In vitro activities of six new fluoroquinolones against Brucella melitensis.

We have tested the in vitro activities of eight fluoroquinolones against 160 Brucella melitensis strains. The most active was sitafloxacin (MIC at which 90% of the isolates are inhibited [MIC90], 0.12 microg/ml). In decreasing order, the activities (MIC90s) of the rest of the tested fluoroquinolones were as follows: levofloxacin, 0.5 microg/ml; ciprofloxacin, trovafloxacin, and moxifloxacin, 1 microg/ml; and ofloxacin, grepafloxacin, and gatifloxacin, 2 microg/ml.