What are the CLSI definitions of S pneumoniae susceptibility?

Updated: Jun 08, 2020
  • Author: Eduardo Sanchez, MD; Chief Editor: John L Brusch, MD, FACP  more...
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The Clinical and Laboratory Institute (CLSI) (2010) has defined S pneumoniae susceptibility as follows [1, 2] :

  • Pneumonia: For penicillin-sensitive S pneumoniae (MIC < 2 μg/mL), penicillin G or amoxicillin is considered first-line therapy. For penicillin-resistant S pneumoniae (MIC ≥2 μg/mL), the choice of antimicrobial agent should be directed by susceptibility testing.
  • Cefotaxime or ceftriaxone considerations are as follows:
    • Susceptible (non-CNS/CNS): MIC is ≤1/0.5 µg/mL, respectively.
    • Intermediate (non-CNS/CNS): MIC is 2/1 µg/mL, respectively.
    • Resistant (non-CNS/CNS): MIC is ≥4/2 µg/mL, respectively.

Strains with intermediate or resistant susceptibility patterns should be considered nonsusceptible and alternate therapy used.

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