[In vitro study of the pefloxacine-ceftriaxone combination against 18 strains of Acinetobacter].

The bacteriostatic and bactericidal activity of the pefloxacin-ceftriaxone combination was studied in Mueller-Hinton broth against 18 clinical strains of acinetobacter calcoaceticus var. anitratum by the checkerboard technique. The bactericidal activity was tested after 2, 4, 6 and 24 hours contact. MICs were 0.12 to 4 mg/l for pefloxacin and 2 to 64 mg/l for ceftriaxone. The bacteriostatic interaction of the antibiotics was synergistic for 5 strains (FIC index = 0.375 to 0.5) and additive for 13 strains (FIC index = 0.51 to 1). The bactericidal interaction was synergistic for 1 strain after 2 hours, 3 strains after 4 hours, 6 strains after 6 hours, and 12 strains after 24 hours. By the FBC technique at 24 hours, the combination was synergistic for 5 strains (FBC index = 0.375 to 5) and additive for 13 strains (FBC index = 0.51 to 1). No antagonism was detected. The combination is mainly additive but synergism is observed for some strains of acinetobacter. Ceftriaxone prevented the late regrowth noted with pefloxacin.