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Updated: Jul 31, 2026

Design and Use of a Low Cost, Automated Morbidostat for Adaptive Evolution of Bacteria Under Antibiotic Drug Selection
Published on: September 27, 2016
Designing fluoroquinolone breakpoints for Streptococcus pneumoniae by using genetics instead of
H J Smith1, A M Noreddin, C G Siemens
1Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Canada. smithhj14@hotmail.com
Abstract:
We determined fluoroquinolone microbiological resistance breakpoints for Streptococcus pneumoniae by using genetic instead of pharmacokinetic-pharmacodynamic parameters. The proposed microbiological breakpoints define resistance as the MIC at which >50% of the isolates carry quinolone resistance-determining region mutations and/or, if data are available, when Monte Carlo simulations demonstrate a <90% chance of bacteriological eradication. The proposed microbiological resistant breakpoints are as follows (in micrograms per milliliter): gatifloxacin, >0.25; gemifloxacin, >0.03; levofloxacin, >1; and moxifloxacin, >0.12. Monte Carlo simulations of the once daily 400-mg doses of gatifloxacin and 750-mg doses levofloxacin demonstrated a high level of target attainment (free-drug area under the concentration-time curve from 0 to 24 h/MIC ratio of 30) by using these new genetically derived breakpoints.
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