TABLE 4

Summary of reproducibility of the various methods to determine colistin MICs for mcr-1-positive Escherichia coli isolates

CDC AR Bank accession no.Colistin MIC (µg/ml)
CDC resultBroth microdilutionBroth macrodilutionCBDE
Day 1Day 2Day 3ModeDay 1Day 2Day 3ModeDay 1Day 2Day 3Mode
34644>4>4>488884444
349a2–4244422222444
350a4244444444444
4938>4>4>4>488884444
4948>4>4>4>488884444
495a4444444444444
  • a Isolates that demonstrated MICs of 2 µg/ml by colistin broth disk elution on initial testing at both sites.