Use of a clinical Escherichia coli isolate expressing lux genes to study the antimicrobial pharmacodynamics of moxifloxacin

Escherichia coli isolate 16,906 expressing lux genes was used for real-time monitoring of moxifloxacin effects on bacterial metabolism compared with effects on cell replication. Viable counts showed concentration-dependent killing by moxifloxacin; real-time measurement of bioluminescence on the same cultures showed metabolic activity over 54 h, but with greater inhibition at 1 x MIC than with higher MIC multiples. Post-antibiotic effect was longer when determined using bioluminescence than by viable counts. The control-related effective regrowth time was consistent with both methods. Bioluminescent bacteria provide a rapid and sensitive means for measuring antimicrobial effects on bacterial metabolism.