Issue number1
StatePublished - Feb 20 2018
Externally publishedYes


  • Cefazolin
  • Ceftriaxone
  • MIC
  • MSSA
  • Staphylococcus aureus

ASJC Scopus subject areas

  • Microbiology (medical)
  • Infectious Diseases


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